Search found 487 matches
- Tue Jul 26, 2022 5:19 pm
- Forum: Technical Discussion
- Topic: Why Is The Supro Thunderbolt Considered A Great Amp?
- Replies: 22
- Views: 7573
Re: Why Is The Supro Thunderbolt Considered A Great Amp?
That's my schematic, and that's way the amp was that I had on the bench. I though it weird too, but I just captured what was there.
- Tue Jul 26, 2022 5:08 pm
- Forum: Technical Discussion
- Topic: Shipping costs going up?
- Replies: 25
- Views: 2600
Re: Shipping costs going up?
I've always found T&M/CE shipping prices to be on the high side. Now I guess they're even higher!
- Thu Jul 21, 2022 6:47 pm
- Forum: Technical Discussion
- Topic: Carvin VTR 2800 distorted output
- Replies: 11
- Views: 758
Re: Carvin VTR 2800 distorted output
Try strapping an appropriately sized cap across the HT line. I've seen (in rare cases) voltage-sensitive motorboating. I'll bet the HT doesn't drop as much with two tubes.
- Wed Jul 20, 2022 6:21 pm
- Forum: Technical Discussion
- Topic: Step-Up Tranny Needed...
- Replies: 3
- Views: 502
Re: Step-Up Tranny Needed...
The label says 200VA so I'd get a 300VA step-up just to be safe. You'll want a transformer type as opposed to anything electronic.
- Tue Jun 21, 2022 6:42 pm
- Forum: Technical Discussion
- Topic: Function of Input Capacitor on Orange Rocker 30
- Replies: 5
- Views: 844
Re: Function of Input Capacitor on Orange Rocker 30
22nF and 1M has a -3db point of < 1hz, so it's pretty much just for DC.
- Thu Apr 21, 2022 6:36 pm
- Forum: Technical Discussion
- Topic: From 6CA7 to 6L6 ?
- Replies: 10
- Views: 1231
Re: From 6CA7 to 6L6 ?
Here in the States, the "120v" nominal might be 127v coming out of the wall, which makes the B+ 6% higher as well, e.g., 400v -> 423v or 450v -> 476v. This is particularly a problem with older amps using a 115v primary. Certainly the old original RCA 6V6s Fender used were robust, but I don't know if...
- Thu Apr 14, 2022 5:00 pm
- Forum: Technical Discussion
- Topic: Diode drops
- Replies: 6
- Views: 551
Re: Diode drops
It's kinda constant, fuzzily. Not really constant. An inconstant. :) I went back and measured a bunch with my meter diode check function (probably very low current) and the Vf readings were all over the place. The UF400Xs were really low, ~0.41 Vf. So much for leftover schooldays assumptions... :ro...
- Wed Apr 13, 2022 8:27 pm
- Forum: Technical Discussion
- Topic: Diode drops
- Replies: 6
- Views: 551
Diode drops
All my life a standard silicon forward-biased junction has dropped .6 to .7 volts when conducting. The Vishay 1N400x data sheet (https://www.vishay.com/docs/88503/1n4001.pdf) says Vf varies between ~.6v (at low current) and 1.1v at one amp. We have a batch of 1N4007s that are forward-dropping 0.45v ...
- Sun Apr 10, 2022 5:37 pm
- Forum: Technical Discussion
- Topic: Pentode / Triode switch
- Replies: 9
- Views: 941
Re: Pentode / Triode switch
You'd likely need bigger (than 25w) resistors for the Robinette solution, and/or they'd need to have access to plenty of cooling air. Note that I've done something similar (have resistors soak up 75% of the output power), and it's not really that much quieter. I agree with the 99%, I put a triode sw...
- Tue Apr 05, 2022 6:47 pm
- Forum: Technical Discussion
- Topic: Transformer for OTS type circuit
- Replies: 7
- Views: 875
Re: Transformer for OTS type circuit
Well, the "Fender 22921" listed on the schematic is a standard reverb driver transformer, available lots of places. Why not just use that?
- Fri Mar 25, 2022 4:30 pm
- Forum: Technical Discussion
- Topic: Tube preamp pedal output impedance
- Replies: 4
- Views: 1005
Re: Tube preamp pedal output impedance
Depending how "pure" you want to be, you could also use a MOSFET source follower on the output, so you could save the triode for gain instead.
- Thu Feb 17, 2022 4:47 pm
- Forum: Technical Discussion
- Topic: Anyone connect suppressor grids to bias?
- Replies: 25
- Views: 2331
Re: Anyone connect suppressor grids to bias?
Nice work, Martin. Thanks for the hard data.
- Wed Feb 16, 2022 9:03 pm
- Forum: Technical Discussion
- Topic: Anyone connect suppressor grids to bias?
- Replies: 25
- Views: 2331
Re: Anyone connect suppressor grids to bias?
The suppressor is there to improve the curves by reducing the tetrode kink. Evidently it works a little better if its potential is below, as opposed to the same as, cathode voltage. That is true. I didn't mean to imply it had no effect, but rather that 'curve improvement' was probably not the prima...
- Wed Feb 16, 2022 9:00 pm
- Forum: Technical Discussion
- Topic: Anyone connect suppressor grids to bias?
- Replies: 25
- Views: 2331
Re: Anyone connect suppressor grids to bias?
> Tone Lizard's Marshall Myths
Aha, you're probably right.
Aha, you're probably right.
- Tue Feb 15, 2022 5:38 pm
- Forum: Technical Discussion
- Topic: Anyone connect suppressor grids to bias?
- Replies: 25
- Views: 2331
Re: Anyone connect suppressor grids to bias?
I could have sworn that I read somewhere (but cant find it right now) that making the suppressor grid negative helps limit max plate current in extreme situations, which makes a little sense intuitively (and is supported by Andy's anecdotal evidence). Since the grid's primary purpose is to direct el...