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Updated version..give it your best shot!!!

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Bas Horneman

(A)

In Reply to: Criticism please!! posted by Bas Horneman on May 13, 2004 at 13:35:33:

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Re: Updated version..give it your best shot!!! - AnandR 05:28:48 05/14/04 (2)
Bas,
I'm obviously not as knowledgeable as some of the other folks here, but depending on what you are going for, you might wanna try replacing (2) of the 6AX4 damper diodes in this full wave bridge to (2) Hexfreds or Schottkey's 1200V types. This is the Hybrid Gaetz configuration that Andre Ciuoffoli first popularized (although designed by somebody else) and I know Kevin Carter uses to great effect on his designs. The sound and characteristics of the rectifier is now of the damper type and not the solid state Hexfred or Schottkeys. Might save you on some filament supply.

Just a thought. Nice job BTW.
Anand.
- Re: Updated version..give it your best shot!!! - Bas Horneman 06:47:24 05/14/04 (1)
  Thanks for the tip Anand,
  ---Might save you on some filament supply.
  Good idea..Will that increase the psu'
  s abilitiy to deliver current quickly as well?
  This rectifier config I have now is a little over the top isn't it. But with the Graetz bridge (Have used it in both my current pre- and power amp) the damper tubes still are the ones that up the impedance of the psu...this was an attempt to increase the capability of the psu to deliver current faster...if the Graetz bridge does that as welll...I'll go for it.
  --Just a thought. Nice job BTW.
  All copied from Keto and Jeff Lessard (And Mike Lafevre). They obviousely deserve the credit ...this is just an implementation of their spadework. I am merely the "paster" ...
  Regards,
  Bas
  - Re: Updated version..give it your best shot!!! - AnandR 20:48:39 05/14/04 (0)
    Bas,
    I can't vouch for the Graetz bridge delivering current any slower, but I do know from breadboarding as well as chatting with other builders that the Graetz bridge really doesn't sound too different from a full wave bridge of dampers. I imagine the actual impedance of the supply should be lower since you have replaced two tube rectifiers with two solid state ones.
    Best,
    Anand.
Cool! - pistoljoe 04:38:31 05/14/04 (2)
Bas-
Pretty much identical to my test mule I've been working over the past year. I thought the blocking cap sounded the same to my ears anywhere from 3.3u to 1.1u. The jury is still out on my .47u + .1u combo. I did like the Ecc99 alot, and was my favorite at 20mA and less, but I tried the 6H30. It sounded not as good at the same current, but really opened up when I took it north of 30mA, right now I'm happy at 34mA. And I'm running HexFreds instead of tubes, but will change those out later, chassis space getting to a premium.
If you use a 120mA current source, I'm not so sure you need another section on the supply. The CCS will really smooth out the ripple for anything under a volt. Havent played with sinks so much yet.
Try it out- Joe
- Hey Joe! - Bas Horneman 04:55:52 05/14/04 (1)
  Where are you going with that pistol in your hand! ;-)
  --If you use a 120mA current source, I'm not so sure you need another section on the supply. The CCS will really smooth out the ripple for anything under a volt. --
  I did not know that!..also when it is a current sink?
  Regards,
  Bas
  - Re: Hey Joe! - Eli Duttman 11:38:35 05/14/04 (0)
    A CCS in the cathode circuit is a sink, while a CCS in the anode circuit is a source.
    The conventional current flows from sources and it flows to sinks.
    
    Eli D.
Re: Updated version..give it your best shot!!! - Kuei Yang Wang 03:20:44 05/14/04 (1)
Konnichiwa,
Unless you want a high output impedance from the Driver valve, here a little trick. If you return the output pair cathode current to the driver cathode you only 12 Ohm to get the bias for the ECC99. This means the output impedance of the valve is raised only by around 250 Ohm vs. 1k6 for the 82R resistor.
Also, adding a 20 - 40uF capaitor (switcable if you like) between the output transformer center tap and the output pair cathodes often sounds better than not having it, subjectively speaking (we tested this several times).
Sayonara
- Thanks KYW San.. - Bas Horneman 04:43:14 05/14/04 (0)
  Will incorporate your suggestions into the design and post the schematic to see if I understand it properly.
  Regards,
  Bas
Re: Updated version..give it your best shot!!! - Eli Duttman 20:15:35 05/13/04 (0)
The cap. in front of the 1st filter inductor should be 10 nF HIGH WVDC ceramic, not 100 nF. That cap. serves only as protection against inductive kickback.
A 100 nF. cap. across the 0D3 is too big; it can cause oscillation. A 47 nF. cap. is enough to kill regulator noise and will not oscillate.
As I indicated previously, a 2nd LC section is in order. The 1st filter cap. can be 22 muF. The 2nd inductor can be 5 H. The 2nd filter cap. is where the bulk of the energy storage goes.
Grounding a 2A3 filament winding is a "no no", when balance pots. are used and doubly so when a CCS is used in the cathode circuit.

Eli D.

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