krips' 5 Channel Chipamp

[krips]

My first DIY amp is based off of Mark Houston's seen here: http://diyaudioprojects.com/Chip/Syn...875-Gainclone/
So far I have the resistors, chips, and capacitors. The hardest thing to find is a toroidal transformer for a decent price and that I can get shipped to canada cheaply. Anybody have any sources?

[djn04]

Not sure if they qualify as cheap but they are located in Canada

http://www.plitron.com/company.asp

[Johnloudb]

You can get Avel transformers of the same power rating for almost half the price of Plitron transformers. They are also a high quality transformer. I don't know where they are located but here's the web link:

http://www.avellindberg.com/

Just checked they are in they have a US distributor in Connecticut, so not sure how much you'd save in Canada.

[cjd]

If you've not gone too far along - I recommend the LM3886 over the LM3875 as it handles low impedance loads MUCH better.

Parts Express ships to CA and does the Avel trafos but not perhaps cost effective.

C

[djn04]

You can get Avel transformers of the same power rating for almost half the price of Plitron transformers. They are also a high quality transformer. I don't know where they are located but here's the web link:

http://www.avellindberg.com/

Just checked they are in they have a US distributor in Connecticut, so not sure how much you'd save in Canada.

Avel are available from Parts Express not sure about shipping rates to the great white north

[Hdale85]

I usually use a guy on ebay Antek Psu's. He has a website as well great quality product for very cheap. What size PSU do you need? I have a 30VAC plitron..... I have no use for it so I'm sure something could be worked out but not sure if that's to much power. I think its 300VA.

[krips]

Plitron has the toroids I want, but unfortunately they have a $250 minimum order or something to that effect. The parts express ones are an option, however I'm going to try and fish for others either located in Canada or that ship here reasonably. I'm looking for about 400VA, with secondaries that are 18-25v. What's that guy's website that sells them on ebay? Does he have more selection that in listed on his ebay store?
I'm already about $125 into this project, so I'd like to keep on this road if I can. The schematic and whatnot on the link I provided seemed to be the easiest for me to understand. This way I can still build a LM3886 later .
I have a few questions about this capacitor bank I'm building:
1) My 10,000 uF caps have short leads. Any ideas how I should get my wire on there and get it soldered?
2) The 10KuF caps are also heavy. Would silicone work well for both holding the cap on the board and insulate against a short between the leads?

[Johnloudb]

Avel are available from Parts Express not sure about shipping rates to the great white north

Avel also sells direct, and a bit cheaper than Parts Express as I remember. Just email them and ask them to quote you a price.


Those caps are snap in caps. They will snap into perf board, after you drill a couple 1/8" holes properly spaced. If you don't already have a PCB, you can buy some perforated prototyping board. (www.allelectronics.com) has some nice prototyping boards for not much money. Digikey charges a lot for there prototype board.

Opps.... looking closer at you're pic, I see you've already mounted the caps.

Just solder some wire to those short leads. And try to make a good physical connection with the wire.

[Face]

I believe Plintrons are known to be quieter than Avel.

[DeanP]

Here's the link for Antek:http://www.antekinc.com/
I bought three from him and used them for my eight channel amp (six channels plus two bass bins). I recently down graded it to a two+two channel just for my mains and bass bins. The gainclones work perfect and are dead silent if done right. I also used an electronic x-over which has to turn on first and last or else I got thumps...

[SQdude]

I've used an Avel and all I can say is keep it far far away from any circuitry, they leak big time; had to encapsulate it in 3/8" steel box to get rid of 98% of the hum.

[krips]

Interesting. This is to some extent common to all transformers because of the AC's magnetic field, yes? How does aluminum do for blocking MFs?

[Johnloudb]

I've never had any trouble with Avel transformers (hum or otherwise), but I've never tried one larger than 120VAC. You should shield any transformer you use from the amplifier circuit, to avoid noise problems. Just don't create a shorted turn (short circuit) through the center of the transformer, when shielding it.

[Johnloudb]

Interesting. This is to some extent common to all transformers because of the AC's magnetic field, yes? How does aluminum do for blocking MFs?

Just make sure the metal chasis and shield is earth grounded, that will block noise. Also, you want to connect the power ground to earth ground using a power thermistor in between to filter out noise. A 5-10 ohm rated at 15 amps continuous should do good. I've seen people use high current diodes too. I'll draw up circuit for this if you need or want it.

[SQdude]

Aluminum does not block EMF; only ferrous metals do (ie: steal)

[Johnloudb]

Aluminum does not block EMF; only ferrous metals do (ie: steal)

:frypan:

(kidding) :B

Steel doesn't block magnetic fields. In fact, it has a high magnetic permeability and that's why they use Iron (even higher permeability) in the core of the transformer.

Any electrically grounded metal will block Electromagnetic Fields (EMF). EMF depends on both the electric and magnetic fields to propagate. So any electrically conductive material that is grounded will block EMF.

Good guess though - I can see why you might think that.

[krips]

Well, the 600W 18V toroid from antek's website is catching my eye. They're cheaper shipped than avel quoted me without shipping .
I ripped apart my old Logitech Z5300-E computer speakers and was happy to find a 19-0-19 toroid! However, after comparing it to the specs on antek's website it appears to only be in the 100VA area. It's a "Tenpao TOU433017F2". Can anyone confirm what size this tranny is? I plan on building a stereo GC for my father after I'm done with this, so if it doesn't work for this project it still might come in handy .
Oh, and I think those heatsinks from the 5300's amp will suit me just fine, perhaps with a little forced air. 8)

[Johnloudb]

Good find on the transformer! It's way overkill for the chip amp but it gives you lots of room to expand, in the future. In fact that power supply would be perfect for driving a this differential Pass design.
Gain Clone Supper Symmetry

Unfortunately, he left out a lot of information. But many people have post various tested designs on this circuit topology in that thread.

[krips]

Do you guys know if 1/4w resistors are large enough/right before I solder them onto the chips? I still am not sure on how to figure that one out.

[BobEllis]

1/4w are fine, even overkill. Among other available equations, P=V^2/R. The 22k resistor in the feedback loop sees the most voltage - perhaps 20V at full power. Plug the numbers into the equation and you'll see less than .02W dissipated - on peaks, average power (all that resistors care about) is about half that.

Measure them with your DMM to be sure that you have the right values if you are unsure how to read the color coding.

[krips]

Well that's good. The 'working voltage' spec on them is what threw me off. Anyway, I ordered my tranny today. 800VA 20V Antek. Ships monday http://www.antekinc.com/AN-8420.pdf

[Johnloudb]

That's a big tranny. :T A bit overkill but why not. The higher voltage rails will help your chip amps. Is that why you went bigger?

[krips]

I just figured if I want to make a bigger amp in the future a bigger tranny would be nice. It's not all that much more money since shipping is about $40 no matter what size I order.

[JonP]

:frypan:

(kidding) :B

Steel doesn't block magnetic fields. In fact, it has a high magnetic permeability and that's why they use Iron (even higher permeability) in the core of the transformer.

Any electrically grounded metal will block Electromagnetic Fields (EMF). EMF depends on both the electric and magnetic fields to propagate. So any electrically conductive material that is grounded will block EMF.

Good guess though - I can see why you might think that.

Uh, any good conductor will block electrostatic fields, but only a magnetic materiel like iron, nickel, etc... will block the electromagnetic field. (both parts are found together, typically)

By hum, did you mean audible hum (audio) or do you mean hum induced into a nearby circuit?

[Johnloudb]

Uh, any good conductor will block electrostatic fields, but only a magnetic materiel like iron, nickel, etc... will block the electromagnetic field. (both parts are found together, typically)

By hum, did you mean audible hum (audio) or do you mean hum induced into a nearby circuit?

Hi JonP,

:frypan:

(kidding again) :B

Magnetic conductors like steel have the ability to store magnetic energy, as their magnetic dipoles align in the direction of the magnetic field. Both transformers and speakers make use of this property.

Some magnetic materials like ferrite cores are "lossy" and attenuate the magnetic fields.

A "perfect conductor" with zero electrical impedance will block electric and magnetic waves. A magnetic wave induces an a electric current perpendicular to magnetic wave at the conductor surface. This current reflects magnetic wave, but out of phase with the generated magnetic field, canceling it. Hence, no magnetic field outside the conductor.

Both magnetic and electric waves in a are canceled by a perfect conductor.

You got me digging through my "Electromagnetic Fields and Waves" textbook by Magdy F. Iskander, and I appreciate it!!!

Really, it's good to try and relearn this stuff. Thanks. :T

If I made a mistake, someone fill me in please. You may get hit with frying pan though.

[krips]

Holy snap this thing is huge. The older lady at the post office had a hard time getting it up to the front desk. :P

8O

[WarTowels]

Well, the 600W 18V toroid from antek's website is catching my eye. They're cheaper shipped than avel quoted me without shipping .
I ripped apart my old Logitech Z5300-E computer speakers and was happy to find a 19-0-19 toroid! However, after comparing it to the specs on antek's website it appears to only be in the 100VA area. It's a "Tenpao TOU433017F2". Can anyone confirm what size this tranny is? I plan on building a stereo GC for my father after I'm done with this, so if it doesn't work for this project it still might come in handy .
Oh, and I think those heatsinks from the 5300's amp will suit me just fine, perhaps with a little forced air. 8)

Hey, I'm a complete audio moron. I wanted to experiement with some parts laying around the house. I have the same Logitech system so I was trying to gut the system as carefully as possible but I failed to do so. I cut some of the copper strands on my "Tenpao TOU433017F2". My plan was to take a old 10" alpine sub, and power it off of the logitech amp. Just to see what it would sound like. Anyway, I'm guessing I ruined my transformer, would you sell me yours?

-Greg