Search found 13103 matches
- Wed Apr 17, 2024 8:49 pm
- Forum: Dumble Discussion
- Topic: Bluesmaster HRM question:
- Replies: 37
- Views: 1195
Re: Bluesmaster HRM question:
I see the 5k1s on the power tubes at grid 1 are soldered directly to the leads heading back to the main board (like an old Marshall or Vox). This looks simple enough, but just wanted to check as to the correct mechanical connection before soldering. Is this a “J” hook situation or is there another ...
- Wed Apr 17, 2024 1:04 pm
- Forum: Dumble Discussion
- Topic: Tweedle Dee on Carter
- Replies: 33
- Views: 890
Re: Tweedle Dee on Carter
5Y3 rectifier will make a big difference too.Stephen1966 wrote: ↑Wed Apr 17, 2024 12:48 pmI'm also thinking that the voltages in this amp are not going to be as high as in the first Tweedle Dee, stock transformers and only three filter stages with a stock (value) 250 Ohm bias resistor on the power tubes.
- Wed Apr 17, 2024 1:00 pm
- Forum: Dumble Files
- Topic: SSS Step filters - Here's what I think
- Replies: 22
- Views: 13589
Re: SSS Step filters - Here's what I think
To be strictly correct in eliminating position 1 you would do this:
- Wed Apr 17, 2024 12:06 pm
- Forum: Technical Discussion
- Topic: Taming amp gain in single channel deluxe reverb build
- Replies: 14
- Views: 272
Re: Taming amp gain in single channel deluxe reverb build
I'm having trouble following you. Maybe refer to the TP (test point) number where you are measuring? What is "PT"?
- Wed Apr 17, 2024 11:04 am
- Forum: Dumble Files
- Topic: SSS Step filters - Here's what I think
- Replies: 22
- Views: 13589
Re: SSS Step filters - Here's what I think
Good to hear you are happy with the result! Yes I have made some small adjustments re the schematic at the top of this thread. What you posted just above is the latest. There are a couple of ways you could do six positions, one would be to recalculate all of the resistor values to keep the "taper," ...
- Tue Apr 16, 2024 10:57 pm
- Forum: Dumble Discussion
- Topic: Tweedle Dee on Carter
- Replies: 33
- Views: 890
Re: Tweedle Dee on Carter
One example of a Tweedle Dee has been documented already thanks to CW, but I suppose there might be some interesting evolutionary changes in this later example.
- Tue Apr 16, 2024 4:19 pm
- Forum: Technical Discussion
- Topic: Output Transformer formula?
- Replies: 11
- Views: 314
Re: Output Transformer formula?
Take a look at the free .pdf download Phil S posted to see if you really want a hard copy. You can get virtually any tube data sheet from https://frank.pocnet.net, and that is what most of the 750 pages of RC-30 contain, and in an abbreviated format. The remaining 200 pages cover circuit theory and ...
- Tue Apr 16, 2024 10:00 am
- Forum: Dumble Discussion
- Topic: Eq's in Dumble 50w out of
- Replies: 11
- Views: 309
Re: Eq's in Dumble 50w out of
Maybe a failed R/J switch that is not closing in Rock setting, resulting in PAB? Measure resistance across switch pins.
- Mon Apr 15, 2024 2:41 pm
- Forum: Technical Discussion
- Topic: Output Transformer formula?
- Replies: 11
- Views: 314
Re: Output Transformer formula?
Is this formula legit? (B+ voltage squared)/(Plate dissipation x number of power tubes) Example: a 50w (6L6GC x 2) build using a known PT and circuit that consistently produces a B+ of ~455vdc- 455x455 = 207,025 35 x 2 = 70 207,025 / 70 = 2,957.5; So the correct primary impedance would be around 3k...
- Sun Apr 14, 2024 1:46 pm
- Forum: Technical Discussion
- Topic: Impedence Selector Circuit Help
- Replies: 4
- Views: 99
Re: Impedence Selector Circuit Help
The wire from the 16 ohm tap back to the main board is the negative feedback, so keep that on the 16 ohm OT tap. If all you want is 4 and 16 ohm outputs, you could just use two speaker jacks, one on the 4 ohm and one on the 16 tap, and eliminate the selector. I would use a switching jack for both, a...
- Sun Apr 14, 2024 1:12 pm
- Forum: Technical Discussion
- Topic: Regarding the B+mosfet reducer and power ground
- Replies: 10
- Views: 267
Re: Regarding the B+mosfet reducer and power ground
...I want the filtercaps to have a reduced differential voltage (that is the sole goal) but, I don't necessarily want the bias voltage scheme to change too widely. So yes, it would make some sense that moving the bias ground with the HT CT to the B+reducer makes sense but, not the filter cap cathod...
- Sat Apr 13, 2024 5:06 pm
- Forum: Technical Discussion
- Topic: Regarding the B+mosfet reducer and power ground
- Replies: 10
- Views: 267
Re: Regarding the B+mosfet reducer and power ground
A MOSFET reducer, just like a zener in the same position, just places the high voltage CT one zener-voltage below the negative end of the first filter cap. As long as nothing else is connected and referenced to the CT, this all works fine, as the high voltage winding is galvanically isolated, and w...
- Sat Apr 13, 2024 3:07 pm
- Forum: Technical Discussion
- Topic: uTracer (Micro Curve Tracer)
- Replies: 297
- Views: 81053
Re: uTracer (Micro Curve Tracer)
As you can see, I settled on three sockets, 7, 8, and 9-pin. Anything else can be jury-rigged, and you can see several examples of that pictured in this thread.
I recall one uT3 build with just three sockets, all hard-wired, two as I described above, plus a second noval for EL84's.
I recall one uT3 build with just three sockets, all hard-wired, two as I described above, plus a second noval for EL84's.
- Sat Apr 13, 2024 1:09 pm
- Forum: Technical Discussion
- Topic: uTracer (Micro Curve Tracer)
- Replies: 297
- Views: 81053
Re: uTracer (Micro Curve Tracer)
I believe Tony D is using uTMax https://ampgarage.com/forum/viewtopic.php?p=450229#p450229 It has been around for quite some time (2015, maybe?), originally intended to increase voltage and current capability of the uT3. The uT3+ with 400V max Va/Vs and high-current mod is more than adequate now. I ...
- Fri Apr 12, 2024 11:45 pm
- Forum: Dumble Discussion
- Topic: Bluesmaster HRM question:
- Replies: 37
- Views: 1195
Re: Bluesmaster HRM question:
Looks that way. One is STMicro and the other is TI. There will be different suffixes for different manufacturers or things like NoPb.Raoul Duke wrote: ↑Fri Apr 12, 2024 8:28 pm Are the LM7812CT and L7812CV functionally interchangeable?