• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

New DHT heater

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#723
#727
The local FM antenna is close indeed, at 600 meters D)

The drawing is creative but correct wrt diodes.

Bas, I'm listening to my favorite music with my favorite audio gear, meditating about the Soul of Music. There will be a switch from AC to DC on my 2A3 SET soon. Break on thru to the other side... like Jim used to sing.
 
#730
Hi Duong,

Single Regulators can deliver up to 6.5A for the 75TL.

They can also be parallel-connected - 2 Regulators can feed the 833C (10.0V 10A).
12.5A may also be possible - but a higher-power device is required for Q5.

Please send me some email, and I will check on the most suitable components.
 
#731
Rod Coleman said:
Hi Duong,

Single Regulators can deliver up to 6.5A for the 75TL.

They can also be parallel-connected - 2 Regulators can feed the 833C (10.0V 10A).
12.5A may also be possible - but a higher-power device is required for Q5.

Please send me some email, and I will check on the most suitable components.
Click to expand...
Rod,
Yes the 304TH is basically 4x 75TH in parallel, except for the filaments can be configured to 5V/25A or 10V/12.5A. Obviously I wouldn't want to run at 5V/25A since the power dissipation would be too much (12.5A is already a nightmare).
Running 2 boards in parallel is interesting, though I'm not sure if it's easy to adjust?
Email's sent, thanks alot.
Duong
 
#732
The Coleman regulator is a current-only control regulator. This allows us to add currents just as Kirchoff's Law says we can. There is no contention between the two regulators.

To balance them, you just measure the voltage across R1, and trim the regulators until R1 has about the same voltage for each regulator. It does not need to be exact, but making them about equal spreads the power dissipation better.

Magz's 833C (10.0V 10A) SE amp "The MidLife Crisis" uses a parallel pair of Coleman regulators to feeds 10A to the 833C, and it works just fine:

http://www.diyaudio.com/forums/tubes-valves/232484-midlife-crisis-my-833c-amp-build.html#post3420189
 
#735
It's a surprise to learn that the Welwyn is actually worse - but - component makers have been skimping lately, and maybe the materials have been downgraded. A shame if so.

The resistors that come in the kits as standard have all been thoroughly tested over many samples and values, and always give vanishingly small (microampere) current-noise levels across the spectrum - measuring for the whole regulator. Other than the effect on the heating current, the resistors have very little influence on the sound, because they are well-buffered from the filament itself.

Try a Mills or two. They will either be a delightful experience - or end forever any interest in boutique resistors!
 
#736
It's a surprise to learn that the Welwyn is actually worse - but - component makers have been skimping lately, and maybe the materials have been downgraded.
Click to expand...
I don't think they are worse or better. I think it is more a case that the resistors in that position have very little influence (if any) on the sound. And that my perception of the sound is imagined.

I'm assuming the quality of the welwyn is the same they have always been.

I'll keep them in there because they appear to be well made and have a 7 Watt rating. And will reserve boutique resistors for places where they'll have more effect. 🙂

I appear to have become a naysayer lately as I also found a CCS vs a resistor on pin 20 on a PCM 1794 DAC to make little to no difference. Where others reported a big improvement. Maybe I expect too much. Or maybe I tinker too often with my system. Perhaps if I listen to exactly the same configuration for months on end. I'll hear changes better. Or maybe they still need to break in...haha. 😉
 
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