Good point. I have to agree with caution about a big increase in capacitance. If the originals had a +75% tolerance, for example, that would be greater than the 33,000uF of the new caps, but those may have a + 20% tolerance which would be 40,000uF per cap which could be problematic.
I went up only 4,000uF per cap on mine for the same concerns.
I went up only 4,000uF per cap on mine for the same concerns.
Oh, I didn't think about that. I'll have to check Mouser and others again, but I'm quite sure that with the right dimensions, I could only find caps with 22.000 and 33.000 microfarads. Do you think 22.000 would be a safer option, or would going down 8.000 microfarads be too much? I don't want to change the dimensions much because of the metal parts and amount of work.
@GKTAUDIO You mention going up only 4.000, but I'm pretty sure I read you saying you used 33.000 microfarads Kemet caps. Am I wrong?
@dastinger - dang, you are correct. I have worked on too many amps now, and haven't had the Forte open in several years, so was mistaking the cap selection for another amp I recently worked on.
I normally don't bump up capacitance that much, but as I seem to recall, choices were not vast, and the original caps had a high % tolerance, so yes - I am running 33,000uF in my Forte. No problems with power-on surge. I changed rectifiers to new 35A ones. My caps are Kemets. Sorry for the confusion - doing too many things at once these days.
I normally don't bump up capacitance that much, but as I seem to recall, choices were not vast, and the original caps had a high % tolerance, so yes - I am running 33,000uF in my Forte. No problems with power-on surge. I changed rectifiers to new 35A ones. My caps are Kemets. Sorry for the confusion - doing too many things at once these days.
@GKTAUDIO no problem, I totally understand, thank you for clarifying.
I'm able to replace the bridge rectifiers as well if that helps, but I need to know the voltage rating. And are they single phase? I found these: https://mou.sr/3S5zIOe
Do you think they'd work or are too overkill? I'm wondering if I can get it down in voltage and maybe spend a bit less.
Also, did you notice any difference in sound with the added capacitance like @xrk971 mentioned?
I'm able to replace the bridge rectifiers as well if that helps, but I need to know the voltage rating. And are they single phase? I found these: https://mou.sr/3S5zIOe
Do you think they'd work or are too overkill? I'm wondering if I can get it down in voltage and maybe spend a bit less.
Also, did you notice any difference in sound with the added capacitance like @xrk971 mentioned?
I routinely replace 30-40 year old rectifiers.
What is your AC mains voltage? Most recommend going double, but I like to go with 800V or 1,000V bridges even for our nominal 120V service. I've read that higher voltage parts are a little slower, but I like the safety margin.
Please don't skimp on rectifier voltage or current rating or quality. I don't recall what is in there now, but you could replace in kind or bump up voltage.
Extreme_Boky made the comments. I noticed an increase in audible firmness of bass, but no negative audible effects.
What is your AC mains voltage? Most recommend going double, but I like to go with 800V or 1,000V bridges even for our nominal 120V service. I've read that higher voltage parts are a little slower, but I like the safety margin.
Please don't skimp on rectifier voltage or current rating or quality. I don't recall what is in there now, but you could replace in kind or bump up voltage.
Extreme_Boky made the comments. I noticed an increase in audible firmness of bass, but no negative audible effects.
Thank you @GKTAUDIO for your continued help.
I just checked and could find some options with the 800V or 1000V so I'll go with that, even though mains voltage where I live is 230V.
And thank you for your opinion on the sound! Tighter bass is always welcome. I'll still check if I can find something that's not as high in capacitance, but I'll go ahead with 33.000 if that's the only option. I was reading something xrk wrote about the ground on these amps and got confused. It was indeed @Extreme_Boky who talked about the possible difference in sound.
Again, thank you, I'll update as soon as I go in and replace stuff.
I just checked and could find some options with the 800V or 1000V so I'll go with that, even though mains voltage where I live is 230V.
And thank you for your opinion on the sound! Tighter bass is always welcome. I'll still check if I can find something that's not as high in capacitance, but I'll go ahead with 33.000 if that's the only option. I was reading something xrk wrote about the ground on these amps and got confused. It was indeed @Extreme_Boky who talked about the possible difference in sound.
Again, thank you, I'll update as soon as I go in and replace stuff.
@Mikerodrig27 @GKTAUDIO checking back guys, can't believe it's been a year since I did the Forte 1A Class A 50, upgrades.. Been rotating the amp in/out between the tube monos a few times. Had not used the 1A in 6 months. Recently started listening to it again first of the year. The bigger 30kuf caps too, it's not slow at all, I really can't complain about anything with the upgrades. Sounds nice. As you suggested, over time, I'd notice certain aspects to the sound, and I have, as you described. Very nice.
Dropped it off at Jon's tonight to have him do a quick health check, bias, and to see if there is anything else to do. He felt there was nothing else as I did all the special upgrades, soldered in bridge rectifiers, and all.
Two things -
Liking the amp so much, I might look for the right Threshold amp and preamp too, and go full-title again on upgrades. If I do, I'll regretfully pass the Forte 1A onto its next happy owner to help fund this next project.
Before doing so, checking back - one of you mentioned trying / testing with other SS preamps you liked more than some of the better Forte' or Threshold preamps, me assuming that was testing with your Forte' amp(s). What I'm looking for will be simple in a preamp, active, two inputs, two outputs (RCA), a good volume control / step attenuator, etc. That's it, simple and more generic looking the better.
Other preamp Thoughts to look into?
Dropped it off at Jon's tonight to have him do a quick health check, bias, and to see if there is anything else to do. He felt there was nothing else as I did all the special upgrades, soldered in bridge rectifiers, and all.
Two things -
Liking the amp so much, I might look for the right Threshold amp and preamp too, and go full-title again on upgrades. If I do, I'll regretfully pass the Forte 1A onto its next happy owner to help fund this next project.
Before doing so, checking back - one of you mentioned trying / testing with other SS preamps you liked more than some of the better Forte' or Threshold preamps, me assuming that was testing with your Forte' amp(s). What I'm looking for will be simple in a preamp, active, two inputs, two outputs (RCA), a good volume control / step attenuator, etc. That's it, simple and more generic looking the better.
Other preamp Thoughts to look into?
I am very glad that you got back to the group here. I have owned a number of Forte' amps over the decades and regretted selling any/all of them. That is just my feeling, but in my defense, I did buy a Threshold T50 that I also liked very much.
My present Forte' 3 is not really a Forte' 3 anymore, due to the very extensive amount of work that has been done to it. Having said even that, it very much surprised me to hear how different preamps can sound through this amp. I suspect it has more to do with matching or something. In my experience, a simple Pass Labs B1K kit preamp has been surprisingly great with the amp whereas a really good design by John Broskie wasn't as good in some ways.
All I can say is that I look forward to what you do next and what your impressions are. Find synergy if you can.
My present Forte' 3 is not really a Forte' 3 anymore, due to the very extensive amount of work that has been done to it. Having said even that, it very much surprised me to hear how different preamps can sound through this amp. I suspect it has more to do with matching or something. In my experience, a simple Pass Labs B1K kit preamp has been surprisingly great with the amp whereas a really good design by John Broskie wasn't as good in some ways.
All I can say is that I look forward to what you do next and what your impressions are. Find synergy if you can.
@lxnay thanks for the note. I remember chatting back and forth over email with PaPa about the B1K kit as he was finishing it up, I had been sharing my usage of 6SN7 tube preamps with Pass amps, and now with my Forte amp. Its a nice combo. Sometimes I want to remove all of the tube gear out of the system, and play all SS. This time I'll either buy an old vintage preamp and have a buddy help me mod it, he use to work for Threshold. Or, even thought to try the new Schiit Kara preamp, looks good on paper yet I don't know if it lacks real finesse.
If you guys come up with a magical match preamp (vintage or new) that mates up with with Forte' amps, under $1k, i'm interested to learn more. I just passed on a Forte F44, I actually want something super simple, good volume control, 2 inputs, 2 outputs, no frills. That's it.
If you guys come up with a magical match preamp (vintage or new) that mates up with with Forte' amps, under $1k, i'm interested to learn more. I just passed on a Forte F44, I actually want something super simple, good volume control, 2 inputs, 2 outputs, no frills. That's it.
Yes sir, I should have mentioned the other ground breaking preamp that just didn't make sense to me when I first heard. What the Hell is that? I wondered if I was just hearing a proud papa moment. Ok, so here goes: I built the Iron pre because I had never really worked with a build that used audio transformers but I have had a great impression from Cenemag products. Connecting the iron pre to my re-engineered Forte' was certainly a rare experience for me. Cleaner sounding than the B1K, but better balanced as well to my ears. Not a difficult build and in your price range as well. Note that I haven't yet completed the build, so that means that i was just using the volume control that I had handy which is a regular Alps RK27? or something. The RCA jacks were barely acceptable, if not slightly loose. And so, in spite of a couple of less than perfect components, this unit projected a deep and open soundstage. Just the right amount of bass. When you sit down and just keep listening, you know that you have something special. Psst, I added an extra output to mine, and dropped one of the inputs. You can pick your own flavor.
Attachments
Spot on. I'll check out more this weekend. ASK: if it's not too much to ask, can you share the links on where to order the same case, kit, transformers or however you pieced it together. This very clean simpleton looking unit is what I'm looking for if I can configure with exact inputs/output RCAs needed. Seeing the 3 x-formers inside, even better. Wanna check this out. Thanks!
I am a simple man. I do not have links, but there is an entire thread devoted to the Iron Pre. That is the good news. Not so good news, I don't think that the circuit board is in stock right now. But if you will take the time to visit the thread on this forum you will be inspired to find a way. And who knows? There could be one come up for sale. If it doesn't have two outputs , no big deal, you can add another drilled right into the chassis. Same with volume control. You want a different one than what comes with a unit replace it yourself. If it comes to pass, you will not regret it.
BTW, ignore Zen Mod. I mean, what could he possibly know, right?
BTW, ignore Zen Mod. I mean, what could he possibly know, right?
Yes, and? I've been away from this site for a year. I remember something about Sissies, thought was about a small amp, duh, no clue. What say you?
@decooney -
https://www.diyaudio.com/community/...er-your-interest.390509/page-145#post-7538406
This is the thread re: the Iron Pre kits. It has links to all the other threads also.
https://www.diyaudio.com/community/...er-your-interest.390509/page-145#post-7538406
This is the thread re: the Iron Pre kits. It has links to all the other threads also.
There seems to be a lot of insider jokes at this forum, so I have no clue either. I just take what I read for real. Actually I enjoy the oddball humor and reply with my own insider comebacks.
FYI, I just checked the for sale thread and got another couple of SE boards from Itsallinmyhead. Check it out. Now to be honest, these are variants in a way of the original board. In this case, it looks as though SMD parts are used, but I have no idea of how and why. It was worth the chance because they are either extremely low cost or free. Didn't really plan on it but when something is this right, it is worth a chance.
Also saw an SE completed build that SOLD in less than an hour. It is very well worth the effort to look at what people out there may have to offer.
FYI, I just checked the for sale thread and got another couple of SE boards from Itsallinmyhead. Check it out. Now to be honest, these are variants in a way of the original board. In this case, it looks as though SMD parts are used, but I have no idea of how and why. It was worth the chance because they are either extremely low cost or free. Didn't really plan on it but when something is this right, it is worth a chance.
Also saw an SE completed build that SOLD in less than an hour. It is very well worth the effort to look at what people out there may have to offer.
Then the Iron Pre is probably a good bet. I believe part of the design was to have the preamp not impart it's own signature into the sound of the system.. Also, the cinemags in the circuit are pretty sweet.
There are a few other solid-state designs that are nice. The BA3, the BA2018 are two off of the top of my head. I have built both and they are nice.
Rather than shooting for a different threshold amp, maybe you should try your hand at building something. The new F5M is incredibly simple and very good for a beginner build for someone who is comfortable working with mains. It should be in the stores soon!!
I said I didn't find the Forte preamp to sound as good as my Threshold preamps with the Forte amplifier, and I have other vintage solid state preamps that I found sound great with the amplifier.
Building something could be a great alternative as well.
@ItsAllInMyHead @Ixnay @Mikerodrig27 @GKTAUDIO
Thank You for the clarifications, links, and info. I was going to get a Threshold Pre, locally modded, but open to options, your ideas. Thx.
I do like the idea of a kit or having a tech friend build it for me if i dont have time to do it well. Exploring for now. 👍
Thank You for the clarifications, links, and info. I was going to get a Threshold Pre, locally modded, but open to options, your ideas. Thx.
I do like the idea of a kit or having a tech friend build it for me if i dont have time to do it well. Exploring for now. 👍