jazzbass wrote: ↑Sat Apr 10, 2021 9:55 amI need a suggestion for the Hammond transformer, which transformer should I look for for the European wall voltage of 220V?
I don't know of any single transformer that has the specs you are after.
Another option would be to use two flat-pack transformers: https://www.hammfg.com/electronics/tran ... er/229.pdf These are quite small in size, and inexpensive.
I would use 229E12 for the heaters, and 229B230 for the plates. The 229B230 has 230VAC secondary voltage with 230VAC input at full load (50mA). The regulation is not very good on small transformers, so the voltage will be quite a bit higher at partial load.
I have a very similar Triad FP230-50 unit here, and I measure 258VAC on the secondary (series connected) at 110VAC input (primaries connected in parallel) with no load. That would result in 363 VDC using a full wave bridge, again with no load. You would of course connect the primaries in series for your 220VAC line voltage. You won't be using anywhere near 50mA, so the voltage will not sag much. If I add a 50k load resistor to the secondary, the voltage only drops to 254, and that would be 5.1mA, more than enough for the two triodes in the D'lator, and that produce just about 360VDC.
Hi Martin,
thanks for the suggestions, I have difficulty in finding these transformers available in Italy, one is available and the other is not.
At home I have a transformer bought years ago for this project which I then never realized, it is a toroidal transformer purchased from Tubetown, the tt-t47 with these characteristics:
P = 47 VA
Pri: 0-220 or 230 or 240 Volt
Sec: 250 Volt - 6.3 Volt - 12.6 Volt
It could go well? I'm worried about the voltage of 250 volts at the secondary .......
martin manning wrote: ↑Mon Jun 22, 2020 4:43 pm
Some recent discussion on the send buffer and cable loss (https://ampgarage.com/forum/viewtopic.php?f=4&t=32162) got me looking into the frequency response. It's true that the buffer is not very well equipped to handle long cables with its 250k send pot, and that will be a problem if the buffer's output is run out to a pedal board. Attached below is a tweaked schematic that addresses that, and includes an alternate power supply using a current production Hammond transformer that will fit in a 1u rack box.
The lower value send pot is accommodated by raising the cathode resistor and tweaking the bias point. If that is all you are after, you can just change the pot, Rk, and Rbias, and leave everything else alone.
Martin! I'm going to build a Dumblelator (why not?) based on this rev schematic you posted—since finding the original branded/speced PTs is seemingly quite the effort. The Hammond is readily available. If you have a moment maybe you could spot-check the layout I made for the power board (using current radial caps)? My understanding of your schematic shows only value changes for the main circuit board, layout is the same. Thanks! I'll still tweak the power board size since the mounting holes are probably a little tight.
(Still LOVE the #183, I'm really only beginning to understand what a gift is as my guitar skills sloooooowly improve—would have been A LOT more work without you and Ian.
Dumbleator_Update_MPM.png
Dlator_Rev_Layout_MPM.png
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Here's a slight adjustment to Martin's boards with measured components that I have, clearly Martin's build is insanely tidy, but parts I have here wouldn't have fit in a few places—including the small L-brackets I tend to use all the time. I also would prefer to mount the socket directly to the G10 as opposed to using standoffs, with a bigger hole and the pins out the back, like we do all the time with chassis mount—had to make clearance for the mounting rim of the socket. I don't have all the components in hand yet—so, not quite tested.
Dlator_Rev_Layout_MPM_r2.png
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I have built a Dumblator following your schematic may 2020, I have a question, I want to use a Stand-By switch, is correct to put after the two condenser 47uf or after the 2K2 2w resistor?.
Not sure why you would want a standby, but you could put it next to the 2k2, either side, or you could switch the PT secondary AC voltage feeding the stacked capacitors. Switching the AC might be the better option.
the stand-by switch is the first thing that came to mind to set the Dumblator's potentiometers, starting from an equal volume with and without its use. I could disconnect the Dumbulator connections from the back of the amp but that's inconvenient and time consuming and I don't have a direct comparison.
I believe that the setting of the "Recover Input", "Recover Output" and Drive potentiometers are done by ear and if I want to perceive the effect on the sound and overall volume I should be able to compare them with the sound of the amplifier, hence the idea of using a Stand-by switch.
Obviously any suggestion is welcome .
Hi all, I'm new here, with a basic understanding of electronics. I have ordered a Elator PCB from AA Electronics and I'm looking for a power transformer for the build. Here in Australia the wall voltage is 240V. I have identified the Hammond Transformer 262EE6 that has a primary of 120v or 240v with a secondary of 120v 93mA and 6.3v 1.2A. (On Martin's advice I've ordered a Toroidal Transfromer 1N1729 125V 30mA secondary)
Looking at the two schematics in this thread, AA Electronics & MP Manning, the target B+1 voltage is 360V dc. B+2 260V dc.
I have the book "Designing Power Supplies for tube Amplifiers" by Merlin Blencowe. Ref pages 67 & 68 it looks like the voltage doubler in the two schematics in this thread is a Delon circuit voltage doubler. Two opposite half wave rectifiers. So with the two capacitors C1 & C2, the circuit could be drawn as a bridge rectifier replacing two of the diodes in a FBR with C1 & C2. C1 & C2 will add as they are in series with each other.
Edited after more reading.
Vout = 2Vpk - 2Vd (diodes) Full Wave Voltage Doubler.
262EE6 Vout = (2x120) - (2x 0,7) = 238.6 Vdc
If secondary was 125 Vdc 262A12, (or 1N1729)
Vout = (2x125) - (2x0.7) = 248.6 Vdc
What am I missing, as the schematic says B+ 365
Current draw through the 2k2 is 2.27mA (5v drop across the 2k2 R). And then, 2.27mA throught the 100K R on the plate of the output stage of B+1 = 227.2V (228V listed on the schematic). All looks good.
I just can't work out how we get to the 365V B+
If I think of the CCT as two half wave rectifiers with C1 & C2 in series, then 125V AC x 1.414 = 176.75 x 2 = 353.5 VDC. This is close enough to B+ of 365. And it makes sence.
Can anyone help?
Regards,
Steve
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Last edited by Steve AA1164 on Tue Jul 15, 2025 11:50 am, edited 2 times in total.
A 120VAC secondary with a FW Doubler will produce (120*1.414 - 0.7)*2 = 338 VDC. You could work with that by adjusting the resistor values to 1k and 68k, and run the recover stage at 330V, but that transformer has much more secondary current than you need, and might well produce higher voltage with the light load. One might consider this transformer and a FWB rectifier: https://www.hammfg.com/files/parts/pdf/ ... 1726162978 Same physical size, with plenty of voltage and current. But in this case, it doesn't look like the E-lator PCB has a FWB option.
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, the idea is simple to implement, effective and without contraindications.