Replacing Capacitors - Adcom GFA-545

PreCd

I have been running a GF-545 for a few months now and decided to replace the capacitors on the PCB. There are two there, a 4.7uf and a 47uf cap. The 4.7 is in the bias circuit so I thought what the the heck, lets do it. No expectations really. Just need to be tinkering if it is constructive. So after replacing the two caps on each side and readjusting bias I was surprised at the results. The amp really came to life. Lively. Musical more than before. Maybe a tad more detailed. Great!

I guard against the results of any change I make being positive due to the fact that I want a change anymore. In the past I have been guilty of that.

For the record I used Panasonic FC capacitors.

Next I will replace the large filter caps. I did this on a GFA-555 a couple of years ago. The results of that was a drastic drop in DC offset. From 39mv to 9mv even on both sides. I will probably tackle that in Feb. early March.

zingo

Congrats on the results, and it is amazing what fresh caps can do to electronics. Pictures? :cheesygrin:

skrol

zingo wrote: »

Congrats on the results, and it is amazing what fresh caps can do to electronics. Pictures? :cheesygrin:

True! I just did my Parasound HCA-800II and am amazed. I haven't done the PS filter caps yet. I also replaced all the caps, even those not in the signal path. It is worth the while as I found a few that were out of spec.

At first listen, it was harsh and grainy but as it played for just a few hours, it all started smoothing out.

The caps to do my pre-amp just arrived yesterday. More fun to be had.

westmassguy

The Panasonic FCs are great, but are being phased out. The FM Series are as good if not better.

skrol

After reading of good experiences, I went with the Nichicon FG and KZ from Parts ConneXion.

cnh

I have a couple of Adcoms that might benefit from such work. The problem, without first doing that work you'll never know what you're missing as everything sounds "fine" to me at the moment?

I'd be curious to hear them after the changes in order to assess the actual "degree" of change. Meaning from barely noticeable to WOW is that the same amp! I suspect I would NOT be blown away but would hear some difference.

I have more experience there with old vintage receivers where I listened to some recapped and some original. I was really not that amazed by the recap. A little cleaner maybe, but the general sound signature and musicality were not that different, or else my hearing is really gone. Which is also possible. My ears ain't getting any younger and I can't hear anything much over 14Kz if that?

cnh

westmassguy

Elna Silmic IIs are probable the best for audio right now. Nichicon Muse would be my second choice.

skrol

I did read about the merits of the Elna Silmic II. Some have described them as having a more tube-like sound signature vs the Nichicon being more neutral. One issue with them though is size. They do tend to be a little larger than most for a given value. I found this to be true of the Nichicon too but the Elna are larger still.

I decided to go with the Nichicon and maybe in the future I'll swap for some Elna in the pre-amp.

westmassguy

The Elnas are big for sure

Phish56466

Sorry to thread jack, anyone have any comments on Mundorf caps? Getting ready to do the input PCB on my 555 and was wondering. They're HUGE compared to what's in them, but I'm thinking superior caps should yet some improvement.

PreCd

Sorry Zingo.........no pictures. The FR series of Panasonic capacitors look promising also. Ultra-low ESR. I used the Elna Silmic II in a preamp that I owned over a year ago and had no issues. I am going to continue listening to the amp with the FCs in there. So far I am satisfied but realize there are other caps out there especially those that carry the "for audio applications".

PreCd

Phish56466 wrote: »

Sorry to thread jack, anyone have any comments on Mundorf caps? Getting ready to do the input PCB on my 555 and was wondering. They're HUGE compared to what's in them, but I'm thinking superior caps should yet some improvement.

I guess if you mounted them to the back of the PCB it would work. You will be spending around $80-$90 for 4 capacitors vs. a few dollars for top of the line electrolytic capacitors.

westmassguy

PreCd wrote: »

Sorry Zingo.........no pictures. The FR series of Panasonic capacitors look promising also. Ultra-low ESR. I used the Elna Silmic II in a preamp that I owned over a year ago and had no issues. I am going to continue listening to the amp with the FCs in there. So far I am satisfied but realize there are other caps out there especially those that carry the "for audio applications".

Although they're listed as general purpose, the FCs and newer FMs are very neutral. I did some research a while back, and they were consistently rated as the baseline for a good audio cap. The Nichicon Muse and Elnas were given higher marks, but for the price the Panasonics are hard to beat. Digikey has the lowest prices on the Panasonics, and Elnas. Their stock of Muse is limited. The site is a PITA to navigate though.

Phish56466

PreCd wrote: »

I guess if you mounted them to the back of the PCB it would work. You will be spending around $80-$90 for 4 capacitors vs. a few dollars for top of the line electrolytic capacitors.

This thing is already a Franken-amp of sorts(stuff already on the bottom of the PCB). Was just curious if there would be any sonic improvement. Cost DID strike me as a bit high, but you get what you pay for.

skrol

What caps do you all recommend for the power supply (18000uF x2) ?

westmassguy

what voltage?

skrol

They are 18000uF 50V. There are also a couple bypass caps across each that I couldn't read the value as they are presently glued down.

Phish56466

Bypass caps-I generally go all off on this. My 555 currently has a 1uF, .1uF, and a .01uF @ 400VDC films on it. Also went from the factory 3.9K@2W to a 3.9K@5W Dale Ceramic. This was done with larger caps for the main rails in mind. I'm going from 15KuF to 30KuF(PER CAP-total will be 120KuF in the supply). Already got larger bridges in it(20A/200PIV to 35A/1200PIV). As long as your main supply is the same voltage or higher it won't hurt anything. It's when you start cramming reallly BIG cans in it (read extremely large capacitance) you have to start worrying about your rectifiers and transformers. A lot of inrush can cause a spectacular sight! Be ready to drop MAJOR coin for large caps, they're not cheap.

stretchl

how difficult is it to replace the capacitors? I've never done any electronic work and I imagine that my lack of soldering skills, etc., would guarantee that I'd be in a worse place after than before I started. Thanks.

lanchile

skrol wrote: »

What caps do you all recommend for the power supply (18000uF x2) ?

I have try many brands, But my favorite is the Mundorf audio grade capacitors.

Phish56466

Depends on the type of caps. Some have screw lugs, some are soldered. If they're soldered in and you've never done it or aren't comfortable doing it-A PAIN(and nerve racking too boot). The screw lugs, just make sure they're discharged and go for it! If they're polarized OBSERVE POLARITY, once you let the smoke out-it's kind of hard to put it back in!