Bottlehead Forum
Bottlehead Kits => Legacy Kit Products => Quickie => Topic started by: paulw on March 10, 2010, 01:44:46 PM
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Put one together last night - 3 hours from start to finish - and just played a couple of tracks to see all was OK. Took the inspiration for my case from corndog71's - but didn't have any foam so used some polystyrene, which will do nicely for now, but there is a Hammond chassis on the way.
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi142.photobucket.com%2Falbums%2Fr81%2F4will8%2FQ14.jpg&hash=bf92beec7d5cf0b739bb3de761e04d153e7bacd8)
Got to say I'm not to enamoured with acrylic, especially in a dark colour as it shows every mark - probably the longest part of the build was trying to polish off (unsuccessfully) all the finger prints.
Just spent the last three hours listening and like everyone else, the tubes are really micro-phonic - not that I'm too worried as it only seems a real problem when switching between inputs. However, the other thing I get is as I go to adjust the volume, when my hand gets near the tubes there is a distinct hum. This increases with the proximity to the tubes but no other part (input/output sockets or plugs) again no real issue just find it a bit curious.
Initial listening (remember only three hours on the clock) provided a detailed overall sound, with a bit of upper mid 'grain' or coarseness and a euphonic bass. The latter I feel is probably down to the tube micro-phonics and may even be a cause of the former mentioned 'grain' but it really is too early to judge - but they are only 6 foot away from my 15 inch bass units! The only other criticism is the volume pot which tracks really badly with an at worst 24k ohm difference between channels and only really gets it together just past where I usually set the volume - 1st upgrade perhaps?
In a previous post I mentioned I was going to do a different top plate layout, but decided to build one stock first. I've also got the PJCCS, but to be honest the last thing I really want is extra gain, it seems just right as it is into my Paramour II's. Would be nice to have the other benefits though, anyway the primary reason for getting Quickie initially was to swap it with my Foreplay which need some essential maintenance to all the switch gear.
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Nice job on the assembly!
To get the finger prints off, look for Novus #1 or Brillianize plastic cleaner, and use a soft cloth (no paper towels). Generally you could buff them off with a microfiber towel.
If the pot is indeed tracking that badly, replacing it seems reasonable. You could also add some series resistance between the selector switch and the volume pot in order to more easily reach the range where the balance is right.
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I notice that as I turn the volume pot from 'zero' onward the right channel is audible first, but then later they 'catch up with each other'. Is that the same symptom that you describe?
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I notice that as I turn the volume pot from 'zero' onward the right channel is audible first, but then later they 'catch up with each other'. Is that the same symptom that you describe?
Yes that's the same problem and is normal with low cost pots, but a bit excessive here starting at 24k out and not getting in balance until just over half way round - my ideal volume position is about at a third of the travel, perhaps it just needs some use.
Paul
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I have the same problem. This is the only issue I have with the Quickie. 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 am going to switch upgrade output caps and volume pot in the next couple of weeks. Does anyone have a recommendation for a decent volume pot for under $50. I saw that Bottlehead used to offer the Sweetest Whispers. Do they still offer that pot in a kit form? I did not see it in their store.
Alternatively, what spec of resistor, or range could I add as a buffer to balance out the sound with the current pot?
Thanks,
Don
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I was going to go with a basic Alps pot.
Paul
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Now looks like this
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi142.photobucket.com%2Falbums%2Fr81%2F4will8%2FQ16.jpg&hash=d2eb1f0fe4b64f7776a2fc0628cde6146d8d49bf)
mounted on a Hammond chassis.
Paul
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Paul, that is a nice neat build but you lost the lottery on top plate colors. I am not a fan of any shade of purple. It is a personal preference. I would have spray painted that one if I got it.
I'm just commiserating with you here.
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If you're looking for a decent upgrade pot, look for the dual log PEC potentiometer on Digikey. Parts Connexion also has some reasonably priced pots.
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.
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Paul, that is a nice neat build but you lost the lottery on top plate colors. I am not a fan of any shade of purple. It is a personal preference. I would have spray painted that one if I got it.
I'm just commiserating with you here.
Have to agree about the colour - but that's the way it goes :-) Got some 12x9 mirror finish acrylic in the garage and a 10x8 wood base, so perhaps a transplant is in order.
Paul
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. . . 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.
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I actually dont mind the purple. Its pretty bold but could blend into an all black setup. Nice quickie.
What brand of tubes are those?
How did you secure the top plate to the chassis?
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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.
What type of resistor and exactly where would it be attached and soldered please?
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What type of resistor and exactly where would it be attached and soldered please?
I would start with a pair of 100k film resistors. Metal film or carbon film is just fine. These are available at Radio Shack or just about any other shop that sells resistors. If that cuts the level too much, step down in value to 47k, if you feel like you could use a little more padding, go up to 200k. (Just don't use wirewound resistors for this purpose)
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I actually dont mind the purple. Its pretty bold but could blend into an all black setup. Nice quickie.
What brand of tubes are those?
How did you secure the top plate to the chassis?
The tubes are branded Aladdin, these aren't the ones supplied which were Motorola. They were a shade less micro-phonic and a better match pair so I used them instead. I already had some 3S4's but never had anything to plug them into - indeed a few years ago I was offering to give them away free to anyone who could use them, but didn't get any takers!
The top plate is held on by 6 self tapping screws. I taped the plate to the chassis and drilled through both with the correct size for the screws, then set the depth stop (got a pillar drill) to just clear the top plate with a drill sized for a loose fit on the screws.
Paul.
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. . . 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
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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.
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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
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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.
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Doc do you folks still sell the Sweetest Whispers as a kit?
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...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.
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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.