Precisely what tech Soderberg told me too yesterday when I checked with him. Jon did replace the main power filter caps on mine during the upgrades he did. He showed me before install, has specific ones he has been using. We also revisited where my amp is biased at, and it's right at the recommended limit. I do recall now we spent a bit of time going over the bias range during the actual first upgrade and the last QA check I did again with Jon again six months later. Still right no target.
Said this exactly in reply, quote "There are no electrolytic caps used in the Forte 1a and 3 design", also noted "as the bias goes down, more grain and etch from the notch distortion is typical".
Update-2: my amp seems fine now after the first six month cold startup. It just needed that first 24hr power-up. Now I can run it for 45-60 minutes and it sounds fine, quite nice, not harsh or anything like that. Tried it again last night and still good two evenings in a row. Was just cold sitting 6 mo. All good now it seems.
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To @Extreme_Boky yes seems so. I will try it again tonight for a 3rd night. I am turning it off each night, not leaving it on as a test.
I recall something similar when I first got my former Cary SA-200.2 amp. It had been built and stored a while, and the first few days it was pretty cold and grainy, and to be expected new but it sure sounded a lot different after it had been on past 72hrs. From that point on and a week later, it was notably different, just better overall. While it's not the same example of comparison, I do recall this on this amp and another too. Should have known better I guess. Admittedly I'm hypersensitive to any grain and my speakers reveal it, easily. And coming from tube amps as my main / primary system, maybe I tend to notice it even more when it's there and when it's not.
I recall something similar when I first got my former Cary SA-200.2 amp. It had been built and stored a while, and the first few days it was pretty cold and grainy, and to be expected new but it sure sounded a lot different after it had been on past 72hrs. From that point on and a week later, it was notably different, just better overall. While it's not the same example of comparison, I do recall this on this amp and another too. Should have known better I guess. Admittedly I'm hypersensitive to any grain and my speakers reveal it, easily. And coming from tube amps as my main / primary system, maybe I tend to notice it even more when it's there and when it's not.
An initial test, followed by a 24-hour soak test, followed by another test (the replica of the initial test), noting down any differences in measurements; the differences will point out to a potential issue(s) - there is no other way.
The amp is old; the above will show any potential problems.
You get a certificate of compliance and peace of mind.
Spot adjustments/checks are not good enough - well, at least not in your case, where you can easily hear the differences.
The amp is old; the above will show any potential problems.
You get a certificate of compliance and peace of mind.
Spot adjustments/checks are not good enough - well, at least not in your case, where you can easily hear the differences.
My error and oversight, and likely premature judgement perhaps. Details below if interested in what we figured out.
Yes. Completely, 100% disappeared. Changed for the better, permanently.
- After 80 hours of use since the last upgrade the final change in sound for the better occurred, and stayed that way last four listening sessions - interestingly enough. Zero changes after 80 hours of full play time. Plays the same every time now since.
- Checking again with my tech [Vintage Amp, Jon Soderberg], there is a theory as to why after upgrading my amp. To recap, about my upgrade 1) reconfigured it to Pure Class A 50 watts, different taps on the Torroidal transform too if it matters, 2) replaced all for main power caps, 3) soldered in bridge rectifiers, 4) upgraded rear wiring some, 5) changed out and soldered in binding posts to Cardas speaker binding posts. Multiple connectors removed in favor of direct wire soldering.
- Here is what occurred leading to the weird changes in sound [temporarily]. Last summer I pulled this SS Forte' amp out of rotation maybe at 40-50 hours of use I'd guess since the last upgrade and service last summer. Swapped in and played my mono tube amps into the holidays. I then swapped out the tube amps an put the upgraded Forte' amp back into rotation. Again had 50hrs on it since the upgrade, was cold, and the first two times I played it only 3-4 hours each time - it just sounded a bit cold and grainy, was not sure why. I wrote the post above, was fishing for thoughts.
- 3rd time I played the Forte' amp I left it on for 24-48 hours, and during that listening session I started to notice a nice smooth change in sound. Like "wow" sound, hey this sounds really nice type of thoughts. All the sudden the music started to become really engaging. I called Jon, he asked "how much time do you have on the amp again since the last upgrade and bias checking?" me: "now over 75-80 hours now, since I put the amp back in rotation". Jon: "That's it, you've got enough time on it now since the upgrade and changes we made", "that's about right for break-in again, that makes sense why you are now hearing the changes", etc.
- Since that time, every time I play the amp, takes about 45-60 minutes of warmup, and consistently sounds good every time. No changes in sound now playing the last 4 times. It's really good now. Extra happy with the upgrade, sound, and consistency now. I guess it just needed more time for big caps and all to settle in. Whatever the case, super happy now.
- Sounds so good now I might do something similar finding some monoblocks to upgrade for my larger speakers.
Hopefully that helps explain it better and for corrections warranted once we figured this out.
Do you hear any sonic improvement from the previous AB configuration to the new pure class A? For 200Watts vs 50Watts, it would seem you'd have a little less umph in reserve...Anyway, I'm glad everything worked out in the end.
Great question.
Yes and No. Probably the first and most important question and concern I had with the decision to reconfigure the Forte 3 180w Class AB to Forte 1A 50w pure Class A operations. Four new and larger power capacitors were installed, all five Mosfet output transistors per side are still in play [and re-checking with Jon again, a correction], bias was turned up to a max 50 degree Celcius / 122 degree Farenheight at the heat sinks. Some suggest 45-47C, yet the tech Jon said something about voltage down, bias up, I don't recall exactly, about the amp "lasting".
Decision:
Note: I really put the trust of the decision and change into tech Jon's hands after 3-4 conversations about this proposed change. When I had the amp in for the service, checks, and upgrde, he kept leaning in to say "are you sure you don't want to convert this to pure Class A, and we'll use these larger power caps too, we'll remove some connectors and solder in a few things while we are at it", etc. He kept at me about this.
Changes in Sound:
Top end is smoother, really nice. There is this aspect about texture and tone that I really enjoy. Sound stage seems a tad larger maybe. Low end grunt is still there, maybe something more with the lower gutteral deep bass - or I'm imaginging that, I don't know, just hearing something more. It turns out now the break-in process [after upgrades] was more of a roller coaster than I was expecting. Last 7 listening sessions have all been the same. It does take at least the full 45-60 minutes for the amp to sound nice, maybe even a tad better at 120 minutes, more body to the sound, this added weight to the sound really becomes evident after its been on, warm, fully saturated.
Background about Power:
This was an experiment for me to try this reconfirgured stereo amp with my custom 4ohm 92.5db speakers. I normally run monoblocks with my other tube amplifiers. I sort of wondered if this would be at the cost of loss of some power, grunt, less body and bass. Oddly enough, still has plenty and then some. My test is I like to listen at low volume levels. Seems just fine. Now I wonder about selling this amp, and doing the same thing all over again with two of these as mono amps just to have it, and because this amp sounds very nice. Necessary, no. Fine as-is.