Practically, with 2 output pairs - some 120W.
Although, with 4 pairs, maximum power will increase up to 200-220W (roughly 40V RMS at the output) - no other modifications required.
I was curious what this amp would actually output with such high voltage rails but so few output devices. Do you think there would be any difference sonically at lower output levels with more output devices? If I ever ran my speaker at 120 watts it would likely blow me out of my chair but they seem to like high voltage.
I don't think more outputs will bring some noticeable benefits at the lower volumes.
Two is enough for 8 ohm load. Four devices will allow driving lower speaker impedance, if required - that's the major benefit of such an enhancement.
Two is enough for 8 ohm load. Four devices will allow driving lower speaker impedance, if required - that's the major benefit of such an enhancement.
I guess the best idea would be to try it. I was really surprised by the CFA-CFP. I was only testing it on 40 volt rails and it still sounded much better than most higher power amps I've tried.
Right.
Well, both of these designs are rather low distortion, in the wide range of output levels, having their own signatures though. My impression - CFA-CFPx2's sound is a bit more "crisp", providing the tightest control over the speaker, while TubSuMo hybrid is more "elastic", very comfortable for long-time listening. Although, both of them provide very high resolution at mids-highs.
Well, both of these designs are rather low distortion, in the wide range of output levels, having their own signatures though. My impression - CFA-CFPx2's sound is a bit more "crisp", providing the tightest control over the speaker, while TubSuMo hybrid is more "elastic", very comfortable for long-time listening. Although, both of them provide very high resolution at mids-highs.
valery,
Thanks for taking the time to work this up. It will take me a bit to digest your plan. I can do balanced input or single ended. Starting with double outputs and a single input looks OK. Here are a couple pics of the amps as they stand now...should be no problem to add a second output stage. 600va transformer and good amount of space. The heatsink with boards attached slip right out of the case for easy playing.
Evan
Thanks for taking the time to work this up. It will take me a bit to digest your plan. I can do balanced input or single ended. Starting with double outputs and a single input looks OK. Here are a couple pics of the amps as they stand now...should be no problem to add a second output stage. 600va transformer and good amount of space. The heatsink with boards attached slip right out of the case for easy playing.
Evan
Attachments
Nice job Evan! Funny, I'm a retired carpenter and I never think to build cases out of wood.
Speaking of power, my P101 uses just two pair of latfets and it runs on +-70v and will do 300W into 4 ohms all day long. It was my first amp build and got a lot of use into 4 ohms. I built it three channel thinking I would use it for the front end of a 5.1 system but ended up just using the center channel for sub duty and it worked beautifully for that too. Unless you are doing DJ work, I'll be surprised if you would ever notice the extra pair of outputs.
Speaking of power, my P101 uses just two pair of latfets and it runs on +-70v and will do 300W into 4 ohms all day long. It was my first amp build and got a lot of use into 4 ohms. I built it three channel thinking I would use it for the front end of a 5.1 system but ended up just using the center channel for sub duty and it worked beautifully for that too. Unless you are doing DJ work, I'll be surprised if you would ever notice the extra pair of outputs.
What kind of DC offset should I expect to see with the servo pulled? Is -6V excessive? One input is around -6, the other is around +4.
The offset seems to move with the tubes. I swapped them and the voltage went with them. I think I'm going to try to sort out the uneven VAS current with the servos out of circuit, then worry about offset later.
Right, tubes tolerance influence is rather significant... Right, makes sense to sort out the VAS current issue first.
Hi Valery,
I'm ready to populate the Fetsumo IPS. I'm planning to run it around +-60V. Can you tell me which parts need to change from the Tubesumo IPS for the Fetsumo? I don't want to miss any.
Thanks, Terry
I'm ready to populate the Fetsumo IPS. I'm planning to run it around +-60V. Can you tell me which parts need to change from the Tubesumo IPS for the Fetsumo? I don't want to miss any.
Thanks, Terry
Hi, Valery. Thanks for providing this interesting design. I bought Terry's last boards, so I'll be following other FetSuMo (and the tube version) builds with great interest.
Hi Soldersmoker,
Thanks for your interest!
The tube version is pretty well tested by myself and Terry. With no soldering mistakes and good components it starts working right away (my second channel started up with no problem). FET option is going to be tested by Terry for the first time - looking forward to see the results as well 🙂
Cheers,
Valery
I would be happy to try the tube version, but it looks like the power transformer I'm dying to finally use will only produce 62 volts at the rails (45-0-45). So, FET it is, at least for now.
You can likely use the 62 volt rails on the input stage with tubes and the 45 volt rails on the output.