My experience building a DRD d3A/300B amp

[Gluca]

Yes, that one. It is pretty simple, you just need a couple of LM1084 a few resitors and capacitors. I believe there is a schematic somewhere on diyaudio.

g

[Bas Horneman]

Hi G,

It is pretty simple, you just need a couple of LM1084 a few resitors and capacitors.

A current regulated supply is indeed real easy ( just set the LM317/LT/LM1084/5 at the current that a tube runs at..et voila. )

a Tube heater apparently does not "like" a low impedance supply (voltage regulator) and a current reg is apparently a high impedance supply.

But Guido Tent's is not "just" a current regulator. I think it can be described as a voltage regulated current regulator. And somehow Guido's heater supply is not just a voltage regulator followed by a current regulator...(which I could do as well )

Don't ask me specifics..I just work here.

[CLS]

About the "DRD" circuit, there's a variant which is "stacked". Each stage has its own power supply, and latter stage is stacked on the previous stage.

Here is a very interesting & magnificent sample-- Axiom 300B.

And my own 300B amp was purchased locally in Taiwan & it's in a similar construction with 6C45 driver (so it's only 2 stages).

This amp is produced by Colin Sound Lab, with 2 power supplies for output & driver stage individually. Each power supply is LCLC.

This is the best sounding 300B circuit I've ever listened to.


PS. The Colin Sound Lab link above is in Chinese, may not be displayed properly in your browser. Anyway, some pictures at least

[Raj1]

I've looked at that axiom schematic a few times, never once have I figured out how I would put it together, I think it's for the more experienced....................

[CLS]

One stage at a time, you'll find it easier.

One step further, replace those damper diodes with simple resistor.

Next, simplify those LCLC power supplies with battery symbols.

Finally, stack all 3 stages together, you'll see the whole picture.

[ThorstenL]

Konnichiwa,

Originally posted by Gluca
Yes, that one. It is pretty simple, you just need a couple of LM1084 a few resitors and capacitors. I believe there is a schematic somewhere on diyaudio.

The simple LM1085 et al CCS needs adjusting for every change of valve. Gets tiring with time. The Tentlabs supply uses a discrete CCS adjusted to get the voltage across the valve heater correct using a very slow averaged feedback loop.

Sayonara

[Gluca]

As usual Tent's products are brilliant ... I studied so long his DAC ... nevertheless I believe ligas (and myself as well) can just try and get a few parts together to see if the amp sounds better heated with DC current (to his ears). DIY is just that, isn't it?

Ciao
Gianluca

[Bas Horneman]

I believe ligas (and myself as well) can just try and get a few parts together to see if the amp sounds better heated with DC current (to his ears). DIY is just that, isn't it?

Ofcourse..I just wanted to say one lm1084 is not a Tent heater.

[ThorstenL]

Konnichiwa,

Originally posted by Gluca
nevertheless I believe ligas (and myself as well) can just try and get a few parts together to see if the amp sounds better heated with DC current (to his ears). DIY is just that, isn't it?

Yup, by all means try. That said, I did and LC filtered Heaters sound better to my ears than single chip (LT1085) CCS heaters with CMC filtering.

The Tent Labs supply is probably a better choice.

Sayonara

[Gluca]

And it is a very different beast... I'd love to hear them.

Interesting enough, I was sure simple DC current heaters sound better than DC voltage. I will try both with/without regulator.

Thanks for sharing your experience.

Ciao
Gianluca