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Old 14th July 2011, 06:08 PM   #1
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Default The MyRefC volume control thread

This was discussed in the 80+ page MyRef C build thread and never created so here it is. You are encouraged to describe how you attenuate Mauro's omni popular contribution to the world of audio here. I suppose we can start where Uriah left off. Is 10K the optimum Rt for the Europe mains only?

Last edited by yldouright; 14th July 2011 at 06:24 PM.
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Old 15th July 2011, 03:50 PM   #2
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If anyone here has used a higher value attenuator to control the MyRef, would you tell us about it?
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Old 16th July 2011, 03:07 PM   #3
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I can't believe everyone with these amps is using a 10K attenuator, come on guys, tell us what differences it made, if any.
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Old 16th July 2011, 07:47 PM   #4
PJN is offline PJN  United States
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I just bought a Chinese 21 step DACT type 20K pot from Gigaworks for 10 bucks on Ebay and tried it with several amps including a MyRefC. I am very impressed with the sound quality. It sounds as good or better than the Twisted Pear preamp that I had been using.

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Old 17th July 2011, 02:43 AM   #5
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PJN
Thanks, this is exactly the kind of information we need here. What improved specifically, bandwidth, tonal accuracy, soundstage or PRAT? Mauro had recommended a value half that in the MyRef so if anyone else can explain why, that would be another step forward.
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Old 17th July 2011, 03:57 PM   #6
PJN is offline PJN  United States
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I had been using two different preamps with my amps, a class A discrete pre with a LDR pot designer by Greg Ball (SKA amps), and an older Twisted Pear chip based preamp design(Kookaberra) which uses a chip to attenuate the volume. Both are nice but the class A outclasses the TP. I was looking for something cheap to use with a class D am and a Chipamp.com LM3886 amp projects that I had recently built. I didn't want to go to the expense of building another pre, and had never just tried a passive pre just using a pot. I was going to get one of the less expensive pots that use a bunch of descrete resistors since many have said that they are superior to standard pots like Alps and the like. Then I came across the really cheap DACT type pots that used SMD resistors so I took a shot and picked one up. I picked 20K because it had been recommended for the class D amp that I have been messing with. I compared the pot with the T.P. Kookabarra pre with a recC, a class D, and a LM3886 chip amp. In all cases the sound was very clear, blacker background, it seemed more direct than with the active pre, maybe the soundstage was deeper. The active pre sounds nice but in a direct A/B comparison it seems to smooth things out, it seems that some low level detail is getting lost. I think that I prefer it over the active pre, at least for now. For ten bucks I think that I'm going to buy a few more, you can't go wrong. I haven't compared it to the Class A pre. But I did compare the Class A to the Kookabarra using a RevC and it had a lower noise floor, allowed more detail to come through, blacker background, deeper image, and had a smoother sound. Don't get me wrong the Kookabarra does sound nice and cost a lot less to make than the class A, but the class A discrete pre made the Kookabarra sound slightly harsh in comparison. By the way the RevC sounds better than the modified Class D amp that I just put together, it's not in the same class. But I have to say that I am impressed with the chipamp.com LM3886 amp, the revC is better but the LM3886 isn't too far behind.

PJN
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Old 19th July 2011, 11:43 AM   #7
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PJN
That is an awesomely descriptive post! We need more just like them to advise those building them.

udailey
I've read your post that states a lower pot value (ie: 5K) will sharpen the amp and raising the value will sweeten it. I like comparisons that fall into one of the four categories above so would you say that a higher value pot will make the MyRef more euphonic? Do you make this assertion based on experience with the same volume controls except for the value? What do you think is going on here to create this effect?
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Old 19th July 2011, 02:17 PM   #8
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Quote:
Originally Posted by yldouright View Post
Is 10K the optimum Rt for the Europe mains only?
I'm not sure what the effect of line voltage might have on attenuator choice (just trafo input to same AC output).

To answer the original question, I have tried a Lightspeed clone and TX102 transformer volco. Both are very good, but I haven't tidied up the grounding in my MyRef chassis (safety earth is fitted, of course), and I have a slight hummmmm with the LS.
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Old 21st July 2011, 09:24 PM   #9
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i'm using a tubed preamp that was about 3 times the cost of the myrefc. it's a silvaweld swc-1000bfa and the transparency of a passive aside, the liquidity of this unit is something i will never trade for. before this i was using the amp straight from modded lite dac 60 with asio foobar internal volume control that's suppose not impart any digital loss. and i think it's correct that myref doesn't need an active buffer because with that previous setup the dynamics and soundstage were just as big if not bigger... actually it's a hair bigger on both aspects. but my silvaweld has a 300b in the power supply and sounds like it's in the audio path!... and of course it gives me that hologram imaging that only tube can. i guess that's enough rant from me.

Last edited by PreSapian; 21st July 2011 at 09:29 PM.
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Old 22nd July 2011, 02:53 AM   #10
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jonclancy
I wasn't thinking along the lines of mains power output as I was about the power variance and cleanliness. I was going on the assumption that there might have been a reason to choose a lower value pot other than the obvious one of source compatibility/matching. What would be the likely sonic result of using a 100K value attenuator instead of the 5-10K recommended by Mauro?

PreSapian
I may be a little confused by your post but I have interpreted it to say that when using your computer as the volume control feeding your modded lite dac 60, you thought the soundstage may have been larger but not as well defined as with your current silvaweld tube line stage. You also believe it may have had greater "dynamics" prior to putting in the silvaweld. Please narrow the meaning of dynamics so it falls within the four parameters above. Was it quieter or more immediate (better PRAT)?
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