Search found 13268 matches
- Tue May 21, 2024 10:24 am
- Forum: Dumble Discussion
- Topic: A SSS Build
- Replies: 33
- Views: 873
Re: A SSS Build
102 amp is still on, Operate, idle-no input. Transformer is very warm, I can only keep my fingers on it for 2-3 seconds. Similar in temperature to SSS transformer. This is after nearly 4 hours operation. Would your SSS run 4h and be at a similar temperature? It has four more preamp tubes, so 1.2A m...
- Tue May 21, 2024 12:47 am
- Forum: Dumble Discussion
- Topic: 2nd Gen Build
- Replies: 81
- Views: 3586
Re: 2nd Gen Build
IMO it would be better if you could get it to cross zero.
- Mon May 20, 2024 10:33 pm
- Forum: Dumble Discussion
- Topic: The Much Anticipated (?) Bluesmaster Build Thread
- Replies: 102
- Views: 3032
Re: The Much Anticipated (?) Bluesmaster Build Thread
- The PAB isn’t quite as pronounced as my 102. Is this a function of the lift pot adjustment? Indeed. - I have the FET biased at a little over V1/Vdd=2 because of what I have on hand. If everything sounds good and there’s no noticeable voltage problems, how concerned should I be about finding the e...
- Mon May 20, 2024 5:42 pm
- Forum: Dumble Discussion
- Topic: A SSS Build
- Replies: 33
- Views: 873
Re: A SSS Build
You could do a shorted turns test on the one you have. See https://ampgarage.com/forum/viewtopic.p ... 11#p445611
Or if you have a power meter you could try energizing the primary with everything disconnected.
Or if you have a power meter you could try energizing the primary with everything disconnected.
- Mon May 20, 2024 3:51 pm
- Forum: Dumble Discussion
- Topic: A SSS Build
- Replies: 33
- Views: 873
- Mon May 20, 2024 2:21 pm
- Forum: Dumble Discussion
- Topic: 2nd Gen Build
- Replies: 81
- Views: 3586
Re: 2nd Gen Build
That lead me to recall some prior discussions here that you are not really balancing the PI as much as the whole power amp. Is that a fair statement or am I misunderstanding? You are correct. The best approach is to arrange the power tubes to get the best DC balance, and then use the PI trimmer to ...
- Mon May 20, 2024 12:55 pm
- Forum: Dumble Discussion
- Topic: 2nd Gen Build
- Replies: 81
- Views: 3586
Re: 2nd Gen Build
I think with 51k/47k plate loads and 22k tail as shown in the 2nd Gen layout, a perfectly matched 12AT7 would have very nearly balanced outputs. Any particular tube might be off in either direction, so keeping the original offset in place with a +/- capability via the trimmer would be the way to go.
- Mon May 20, 2024 9:10 am
- Forum: Dumble Discussion
- Topic: The Much Anticipated (?) Bluesmaster Build Thread
- Replies: 102
- Views: 3032
Re: The Much Anticipated (?) Bluesmaster Build Thread
Frankly, I'm sick of this. If you don't believe it or refuse to try it, good for you, whatever... Marc clearly heard a difference, as have numerous other folks, I applaud him for trying it for himself and making up his own mind. I have never said that I don't believe it makes any difference (and I ...
- Mon May 20, 2024 8:46 am
- Forum: Dumble Discussion
- Topic: 2nd Gen Build
- Replies: 81
- Views: 3586
Re: 2nd Gen Build
While waiting on some parts to arrive I "balanced" the PI. Scare quotes because with the 5K trimmer I installed and the tubes in the amp, I could get close using the ampeg method but not all the way to a 0v offset. It settled around 1.7. I do have another 12AT7 and may try that to see if it gets me...
- Mon May 20, 2024 7:29 am
- Forum: Dumble Discussion
- Topic: A SSS Build
- Replies: 33
- Views: 873
Re: A SSS Build
Replaced rectifier diodes, no change in how it acts. B+ back up to 420vdc range with +/-2vdc drift. Transformer too hot to touch more than a few seconds, maybe 110°F to 120°F. PT's biased to ~15watts (36 mA @ 420 volts).voltages periodically. Still can't figure out why B+ is now 25 volts less than ...
- Sun May 19, 2024 10:36 pm
- Forum: Dumble Discussion
- Topic: The Much Anticipated (?) Bluesmaster Build Thread
- Replies: 102
- Views: 3032
Re: The Much Anticipated (?) Bluesmaster Build Thread
I have to mention how I’m always surprised by the differences in preamp voltages dependent upon the given tube and position - and how they interact both voltage and sound-wise. Below is the combination I like today, lol. Tubes will typically have so much variation in current that the voltages will ...
- Sun May 19, 2024 5:32 pm
- Forum: Dumble Discussion
- Topic: The Much Anticipated (?) Bluesmaster Build Thread
- Replies: 102
- Views: 3032
Re: The Much Anticipated (?) Bluesmaster Build Thread
I currently have it going to the OD relay NO2 per the board plans - but nothing connecting to that cap on the board. I think I’m going to try a jumper from OD relay NO2 to that cap.... Going to try the simplest way first and jump relay to board. That's it. The Eyelet board plan relay connections sa...
- Sun May 19, 2024 2:48 pm
- Forum: Dumble Discussion
- Topic: The Much Anticipated (?) Bluesmaster Build Thread
- Replies: 102
- Views: 3032
Re: The Much Anticipated (?) Bluesmaster Build Thread
Just OD; and with everything maxed out and PAB on. Worst (or best) case for starting an oscillation. Try chopsticking and see if you can make anything change. How would I drive the power amp with 102? Preamp out from 102 plugged into power amp in on BM? Would I use regular cables or speaker cables?...
- Sun May 19, 2024 1:11 pm
- Forum: Dumble Discussion
- Topic: The Much Anticipated (?) Bluesmaster Build Thread
- Replies: 102
- Views: 3032
Re: The Much Anticipated (?) Bluesmaster Build Thread
The OD section volume acts more like a master and the Drive like a pre-amp volume; but even cranked all the way up - still weak. If I dime the master, OD volume, and drive (and pre-amp volume) then switch on PAB - I get a high-pitched whistle (oscillation?). The strange preamp behavior could be an ...
- Sat May 18, 2024 5:43 pm
- Forum: Technical Discussion
- Topic: Can I Parallel 2 Mosfets in VVR?
- Replies: 31
- Views: 784
Re: Can I Parallel 2 Mosfets in VVR?
No slight intended, I just thought it made an interesting plot.