😱 sorry I meant if the reg can take like in the second stage 41v bias on 33r plus 7.5 on filament + some volt for regulation =55/60v ?
in this filament bias if I understand well what is fix is the filament current 1.25A the bias is set by voltage drop on resistor rigth ?
plus add the 7.5v we have the psu B+ after the reg...
Oh nice with the ccs we can match the tubes with resistor the bias pont
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O, I see - you mean how much voltage durability?
I can make a 60 to 80V version, or even higher.
I can make a 60 to 80V version, or even higher.
Hi Rod, I recieved the boards and bits yesterday. WOW, is it small....but very solid. I am a large metal sculptor and I work in tonnage. I direct wire all my amps so this will be interesting. I stopped by Radio Shack after I got the boards and bought a new small pointy tip for my soldering station.
This is all very timely as I have been working for the last three days finishing the chassis for the GM70 amp. It has turned out beautiful...even if I say so myself. This week I will assemble your boards and wire up the PS and then start working on the signal path.
Thanks again. Dennis.
This is all very timely as I have been working for the last three days finishing the chassis for the GM70 amp. It has turned out beautiful...even if I say so myself. This week I will assemble your boards and wire up the PS and then start working on the signal path.
Thanks again. Dennis.
There's still some kits available, from 100mA DHTs all the way up to big Transmitters. Just click on my username to send me some PM. I can send PDF manuals covering the build and use of the regulators, and a list of the different types, and the prices (DIY-friendly) etc etc!
Here is the chassis in the rough. I should have it done this week and ready for wiring. The top plate is 1/4" aluminum and measures 19" w x 16" d. I am thinking it will weigh in at 50 lbs or so. The two holes in front of the cab are for the 6D22S reg tubes, the big holes next to the potted choke are for the GM70 and the little holes in front of those are for the 12HL7 driver tubes. Two stage SET with CCS on the driver tubes. I am thinking about 10 wpc or so. B+ is 870v.
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I wired the Rod's regulators a couple hours ago on my 211 preamp. Embarassing ... I was using CLC and a LM1084 CCS. The difference is really HUUGE. Thanks Rod!
Rod
I'm not much of a buyer , but I'll be grateful to have handy complete documentation of your excellent work with these heating circuits
if that is convenient to you , just shoot me with pdfs on >sasica5@gmail.com<
if not - I can always go back to this thread and dig
Thanks Gianluca! The IC regulators like Lx108x are a long way from showing what CCS/double buffered heating can sound like. The IC's current-control loop is exposed to the anode current (via the ac-voltage across the filament), and this gets mixed together with the heating-current control. The SIGNAL voltage across the filament is very small, so it doesn't need a very big error (% of heating current) to have a bad effect.
Guido is a professional, so I would expect a good performance from his solutions.
His DHT heater module is very different from mine - I *believe* he uses a single Power-FET current sink, with an opamp control loop. My solution is all discrete, buffered on both sides of the filament.
I have compared my circuit with many other voltage-loop and current-loop designs, including the IC regulator current sources - and found the discrete solution to be the best sounding; but I have not tried the Tentlabs solution, so I can't compare the performance. But I believe that some of the buyers of my kits have tried both ..... anyone out there like to make a comparative review???
His DHT heater module is very different from mine - I *believe* he uses a single Power-FET current sink, with an opamp control loop. My solution is all discrete, buffered on both sides of the filament.
I have compared my circuit with many other voltage-loop and current-loop designs, including the IC regulator current sources - and found the discrete solution to be the best sounding; but I have not tried the Tentlabs solution, so I can't compare the performance. But I believe that some of the buyers of my kits have tried both ..... anyone out there like to make a comparative review???
Hi Rod or anyone else who would care to comment,
As per your suggestion I got some MBR 1045 diodes for my GM70 supply. And 3 4700uF/63V Panasonic HA.
Anyway. My question is. Should I heatsink the diodes? (GM70 pulls 3A/20V)
Kind regards,
Bas
As per your suggestion I got some MBR 1045 diodes for my GM70 supply. And 3 4700uF/63V Panasonic HA.
Anyway. My question is. Should I heatsink the diodes? (GM70 pulls 3A/20V)
Kind regards,
Bas
Hi Bas, I have run MBR1045 in a bridge - supplying GM70 at 3,0A for hours at a time without heatsinks. BUT they do get quite hot, so it would be kind to give them a little heatsinking.
A piece of 2mm thick Alu sheet, maybe 75mm x 120mm should be plenty; or attach them to the chassis.
If you have the non-isolated diodes, then please use insulation/mica sheets - I think the Tab is connected to one side of the diode.
Look forward to hearing how you like the GM70 sound!
A piece of 2mm thick Alu sheet, maybe 75mm x 120mm should be plenty; or attach them to the chassis.
If you have the non-isolated diodes, then please use insulation/mica sheets - I think the Tab is connected to one side of the diode.
Look forward to hearing how you like the GM70 sound!
hello Rod,
Thanks for your comments. I am following your work here once and a while, and would like to ask you why you create high impedances at both sides of the filament ? Oe of the ends should be connected to ground (or cathode resistor) anyhow, hence sees a low impedance to ground.
The downside of 2 active devices at each side is heat dissipation, you'll probably be aware of that 🙂
Since I deliver to a variety of customers, I decided to optimize for low dissipation as well, hence the single FET.
keep up the good work
best
Guido
So Bas ... are you building the GM70 amp? Eventually ... I believe I first heard about you building that amp 3, maybe 4 years ago?? LOLz
That is a great tube! It deserves a great driver.
Gianluca
That is a great tube! It deserves a great driver.
Gianluca
It'll be a while. 🙂
Thanks Rod. I'll add a little heatsink to each diode.
I have done little for years accept hoard transformers. And biding my time. I just recently got mains transformers. (Rejects) So I got my hopes up.
But I am "active" again. Building a guiter amplifier. A little refurb for my brother. Still putting the finishing touches to my Baby Huey. Added a srpp tube stage behind my passive (transformer/resistor) i/v dac stage. Going to build an amp with one of my boys. Just built Rod's heaters for a 300b and for a future 2a3 and for a future preamp 801A. Reading your posts over at MQ forum. Etc. Etc. Etc. 😉 O I forgot... and I have to go to work to. And dancing lessons. And gym. And cycle. And play rugby. And watch movies. I've given up on pleasing my wife.
So I will hopefully have the GM70 running early next year. 🙂
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