Help Needed Power Amp lacks punch

In case you didn't know it, you have a Mosfet amp. As a general rule, most Mosfet amps have less "slam" or "impact" than a well designed Bipolar unit. Mind you, not all Mosfet amps are "weak" on bass output, but they do tend to sound softer and more rounded. Part of this is why people say that they tend to sound "more tube-like" than Bipolar's along with a few other reasons.

If you haven't already been doing so, leave the amp powered up 24/7 for a couple of days. I've found that this tends to even out their tonal balance much better / faster than powering them up and using them as needed. If the amp hasn't been run in a long period of time, 48 - 72 hours of continuous power will get you most of the way there. After that, the unit will be pretty much as good as it gets within about two weeks or so. Mind you, these are just my sonic observations, so take them for what they are worth. Sean
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I put an Adcom 555 to shame in my system. My little McIntosh dished it out way more readily in the bass despite the Adcom's big power rating. Maybe you need a different amp? You could be having mismatch issues too which are compromising it. Arthur

I've found that the power cord can make quite a difference on big, mid-fi and above amplifiers. No experience with an Adcom specifically, though.

After doing some research I found the 555mkII had the most slam and for some reason the newer adcoms lacked a little.I don't know if they started doing something different but thats what I found.Good luck

Could be electric power issues. Is your AC power clean? Are you still using a standard OEM power cord? Don't plug the amp into a power strip; put it right into the wall.

Kgveteran: The 555's were bipolar amps, hence my comments above.

Sugarbrie: While your basic suggestions are good ( heavier gauge cord directly into the wall ), "dirty" AC typically sounds "fuller" than clean AC on the bottom end and harder / grittier as frequency rises. The increased warmth has to do with all of the harmonic distortion of the 60 Hz AC signal itself being further amplified through-out the chain. Cleaning up the incoming AC and then minimizing the ringing that takes place in the equipment itself via replacing slow rectification devices tends to lean the sound out a bit.

Rainchild: If my suggestions above don't give you what you want, you might want to think about modifying your amp. That is, if you like it enough to want to keep it. These amps were notorious for starving the earlier stages of amplification when dynamic swings or sustained high level spl's were taking place. There are several different approaches that one can take to rectify this situation with the two most common being to add massive amounts of filter capacitance and / or install a regulator circuit. You can find the circuit boards for the regulators at this link that i've provided for Audio Xpress aka "Old Colony Sound Labs". Sean
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I agree that the 555II has got better tautness in bass region and the 5500 is a tag soft in this area. Compare to Plinus SA100 MKIII which only fetch 100w/ch, The 100 is way ahead in making my Hales Relevlation 2s sing. But again, it's price also very far ahead. Do you guy think Carver FTM-35 will do better in bass? I know the Bryston can do a good job but now my budget doesn't allow to fulfil this wish yet. I got Acurus 200 in mind too.

Big power helps, but the quality of the power is more important. I have seen 75 wpc amps absolutely stomp 250 wpc amps in terms of "punch" and ability to drive difficult loads. As such, i would avoid all makes / models that you mentioned short of the Plinius. Sean
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Thanks Sean,

I think this is too profound for me to understand. Should we go for tubes? I used a Electrocompanient ECi3 rated 70 watts class "A" before but I found that the ECi3 sounds more like a 40 watter to me. I also heard the YBA Integre DT and it sounds like a 150 watter driving a pair of Spendors. Matching equipments is a deep thing really. Can someone tell me what to use to drive a pair of Hales R2?

One thing to check is the receptacle in the wall; most all home wiring is done with "push pins" meaning that the house wiring is pushed into the receptacle where it is held in my tiny little contact points. By far the greatest loss is occuring here. I have seen cases where a drill-motor would hardly run!

Get an electrician to put in some hospital or industrial grade receptacles and make sure he wires then via the nice tight screw!

That being said I do remember that particular Adcom as being a bit laid back in bass transients. Get a Bryston (for instance). That is among a class of amps that are only beaten by Krell in the bass (and the Krell is not quite...well...right...). Plinius is another good choice, though I think that you get more bang for the buck with Bryston (dollar value and amazing warranty). Just my bias of course....

I had no idea about my Adcoms and bipolar outputs.I guess that makes sense.Thanx for the info.

Don't give up that 5500!Ihave one I felt exactly the same about,warm bottom.What it did have after break in of about hundred hours was very musical top end up to point where it shifts from A to AB(To my understanding 5500 is biased class A to 25wpc).
This second sytem with a 5500 doing mids and highs and a 555II on bottom fed via 565 pre-amp.The 555II had very good low end but grainy mids and highs,the 5500 has really good top end.My one worry about how the 2 truly different designs would playback through a single set of speakers was set at ease as coherence was fine.The 5500 sounds much better in this vertical bi-amp setup My guess is it can now remain in its class A zone for most listening levels having only to power the top.Also I placed the 5500 below the 555II to act as a preheater for the cold blooded 555II.
A step up would be a better pre-amp.But most this stuff can be had for cheap saw a 565 and 555 here on agon'.