New DHT heater

[petavgeris]

Check!

[djn]

Thanks Rod. As it is designed now, the main B+ is on the main chassis, but I still need room for the GM70 filly supply, 6.3v for the 12GH7, 5v for the rec tubes, and 350vB+ for the 12GH7. When I looked at the main chassis there just is not that much room. I'll let you know how it turns out.

[petavgeris]

Originally Posted by Rod Coleman

You're doing the right thing, for sure!

Keep the transformer/caps/rectifier in the PSU chassis, and run the raw dc to the signal chassis. The regulator should be within about 150-250mm (6-10") of the tube socket. Put 1000uF/35V on the PCB supply input terminals, and let us know how it sounds!

A little add-on here...
If it is unavoidable to use capacitors in both two chassis, try not to parallel them. Paralleling power supply capacitors either on filament or on HV supply does something really bad on sound. Do not place caps on both chassis. I would prefer the diodes on one chassis and the caps on signal chassis. Best solution is of course to use a pi filter C-L-C with the first CL section on PS chassis and C with the regulator on signal chassis.
Just my two cents...

[dixchen]

Originally Posted by petavgeris

One more surprised victim here :-)
Yesterday I finished the DHT regulators. Last stop was Rod's solution. I have tried crazy and out of this world ideas there, even tripple chokes, two differential and one monstrous common mode right before the filament.
Rod's circuit gave something I was missing till now. When switching back to common mode choke (22H of inductance!) I felt I missed a great part of immediacy and dynamism of music. I will try to replace 1-2 parts with better sounding ones, I think it deserves so because the result is fantastic.
I will be back with more news during the days ahead.

Immediacy and dynamism of music, you got that right mate!

I owe this post to Rod as I promised him a review of his regulators sometime last year after implementation of it in my various customized DHT amps.

To date i have bought no less than 5 pairs of his regulators with the initial implementation in my troubled customized built for me type 26 line stage.
This line stage arrived at my door step with hum and rf noise issues and when I questioned the builder he told me it was normal and was beyond what could be done for the very hum my type 26 tube. I was not convinced!

Various postings and links on the very long type 26 preamp discussion also in this forum led me to read bout rod's regulators. I mean dc regulators aren't new so what's diff on this one, I really don't know then. I wrote to rod and got a reply with very favorable response as well as a no brainer purchase since it costs absolutely nothing compared to the ones being sold out there. I mean regulators are just regulators right as long as they reduced or eliminated hum?

No way! Various implementation of his regulators including on some of my newer projects has yielded a very interesting common feature bout rod's regs. I implemented them in high mu DHT triodes such as the EML20B as well as the ultra rare VT 64 /800 triode in a line stage application.

With these every implementation I find there is a surrealism bout the music where it really comes alive and draws you right into the music. Most will say all DHT's do that don't they, the fact they don't. I have in my collection amps build on AC heaters, unregulated DC heAters, regulated DC heaters using the more common current and voltage based regulators, and lastly Rod's units.

The difference, I remembered how when reading bout the practices of many amp builders or designers in the early days , AC heating was the preferred method. DC especially unregulated DC sucks the life out of the amps implementing them and I truly agree.

Rod told me then that even AC to him is bad and his regs will render them pale in comparison. I was skeptical but went with the idea.

To date the amps and line stages I have implemented them are the most musical sounding I have ever heard, for those who has referred to his manual stating' Your DHT amplification will sound so good that you will want to listen to your system for long periods of time' I couldn't agree more!

Rod, only 2 nights ago I replaced the LM regulators originally used in my 26 line stage to yours,( yes I have been really lazy! ) for doing so requires implementation of individual heater Trafos and means total re configuration of my ps chassis. Current configuration is a pi filter clc with the second cap in the signal chassis.

Only this morning I fired it up and was absolutely floored by the difference, as mentioned above immediacy and dynamism to the music! I never heard the 26 pre sounding this good, my previous regs were making the music mellow and overly smooth in other words boring.

I could rave on about his regs for pages but I think you pretty much get an idea of what I like bout these regs. If most of us think that dc regs are there to remove hum, think again, they could and will redefine music played from your gear at a whole different level!

kudos to rod on his awesome design I can only imagine with better component used what great improvements it could bring but anybody building a DHT gear should know that these are a bargain for the gobs improvement in sonic presentation.

Will post photos of my gear when I get a chance!

[regal]

Are the Hammond dual bobbin transformers suitable? (Is there a difference between dual bobbin and split bobbin?)

http://www.hammondmfg.com/pdf/5c0018-19.pdf

Also I remember we need a regulator for each tube, but is it OK to use one transformer per two regs/tubes?

[manollo]

Originally Posted by petavgeris

Check!

HI
Can you tell me how you made those resistors?
You have entered one psu for one tube or something else?
I have a audiorome SET amplifier with 813's tubes(also has 12au7 and 6sn7)
In witch tubes do you think that I will expect to hear better things?
Tnank you Manolis

[triode_al]

Originally Posted by Rod Coleman

Thanks John.

The board is also configurable to work with indirectly heated tubes - which is useful when you are working at low levels or RIAA stages etc. Each heater can be independently adjusted - so you could experiment with fine-tuning the heater voltage in first-stage amplifiers with 6Ж32П (6J32P) or EF86 or 6BS7 etc. These can sometimes be improved in noise (and sound) with the heaters reduced to 5.0V or 5.5V.

The cathode CCS can be used for differential stages, and B+ divider resistors & capacitor positions are provided on the board - so that raising the heaters to +30 or +50V is easy.

and a tip (i read in an electronics magazine of the 60's) is: on for example an ECC83 you can balance the tube halves completely this way without adjusting the circuitry itself. Their application: tube volt meter.

[petavgeris]

Originally Posted by dixchen

My previous regs were making the music mellow and overly smooth in other words boring.

Exactly! I totally agree!

[Captn Dave]

Originally Posted by pietjers

It has been brought up here a few times that high quality split bobbin transformers are important to lower the coupling capacitance between primary and secondary windings. It seems that R Core transformers also have split primaries and secondary’s. Has anyone used those and do they have other drawbacks?

Peter

Has anyone seen a source for an R-core suitable for a GM70 filament application?

[Furax]

Hi Rod... I am using your filament supply now with my 45 DHT: that's clearly an improvement over AC supply...
I agree also with Petavgeris : the plastic 220 nF capacitor is a dead end, a good capacitor (I use MKP sprague orange drop) is clearly an improvement . Replacement of R1 by two cheap carbon: again, one step higher. Well , in this tweak session, I give 66% to the capacitor, 33% for the resistor... Next step: Duelund for the resistor, a Jupiter for the capacitor...