• 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.

Need opinion on PS for tube preamp.

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leadbelly

leadbelly

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Joined 2002
#1
I thought I had this worked out, but with the CRC and CLC threads on the other forums I have started to doubt myself and wanted some opinions.

I am building a 6922 preamp. Voltages are +120VDC, -15VDC.
I am trying to keep costs down, so I am avoiding big iron. But I have enough different transformers in hand that I can choose whether to use CRC or not and burn off some voltage or just go CLC with a smaller coil. So I was trying to compare a CLC using 1000uF caps and a 10mH coil vs a CRC with 1000uF caps and say a 100R or 220R resistor.

I can play around PSU Designer II all day and that shows the CRC has lower ripple, but is that all I should look at? Does anybody insist CLC sounds better than CRC, or viceversa?
 
#2
Hi leadbelly,
Why not pour a little sand in your preamp with a SS regulator. You can R-C the input and the output to each circuit. The R-C will decouple the circuits from each other and the regulator. No, you can't hear the regulator unless you mess up the design.

-Chris
 
#3
I don't mess with negative voltages much but it seems you will need to use a full wave bridge get the required polarity for your project. I used a integrated Hexfet bridge from Michael Percy for the PSU for my preamp and it sounds very natural. If you want to use 1000uF caps I would obviously recommend that you use the same bridge that I used (IXYS 30A). Definately use the inductors. They also make for a nice sounding circuit. How about a SS HexFet bridge, choke loaded, with a tube shunt regulator? It will sound nice and look nice also.
 
#4
leadbelly said:
I thought I had this worked out, but with the CRC and CLC threads on the other forums I have started to doubt myself and wanted some opinions.

I am building a 6922 preamp. Voltages are +120VDC, -15VDC.
I am trying to keep costs down, so I am avoiding big iron. But I have enough different transformers in hand that I can choose whether to use CRC or not and burn off some voltage or just go CLC with a smaller coil. So I was trying to compare a CLC using 1000uF caps and a 10mH coil vs a CRC with 1000uF caps and say a 100R or 220R resistor.

I can play around PSU Designer II all day and that shows the CRC has lower ripple, but is that all I should look at? Does anybody insist CLC sounds better than CRC, or viceversa?
Click to expand...
1: Use a seperate tx and bridge, caps etc for the neg supply. Small transformers are cheap. Maybe even throw in a regulator.
2: A 10milliHenry coil is too small to be of much use at all. No wonder the CRC option looks better in the sim. Try something like 10H, or more. Small open frame Hammonds are cheap.
3: You won't need 1000u. 100u - 15H (Hammond 155J) - 200u would be better to my ears.
4: 6922's always sound better to my ears with some serious current through them, especially as you're running at low voltages. I prefer them run at higher voltages too.
 
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