regulated bench power supply for tube builds

[beatnik]

i am looking for a high voltage regulated power supply for testing and experimenting with tube circuits and guitar amplifiers

i have seen there are a few vintage tube based supplies but they come up quite rarely and often expensive, for example the fluke 407

i have found a few diy circuits on the net but most of them seem to have a lower current supply for the hv section

this circuit i found has a rating of max 350V at 100mA which might be ok for some preamp designs but not enough for bigger guitar amps

i am wondering if you have anything to suggest. what about switch mode supplies ?

 

[PRR]

> regulated power supply for testing and experimenting with tube circuits

Why?

Tubes don't need regulation.

Build a small ~~400V raw supply and use R-C droppers/filters to get your 300V, 250V, whatever.

POWER amps are so integrated with their power supplies that IMHO a "Universal" big power supply is not warranted unless you are in the business of prototyping power amps. Even then, a collection of DeLuxe, 5F6a, and Twin power supplies will cover most cases, at least far enough to specify a specific supply.

 

[PRR]

> this circuit i found has a rating of max 350V at 100mA

So? Double-up the PT and big bottles, it is 200mA, etc. Raise the PT's V rating, it can be 600V. At this point you may be stressing the 250V 6080's to get lower output; triode-strapped 6L6 or 6550 will stand the strain and are more in the guitar-amp family. Though I would seriously consider MOSFETs. And BIG heatsink.

You see this can quickly become a much bigger project than a whole heap of amplifiers.

 

[beatnik]

Why?

Tubes don't need regulation.

in fact it doesn't have to be regulated, but variable at least.

i am currently experimenting with a few circuits and i think it would be much easier to use a single power supply with a voltage adjustment, instead of tweaking the power supply resistors for every different circuit

i think i am going to give the circuit in the schematic above a try. probably will swap the bottle rectifier in favour of diodes

Double-up the PT and big bottles, it is 200mA, etc. Raise the PT's V rating, it can be 600V. At this point you may be stressing the 250V 6080's to get lower output; triode-strapped 6L6 or 6550 will stand the strain and are more in the guitar-amp family. Though I would seriously consider MOSFETs. And BIG heatsink.

the power transformer in the schematic is rated at 700V center tapped, why are you suggesting to changing to 600V ?

are 6L6 / 6550 capable of delivering more current as well ?

the idea of using mosfets sounds good and possibly cheaper and more reliable on the long term, however i don't know any circuits that i can copy from. let me know if you have any suggestions

 

[emrr]

I have a lovely variable supply from the 1930's which is a standard CLC circuit, but with a variac as input.  One idea.  Many console supplies of old use a power rheostat (those are getting expensive) as one of the series R elements.  Another idea.  Similar, there are also tapped power resistors, not as user friendly. 

 

[CJ]

Heathkit 

has B+ and C- variable.  and heater.

150-220 $ on evilbay, about the same cost as your materials and labor,

just the coolness factor is worth 300. 

 

[gridcurrent]

Hewlett-Packard (Agilent/Keysight) 6209b
https://www.keysight.com/en/pd-1000001527%3Aepsg%3Apro-pn-6209B/single-output-power-supply-0-320-vdc?cc=US&lc=eng

Eico 1030

Heathkit IP-17
aka SP-2717a

 

[Bo Deadly]

London Power PSU-10 sounds like what you want. Although at $320 USD it seems strangely expensive for what it is. And for a guitar amp I think it's important to use a EL core transformer and dropper resistors and caps of just the right size so that when the power amp section is overdriven the PT saturates and sags as it would in a real amp. It's a legitimate form of compression I think.

 

[buildafriend]

I have a lovely variable supply from the 1930's which is a standard CLC circuit, but with a variac as input.  One idea.  Many console supplies of old use a power rheostat (those are getting expensive) as one of the series R elements.  Another idea.  Similar, there are also tapped power resistors, not as user friendly.

I began to wonder just a few weeks ago why I have not yet built an RC HT supply with a variable voltage from the mains xfrmr. It would be great to have something similar for filaments as well.

 

[rackmonkey]

A company called Buck Engineering made cheap, simple, virtually indestructible variable power supplies for schools and vacational training with variable B+ and filament voltages under the Lab Volt brand.  All based on a variac like EMRR suggested. You can find them on eBay cheaper than the Heathkits and the HPs.  They used the old paper tube electrolytics for filters, so you’ll almost always have to replace those. But they work well enough for a bench supply. I picked up a model 354P that will supply up to 400v B+ at 100ma for $39 about 5 years ago. Also have 3or 4 variacs made by them. Built like tanks and most are olive drab color to drive that fact home. I’ve seen higher current versions of the PSs for sale before, so I’m sure you could eventually find one of those for guitar amp work.

Had to put a voltage regulator circuit in for the filament supply, probably because mains voltages in the US were lower back in the day and it was putting out almost 2 more volts than it should have once I replaced the caps.  But works fine and I test all my small signal stuff with it. I use actual guitar amp PSs for power amps like PRR suggests.

You might also look for an Oregon brand bench supply. Less common than Lab Volt but they look like they’d do the trick too.

Just spitballing here.

BT

 

[emrr]

Lab Volt!  Yes, I have one of their large instructional console models with several variable supplies and a bunch of different metering, etc.  Takes 2 people to carry, almost.  I haven't seen any of their smaller product, but this one is really well made.  Practically free at a Hamfest. 

 

[Gene Pink]

Practically free at a Hamfest.

Gotta love hamfests. Catch up with old, similarly minded friends, find that certain widget you have been seeking for years.... that you no longer need. And can't remember why you needed it in the first place.

A Lambda model 50 supply.

* 0-500V/500ma, regulated
* Bias supply 0-50V, or 0-200V, switchable
* Two 6.3V/5A filament, can be in series for 12.6V
* Holds the record around here for the most 6L6's in a single chassis. A literal forest of 'em.
* Weighs more than my wife.

FWIW,
Gene

 

[gridcurrent]

Lambda C-881m
0-350 VDC @ 800 mA
6.5 VAC @ 20 A

 

[emrr]

I have an HP that does variable up to 320 @ 1.5A

 

[Gene Pink]

I fold.

Gene

 

[emrr]

I'm actually a little scared to use that thing.  Who needs that?!?!

 

[rackmonkey]

Lab Volt meter panel. Another hamfest find. Traded a Heathkit audio analyzer (I had 2) for it. Bigger than it looks - about 24 inches wide. I clip the inputs to test sockets when building/repairing stuff on the bench.  Probably made from scrapped armor from Sherman tanks from WWII.

Doug, I think I've seen the unit you mentioned you have. Does the meter section look something like this?

BT

 

[emrr]

Yes, that looks like the top of mine, though I don't think mine has separate panel sections. 

 

[Whoops]

i am looking for a high voltage regulated power supply for testing and experimenting with tube circuits and guitar amplifiers

i have found a few diy circuits on the net but most of them seem to have a lower current supply for the hv section

this circuit i found has a rating of max 350V at 100mA which might be ok for some preamp designs but not enough for bigger guitar amps

i am wondering if you have anything to suggest. what about switch mode supplies ?

For less than 5 dollars you can get this module, 45 to 390V Variable output, 200mA maximum output current.
You just need to inject between 8 to 32V at the input. I have quite a few of these units and it works great. Probably the cheapest and easy you can have,  you just need to replace the trimmer with a POT and put it in a box:

https://www.ebay.com/itm/DC-DC-8-32V-to-45-390V-High-Voltage-Boost-Converter-ZVS-Step-up-Booster-Module/172766818056?ssPageName=STRK%3AMEBIDX%3AIT&var=471553905847&_trksid=p2057872.m2749.l2649

 

[PRR]

> For less than 5 dollars you can get this module

Shows $6.67 today--- maybe pegged to BitCoin?

And..... "Applications:  Hunting,eradication of mice"  ?