First of all the power amplifier should be turned off first before turning off ANY line stage or preamp.
To answer your question.... None of my Aikido's exhibit a turn off thump. The first is the unit that I bought from a group buy here (thanks again Bas). I also bought the power supply circuit board that was part of the group buy and built it according to Bas's outline.
The others have a power supply that was my own brain child and I will look for a schematic to send you.
But I wonder why you need it. As long as your main B+ power supply keeps going for a few seconds (ie you have a big enough cap) then you should be able to turn it off...it's basically just turning off the heaters, and that should not cause a thump in the aikido circuit... the tubes will slowly stop conducting, and the resistors will maintain pretty much the same voltage. Then the B+ will slowly drain down, which will also not cause a thump. That's the way JB designed it.
I have big subs connected to my aikido preamp, as well as a power amp, and neither thump when I turn mine on or off.
Might be easier just to figure out why your one is thumping. Measure the DC voltage just before the output coupling cap. When running it should be about half B+...when you turn it off it should slowly drop to zero. See what your one does. Also try measuring the voltage there with the tubes pulled out. It should be pretty much the same.
I have big subs connected to my aikido preamp, as well as a power amp, and neither thump when I turn mine on or off.
Might be easier just to figure out why your one is thumping. Measure the DC voltage just before the output coupling cap. When running it should be about half B+...when you turn it off it should slowly drop to zero. See what your one does. Also try measuring the voltage there with the tubes pulled out. It should be pretty much the same.
If you can fix your switch off thump that's best but if you like your choke based ps and that's the culprit you could go down the protection route. I've looked at the Vellemanm, the problem with that one is that you have extra connections to your speakers, so it's not sonically invisible. If you use a tube power amp it could misbehave with no speaker load.
The Transendent Sound Rozenblit circuit is designed for exactly your problem. It shorts the preamp output to prevent any nasties. You could power it from a heater supply (if 12V) or gut a wallwart you may have spare.
The Transendent Sound Rozenblit circuit is designed for exactly your problem. It shorts the preamp output to prevent any nasties. You could power it from a heater supply (if 12V) or gut a wallwart you may have spare.
Might as well use a DPST manual switch and save yourself some money or better yet just turn off the power amps first.
If you can hear the difference of having the Velleman in the circuit
I'll take my hat off to you man because you've got super good hearing. I doubt that ANY damage would be done to a tube amplifier when it is sitting there waiting to be turned off with no program running thru it. I've been using my Velleman 4700 with EVERYTHING that I connect to my speakers WITHOUT any issues.
This includes both the tube gear and SS gear. The Velleman has a 5 second delay to latch up upon turn on and thus it latches up BEFORE my tube amp even gets the power supply up to voltage.
I use the Velleman in case there is a problem because it is a heck of a lot cheaper than even trying to replace even one driver.
So, if we are going to have an opinion here lets please base it on practical experience.
I agree that turning off the preamp last is simplest of all, that's what I do with my phono stage, no need to additional circuits. A problem would only arise if others need to use the system, they won't be versed in the procedure.
As for not being able to hear an extra 2 pairs of speakers connections, this will depend on the resolution of the entire system. There are quite a few people who hard solder cables because they are sure they hear improvements from this. Certainly I can hear how push on connectors for speaker drivers damage sound. Personally I prefer a balance between usability and sound so I don't hardwire my external cables but I'd prefer not to introduce needless connection. But....this is all personal choice, I'm merely providing some input.
As for amps not being damaged by having no load across their outputs, certainly just about any solidstate and zero feedback SET tube amp will be fine. The same cannot be said for all tube push-pull amps. This is based on very common advice, it's not something I want personal experience of! Also, I really don't want to be to blame for someone damaging their equipment.
As for not being able to hear an extra 2 pairs of speakers connections, this will depend on the resolution of the entire system. There are quite a few people who hard solder cables because they are sure they hear improvements from this. Certainly I can hear how push on connectors for speaker drivers damage sound. Personally I prefer a balance between usability and sound so I don't hardwire my external cables but I'd prefer not to introduce needless connection. But....this is all personal choice, I'm merely providing some input.
As for amps not being damaged by having no load across their outputs, certainly just about any solidstate and zero feedback SET tube amp will be fine. The same cannot be said for all tube push-pull amps. This is based on very common advice, it's not something I want personal experience of! Also, I really don't want to be to blame for someone damaging their equipment.
If you had researched the Velleman kit you would have realized that the kit allows a load resistor for each channel and therefore not taking a load away from the amp.
Its just plain amazing how manaufactures like Parasound just to name one for an example can get around the marvelous set of ears that some posess. If for example there was a difference caused by the audio signal going thru a pair of relays wouldn't the designers and engineers choose to leave off these features for the purity of the sound? There is a lot of snake oil being sold leaving people to believe about anything so if for example you choose to think there is an audible difference then who am I to differ?
If you look at the Velleman board picture that I posted you will see a blank space for R25 and 26 between the two relays for the load resistors. I did not use them.
I don't have any turn-on thump, so that is not a worry at all (it appears that Rozenblit circuit is only for turn-on thump prevention...odd, since I don't have turn-on or turn-off thump on my transcendent sound grounded grid preamp).
The Vellman is interesting, but I'd rather try to solve the problem than treat the symptoms.
I've tried various B+ cap values in my CLCLC psu, up to 140uF as the last cap. The larger that last value, the weaker the thump...but even 140uF doesn't eliminate it.
The Vellman is interesting, but I'd rather try to solve the problem than treat the symptoms.
I've tried various B+ cap values in my CLCLC psu, up to 140uF as the last cap. The larger that last value, the weaker the thump...but even 140uF doesn't eliminate it.
Jamye,
I believe the Rozenblit circuit will cover switch off thump as well as switch on as the relay shorts the preamp outputs on switch off - but I don't claim to have read the manual!
Burnedfingers,
Sure, I haven't read the Velleman manual....but it seems that they appreciate there can be a need for load resistors, which is what I was saying.
As for the sonic of effects of relay contacts, that is not what I was referring to, I said connections - meaning the connectors you showed in the one of the pics you posted, 4mm plugs and binding sockets. Relays are much less of an issue though I personally would prefer to use relays at line-level, not speaker-level.
I don't understand why you're taking my comments so badly. We're so close to violently agreeing.
I believe the Rozenblit circuit will cover switch off thump as well as switch on as the relay shorts the preamp outputs on switch off - but I don't claim to have read the manual!
Burnedfingers,
Sure, I haven't read the Velleman manual....but it seems that they appreciate there can be a need for load resistors, which is what I was saying.
As for the sonic of effects of relay contacts, that is not what I was referring to, I said connections - meaning the connectors you showed in the one of the pics you posted, 4mm plugs and binding sockets. Relays are much less of an issue though I personally would prefer to use relays at line-level, not speaker-level.
I don't understand why you're taking my comments so badly. We're so close to violently agreeing.
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