Search found 13266 matches
- Mon May 20, 2024 10:33 pm
- Forum: Dumble Discussion
- Topic: The Much Anticipated (?) Bluesmaster Build Thread
- Replies: 101
- Views: 2974
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: 29
- Views: 765
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: 29
- Views: 765
- Mon May 20, 2024 2:21 pm
- Forum: Dumble Discussion
- Topic: 2nd Gen Build
- Replies: 80
- Views: 3527
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: 80
- Views: 3527
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: 101
- Views: 2974
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: 80
- Views: 3527
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: 29
- Views: 765
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: 101
- Views: 2974
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: 101
- Views: 2974
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: 101
- Views: 2974
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: 101
- Views: 2974
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: 30
- Views: 756
Re: Can I Parallel 2 Mosfets in VVR?
No slight intended, I just thought it made an interesting plot.
- Sat May 18, 2024 11:44 am
- Forum: Technical Discussion
- Topic: Replace overdrive pedal with real tube?
- Replies: 7
- Views: 242
Re: Replace overdrive pedal with real tube?
Guyatone tube pedal? There are a couple of versions: https://juggbox.blog.jp/archives/15803877.htmlSpeedypancake wrote: ↑Sat May 18, 2024 9:39 am Can you help me turn it into a simple overdrive circuit to replace the Guyatone pedal??
- Sat May 18, 2024 10:34 am
- Forum: Technical Discussion
- Topic: Can I Parallel 2 Mosfets in VVR?
- Replies: 30
- Views: 756
Re: Can I Parallel 2 Mosfets in VVR?
When the voltage drop across the MOSFET is larger, the voltage on the tube plate is smaller. When the voltage on the tube plate is smaller, the tube draws less current. So when the drain-to-source voltage increases, the drain-to-source current decreases. Let's graph that: MOSFET Dissipation 1.JPG T...