Adcoms (535, 545, 555)?

cnh

Hi,

I was on another site a while ago and a number of people said that they would not consider this series of Adcom amps because they have no 'relays' to protect your speakers. Is that a concern or even a valid reason for not choosing an amp?

Also, Adcom can hardly be 'alone' in such a design, no? I have both a 545 and a 555 and have 'never' had any major problems with either. I've also seen very little posting that complains that someone has blown a set of speakers with an Adcom?

Thanks!

cubdog

I've heard similar complaints but have yet to talk to anyone with a first hand experience. I owned a 555II for years without any problems.

cubdog

heiney9

Nope, not a concern but I would check DC Offset on amps that old before buying/using just to make sure there isn't an issue. That goes for all aged amps.

FYI, 555II had DC Servo's to block DC from getting to the speakers.

H9

FTGV

Pass designed this series with the goal of keeping it simple without adding any protection circuitry beyond the standard rail fuses that could have a negative influence on SQ.They are capacitively coupled at their inputs to prevent any DC from the source being passed to the gain stages.

As for output relays they may be common place in low powered recievers and int. amp's etc.but a rarity in higher powered "audiophile"amps.In part because the relays contacts would be subject to potential long term reliability issues having to carry the high currents required.
However some hi performance amplifiers utilize smaller relays in their voltage gain stages to mute the signal at turn off so you don't hear music for the short duration as the filter capacitors are discharging.

leftwinger57

Again I also have owned my rack mount 555 for about a year w/ absolutely no problems .I have never experienced any thumping or speaker pop on power up/ down and always make sure when powering up my volume is set relatively low. Lots of ss power for a very reasonble price of $300 and really pleased w/ the performance.I have heard of speaker circuit breakers but only on very expensive models.

unc2701

Not really a problem. You get a turn on thump and they'll keep playing for a couple seconds after you turn them off, but I've had: 545, 555, 565, and 585's with no relay related issues.

HTguru1982

I experience popping with my 545 every time I turn it on and off and also whenever I change chapters on my dvd player, pause, press play, or press mute on my receiver. I do not experience this with my newly acquired HK PA5800, though.

Should I be worried?