quickie at full volume

[earwaxxer]

Observation: I noticed that when playing my amp at full volume using the quickie as a preamp/volume control I was experiencing less than desirable sound quality the louder the volume became. I hadnt noticed this at lower volumes. Bypassing the quickie, the problem (distortion?) was solved, but of course I lost the tube magic. I thought to try something that didnt make much sense to me, which was to max the volume on the quickie and use the power amp as an integrated (it has a passive pot/volume control). The sound was fantastic. Great bass punch, resolution, clarity - all that one could ask for! I expected the noise from the quickie to increase with volume, hence more desirable to keep the preamp gain low and increase the gain with the t-amp.  That doesnt seem to be the case.

Any feedback on this? Is it related to impedance issues between amp/preamp? The Mouse is rated at >15K ohms.

 

[Paul Joppa]

You're right, it does seem counter-intuitive.

It's late so this is just off the top of my head. Perhaps the Quickie volume control has a poor contact, and maxing it out takes it out of the signal path? Some contact cleaner might answer that question.

Normally I would expect Quickie to get distorted only when over-driven. Its internal noise however will be independent of its level control, which just attenuates the input. So your new arrangement would increase the distortion and reduce the noise of the Quickie - again, going by usual practice and assuming there is nothing strange going on.

There is some chance if the Quickie is driven to its maximum but not much beyond, that it can act as a limiter by soft clipping - which allows the power amp to produce greater sound level without going into hard clipping as solid state amps do. If the t-amp is not especially powerful, or you speakers are not very efficient, this is a possibility.

Well, just some thoughts.

 

[earwaxxer]

thanks Paul - food for thought - bottom line - This little "preamp" has transformed the sound of the Winsome Labs Mouse! As I was listening I was thinking to myself - "if I just paid $2K for a new amp and was listening to it now, I would be quite pleased!" What I may do is take the pot out of the circuit and see how that sounds.

 

[Wanderer]

I am wondering if there is some issue with the T-amp when it's onboard volume pot is at max.

Might be interesting to rig a passive volume pot in from of the Mouse and peg the Mouse's pot at max again and see if you have the same issue.

Have you tried listening with the Mouse's pot at say 3/4 instead of wide open and still using the Qucikie as a volume controll?  How's that? 

As an aside - do you find the Mouse has enouph power for the MMGs? In years past I drove Magnepan MG-Ia with a Dyna ST-70 (35 watts per channel) and it seemed fine to me. However, current word on the street is MMGs need 100+ watts to get up and walk around.   

                            Kevin R-M 

 

[Grainger49]

I'm not sure running the Quickie wide open is wise, the tubes can soft clip.  But since the Quickie volume pot is before the tubes I would vote for the problem being an interaction of the T-Amp's volume control and the output impedance of the Quickie.  

The volume control can be replaced with a 50k resistor of your favorite flavor.  It should be easy to lift the volume control input wire, place a few jumpers to insert the resistor just to try.

 

[earwaxxer]

I am wondering if there is some issue with the T-amp when it's onboard volume pot is at max.

Might be interesting to rig a passive volume pot in from of the Mouse and peg the Mouse's pot at max again and see if you have the same issue.

Have you tried listening with the Mouse's pot at say 3/4 instead of wide open and still using the Qucikie as a volume controll?  How's that?   

As an aside - do you find the Mouse has enouph power for the MMGs? In years past I drove Magnepan MG-Ia with a Dyna ST-70 (35 watts per channel) and it seemed fine to me. However, current word on the street is MMGs need 100+ watts to get up and walk around.     
                           Kevin R-M 

Hi Kevin - this last question being the easiest to to answer - the maggies do "need" a good chunk of power. To get the volume up there to "rock and roll, fill the room" levels, sure 100+ is required. I do mostly near-field listening. I know how much I can get before it clips. With the mods on the MMG's the efficiency is quite good for low/medium levels. I have toyed with going with quaduple the 50wpc I now have, and that will probably be my next "upgrade". One thing about t-amp sound. Its hard to give up! Unless you go to big buck tube power amps. 

Back to the Quickie discussion: I have tried various volume combinations from low to high/max on Mouse end (the Mouse has an Alps Blue Velvet pot by the way.) It seemed on first blush that the quickie sounded better with the Mouse at full volume and adjust the quickie as needed. I hadnt really tried cranking it a bit. Moderate levels sounded so good. When I first started questioning what I was getting with mouse at full and cranking the quickie, I disconnected the quickie and went direct to the mouse at the same volumes. For sure the sound "cleaned up" to what I was used to. No magic though. Thats when I thought I would try the opposite. Listening to it now, but at low volumes. Again very good, magic present.  No real answers. Thanks for the thoughts!

 

[earwaxxer]

I'm not sure running the Quickie wide open is wise, the tubes can soft clip.  But since the Quickie volume pot is before the tubes I would vote for the problem being an interaction of the T-Amp's volume control and the output impedance of the Quickie.  

The volume control can be replaced with a 50k resistor of your favorite flavor.  It should be easy to lift the volume control input wire, place a few jumpers to insert the resistor just to try.

I was wondering about the impedance interaction. I have not noticed any tube clipping. That is what is so puzzling.

 

[Paul Joppa]

Tube clipping is very soft; you have to be pretty far into overload before you hear it as "clipping".