Bottlehead Forum
Bottlehead Kits => Stereomour II => Topic started by: denti alligator on June 22, 2021, 06:42:42 AM
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A search for those who’ve upgraded the attenuator to the MourQuiet in their Stereomour II yielded very little. Could those of you who have installed this upgrade comment on the differences? Thanks!
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Sam, I installed the Mourquiet, about three years ago. My take on the upgrade is that it absolutely improved midrange clarity, but it came at the cost of some insertion loss. If you have a preamp in front of your SII this is probably not an issue, but if you like to run your source right into the SII you may not appreciate the loss in gain.
Jamie
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I'm also using the MQ upgrade in my SII (plus 2 shameless copies in my S.E.X. amps). It works perfectly and the steps are small enough to get the volume where it belongs.
While I concur with most of the positive aspects of the upgrade (I can't speak to the low level imbalance of the original pot with my 94dB speakers) there are times I miss the original balance control. Likely listening area issues, certain recordings highlight a shift in the image that can no longer be simply adjusted out. Just my $0.02.
Karl
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Hm. Two downsides. Not what I expected.
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Sam, I don't believe either of us were trying sound negative - heck, I like it enough that I had chassis plates made and chased down parts so I could duplicate it in my other amps. As Jamie said, it does what it is purported to do sound-wise. Only you know your system and what you are looking for.
Karl
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No, I hear you, but the balance is a feature I use, and I don’t have a preamp (except for an old Quickie), so a little loss in gain is something to consider.
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I don’t want this discussion to leave those w/o the MQ believing that it is not a worthwhile addition to their SIIs. It’s a bit like the DC filament upgrade, not everybody needs it, but if you have speakers over, say, 92db sensitive, then you probably do. The MQ is a real step up if you have a smallish listening area and listen near-field or semi near-field. You don’t need the gain in that situation but you will really appreciate the improved midrange (and bottom end).
I have MQ installed in an SII that I use in a relatively small area (12x14). The SII drives the MT section of a semi-active 3 way. The xover point with the Woofer section is about 200Hz / 12 dB/oct. In this application the MQ is really a plus. With the SII working above 200Hz there isn’t a need for lots of gain but the improved sonic performance is nice.
Jamie
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The MorQuiet and the stock attenuators have roughly the same insertion loss, so there shouldn't be much of a difference in gain (maybe 1dB).
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The gain is less of a concern for me than the balance. I’m assuming the balance is pretty, um, balanced with the upgrade and that adjustment isn’t normally necessary?
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The use of precision resistors in MQ puts the balance precisely in the middle. I myself never used the balance control when my Stereomour II was stock. I appreciate the even steps of the MQ especially at low volume where a two gang potentiometer can be "lopsided" at times. Aside from that I heard an improvement in sound quality as well with the MQ.
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Natural Sound makes a good point - the biggest reason for a balance control is to allow correction for an ordinary volume control at the lower settings. That's one reason it is usually not needed with a stepped control. There are other reasons, but they are much less frequently needed.
(1) sometimes the exigencies of architecture and communal living require speaker placement that is unsymmetric enough to need compensation;
(2) occasionally, you may have tubes with unmatched gain - usually not significant, but not always;
(3) sometimes you might want to listen to each speaker separately, to identify problems;
(4) you may have unbalanced hearing loss;
(5) the recording itself (or a phono cartridge) could be unbalanced
All but (2) are unrelated to the amp itself, and most people, most of the time, don't need or use the balance control. When PB developed the MourQuiet/BeeQuiet coarse/find level control, I started adding them to preamp designs as an inexpensive way to do something functional with the second hole in the chassis. Off topic but possibly interesting, that's the same way the shunt-regulated driver in power amps came about - looking for something useful to do with the second triode in a dual triode driver. :^)
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PJ. In my opinion answers 1 and 4 apply to me in my living room although in my evil laboratory I listen in near field and can move the speakers as needed. I also listen to headphones and really enjoy the C2A with the balance control. We are all different and weird in our way.
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I think my main concern is the balance, which I definitely use, meaning the knob is nowhere near the center to get a properly balanced sound.
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I think my main concern is the balance, which I definitely use, meaning the knob is nowhere near the center to get a properly balanced sound.
But are you using the balance control because the channel balance of the stock pot isn't that great? Or for some other reason?
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But are you using the balance control because the channel balance of the stock pot isn't that great? Or for some other reason?
Not sure why the balance is appears to be off. I remember asking in another thread if the reason I need to use it so much is a sign of something else being wrong and was told no.
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You can play a 60Hz tone into the inputs of your amp, then measure the AC voltages at the speaker posts (you can leave the speakers hooked up) at a normal listening level to see if the outputs are playing at the same level or if you're correcting for some other imbalance that isn't electrical.
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You can play a 60Hz tone into the inputs of your amp, then measure the AC voltages at the speaker posts (you can leave the speakers hooked up) at a normal listening level to see if the outputs are playing at the same level or if you're correcting for some other imbalance that isn't electrical.
OK, I’ll try this and report back. Thanks.
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As a general rule pot tend to track better at higher settings. Do you notice this?
Something you can try, with the amp switched off compare the resistance from one channel to the other at a few different pot settings. You would be looking for significant difference in one channel at a few settings..John
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Sam, you can experiment with the technique that PB recommended. I do this for setting up my system. Try it a different volumes. Put on something that you enjoy to listen to at a low volume, then switch to the 60Hz tone and measure the voltage. Move on to music that you like at higher volumes and repeat. This will help to set you preferred listening levels.