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    Building, troubleshooting and testing of these amplifiers should only be
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#26 pre amp

I checked the pre out using a multimeter and observed a little bit of residual DC :
can be a fake reading...try misure dc current.
I haved problem with pumping cone changing psu coke with hight resistence in my tube amp,ie the clc frequency of psu ....

I use Salas HV after a LC circuit. Choke is 430R/5H. As well there are 200H plate chokes between the HV supply and plates. Would this setup create any anomalies like this?
 
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diyAudio Chief Moderator
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Pumping in passive filtering is a classic problem that arises in such schemes. When the charging cycle hits some unfortunate phase condition of the client circuit, or there is fluctuation. Passives don't have a reference Vo fixing mechanism. Don't be afraid of tonally synergistic regs. Its a far better and most economic solution. (With 5k6 MJE's load for those who wonder about a specific one :D).
 
Thanks guys..removing chokes got rid of the fluctuation. But I am missing some of the details now with CCS which replaces the plate chokes :(. If I want to continue with passives will there be any harm to my other equipments?

Salas..one question for you. After I remove the chokes and replaced it with CCS load, your SSHV supply start behaving differently. Earlier it allows to change the voltage between a wide range but now this got narrowed and it seems the SSHV is putting more current in to the tube than expected. It lost control over current and voltage both. Can you think of anything why the SSHV is behaving like this? Haven't done any other change than removing the passives.
 
Does the CCS have a local bypass lytic where it gets its B+?

This is similar to what I have. Resistor values are slightly different and I use 1K trim-pot to adjust the current.
 

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diyAudio Chief Moderator
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Give it an electrolytic locally from where it receives its B+ to ground. See if that will change something. Its a cascode and if it upsets the reg in very high frequencies there will be not much we can do, it will be one or the other. Try 1k R2,R3 also. With R1 120R it pulls circa 30mA. Is the reg having spare?
 
Give it an electrolytic locally from where it receives its B+ to ground. See if that will change something. Its a cascode and if it upsets the reg in very high frequencies there will be not much we can do, it will be one or the other. Try 1k R2,R3 also. With R1 120R it pulls circa 30mA. Is the reg having spare?

Thanks Salas. I'll try this.

Salas..what sort of harm it will do if I continue using passives instead of other plate loads? Will this residual DC cause problem to my other equipment in a long run? I like the sound using passive as the plate load and wish to continue if there is nothing much of a concern.

Anyway, what do you recommend for plate load with SSHV?
 
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diyAudio Chief Moderator
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If you like it best (it is better) try smaller/bigger coupling capacitor and 1Meg resistor from its output to gnd. Maybe you will find a phase turn more compatible. If the next in chain has capacitor input, DC will not pass. Still, you did not tell me, what is the set current in the Reg CCS? Should be 55mA to feed such an anode CCS to start with.
 
If you like it best (it is better) try smaller/bigger coupling capacitor and 1Meg resistor from its output to gnd. Maybe you will find a phase turn more compatible. If the next in chain has capacitor input, DC will not pass. Still, you did not tell me, what is the set current in the Reg CCS? Should be 55mA to feed such an anode CCS to start with.

Bit confused. What you mean is the SSHV needs to be set to 55ma?

What sort of plate load best goes with SSHV? I will try what ever you recommend.
 
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diyAudio Chief Moderator
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Its simple. If you use a 30mA anode CCS on your audio circuit, the local reg's CCS has to be set higher, so to provide for the audio circuit's consumption plus 20-25mA minimum for its own reg use. So check the voltage drop on your reg's CSS setting resistor, divide it by its value, and know first of all that there is enough current. We should know before going further.
 
Here is the concept I have been kicking around. It seems the advancements in SS powersupplies by Slas and Coleman may make it possible (ie hum free with 32 ohm 98 spl 1mV headphones.) The pream should be strong with the 600 ohm tap. The headphone out of a preamp is usually an afterthought and a huge compromise, not the case here. Headphone amps aren't easy to get right but magic happens with a good design and quality headphones. Anyway I am considering building this, any thoughts/criticisms appreciated.


DHTHeadamp.jpg
 
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diyAudio Chief Moderator
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Its all a matter of testing together. A couple of people have reported on using the SSHV on small tube headphone amps with OPTs successfully. But its not universal. There is 85 degrees of phase margin. If violated, music stops, lights go down. If not, party time. Just do a real test, if it won't work, plan B is a Maida. Tone worsens against an SSHV, still quiet though. You can't do more. ''Slas & Coleman'' sounds cool, like a banking firm from Oliver Stone's Wall Street - Money Never Sleeps, by the way.:)