To mod or not to mod Adcom GFA 565

Pstores · « **on:** 1 Jul 2018, 09:24 pm »

I Am getting up a AVA Fet Valve CFR preamp soon. Going to do the Tube over SS thing. Here is my question for you all. I have the Musical Concepts LX elite with the mini Platinum Mods not. And they sound pretty good. Huge difference when I A/b'ed them against a stock pair. And up against a Krell KSA 250 they are close. They each do a couple things better. Adcoms smoke the Kelll low end. Has more clarity on the highs, and both sound stage. Krell is alittle smother more refined I would say. So here is the question...... Would it be worth doing the 20 resistors in each and replace the filter caps with Mundorfs or Jensons? I believe that would be the last thing that Musical Concepts would have left to do. Filter Caps are originals so about 20 or so years old. Just not sure how much of an impact the Filter Caps would have. That is the biggest question. I know I will never see a return on that money if I ever sold them. That's not a factor. Or should I just bite the bullet and sell these and buy a new SS Amp?
My system is as follows
Adcom GFA 565 mono with Musical Concepts mods LX. Elite with Platinum
Ava Fet Valve CFR coming soon
Bel Canto Dac 3
Vandersteen 2ce sig ii

OzarkTom · « **Reply #1 on:** 1 Jul 2018, 11:10 pm »

How much for the mods?

Pstores · « **Reply #2 on:** 1 Jul 2018, 11:53 pm »

About $1300 installed for the pair

WireNut · « **Reply #3 on:** 2 Jul 2018, 12:20 am »

If you can solder, get the Service manual here (http://www.analogalley.com/m_adcom.htm) or other source(s) and replace some of those
old parts and see how it sounds first. If you don't like it, then ship it to Musical Concepts.

That's the plan for my two 555's, DIY. Parts replacement only, no mods to any circuits.
Get it running right before doing any kind of circuit modifications.

Take your time, double check your work, build an easy Dim Bulb Tester to safely test it on first power up.

It's loads of fun and that feeling of doing it yourself is pretty awesome when you flip that switch for the first time.

Search forum's for Adcom upgrades if you need help or would just like to read what people are doing.
IE: AudioKarma, Diyaudio, Pinkfish, Polk, the list goes on............

Good luck.

OzarkTom · « **Reply #4 on:** 2 Jul 2018, 12:29 pm »

Quote from: Pstores on 1 Jul 2018, 11:53 pm

About $1300 installed for the pair

For that kind of money, some of these newer class d amps will compete or better the low end of the Adcoms, and some will also compete with the power and smoothness that the Krell will give. You would also have a very resellable amp, not waste near as much money. If size matters, stay with the Adcoms. These Class D amps are tiny in comparison, but not in power, or bass.

Check out the,
1200as Edge icepower amps, Nord, Bellisimo, Apollon, Rouge, Mivera(over $1300 in the deluxe case)
DAC SMT integrated amp-$1200
Nuprime 10 amp
Bellisimo Ncore NC502 amp or Icepower 1200as amp
Other NC502 amps but most are over $1300

A 30 day return policy is recommended in case you don't like it. Nuprime may have it, but might be slightly higher than $1300. DAC offers a 30 day return policy, I am not sure on any of the others.

Pstores · « **Reply #5 on:** 2 Jul 2018, 02:12 pm »

I have listened to quite a few class d amps. The all seem to have that sterile, lifeless, edgy sound. And yes I would miss the power of the Adcoms. Especially in the tight low ends and bass. The 565's seem to sell for about $1100 still. Not bad from the $1900 retail back in the early 1990's. Maybe I'll try to demo a few more amps at home.

Rusty Jefferson · « **Reply #6 on:** 2 Jul 2018, 02:29 pm »

I use Musical Concepts/Design gear and also use a tube preamp in front of SS amp. Those amps at that level probably sound pretty good already. If you lived in St Louis and could walk them in for the update, sure I'd probably do it and have (essentially) new keeper amps for the duration. But I probably wouldn't ship them cross country at this moment cause heck, they sound pretty good and there may be other things that will make a larger improvement.

That preamp looks like a nice upgrade to your system. Looking over your other parts, if you're happy with the speakers (biggest piece of the puzzle), I'd probably consider using that money to get some quality tubes for the preamp, and/or consider an upgrade to the dac or server upstream of the dac. Digital has come a lot farther in the last decade than amplifiers for improving sound. And of course, cables. You're more likely to get larger improvements with tubes, digital upgrading, and cables than modding/replacing those amps at this time, imo.

Pstores · « **Reply #7 on:** 2 Jul 2018, 06:43 pm »

Thanks Rusty that was my concern if with shipping and such would it be worth it. And was hoping to find someone that may have experience with these. I may find someone to replace the large cans local as they are 20 plus years old.

Pstores · « **Reply #8 on:** 2 Jul 2018, 06:44 pm »

And yes my Dac will be next upgrade.

timind · « **Reply #9 on:** 3 Jul 2018, 01:43 am »

Those large filter caps have screw terminals, they'd be a pretty simple replacement as long as you find the correct size. It would take less than an hour I'd think for a qualified tech.

Pstores · « **Reply #10 on:** 3 Jul 2018, 01:51 am »

Yes you are correct.

Bemopti123 · « **Reply #11 on:** 3 Jul 2018, 11:43 am »

I would not do it. $1300 is no small change for an amp of that vintage. You can easily surpass the performance of those amps with buying newer amps add some more hundreds to your budget. Class D has come a long way from the time when they were sterile and hollow in quality. I would look into Class D amps with massive analogue power supplies, they will surprise you. H2o amps by Henry Ho, if you can find the contact or see when he has them on sale on Audiogon.

Letitroll98 · « **Reply #12 on:** 3 Jul 2018, 03:52 pm »

I remember reading there is something amiss with the filter caps on the 565 and they should be replaced after all these years, but I can't find the site to post a link to. I believe it was the caps leaking on the circuit board, there is an Adcom service bulletin on how to properly clean the board. All from memory so it might not even be the right model, but since you're considering this it might be worth running down. Being that the PS is already very beefy on these brutes I don't know if you'll get any improvement in SQ, it just prevents catastrophic failure.

Pstores · « **Reply #13 on:** 3 Jul 2018, 05:21 pm »

It wasn’s the PS Filter caps that had the issue. But the input caps. All mine had been replaced before a leak issue. So I am good. Tried to find some direct replacements, Not So easy. I may have to wait till next year and get a kit. To replace to get the same Values.

timind · « **Reply #14 on:** 3 Jul 2018, 06:39 pm »

Have you asked John Hillig if his PS kits will work in the 565? Two of his PS100 kits aren't expensive if you order the bare bones kit and source your own caps and rectifier. Easy to install if it works for your amp.

edit: I looked up the value of the filter caps and what I found was 36000uf 125v.

Good luck finding those.

Pstores · « **Reply #15 on:** 4 Jul 2018, 01:48 am »

Yes like you said good luck finding those. I’ll most likely send them
In at one point. Or get the kits and caps from him. And have them installed locally. Only issue with selling is these do sound really good and compete with some fairly high end stuff. So hard to make that leap.

JLM · « **Reply #16 on:** 4 Jul 2018, 10:52 am »

Quote from: Bemopti123 on 3 Jul 2018, 11:43 am

I would not do it. $1300 is no small change for an amp of that vintage. You can easily surpass the performance of those amps with buying newer amps add some more hundreds to your budget. Class D has come a long way from the time when they were sterile and hollow in quality.

+1

I've owned the physically tiny Temple Audio 70 watt class D mono-blocks ($750/pair depending on current exchange rate) for a year now that are very nice, if 18 dB of gain is enough for you. Previously owned the original Channel Island Audio D-100 (100 watt class D, one of old designs) and have heard class D amps (cheaper, well built) and Crown 1502 class D amps (cheap, but used with $20k JBL M2 mastering speakers) that the Temple Audio out classes.

The Adcom is a classic, but only viable if you're into vintage gear.

Wind Chaser · « **Reply #17 on:** 4 Jul 2018, 02:21 pm »

Yeah, I will echo what JLM and Bemopti123 said. For less than half of that you can buy a very serious amp.

https://www.audiocircle.com/index.php?topic=158669.msg1694846#msg1694846

Class D has arrived in a very big way; the amps I have now easily surpass all the tube amps I’ve owned over the past 30 years.

JLM · « **Reply #18 on:** 4 Jul 2018, 03:03 pm »

Quote from: Wind Chaser on 4 Jul 2018, 02:21 pm

Yeah, I will echo what JLM and Bemopti123 said. For less than half of that you can buy a very serious amp.

https://www.audiocircle.com/index.php?topic=158669.msg1694846#msg1694846

Class D has arrived in a very big way; the amps I have now easily surpass all the tube amps I’ve owned over the past 30 years.

Windy, that appears to be a chip amp, not class D. Named for the use high powered integrated circuits. First introduced by 47 Labs. Spin-offs are called 'gain clones'. They were a favorite among DIYers. Exact circuit physical layout (typical shorter the better, down to 9 mm) has a significant impact on the sound. A variety of chips have been used. Power is limited to 40-50 watts at 8 ohms. Peter Daniels was one of the more popular builders. I had a pair of Channel Island Audio VMB-1 (40 watt mono-block gain clones) years back that their D-100 beat out sonically and that has been beat out by my Temple Audio (faster, more detailed).

Wind Chaser · « **Reply #19 on:** 4 Jul 2018, 03:40 pm »

No, it’s not class D, but I bet it’s a far more sensible option to putting $1300 into a vintage amp.