Yet another one up and running

[paulw]

 .  .  .    Still, I would put resistance in series with the stock pot, as that will move the "listening range" on the pot up a bit, away from the low end where the matching can be iffy.  

In addition to moving the range each degree gives a smaller increment in sound.  That allows you to get the "right" level more easily.  Well, that is the reason I do it.

I've temporarily resolved the problem by moving to the variable output of my DAC and not using the Seduction as my other phono-stage has multiple output gain settings which is now set to the lowest.  The volume pot is now nicely balanced with normal listening levels at just over half way round the dial.

Paul

[TheSparkle]

PB, thanks.  I found these articles after I posted the question, and I was thinking of trying a 22k Ohm resistor.  I'm glad you mentioned using larger values though.  How does using the larger resistors as you suggest compare to the use of a 22k or 15K Ohm resistor as suggested in these articles?  Do I need the larger resistor value to boost and 'balance' the volume curves more noticeably for this particular circuit design?

http://sound.westhost.com/pots.htm
http://sound.westhost.com/project01.htm

And, I'm glad this topic was addressed.  After I finished my Quickie I thought maybe there was something wrong (that I did) between the channels.

Paul, I like the purple!  I got a pearl plate and Sylvania tubes from the 1950's I believe.  I'm not sure how microphonic they are because I'm new to tubes and have no other tubes to compare.

[paulw]

Paul, I like the purple!  I got a pearl plate and Sylvania tubes from the 1950's I believe.  I'm not sure how microphonic they are because I'm new to tubes and have no other tubes to compare.

95% of the time I would expect there to be no micro-phonics audible in normal use.  I believe it adds some 'euphony' to the overall sound, but I'm not to worried as I only become really aware of the issue when switching between sources or 'tapping' the top plate, so I've stopped tapping the top plate and use the switch gently ;-)

Paul

[Doc B.]

I only become really aware of the issue when switching between sources or 'tapping' the top plate, so I've stopped tapping the top plate

Excellent solution! Some tubes are worse and they will ring when music plays or even oscillate a bit. But most are fine as long as you don't tap on them. This is one of the characteristics of a small signal directly heated triode. To get that great DHT resolution you often have to live with some microphony. Even $500 Eastern European output tubes can ring.

One thing folks can try is to wrap the tube with copper tape. And of course you can buy whatever tube damper is in fashion this week too. Isolating the chassis from vibration can help too.

[IceOgre]

Doc do you folks still sell the Sweetest Whispers as a kit?

[Paul Joppa]

...The imbalance of the left and right channel at low volume is frustrating (especially when you was to listen after the kids go to bed). ... I saw that Bottlehead used to offer the Sweetest Whispers.  Do they still offer that pot in a kit form? 

This is a common problem with stereo pots. To get really decent matching at when the pot is turned way down you have to spend really big bucks. So much in fact that you might as well go for a switched attenuator, which probably sounds better as well.

On the original Foreplay, two mono pots were used. We got lots of complaints over the years about that too! With FP-III we stepped up to switched attenuators, but the switches that were affordable were only available in mono, so we had to stick with that. That is the Sweetest Whispers, which I'm pretty sure is available but you'd need another hole to mount the second mono control.

For the SEX amp, where the control is usually in the upper half of the range, balance is OK and we used a stereo pot. That pot got re-used for Quickie, and it will be used in the Stereomour as well.

[Paul Birkeland]

PB, thanks.  I found these articles after I posted the question, and I was thinking of trying a 22k Ohm resistor.  I'm glad you mentioned using larger values though.  How does using the larger resistors as you suggest compare to the use of a 22k or 15K Ohm resistor as suggested in these articles?  Do I need the larger resistor value to boost and 'balance' the volume curves more noticeably for this particular circuit design?

http://sound.westhost.com/pots.htm
http://sound.westhost.com/project01.htm

All I saw at a quick glance was adding resistance across the pot to fake a linear pot into a log pot. In what I suggest, you add resistance from the selector switch to the input of the pot.  With a pair of 100k resistors, you basically shed half of the signal coming into the Quickie, so if your comfortable listening position is only 1/4 of the way of the pot's travel, you will find that same listening level with the pot turned further along.  Since you really have hair-trigger gain in your system, 27k just isn't going to do it.  In fact, I would say that 100k may not quite be enough for you.