1098 mods: very good result !!!!

[microfast]

Finally i have had the time for do and test the op-amps mod.

I have replaced 3 of 4 ( for me a 5.1 configuration is sufficient ) of the cheap and sonically modest TL072C of the multichannels input ( normally used for listen SACD and DVD-Audio ) and one of two ( always for the 5.1 conf. that i do use ) of the JRC5532s of the output stage, using the well sounding BB/Texas OPA2604 that Rotel use only on the output stage for the frontal L/R, central and LFE channels.

The result are very impressive: now sound very well, more transparent and detailed, the voice and high frequency are more natural, the bass more rich and punched.

Next step: replace the 3 ( or four for 7.1 conf. ) TL072c after the Crystal DAC ....................

Regards
Marco

[Kevin D]

Just curious, how many of these be on the removeable cards? I imagine the multi-in ones would be, but how about the others? I might be willing to try it if they were on the cards, but don't think I would tackle taking the whole thing apart.

Thanks, keep us posted.

Kevin D.

[aud19]

Yes, it will be interesting to hear your results... I assume this voids the warranty though...lol

Jason




Need a new display? Questions about new display technologies? Visit RPTVs, plasmas, and other monitors @ HTguide

[microfast]

They are all on two removable card.

Regards
Marco

[microfast]

They are all on two removable card.

Regards
Marco

[Azeke]

Marco,

Just a quick sophormoric question. If you replace the mods will you still be able to upgrade your firmware will Rotel comes out with newer versions?

Regards,

Azeke

[microfast]

Marco,

Just a quick sophormoric question. If you replace the mods will you still be able to upgrade your firmware will Rotel comes out with newer versions?

Regards,

Azeke

Azeke,

The mod do not change any aspect of the features of the 1098, it do works normally, only the sound is better

Now it is more similar to higher price pre/dec

Regards
Marco

[Aussie Geoff]

Microfast,

Interesting - are these components one for one swaps or do you need to trim signal levels, impedances etc in the circuitry through different specifications of the components?

While you still have some new / some old components - I suspect there are a few of us who would appreciate pictures showing the impacted board with the new and old component highlighted....

I'd better stop right now and have a cold shower - I'm getting tempted....

Geoff

[microfast]

Microfast,

Interesting - are these components one for one swaps or do you need to trim signal levels, impedances etc in the circuitry through different specifications of the components?

While you still have some new / some old components - I suspect there are a few of us who would appreciate pictures showing the impacted board with the new and old component highlighted....

I'd better stop right now and have a cold shower - I'm getting tempted....

Geoff

Geoff,

The work is very simple ( but you must have the right equipment and good experience in soldering ).

The board for the mods that i have already done is that with the multichannel input and the pre-out connectors.

It is sufficient replace the chips, no others modifications are request and the chips to replace are easy to find.

For a 7.1 configuration there are four chips TL072c near the multichannels input connector to replace with four chip OPA2604AU ( smd type ) and two chips JRC5532 of the output stage beside the two OPA2604 not smd ( the only good op-amp originally used from Rotel ) to replace with two OPA2604AU ( smd type ).

The other four TL072c chips to replace ( always with OPA2604AU chips )are on the little pcb near the four DAC CS43122 fitted on DSP the cirrus board.

Best regards

Marco

Ps. Is possible have the schematic ?

In Italy this is top secret

[Bam!]

Hey guys!

Interesting and gutsy!

Question though...Does this mean the warranty is out the door? :roll:




Bam!

[Aussie Geoff]

Marco

Edited on 10 April – in Indigo to reflect clarifications from microfast in post below on 8 April.

So I’m clear (and for any others who are interested!), let me “play back” your instructions and what I think you are trying to achieve and have done: (If I understand you - this seems to be a relatively common “tweakers” mod in CD players etc.)

Let me first refer to your original post here

All do know the good DAC CS43122 and the op-amp OPA2604, used for the output stage for the front channels and ( in a more simplified circuit ) for the center and the subwoofer channels, in the RSP1098.
This is good, but anyone have never said that are been used also two NE5532 ( cheap, but decent op-amps ) for the output stage for the rear and back channels, and ten TL072C ( very cheap and noisy op-amps ) for the multi-channels input, the others analog inputs, and directly after the DACs as buffer ( on the little DAC board ) !!!!!

7.1 Multi-input / Pre-out output Board
For the Multi input you have discovered that all channels only use the lower quality (but compatible) ST TL072CD surface mounted op amps.

For the Pre out Output you have discovered that the 4 rear channels use the JRC5532 op amp instead of the OPA2604AU unit and have also replaced these with the OPA2604AU op amps.

You have therefore, used specialist soldering equipment to remove the existing solder without heating components etc, and upgraded the TL072CD and JRC5532 units to the OPA2604AU units.

DSP Board
You have discovered the same parts setup in the DSP board for processing the analogue outputs of the Crystal DAC CS43122, with the ST TL072CD surface mounts used for all channels instead of the OPA2604AU op-amps.

Here you intend to substitute these for audible improvements.

Analog Inputs
In your original post you mentioned that the TL072C op amps were also used for “the other analog inputs”. If this is the case – do you still intend to replace any of these and what board are they on?

Questions
Please let me know if I have anything wrong in my understanding (e.g. you are changing from DIP to surface mount with any of the ST TL072 or JRC5532 etc.)

I know some tweakers favour using two of the (much more expensive) Burr Brown OPA627AU or the Analog devices AD825 instead of the OPA2604AU – any thoughts on this?

Are there any other areas where you are being tempted to make changes?

Schematic
Sorry have no idea how to get one...

Thanks...

Geoff

[Bam!]

Super!

So can anyone answer my ?...Warranty out the door? :roll:

Thanks!




Bam!

[Aussie Geoff]

Bam,

I think the short answer is YES.

Basically the Rotel manual etc is very clear about no user serviceable parts and needing a specialist technician. Changing the Op-Amps on the board will invalidate the warrantee for those boards (and we are talking 2 or 3 boards here - 3 if you include the analog inputs). Removing and soldiering surface mount components is a specialist task with the right temperature controlled soldiering iron and solder suckers etc. Too much heat will damage the surrounding components on the board and we are talking tiny components with very small dots of soldier. Also if a fault on those boards is felt to cause damage to other parts of the RSP-1098 then there will be flow on impacts on the warrantee.

So such changes are for the brave... The safest way would be to persuade an authorised Rotel service centre to do it for you - since the op-amps are functionally compatible (looking at their specs on the web). My expectation would be that any impact on the warrantee then would be limited to the impact of the op-amps.

However there is a whole dedicated community of tweakers out there such as here who seem to have lots of fun – doubtless living with the risk of having to pay for repairs themselves...

Geoff

[Bam!]

Thanks Geoff!

Double wow on the gutsy move then...I guess it is no different from guys who modify their cars...their warranty is out the door too!




Bam!

[Adz]

Geoff,

A reputable company in Canada which does mods sent me an e-mail in response to my question asking if they can mod the 1098 and the answer was, " Yes...for sure...they are op amp (as opposed to discrete transistor)
based units...lots we can do (and results are astounding)....to give an
accurate quote, we'd need our hands on them....also, we can work (in a hierarchy of sonic importance) with any budget provided."

For the novices out there what does this mean exactly and do you recommend something like that (knowing full well that the warranty is voided). My interest would be to upgrade my audio with respect to playing DVD movies as opposed to CDs. Is that possible?

Thanks




Adz

[Ossi]

Folks let me ad some personal experience with mods.
I have a Sony XA 50 ES CD-Player which was the last real good player Sony made before they concentrated adding SACD to every player. While this player was praised everywhere and got glories reviews, it was and still is the modders love affair. The drive of this player is really exceptional.
So, I modded the player. Over 60 parts were changed and that had a tremendous impact on the sound as the slightly cold presentation vanished to a real musical experience.
So is modding worth it: Big Yes.
However in case of the Rotel RSP 1098 my first reaction, knowing how poor some of the parts used are and especially knowing that these parts are in the most important analogue section, would be to say: shame on you Rotel! I heard from different sources that using the internal D/AC on the unit sounded better using even a very sophisticated CD-Player analogue path. That just means that the RSP ruins your whole analogue gear. And that is the same for DVD-A or SACD as the RSP 1098 only knows the analogue route because there is no i-Link.
So would I mod it? For sure not. I do expect more for 3000$, in Europe even 3500 Euro than a FFT screen. And the idea of buying a new top of the line toy is not to have to change parts right away to bring is to a desirable standard. That is something to do after the warranty is gone and when the unit gets older.
Now the RSP 1068 surely will not be any better in term of parts, however given the price, I feel that a mod is much better invested here. With the result that you can get for much less probably much better sound. And if you void the warranty, we are talking half the loss of a 1098.
But anyway, modding is in principle quite worth it. But always needs to be taken in account that investing a certain sum you could expect a bit more right from the start. It is to the manufacturer to deliver you the product you want. If you did not get what you hoped for, than you should have looked somewhere else.

[Adz]

And just to add some additional details to my prior post, the Company also wrote to me the following:

"For the 1098 PRE-PRO (like we do on the ANTHEM AVM-20):

- hyper-critical input and output buffer op amps and associated series
resistors and coupling caps (per analog input and/or analog output
channel)"

So, myquestion still stands: what does this exactly mean and most importantly will this noticeably improve DVD sound quality performance?




Adz

[Ossi]

- hyper-critical input and output buffer op amps and associated series
resistors and coupling caps (per analog input and/or analog output
channel)"

So, myquestion still stands: what does this exactly mean and most importantly will this noticeably improve DVD sound quality performance?

Yes it will. Period.

[Aussie Geoff]

Adz,

Edited on 10 April – in Indigo to reflect clarifications from microfast (Marco) in post below on 8 April.

For the novices out there what does this mean exactly and do you recommend something like that (knowing full well that the warranty is voided). My interest would be to upgrade my audio with respect to playing DVD movies as opposed to CDs. Is that possible?

Good questions. Let me first give you some context
Most modern Audio electrical circuits are constructed using combinations of 5 types of parts: Operational Amplifiers, Transistors, Capacitors, Resistors and Diodes. (Operational amplifiers, or Op-Amps, are small integrated chips that combine transistors, resisters and capacitors to produce a circuit with a defined amplification characteristic). Almost all analog circuits are derived from interlinking these components. In addition in digital processing people use Digital to Analog Converters (DACs) and Analog to Digital Converters (A/Ds).

Now the quality of the sound delivered depends on a range of physical factors, including power supply quality, shielding and connector quality, as well as the overall design of the circuitry and the quality of key parts (those Operational Amplifiers, Capacitors and Resistors). Dedicated high quality audio manufacturers do a lot of listening to different parts to get the sound quality they require within budget parameters. Indeed this is at the heart of Rotel's "Balanced Design" Philosophy.

However except in the highest end, money no object audiophile grade equipment, there is always compromises made in the quality of components to achieve a price / quality benchmark. Essentially by spending more on components a better sound could be achieved at a higher price, but the manufacturer needs to make a choice to deliver an affordable product. A good example is the Texas Instruments Burr Brown OPA2604AU Op-Amp, which wholesale for about $1.90 each in quantities of 1000. This is recognised as being a high quality Op-Amp delivering a worthwhile audio upgrade compared to some mid priced Op-Amps like the Texas Instruments TL072 which wholesales for $0.18 in quantities of a 1000. In turn the TL072 is recognised as being a good quality upgrade for still cheaper Op-Amps. And of course there is the outstanding Burr Brown OPA627AU for $12.25 (and you can spend more!).

A similar situation exists for resistors and capacitors, which are simpler devices, but for which there are a variety of materials and construction techniques, as well as levels of accuracy in the conformance to stated value (for example resisters can have a +/-10% tolerance or a +/- 1% tolerance. Even in well respected audiophile brands such as the QUAD 44 pre-amp this type of compromise is made. So the key Op-Amps in this very well reviewed product are TL072 (remember the $0.18 each) which are those being criticized by some for the RSP-1098’s use on Rear Channels.

So a around 20 years ago number of dedicated audiophiles who had electronics engineering experience started to think –what if we upgraded key parts in already good components to improve the sound. What had been found after extensive trials is that significant quality improvements can be achieved with already good equipment by upgrading the quality of selected components in key circuits. Typically this will look at the Op-Amps, Capacitors and Resistors in selected circuits and, on a cost / value basis selectively upgrade these. The overall impact of such upgrades is limited by factors such as the fundamental quality of the power supply and the other circuits and components. It is important to consider all components in a given signal path and upgrade them to a consistent level. Note however this does not mean all components, just those that particular signal path may go through.

Upgrading these parts requires experience and dexterity in soldering and removing replacing small components. Deciding what parts can be changed safely and should be changed can require a reasonable level of technical expertise. So a number of (often well respected) companies have sprung up to offer audiophiles the option of upgrading the components in their systems. Whether it is a Rotel, Anthem or Lexicon, they can always find ways of upgrading the components to the next level in quality – in the same way as you can (almost always) spend more money on cables.

At least one company (Marantz) offer a range of specially upgraded equipment (the Ken Ishowa Signature range) where many of the key components of their standard products are upgraded to high specification units. These KI signature models sell (new) for around twice the price of the standard model. Equally a common recommended upgrade for the QUAD 44 pre-amp is to upgrade the TL072 op-amps to the OPA2604AU (as Marco is recommending for the Multi Inputs and DSP/DAC Outputs of the RSP-1098 )

What it may mean to the RSP-1098
Now, if Marco is correct, then there are some obvious areas to upgrade in the RSP-1098. Essentially all the channels of the DSP (Digital Signal Processor) are linked to lower quality TL072C Op-Amps than the OPA2604 op amps used in some areas of the RSP-1098 – so upgrading these to the same quality should improve the sound for the rear channels. The same thing applies to the Analog Multi Inputs and the 2 channel analog inputs as well as the rear channels of the pre-outs This isn’t a surprise since we are talking about 4 op-amps on the multi-inputs, 4 on the pre-outs, 4 more on the DSP and 6 on the stereo analog, so parts costing 11 times as much (TL072 to OPA2604AU) make a significant difference in the cost of the unit. Almost certainly there will be areas where higher quality capacitors and resistors will make a difference. Hence the confidence of the company you contacted that they can make an improvement. With Processors containing thousands or mare parts, differences like $1 in the cost of a part can make a BIG difference to the final product cost, and manufacturers need to carefully select parts for the best trade off of quality / price / market acceptance.

To put things in perspective - the RSP-1098 has received deserved recognition and awards for the quality of its sound and many key parts such as the DACs. The Op-Amps being criticised for the rear channels are the same as those used in the main channels of some very well respected stereo pre-amplifiers. However the ones in the front channels are even better – leaving a very clear upgrade path. Very fortunately the RSP-1098 has a very impressive power-supply stage with high quality toroidal transformers, slit foil capacitors etc, providing a excellent foundation for further upgrades.

Your question re DVDs
So to make DVD’s sound better you would (at a minimum):[*]Upgrade the Op Amps on the DSP Outputs to OPA2604[*]Upgrade the Op Amps on the Pre-outs (rear channels to OPA2604, and fronts could go further to OPA627 or AD8066 etc)
If you used the multi-inputs you would also upgrade the Op Amps for these as well to OPA2604 or better.

Further upgrades of selected capacitors and resistors on all channels have the potential to also increase the sound. Most of these basic upgrades are nearly invisible with the new components the same size (and often color) as the originals. Equally one could go further, upgrading some of all of the Op-Amps to even higher performing (and price) ones than the OPA2604. Really there are no limits other than common sense.

The firm you are dealing with (if experienced and reputable) will be able to discuss with you a focused upgrade to improve the sound within the budget and sound signal paths you listen to the most. As to whether or not you go down this path – it has to be a personal choice. As with any upgrade the sound improvement will be limited (or revealed) by other components in your system. Equally you need to seriously consider any warrantee implications. However, for many that have done this for other components, they would never go back. People have experienced (or claimed to at least) sound improvements for $500 equivalent to a more up market product at double the purchase price. It is easy to become “addicted” to this and to routinely have CD players, DVD players and pre-amps and processors upgraded. Then of course there is the wiring and cross-over network in speakers....

In my stereo days I got into upgrades and really appreciated the benefits. However I haven’t yet given in to the temptation to do this for the RSP-1098... But the temptation is growing.

I hope this helps....

Geoff

[Adz]

A-Geoff,

Great summary. Truly helpful. I too am very very tempted to try and take the 1098's sonic qualities one or several steps further. I will probably take the plunge and report back, but first I want to upgrade my software from 1.1.6 (the catastrophic postings on the upgrade have made me hesitant and if somwething goes wrong, I don't want to send it back to Rotel already moded). I am alo somewhat hesitant because I think in less than one year, Rotel will be out with a next generation pre/pro 1098.

Some updates...The company recommends that if I am purely a DVD movie listener (as opposed to SACD or DVD-A), then I should leave the rear channels alone on the Rotel and focus efforts on upgrading the LR&C channels only. They would also mod the power supply on the 1098, and then would supply upgraded power amp cords. Cost not including the power cords, perhaps around USD 700.

Here is where I need your input again. They also do analog input channels as necessary...but they said that is based on
whether the DAC on my Denon 3800 has a better D/A section, than the PRE PRO. If it does, then they recommend to do at least an input pair (just for 2-channel music)....and I still have a digital connection (on another selected input) for my DD and DTS movies....which benefit from the output side of the mode. I am hopelessly lost again on what this and don't know whether it makes sense with my Denon. As an added fact, I find that my Denon 3800/1098 combo sounds best for 2 channel music when I run the cables from the Denon to the analog CD inputs and run it stereo bypass mode, so maybe the mod won't be helpful here.




Adz

[Aussie Geoff]

Adz,

Edited on 10 April – in Indigo to reflect clarifications from microfast in post below on 8 April.

Thanks for he feedback. It’s a complex topic and I wanted to try and deal with some of the common emotion and misunderstanding that exists over the issue of component upgrades.

The company recommends that if I am purely a DVD movie listener (as opposed to SACD or DVD-A), then I should leave the rear channels alone on the Rotel and focus efforts on upgrading the LR&C channels only. They would also mod the power supply on the 1098, and then would supply upgraded power amp cords. Cost not including the power cords, perhaps around USD 700.

I understand. Some questions and comments:

Has the company you are dealing with ever upgraded an RSP-1098? The reason why I ask this is that Rotel’s are famous for their nearly obsessive over engineering of the power-supplies – with toroidal transformers and selected slit foil capacitors etc. They are already better than 99% of the power-supplies in processors and pre-amps. So It would really need to be some significant upgrade to the power supply to make a difference compared with the fairly “ordinary” power supplies in most processors and pre-amplifiers. You may be able to transfer some of the expenditure here to some of the ideas below.

Re the power cord – good idea – especially in the USA where the standard 110V power cords used by Rotel and others are very limiting. Get a price though - power cords can be just “silly” prices if you let them. There are several posts here for sources of quality replacement 110V power cords at reasonable prices.

Re the front L,R & C channels upgrade for the $ they are talking this sounds like a serious upgrade – something like the dual OPA627s (you need two on a special board to replace one OPA2604. This leaves the question of what happens to the 2 OPA2604’s on the front channels – I would be included to ask them to move these to the rear channels. That way your rears are as good as your current fronts, and your fronts are even better.

They also do analog input channels as necessary...but they said that is based on
whether the DAC on my Denon 3800 has a better D/A section, than the PRE PRO. If it does, then they recommend to do at least an input pair (just for 2-channel music)....and I still have a digital connection (on another selected input) for my DD and DTS movies....which benefit from the output side of the mode. I am hopelessly lost again on what this and don't know whether it makes sense with my Denon. As an added fact, I find that my Denon 3800/1098 combo sounds best for 2 channel music when I run the cables from the Denon to the analog CD inputs and run it stereo bypass mode, so maybe the mod won't be helpful here.

I think you have answered yourself in your own post. When the Denon 3800 is in stereo bypass, on the RSP-1098 this means that you are using the DACs in the Denon and the Op-Aps on the inputs and outputs of the RSP-1098. So if the Denon already sounds better this way it already means that the 2 channel DACs in the Denon are doing a better job than those in the RSP-1098. In turn, this means that upgrading the 2 channel analog input will further reveal sound quality improvements in the Denon on 2 channel. Again I would pick the front L and R channel on the multi-inputs and have the current OPA2604 op amps moved to the rears to get a relative upgrade to both sound sources (they could slip in 2 more OPA2604s for the rears while they are at it to give you balanced sound.. You just never know when you want to have SACD and DVD-A.

The price they are charging you for what seems to be the power supply and 3 output channels I think is a good illustration of why companies such as Rotel (and 99% of others) just can’t afford the best components. Imagine the cost if you did all 34+ analog inputs and the 8 outputs!

Geoff

[Adz]

Geoff,

The company has never upgraded a Rotel before but the owner who I talked to (I think its a one man operation anyway) told me he has upgraded over 75 Anthem AV20, B&K 50 and I think he mentioned Lexicon as well. He is eager to check out the innards of the Rotel and told me over and over that he needs to see it first and that most of our talk is speculation based on what he might find. He does plan to replace the LR&C with the dual OPA627s - you were right on with that one. And great tip about replacing the rears with the old Op amps on the LR&C, although I think most of the budget is in the labor so it might make things too expensive. Lastly, I think you told me that since I run the stereo bypass on the 1098, I should upgrade the 2 channel CD input on the 1098. Let me know if thats not correct.

Regards,




Adz

[Aussie Geoff]

Adz,

He does plan to replace the LR&C with the dual OPA627s - you were right on with that one. And great tip about replacing the rears with the old Op amps on the LR&C, although I think most of the budget is in the labour so it might make things too expensive.

I think you'll like the dual OPA627s - a very detailed but with a smooth almost "valve like" sound. But they will be visible upgrades due to the little custom circuit boards needed for the two of them - so I'd do that EEPROM update etc now There is also the possibility that he may not be able to fit them on the boards - the removable circuit boards on the RSP-1098 are quite tightly spaced, so the mini circuit board will have to be carefully fitted. If he can’t the fallback would be the better capacitors and resistors etc for the fronts and definitely the OPA2604s on the rear channels.

In terms of reusing the OPA2604 op-amps on the output stage from the front on the rears. This should be very cheap. It will take an extra 5 minutes or so each to remove the old TL072 and put in the OPA2604 that has been removed. You will need one extra OPA 2604 (he may have spares he has removed from other units). I would personally DEFINITELY do this for the other output stages - it will balance up the sound quality better for 5.1 and 7.1 listening. You will probably find that the upgrade with the OPA627s comes with new audiophile capacitors and resistors etc (not cheap) making the front upgrade more expensive. However there is no need to do this for the rear channels - just (as microfast did) move the OPA2604s - better capacitors etc would be better again - but this will start adding to the cost.

Lastly, I think you told me that since I run the stereo bypass on the 1098, I should upgrade the 2 channel CD input on the 1098. Let me know if that’s not correct.

Not quite. I was suggesting that you upgrade the L and R (and if possible the C) channel of the analog Multi-Input and use this for your Denon 3800. The reasons for this is that you can enjoy CDs now and then enjoy the benefits when you succumb to the DVD-A and SACD "bug" (the Denon 3800 plays DVD-A well). Also my understanding is that the L,R and C of the Analog Multi-Inputs already has the higher quality OPA2604 op amps so you can (again) reuse these on the rear multi-inputs, just adding one more!

You could do the CD analog input instead - but this doesn't (to me) make sense with the Denon 3800 which has the full 5.1 analog outputs that you should plug into the Multi-Input. Now if you EVER think you will get a high quality separate CD player - then I would also do the CD L&R inputs as well. Dual OPA627s with capacitors and resistors etc for the best sound - OPA2604 only for a very cost effective and worthwhile improvement.

I hope this makes sense –I am conscious we are dealing with a technical subject here. If you are still unclear – ask some more... Also I’d give the guy a print of this full thread to help...

PS – I can see your temptation growing. Warrantee / sound quality – it’s tough. It’s growing in me too each time I answer your questions!

Geoff

[Adz]

Thanks Geoff. I'll upgrade to the 2.1.2 first which might take me awhile to get set up, then e-mail him this thread and confirm that he has read it before sending out the unit. It is very exciting but it' hard to part with the 1098 for probably a solid 10 days. :cry:




Adz

[squigly1]

Hope you guys don't mind me jumping.

I would like to know more about the guy/place in Canada that performs this type of modification(name,location,website,phone#, etc). It would be good to have for future reference, especially if Adz comes back with a good report.

Thanks

[Adz]

Sure its as follows:


PARTS CONNEXION
2885 Sherwood Heights Drive
Unit #72
Oakville, Ontario
CANADA L6J 7H1

Toll-Free at 1-866-681-9602 (US & Canada)

Tel: 905-681-9602
Fax: 905-631-5777
E-Mail: cjohnson@partsconnexion.com
Web Site: www.partsconnexion.com




Adz

[zeppelin]

Instead of the 1098 mod, I'm trying to mod my 1066 later maybe this few weeks. I'm gonna use a better OP that is either a OPA2604AP or OPA2132.
someone suggested me to use OPA627 or 637 but that will be a bit difficult cause I got to mod a daughter board for it and further more the chip is expensive in price.
So if nothing goes wrong I will let you guys know.

[microfast]

For be accurate, this is the 1098 situation :

1)Multichannel input : all the 8 channells use TL072c ( every TL072c and OPA2604 contains two op amps ), for this mod. are so necessary four chips.

2)Dac Output : all the eight channells use TL072C, again four chips OPA2604 for the mod.

3)Output stage: very good design ( opa2604+ discrete components ) for the left and right front channels, semplified OPA2604 design for the central and LFE channels, for the surrounds and backs channells are used two JRC5532 in semple schematic; for the mod of the output stage must be used two OPA2604.

4)Other TL072c are used for the others inputs.

Please consider that the OPA2604 use more power and produce more heat; my advise is of replace only the multichannel input ( four chips), the DACs TL072C ( four chips ) and the two JRC of the output stage, or better if you do use only a 5.1 setup 3 chips for the multi channells input, 3 chips for the Dacs buffers, and one chips on the output stage.

Regards
Marco

[tombowlus]

Instead of the 1098 mod, I'm trying to mod my 1066 later maybe this few weeks. I'm gonna use a better OP that is either a OPA2604AP or OPA2132.
someone suggested me to use OPA627 or 637 but that will be a bit difficult cause I got to mod a daughter board for it and further more the chip is expensive in price.
So if nothing goes wrong I will let you guys know.

While I had been leaning towards replacing my 1066, I would certainly be interested to hear how your mods go. My main concern is upgrading my 2-channel performance.

Tom.

[Aussie Geoff]

Marco,

Thanks for the clarifications - it makes more sense to me now how the RSP-1098 is set-up I have edited the relevant parts of the posts I made above to reflect your clarifications. The changes are shown in indigo text in those posts.

A couple more questions, if I may:
Your Changes - Have you now done all the OPA2604 changes - in your earlier post you had only done some of them and still needed to do those on the DSP/DAC board? How did they work out?

Room on Boards - You will see from the posts above that one reader is considering a 3rd party firm who does dual OPA627 upgrades for output channels etc. Do you have any views on whether this type of upgrade would fit on the RSP-1098's boards. The only time I looked was when my RF shield upgrade was done for the digital card and some of the cards seemed tight for space - but I wasn't thinking about an upgrade then - so I didn't take much notice...

Geoff

[Iggurk]

Hi all!

very interesting mods done here, saddly no pictures to see what it look like after mods..

Microfast can you put some?

How do you solder the 2604 in place of the surface one? the distance between soldering points is not really the same, did you bend the legs?

I've already changer the 1 cent RCA connectors.
By vampire CM2F Copper Base, and the sound is better on mediums. below some pictures:



Soldered with 4%silver and Mundorf 99% silver and 1% gold 0.5mm2 wire.

Now I've planned to replace the two 2604 by high end op-amps, and re-use these 2604 to replace output rear channels.

But what about the other eight?


Any help appreciated.

Regards
Yves

[Iggurk]

ok,

got an answer from Microfast, and the op-amps to change are the following on that board:



Other four to change on digital board too.

I'll change all of them by OPA2604AU as suggested by Microfast, and the two OPA2604AP (for fron R/L, center & sub) will be replaced by dual op-amps from reference audio mods.

I keep you in touch with the mods.

regards
Yves

[BlazeMaster]

How much does that company in Canada charges for replacing the chips for best 7.1 and 2 channel playback for the RSP1068?

OTOH, I have a friend that has an electrical engineering degree, maybe I can have him do all the upgrades for me. Is it hard to open up the chasis of a 1068? Most electrical engineers should be qualified for the task right? He did briefly mention that he knows how to do these upgrades.

[voxy]

ok,

got an answer from Microfast, and the op-amps to change are the following on that board:



Other four to change on digital board too.

I'll change all of them by OPA2604AU as suggested by Microfast, and the two OPA2604AP (for fron R/L, center & sub) will be replaced by dual op-amps from reference audio mods.

I keep you in touch with the mods.

regards
Yves

Hi, I am also thinking of modding the 1068 to prolong the pre-amp life. I was thinking of swapping the OPA2604 in the analog section with either AD825 or OPA627. Which one would be better sonically with Rotel elctronics and I believe both the input and ouput stage needs to mod? Thanks.

One more question, is there a clock in the RSP1068 and is it possible to mod it with better clock as well?

[Iggurk]

Hi !

so, I've changer all the op-amps of the multi board, that was not trivial....

un-soldering all the op-amps without broking the board was not as easy as expected, but lucky me the board is still working well.

What to say regarding the result.... as Microfast already wrote it, the sound is more open, more detailed, more crystalline.

I didn't notice lot of change on bass, perhaps just slightly more detailed, nothing amazing.

The biggest change for me are the global warm of the sound, the device now sound more cold than before, and it's too early for me to say if it's finally better or worse than before.
Don't know too if the op-amp need burning or not.

I'll still change the two output 2640 op-amps for R/L, center and sub.

I cannot really recommend to do the change, first because that change the sound from "warm" to "cold", and also because it's really risky to break the board.

I'll keep you in touch within the next two weeks.

Yves

[voxy]

Thanks. When you say "cold", is it in bypass mode for analog playback or in analog mutichannel playback? I presume now you have better HF extension, soundstage as well? Maybe you need some run in.

[Iggurk]

Thanks. When you say "cold", is it in bypass mode for analog playback or in analog multichannel playback?

I didn't really understand the question, what's the difference between analog playback and analog multi playback supposed to be????

I use the multi input for my SACD, and the output to go to amplifier, SACD listening in bypass mode always.

Yves

[joetama]

Hmmmm going to break out the screw driver tonight and have a look....

[voxy]

I didn't really understand the question, what's the difference between analog playback and analog multi playback supposed to be????

I use the multi input for my SACD, and the output to go to amplifier, SACD listening in bypass mode always.

Yves

true, should be the same. I just PMed you.

[Iggurk]

Hello!

ok, I've spend more time for listening, and I come to a final verdict of the 2604 mod.

To be quick, my recommendation is not to use 2604 everywhere.

As said before, the sound seems to be more open, more crystalline, and colder.
Globally I've the bad feeling that I've lost something, it's "less alive".

I still have to replace the two non smd output 2604 (for front L/R, center & sub) by the higher end module, hope that the global result will be better.

I think that I will change the input once again.

Best solution could have been to solder adapter to be able to switch easily the op-amps and do some comparison.

Original setup by Rotel sound better to me than the mod.

Regards
Yves

[voxy]

Hello!

ok, I've spend more time for listening, and I come to a final verdict of the 2604 mod.

To be quick, my recommendation is not to use 2604 everywhere.

As said before, the sound seems to be more open, more crystalline, and colder.
Globally I've the bad feeling that I've lost something, it's "less alive".

I still have to replace the two non smd output 2604 (for front L/R, center & sub) by the higher end module, hope that the global result will be better.

I think that I will change the input once again.

Best solution could have been to solder adapter to be able to switch easily the op-amps and do some comparison.

Original setup by Rotel sound better to me than the mod.

Regards
Yves

Hi Yves

Are you gonna try 2132? I think this opamp is more suitable bec of the 10v supply. You can try out in the input first to see if there are any improvement. Overall experience diy guys recommends this over the 2604.

[Iggurk]

Hi,

I've planned to try AD825 dual and OPA627 dual.

Yves

[Destruction]

However there is a whole dedicated community of tweakers out there such as here who seem to have lots of fun – doubtless living with the risk of having to pay for repairs themselves...

I would be very careful here as Rotel service centres also have the right to refuse to repair a product if it has been tampered with, and it is unlikely that an independent repair centre will be allowed the schematics for this processor, given that it is a flagship model. :E

So, the worst-case scenario is that you could end up with a faulty processor and nobody to fix it, however I am sure there are benefits for 'tweaks'.

8)

[Iggurk]

It's a really good comment, but personally I doesn't really care about that, if I burn something I buy a new one.

And that 1098 will be changer in the following months, so for me it's good occasion to play with before moding the next device.

And I tweak everything I have by principle

New op-amps on the way (much much more expensive...) jope they will sound better than these poor 2604.

I've some hifi friends at home tonight, curious to see if they will like the mod or not.

Yves

[voxy]

It's a really good comment, but personally I doesn't really care about that, if I burn something I buy a new one.

And that 1098 will be changer in the following months, so for me it's good occasion to play with before moding the next device.

And I tweak everything I have by principle

New op-amps on the way (much much more expensive...) jope they will sound better than these poor 2604.

I've some hifi friends at home tonight, curious to see if they will like the mod or not.

Yves

Much much expensive... may I know what are these? :B

I just read that the Krell showcase uses OP275... USD1.2 per pc. Looks pretty good on paper esp with distortion.