Search found 2606 matches
- Mon Jul 10, 2023 3:01 pm
- Forum: Technical Discussion
- Topic: cold clipper
- Replies: 13
- Views: 2272
Re: cold clipper
I appreciate the statement about local feed back, stability and a cold clipper. In some jcm 800 bass amps, a 10k biased stage is used very early in the pre for stability. De-generation is useful.
- Sat Jul 08, 2023 3:00 pm
- Forum: Technical Discussion
- Topic: 70s Fender Bassman 100 Head Sounds Harsh
- Replies: 21
- Views: 1963
Re: 70s Fender Bassman 100 Head Sounds Harsh
If the rig was run with no load, your gonna have to start with the power supply and the power side of the amp. You can isolate the input of the phase invertor, grounded to check static conditions, or as a signal input to isolate the power side for testing, signal thru and O-scope analysis. Scrutiniz...
- Wed May 17, 2023 1:47 pm
- Forum: Technical Discussion
- Topic: Single ended EL34 amp design
- Replies: 127
- Views: 9267
Re: Single ended EL34 amp design
El34/el84 are power pentodes, verses 6l6/6v6 which are beam power tubes. The "knee" that optimizes power output curves with the beam tubes has a tone character that is different than the older power pentodes. In general terms, if you mind the limitations of your available parts, like the max heater ...
- Thu Mar 23, 2023 11:40 pm
- Forum: Technical Discussion
- Topic: OPT driven reverb into second amp input
- Replies: 8
- Views: 1041
Re: OPT driven reverb into second amp input
Thats an echo jet. Its a "F" type verb tank, the Input from the speaker + is a RC filter, 300 to 1k paralleled by a large value 50uf (you can play with the value) non-polar cap. You can plug the out put into any thing, any second amp. I've built that one. Fun to gig with, the effect is more of a "di...
- Sun Sep 11, 2022 10:08 pm
- Forum: Technical Discussion
- Topic: Disbalancing paraphase inverter?
- Replies: 22
- Views: 2732
Re: Disbalancing paraphase inverter?
LTP are self balancing, they hold up well and maintain balance, as the tube ages and the dynamic characteristics drift. Paraphase invertors are actually harder to maintain a good balance, the balance changes with gain. The harder you hit it, the more the balance drifts. Remember the basic requiremen...
- Sun May 15, 2022 1:44 pm
- Forum: Technical Discussion
- Topic: Amp shielding
- Replies: 7
- Views: 1285
Re: Amp shielding
I found issues with how the input is grounded, and wire dress, the actual physical wire lay in the chassis, was more important than adding extra shielding. Inside the chassis, some points in the layout are prone to capacitive coupling, long grid wires. Sometimes the choice of wire in a build will in...
- Mon May 09, 2022 3:14 am
- Forum: Technical Discussion
- Topic: Power tube output transformer mismatch
- Replies: 21
- Views: 3774
Re: Power tube output transformer mismatch
Exclude the tube for the moment, and look at the PT and the OPT. The transformer set has its own limiting specifications. The power transformer has a ma. rating for the voltage it provides, and the output transformer has a max primary DC bias ma. rating. Both need to be respected as a limit for your...
- Fri Mar 25, 2022 5:10 pm
- Forum: Technical Discussion
- Topic: Tube preamp pedal output impedance
- Replies: 4
- Views: 994
Re: Tube preamp pedal output impedance
matching transformer
- Fri Mar 25, 2022 3:00 pm
- Forum: Technical Discussion
- Topic: Got lucky and got some tubes
- Replies: 4
- Views: 989
Re: Got lucky and got some tubes
That is a piece of happy. Yup,... I keep my eye's out for old US tubes. Even so far as abandoned TV's in forgotten junk piles in the woods. Having a N. American MFG with an eye towards overall quality is enticing. The Russian stock is/was sometimes pretty good with the commonly consumed tube types, ...
- Thu Mar 24, 2022 7:32 pm
- Forum: Technical Discussion
- Topic: Got lucky and got some tubes
- Replies: 4
- Views: 989
Got lucky and got some tubes
Its a mad house, a mad house,... I got a pair of Tung-Sol EL34B. Totally not expecting the crush and demand. I had to source them in Canada. Every supplier is out of stock and swamped,... Holy Moly So,... New production Tung-Sol EL34B What are your experiences with the current Tung-Sol brand and the...
- Wed Feb 09, 2022 3:37 pm
- Forum: Technical Discussion
- Topic: Best way to start learning about amps? And in what order?
- Replies: 9
- Views: 1738
Re: Best way to start learning about amps? And in what order?
Second that,.. I started before the web,... it was beg bum borrow and steal the informational resources. The more informational resources the better. But, ultimately I pulled together a box of junk and built an amp. Get an iron, a multi-meter, a signal generator and an O-scope. Non of it has to be t...
- Wed Feb 09, 2022 3:18 pm
- Forum: Technical Discussion
- Topic: Fender Blues Jr IV: crackling noise -> no sound
- Replies: 15
- Views: 1967
Re: Fender Blues Jr IV: crackling noise -> contact cleaner -> no sound
spray out the the controls with a good contact or wire harness cleaner, but make sure you re-lubricate the controls with a control/contact /lubricant. I been in too many of those for the same issue for bad resistors in the signal path. Once you re-establish signal thru you can "chop stick" the compo...
- Wed Feb 09, 2022 2:55 pm
- Forum: Technical Discussion
- Topic: 12V to 250V schematic? (Tube in pedal platform)
- Replies: 5
- Views: 1521
Re: 12V to 250V schematic? (Tube in pedal platform)
Back to back 12v/120v transformers. A 12v ac wall wort (120v to 12v) externally with sufficient ma. 12v to 120v internally with a voltage doubler.
From DC you could run a chopper. Old school, just like an old car radio, step up to the required B+.
From DC you could run a chopper. Old school, just like an old car radio, step up to the required B+.
- Mon Jan 03, 2022 1:57 pm
- Forum: Technical Discussion
- Topic: 12AX7 test power supply
- Replies: 15
- Views: 1344
Re: 12AX7 test power supply
You can use a single 12ax7/12at7/12au7 as an adjustable voltage regulator. You'll lose around 50v off the top, with the insertion loss, and a gain a usable voltage range. Simple circuit, tube/socket, a 100r and a 10k ww pot. Has around 5w capacity. From there you can step up the watts by using a pen...
- Fri Dec 31, 2021 6:51 pm
- Forum: Technical Discussion
- Topic: Phase Inverter Choices
- Replies: 16
- Views: 2850
Re: Phase Inverter Choices
LTP came out the need for stability, from oscilloscopes. Self stabilizing and resistant to tube characteristic changes that come with age. Solid, but it operates using feedback, and it cancels even order harmonic distortion. They can sound a bit "hard" or "cold". Good thing is that you can be critic...