Bottlehead Forum
Bottlehead Kits => Crack => Topic started by: EarWorm on August 10, 2014, 09:26:17 AM
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Anyone have working knowledge of 40+ stepped attenuators in their Cracks?
I'm afraid the 20 or so steps just won't be enough control. I know the 40+ are expensive but...
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You could add a DPDT switch make a 20 step switch into a 40 step switch.
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The 36 step set up with the course and fine adjustment like the Submissive is a joy to use.
If you have not seen it http://bottlehead.com/submissive-volume-source-control-kit-specs/
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Hi all instead of creating another thread i decided to post my question here.Anyone is familiar or have used KHOZMO 48 STEP ATTENUATOR?This one is from Partsconnexion for $179 i think it's not bad.Thanks!
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That Khozmo attenuator looks even sweeter when Parts Conexxion runs it 20% off sale.
I fell under the 20% spell last month and now I own capacitors the size of trash cans. ;D
The 41 stepped attenuator from Acoustic Dimensions seems to be popular among folks who are left wanting from 20 stepped attenuators. Not sure how many folks put the 40+ in a crack because of their price. I am very sensitive to volume changes and channel balance so the 40's seem the place to start for me. I always seem to want a volume on the 20's that falls in between settings. I blame my editing battered ears which have endured 24 years of high end editing in NYC. That's a lot of volume adjusting through the years and ones ear gets sensitive to that kind of thing.
I'm not opposed to a smooth well made continuous control though.
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There is a pic of a Crack with a Khozomo fitted somewhere it is a big unit seem to recall the small speedball where moved or left flying on their leads to make enough room for it.
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Yeah i installed this PoS and i'am not liking at all it sounds like congested and reduced in bass and details.According to the vendor this PoS is stereo but it could be Mono.
https://www.head-fi.org/content/type/61/id/1168192/width/500/height/1000/flags/LL
(http://)https://www.head-fi.org/content/type/61/id/1168191/width/500/height/1000/flags/LL
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Before buying a Foreplay 2 I had an Audio Research Corp. SP-14. It had 3 ranges for volume and many steps on the volume control. I could usually reach the same physical volume level on all three ranges. So it was redundant. But the suggestion of a selector switch with a dropping resistor for a low range, the first response to your post, would give you a lot of versatility.
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Now i'am done with this attenuator shopping no more expensive Attenuators but since my stock POT developed some kind of a sticky spot if i turn the shaft.I will get one of those ALPS pot and Mundorf caps.
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How might one go about adding a selector switch with a dropping resistor for a lower range?
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What is the impedance/resistance of your attenuator?
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Grainger I don't have one yet. I'm looking for advice on possibly getting a 40+. Size won't matter because I intend on making a larger chassis.
As a side note to the Audio Research gear, I once owned an SP 8 and an SP 10. Loved the sound of both units. I eventually sold both units because I really want to see the tubes in a piece of gear on the outside. Had some Conrad Johnson stuff also. Same thing. Tubes hidden inside. Free those valves! Tubes should be seen and heard.
ILuvmusic 2' perhaps you have seen the video from HiFi Collective on tweeting the Khozmo.
http://youtu.be/wx9qqDDlZeM
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Ok, I'm screwy about dB and attenuation. So here goes....
If you have a 100k Ohm attenuator (a standard value) you can put a 100k Ohm resistor and cut the voltage in half. According to the internet that is 1/2 the voltage. For more attenuation you can use a 220k Ohm resistor. All these are standard values.
You would bring the inputs that would go to the volume control to the DPDT toggle switch. You solder them on the center lugs. A DPDT toggle switch has 6 lugs on it. So the center ones are fairly obvious.
From one of the end lugs you would take the resistor to the "input" of the stepped attenuator. From the other two lugs you take wire to the same two input lugs of the stepped attenuator.
Be careful not to cross up right and left.
Imagine the 6 lugs being split into right and left three lugs, down the center. Here is what isn't intuitively obvious: when the switch is "down" it attaches the top and center lugs for left and right. When the switch is up it connects the bottom and center lugs for right and left.
Is this helping?
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Thanks Grainger that does help quite a bit. Not sure if I'll go that route just yet but now my brain is sifting it around.
When you say you are screwy about dB and attenuation do you mean theoretically or being very sensitive to level changes?
Since we are on the subject of volume controls and I have limited knowledge, it is not totally clear why folks are so fond of stepped devices. Are they a preference for quality volume control because of a design inherently superior to other types?
My sonic gut tells me that even 40 steps might prove a bit annoying in time so I'm also open to a high quality continuous volume control of which I know nothing about.
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It is not hard to add it afterward.
I couldn't find a true formula for dB attenuation relative to voltage. I know it is a Log10 function but will have to drag out a text book to follow it.
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I remember text books.
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I've got one of the best under my forearm as I type. It is Circuit Analysis, but doesn't cover dB.
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No textbook required (http://lmgtfy.com/?q=voltage+dB+calculator)
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Paul, thanks, that is what I thought. It is now bookmarked.
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History explains some of that:
A "Bel" (named fro Alexander Graham Bell of course) is a factor of 10 in power - 10 watts is one Bel greater than 1 watt. So Bel = log10(power ratio).
A deciBel is a tenth of a Bel, so dB = 10*log10(power ratio).
Power is proportional to voltage squared if the resistance does not change, so dB = 10*log10(voltage ratio squared) = 20*log10(voltage ratio). That's why logs are so useful, exponential powers turn into multiplication in the log-world.
Power is also proportional to current squared if the resistance does not change, which you can remember with "twinkle twinkle little star / power equals I-squared R".
DO NOT use the second verse "little star up in the sky / power equals R-squared I" - you will flunk the test as many before you have done!
More historical nonsense - current is I for Intensity, voltage used to be EMF for Electromotive Force, E for short. Mostly people use V for Voltage and let the history go, but so far I remains with us. ... yes, we no longer let the Force be with us, just the Intensity. Kind of sad.
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Are there any folks who have forgone an attenuator all together and made the Crack a stand alone amp onto itself to be driven by a pre amp or variable source?
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Yes, this is one of the roles we intended for the Submissive.
-PB