HELP: Classe CA-M400 / Power on thump

[SoundEngine355]

Hi,

I noticed with my new pair of M400's that when I power them on I get a low level thump from the speaker while its obviously powering on the circuits/modules.

I rechecked my speaker cables and removed the RCA/XLR inputs so its just the power/speaker cable connected to the M400 and still the same thing.

Is this normal? What about other Classe Delta amplifiers?

All the other amplifiers I have used have a very very quite "soft start" function....

[SoundEngine355]

The thump isn't loud, but its definately there.

[SoundEngine355]

After pushing the power on button, the first click is fine, the 2nd/3rd clicks are when I here the thumps, the following clicks are fine.

[SoundEngine355]

Doesn't anyone own another Classe delta amplifier that can provide information?

[style]

Hi SoundEngine355,

well I don't have experience with a plyer connect directly to the ampli ....

I can think you have the connection in the right modus ??
you have a direct power linie (electricity)?

the "click" in a CAM400 as mono is not only one? (one pro channel!)?

with thump, is in HF to LF?? or only on the woofer? (sure more audible in the woofer...)

a electricity comeback? you don't have a preampli at home to tried in a standart modus?

Style

[SoundEngine355]

Hi SoundEngine355,

well I don't have experience with a plyer connect directly to the ampli ....

I can think you have the connection in the right modus ??
you have a direct power linie (electricity)?

the "click" in a CAM400 as mono is not only one? (one pro channel!)?

with thump, is in HF to LF?? or only on the woofer? (sure more audible in the woofer...)

a electricity comeback? you don't have a preampli at home to tried in a standart modus?

Style

Hi,

I've tested it without any input connection i.e. RCA/XLR. Only the power cable and speaker cable, nothing else.

Yes the 2nd "click" is the woofer and the 3rd is the midrange.

Even though its a mono block it obviously has several modules (Not amp modules) inside which it needs to power on during the cycle.

It might be a ground connection, but I have never had this problem before with any other amplifier, I've tried different cables, wall sockets. Both amplifiers are doing it.

[style]

Hi,

a ground problem is sure no.

this thump is "new" or with the first connection don't was presnet?

try with a rca cables in place of Xlr...,

i don't have no more the denon3808 to try a connection without a playr to ampli?

yuo using a bi-amp spealer cables?
Style

[SoundEngine355]

I've been testing it without RCA or XLR cables. Only using the power cable and speaker cable (I've tried 4 different cables).

I only just got the amplifiers this week.

[style]

Hi,

well if all the 2 power ampli make the same "work/problem" is in a side beterIs not a CAM400 ampüli defect!

Like wrote I don't have experience with a configuration without preampli....
I can only immagine a intruduction of a pre to of a response from your problems .....i'm not a technician but a peampli between the payer and power ampli...(personaly give you a better sound too)

is possibile that without the preampli the strom/netz dont' have a filter and you go hear thîs "noise"..

this thump you have only at the start from the system or?
Style

[ShadowZA]

Just a guess.

I leave my amplifiers on permanently but in standby mode. When I turn on from cold (ie completely off) there is a simultaneous "pop/thump" like sound from the speakers. Not too loud but noticeable. When I turn on from standby mode, this does not occur.

A thought regarding the "thump" sound that you are experiencing is that maybe the amplifiers have not been in standby mode for too long & are not "warm" enough yet.

[Glen B]

All the other amplifiers I have used have a very very quiet "soft start" function....

The other amplifiers are quiet because they all likely have output relays that connect the speakers following a delay of several seconds, after the amplifier circuits have had time to stabilize.

The soft-start has more to do with reducing inrush current (and preventing popped circuit breakers and stress on the power supply components upon turn-on) than eliminating turn-on thumps.

I believe the Delta amps do not have output relays, and that would account for why you are hearing a slight thump. Leaving the amps in standby as mentioned above should elmininate your thump issue.

[sikoniko]

I apologize for not getting back to your PM, but I'm fairly certain the above information is correct.

[SoundEngine355]

Just a guess.

I leave my amplifiers on permanently but in standby mode. When I turn on from cold (ie completely off) there is a simultaneous "pop/thump" like sound from the speakers. Not too loud but noticeable. When I turn on from standby mode, this does not occur.

A thought regarding the "thump" sound that you are experiencing is that maybe the amplifiers have not been in standby mode for too long & are not "warm" enough yet.

This is all from standby mode.

[SoundEngine355]

The other amplifiers are quiet because they all likely have output relays that connect the speakers following a delay of several seconds, after the amplifier circuits have had time to stabilize.

The soft-start has more to do with reducing inrush current (and preventing popped circuit breakers and stress on the power supply components upon turn-on) than eliminating turn-on thumps.

I believe the Delta amps do not have output relays, and that would account for why you are hearing a slight thump. Leaving the amps in standby as mentioned above should elmininate your thump issue.

The thump/pop issue is from standby mode, and I get the same result from a cold power on.

[SchH III]

In my system I am using 5 CA-M400s; 4 are bi-amping the 800D's and one powers the center channel. Connections to the SSP-800 are XLR. Turn on is silent for all CA-400s as well as for the CA-2200 that drives the surround channels.

[Glen B]

The thump/pop issue is from standby mode, and I get the same result from a cold power on.

A few mV of DC offset at the output of your amps could be the source of your thump. DC offset below + or -5mV in an amp is fine and no cause for concern. The high sensitivity and low end response of your 800Ds also could just be making the thump more audible. I would be curious about what the Classé factory has to say on the thump issue.

[SoundEngine355]

A few mV of DC offset at the output of your amps could be the source of your thump. DC offset below + or -5mV in an amp is fine and no cause for concern. The high sensitivity and low end response of your 800Ds also could just be making the thump more audible. I would be curious about what the Classé factory has to say on the thump issue.

I'll let you know, hopefully find out shortly.

[sikoniko]

Somewhere in these thread this question has been asked. I'm feeling extremely lazy right now, but you should be able to find it by searching a year or two back.

[SoundEngine355]

Somewhere in these thread this question has been asked. I'm feeling extremely lazy right now, but you should be able to find it by searching a year or two back.

In the main classe thread?

[SoundEngine355]

Opened up the M400's today and noticed the input cable for the XLR/RCA uses Chord Chameleon ( http://www.chord.co.uk/chordweb/chor..._technical.htm )

[SoundEngine355]

Somewhere in these thread this question has been asked. I'm feeling extremely lazy right now, but you should be able to find it by searching a year or two back.

Found this in the thread:

"According to Classe' technical support this effect is normal behavior for the CA-M400's and all other Delta Series amplifiers. Classe' made a purposeful design decision not to unduly interfere with the delicate audio signal that gets amplified. They could have introduced sound degrading relays into the signal path ways, as many other amplifier manufacturers do, and avoid the audibility of the low level thump on power up, but only at the expense of sound quality. Designing "direct drive" amplifiers as Classe' did invariably eliminates signal compromises relays bear."

[SoundEngine355]

Response from Classe Audio:

"Like all Classe amplifiers, the CA-M400 is a direct drive amplifier with no buffer between it outputs and the speakers. This is a deliberate design decision because we believe that the highest audio quality is delivered when the amp is separated from the speakers by the speaker cable only.

The reason the pop is occurring is due to the power supply. As you power up, the mute relays open, generating clicks you are hearing, and this allows signals to pass to the speakers. At the same time the amp capacitors are charging. The positive and negative charges into the capacitors are not exactly equal and the minor difference between them creates a potential (technically called a DC offset) which results in the sound you perceive. It is not universal but when it occurs, it is particularly noticeable on very high quality speakers.

The DC offsets are minimal, about a 1000th of the incoming voltage, which is literally a fraction of the voltages involved in reproducing music. They therefore do not represent a risk to speakers. Furthermore, we set specific offset parameters for our units. Source components, pre-amps and processors are limited to 1mv since these tiny signals can be amplified when they reach an amp. Amplifiers are limited to 20mv, since this level of voltage is virtually silence to speakers.

We could add any number of capacitors and filters to eradicate all offsets to 0mv but this has been proven to dramatically alter the sonic performance of our products. We are not willing to do this because we consider a slight movement in the speakers to be a price worth paying for better sounding products."