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making my own volume attenuator? - Page 2

post #16 of 30
3/9/10 at 11:32pm
Thread Starter 
well, the shure attenuator will do until I get the burson headamp...I was hoping that soldering a pot to two 1/8" connectors would fix my problem, but it most likely won't.

I'll put the headamp stepped attenuator as low as needed and finetune w/ digital attenuation(in 64bit float)...that sounds like an acceptable solution to me
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post #17 of 30
3/10/10 at 12:15am
if you have the pot *close to* the amp, then it becomes part of the active circuit and no longer a 'passive preamp'.

if the pot is in a box and on a cable that goes even a little distance, it then needs a buffer (for proper design). so then you get back to style 1, which is keeping the volume control element close to the next stage that you are attenuating in front of.

the general idea is an old one: run your source hot at full '0db' level out, have it drive whatever cable length you need, then attenuate at the very tail end of that run, right where the next stage is.

a middle passive box is just not the right way to vary volume, even though it seems very convenient. make it an active buffered stage and then you'll be fine.
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post #18 of 30
3/11/10 at 6:34am
I just looked up the price for an ALPS RK50.....$995......are you freaking serious?
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post #19 of 30
3/11/10 at 10:30am
overpaying for 'just a pot' does seem quite insane to me.

that's why a lot of us are going with relay attens or other non-pot solutions. I would put a relay bank up against a pot (of any time) and the relays will always win on tech specs.

my price limit is much much lower if I'm asked to pay more than $50 for a resistive pot, I'll look for an alternative.
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post #20 of 30
3/11/10 at 10:44am
Thread Starter 
hehe, ok..you guys nailed it! I'll use a mixture of stepped attenuator on the burson amp + slight 64bit float digital attenuation, that will do nicely.

I still wonder why the Shure attenuator gives me a far more balanced sound on my cd1k than the straight DAC output, but it's obviously an impedance mismatch again...I'd need to document myself about impedance

Burson and Audio-GD are selling buffers that only do one thing: match the input/output impedances: Audio Buffer 160
Quote:
Different circuitry designs produce different input and output impedance. Therefore, impedance compatibility needs to be considered
I just wish someone came up w/ a higher grade attenuator than this Shure "toy", but its bang for bucks ratio is still very high nevertheless
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post #21 of 30
3/11/10 at 2:18pm
Quote:
Originally Posted by leeperry View Post
hehe, ok..you guys nailed it! I'll use a mixture of stepped attenuator on the burson amp + slight 64bit float digital attenuation, that will do nicely.

I still wonder why the Shure attenuator gives me a far more balanced sound on my cd1k than the straight DAC output, but it's obviously an impedance mismatch again...I'd need to document myself about impedance

Burson and Audio-GD are selling buffers that only do one thing: match the input/output impedances: Audio Buffer 160


I just wish someone came up w/ a higher grade attenuator than this Shure "toy", but its bang for bucks ratio is still very high nevertheless
Using a normal stepped attenuator on the output of your sound card will not work. They use resistors of much higher values than your headphones and every step will be mute. You either need to add an amp/buffer afterwards or use resistors of much lower values than would come preinstalled.
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post #22 of 30
3/11/10 at 2:54pm
he doesn't like the idea of a buffer or gain stage, but it keeps coming back to that. just can't get away from it. its how things work
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post #23 of 30
3/11/10 at 3:10pm
Quote:
Originally Posted by linuxworks View Post
he doesn't like the idea of a buffer or gain stage, but it keeps coming back to that. just can't get away from it. its how things work
The second poster posted some hints that may be helpful to the OP's query.

Quote:
Originally Posted by nikongod View Post
If you are interested in this sort of thing, I would czek out dsavistik's webpages.

Somewhere in there he mentions the idea of using an autoformer directly off of the output of a CD player. This effectively allows for volume control as well as low output impedance.

A pair of nice autoformers (with switches) can be had for a hair less than an RK50. After that its all the same junk of a case, knob, and jacks.
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post #24 of 30
3/11/10 at 3:14pm
Thread Starter 
humm? I gave up on the idea a while ago already...we're cool! I've ordered a Burson HA-160 anyway.

but, again, I still wonder why the $15 Shure attenuator gives me a far more balanced sound on my cd1k(even when set at the max volume) than the straight DAC output...but that will have to remain a mystery, I guess
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post #25 of 30
3/11/10 at 3:34pm
Quote:
Originally Posted by leeperry View Post
but, again, I still wonder why the $15 Shure attenuator gives me a far more balanced sound on my cd1k(even when set at the max volume) than the straight DAC output...but that will have to remain a mystery, I guess
for some people, adding distortion is very pleasing.. some people have tin ears. perhaps one (or both) of the above?
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post #26 of 30
3/11/10 at 3:56pm
Quote:
Originally Posted by leeperry View Post
humm? I gave up on the idea a while ago already...we're cool! I've ordered a Burson HA-160 anyway.

but, again, I still wonder why the $15 Shure attenuator gives me a far more balanced sound on my cd1k(even when set at the max volume) than the straight DAC output...but that will have to remain a mystery, I guess
It could be that when you attenuate the signal digitally down to 1% of the original, the digital errors become more significant and sound worse than a low end analogue solution.
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post #27 of 30
3/11/10 at 4:40pm
Thread Starter 
Quote:
Originally Posted by luvdunhill View Post
for some people, adding distortion is very pleasing..
the difference w/ or w/o is anything but plain THD distortion...it's most likely a matter of impedance, the same reason ppl would add 75Ω resistors on their IEM: headphone impedance adaptor - Google Search
Quote:
it sounds 'brighter' (sparklier?), like the music was moved up the spectrum. I thought the bass was lighter than without the adaptor but it's now probably what most people would call 'tight'
it does affect the FR to add resistors upfront...and as I understand it, the shure thingie is just a variable resistor.

and here, auzen says that plugging headphones to a plain line-out would be a terrible idea impedance-wise: http://www.auzentech.com/site/images...l_3498a465.png
Quote:
Originally Posted by luvdunhill View Post
some people have tin ears.
so you don't just love dunhills after all, you would also appear to like talking about your personal issues on internet boards? I'd suggest making your own thread.
Quote:
Originally Posted by mugdecoffee View Post
It could be that when you attenuate the signal digitally down to 1% of the original, the digital errors become more significant and sound worse than a low end analogue solution.
64bit float volume attenuation is anything but significant.
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post #28 of 30
3/11/10 at 4:51pm
Quote:
Originally Posted by leeperry View Post
64bit float volume attenuation is anything but significant.
At the end of the day, however the signal is handled in the digital domain, if you want a signal out of a 16bit DAC chip that is 60db below peek you have only 6 bits to screw around with (and thats before considering dynamic range). good luck with that. The difference between a 6bit signal and 11 is clearly audible. If you have a 24bit DAC chip your a little better off. This is about to turn into a debate over whether attenuation in the analog domain is really worse than attenuation in the digital domain. What fun.

I suspect your issue is a combination of that as well as your DAC's inability to drive the load directly. Not so much that the sony headphones perform better with a higher source impedance as that is quite contrary to my own experience with other sony headphones (MDR-R10, MDR-CD900st, and MDR-f1 without the funky zobel/impedance network), but that the DAC fails hardcore when driving such a low impedance load.

What is the impedance of the shure thingy with the headphones plugged in measured sleeve to tip (or ring to sleeve)? I betcha its around 350 ohms. perhaps more.
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post #29 of 30
3/11/10 at 5:25pm
Thread Starter 
you're entirely right...but I only listen at very low volume, so I have yet to max out 16bit tbh..I'd guesstimate that I'd peak around 60/70dB, so as I understand it that'd still leave a lot of headroom...plus my media player applies some dithering in the end from 64float to 16int.

I read someone complaining about this shure toy, saying that if he played around lowering the volume on his player and increasing it on the shure(and the other way around), the FR would drastically change!

I've just used some crappy 32Ω/106dB phones I keep for tests(the cd3k drivers being a close call at 32Ω/104dB)...they read 35Ω w/o the shure, 40Ω w/ the shure at max, and 800Ω at min.

the catch is that the resistance increase is ANYTHING but identical on both channels, and it gets worse the more I attenuate the volume(at max attenuation it's like 800Ω L/500Ω R)..I guess this cannot screw up my cd1k drivers, right? or possibly my DAC?

tbh, the stereo imbalance is really annoying...but some positions appear to be not too imbalanced.
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post #30 of 30
3/13/10 at 11:20am
Thread Starter 
I guess I don't deserve a reply, but so far both my cd1k and spitfire are still very much working

anyway, that sounds interesting: http://www.head-fi.org/forums/f5/rev...-black-321463/
Quote:
The Stepped Attenuator is actually still a swept potentiometer, with notches that simply click and hold the knob. It is possible to select volume levels in positions between the clicks, and it is a higher quality pot with less channel imbalance at the lowest volume levels.
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