let's talk about tubes for Quickie

[charger]

which brand of tubes are better for the Quickie ?  which are less microphonic ?

[4krow]

 While these tubes seem to be microphonic by nature, I have found that Telefunken tubes have a bit less of the problem. I have only tried the originals and the Tel's so there may be other observations out there. I use Herbies dampers on the tubes as well.

[denti alligator]

which of the Herbies dampers do you use?

[4krow]

  I don't recall the model, but I went for the one that cost $13 ea. After reading through the website, I found that this damper had all of the benefits of their top of the line at that time, and was cheaper. The difference that I notice is small, but to be fair, I haven't listened very much yet, as the Quickie is getting remade. I am working on it today.

[denti alligator]

one of the these, I assume:

http://herbiesaudiolab.net/preamp.htm

what's the size of the Quickie tubes? 5/8" to 3/4"?

[4krow]

   You are correct sir.

[4krow]

  One thing that I would like to mention about the Telefunkin tubes, is that near full volume, they have a lot of distortion. To be fair, I rather think that it might have to do with something else that I have done with the circuit. So far, I have changed the original volume control to a stepped attenuator, but I'm thinking that's not it. I have changed out output caps twice, and the problem has occurred with both caps. Other than those two things nothing much has been done. That is why I tend to think that these tubes might be the reason. Ok, now I have to switch back to the originals just to check.

[Paul Birkeland]

You might measure the plate voltages with the Telefunken tubes installed, they might be a little higher than desired (which could cause earlier clipping).

[earwaxxer]

Dont forget about the definitive reference for Q technology:
http://www.bottlehead.com/smf/index.php/topic,3491.0.html
IMOSSMS. 

[4krow]

  Would this even occur if voltages and resistances checked out?

[earwaxxer]

  One thing that I would like to mention about the Telefunkin tubes, is that near full volume, they have a lot of distortion. To be fair, I rather think that it might have to do with something else that I have done with the circuit. So far, I have changed the original volume control to a stepped attenuator, but I'm thinking that's not it. I have changed out output caps twice, and the problem has occurred with both caps. Other than those two things nothing much has been done. That is why I tend to think that these tubes might be the reason. Ok, now I have to switch back to the originals just to check.

Distortion at high volumes (gain) I have not noticed before. I even took the volume control out and didn't notice any real change in distortion. In the end the pot sounded better than the digital volume control. Not sure why the tube is getting overdriven like that.

[4krow]

 Just a shot here. Would heater voltage have any effect?

[earwaxxer]

Like too much? I use rechargeables so I'm always less than 1.5V. Experts can chime in here, but I dont notice any difference in sound as the heater batteries go low. I usually just hear one channel cut out when the voltage gets too low.

[Paul Joppa]

The Quickie has fairly limited output voltage capability. Into a high impedance load, clipping would be expected at 3.5vRMS with fresh batteries, 2.3vRMS at the end of battery life. For myself, I'd prefer to keep it below 1.0 volts to avoid audible coloration - but it depends a lot of what the meaning of "audible" is! For comparison, BeePre or Foreplay should put out 20vRMS before clipping.

If your amp/speaker combination needs more that 1vRMS peaks, Quickie can run into trouble.

[4krow]

  I will look into this tomm.