Pot shunting

[Smeggy]

I've been mildly interested in pot shunting since I first heard about it, not for any reason other that it looked different and interesting. Anyway, I shunted my EHHAs RK27 earlier and call me nuts, but it sounds a shitload more detailed and clear to me now than before. I'm hearing all sorts of subtle little things quite clearly than never caught my ear before and I wasn't even trying to listen for it, they just appeared in a way they never had before.

Maybe shunting really is that good or maybe my ears are just super sensitive right now, whatever, it seems clarity is greater, detail and spaciousness have improved and soundstage has expanded too with a much more natural sense of space. The amp was pretty incredible already, changing tubes and feedback made a big difference to the bottom end while the origial tubes still had the top end sewn up. After the shunt the tops are now as good/better than the original tubes while retaining that awesome bass power and body.

I'd be interested to see what experiences anyone else has had doing this, and if not, a quick bit of rearranging and two resistors are all that's needed to try it. I didn't think a volume control could have this big an impact and I'm assuming the RK27 is pretty decent in it's price range. I'm wondering if this type of difference occurs with those spendy pots out there.

I like this a lot

[n_maher]

Your topic is very, topical, for me today. I decided last night to finish up my little balanced PIMETA project only to find out that the 4-gang alps pot that I have only has three functioning decks. So I'm thinking that I'll have a go at the whole shunted pot thing. I'm pretty sure that I understand what's going on and that the illustration below is how I'll want to wire things.

I could have sworn that I'd seen a picture similar to this one that showed the actual wiring scheme (the "for idiots version").

If someone has a working drawing like that of the balanced setup it'd be appreciated as a sanity check.

[Looser101]

Like this?

[Spiug31]

I`d expect the balanced shunted pot plan to be this

simply replacing the fixed value resistors used in this design http://www.tweakaudio.com/Ultimate%20Attenuators.html

with variable resistors.

[n_maher]

Like this?

That's essentially the same schematic (of the pot anyway) that I posted above. What I was looking for is a drawing showing the actual pot like the second pic that I posted. What seems odd to me is that in both schematics it would appear that the connection point #1 which is normally ground in traditional use and output in the single-ended shunt config goes unused in the balanced shunt config. Is that right?

Actually now that I look at it the scematic that I posted doesn't match the one that you did. At least it doesn't look like it does to me. Clearly I'm having issues understanding this fully which stinks since the SE shunt config makes perfect sense.

[Spiug31]

Head-Fi: post by dsavitsk - View Single Post - Shunt pot volume control

is that of any help ?

[Looser101]

That's essentially the same schematic (of the pot anyway) that I posted above. What I was looking for is a drawing showing the actual pot like the second pic that I posted. What seems odd to me is that in both schematics it would appear that the connection point #1 which is normally ground in traditional use and output in the single-ended shunt config goes unused in the balanced shunt config. Is that right?

Actually now that I look at it the scematic that I posted doesn't match the one that you did. At least it doesn't look like it does to me. Clearly I'm having issues understanding this fully which stinks since the SE shunt config makes perfect sense.

There is a bit of description of how it works in paragraph 4 HERE.

What to do with the extra pin comes down to which is more detrimental if the wiper lifts off the track (open circuit or max value of pot).

[nikongod]

That's essentially the same schematic (of the pot anyway) that I posted above. What I was looking for is a drawing showing the actual pot like the second pic that I posted. What seems odd to me is that in both schematics it would appear that the connection point #1 which is normally ground in traditional use and output in the single-ended shunt config goes unused in the balanced shunt config. Is that right?

Its about time you came around

In the balanced configuration the pot does not have a ground connection. The 1Mohm (or whatever value) resistors at the input of the pimeta will provide a ground reference.

I dont have a drawing, but hopefully this will help:

pins 3&2 tied together, with a resistor between the pot and the XLR. then off to the side goes the output exactly like whats on pin1.

I always wire it backwards the first time (when volume is at minimum the resistance between the 2 resistors should be minimum where connected to the pot) so it may be best to test with sacrificial headphones. Balanced Koss FTW! with alligator clips you can just use one side of the headphones just wire tip and ground to one channel of the balanced amp.

[Dusty Chalk]

gerG on head-fi went even further and did a preamp-less speaker system. He said it was a bit loud. I suggested different amps for different volumes, and he liked the idea. He said he wanted to implement it with huge electric-chair type throw switches. I liked the idea.

[dBel84]

Hi Nate, I first heard of the single pot shunted for balanced when Ari posted in this thread.

" use 2 resistors each 1/2 the recommended value. one on each "end" of the pot.” "

I have never done it myself but I don't think the swiper end should be connected to either "leg" . if it is, it looks like it will for a voltage divider network and cause imbalance - more like a balance control.

Smeggy , to answer your question. I have done this a few times and is now my default option for wiring up a pot ( I have not shunted expensive attenuators as I don't own any , the RK27 shunt mod is plenty good for my sanity )

..dB

EDIT:

jeez - a few seconds go by and all this activity

[dBel84]

I dont have a drawing....

this needs to be corrected - I think I have the concept down too but a simple idiots guide for ( my ) sanity will go a long way. Get out that paper and sketch one, mail it to me, I will scan it in

..dB

[Spiug31]

I think I may be understanding it

(or not )

A standard pot / voltage divider when the ground terminal is left unconnected changes in function from

to

so this

will function as a stepped variable resistor when when the ground terminal is left unconnected.

[cetoole]

If someone has a working drawing like that of the balanced setup it'd be appreciated as a sanity check.

I cant say no to a chance to show off my amazing paint skills.

[Looser101]

Edit: Nevermind!

[Smeggy]

Nice , glad to see I'm not totally deranged for listening to Ari

Very good improvement overall and prolly the cheapest awesome upgrade ever.

[n_maher]

I cant say no to a chance to show off my amazing paint skills.

Time to give this a shot. If I blow up my treasured HD201s Colin I expect some O2s in the mail.

[Smeggy]

I wait with breath bated. I'll be interested in your take though I imagine a cheap pot will give the more profound effect. What pot are you trying it on?

[cetoole]

Time to give this a shot. If I blow up my treasured HD201s Colin I expect some O2s in the mail.

Be that the case, feel free to have your council contact my council.

[n_maher]

Does 33k sound like an ok value for use with a 50k pot? It's that or 10k for now.

[Smeggy]

Ideally 47k is supposed to be best, I didn't have that so mine are 51k, 33k will probably reduce you available volume a bit but should work fine from what I've read.

[n_maher]

That didn't go well. Time to try again, and hopefully get it right this time.

[edit]Nope, NFG. Hard to imagine what is screwed up this time, going to try it on another source and make sure that isn't the issue but I don't expect that to change things. I definitely had the wiring wrong the first time but I'm pretty sure that I have it now. Each channel output is connected across one wiper of the pot with the (#2) wiper pin tied to the (#3) input pin and the in-phase signal connected to this side. The out-of-phase signal is connected to the (#1) ground pin. This is with an Alps RK27. Each channel input is done similarly with a 33k resistor in series with each connection. The output wires are connected to the PIMETA boards at the center two connections in the RK27 footprint, that seemed like the only logical place to do so. I guess I'll post pictures later.

Edited August 9, 2009 by n_maher

[nikongod]

That didn't go well. Time to try again, and hopefully get it right this time.

what happened?

to answer the Q on the previous page, 2*33Kohm is a good starting point for a 50Kohm pot.

[n_maher]

what happened?

to answer the Q on the previous page, 2*33Kohm is a good starting point for a 50Kohm pot.

Read my edit above, I definitely had things wrong the first time but after fixing my mistake (at least I think I did) the problem persists.

[Looser101]

Read my edit above, I definitely had things wrong the first time but after fixing my mistake (at least I think I did) the problem persists.

What did you do with the input ground?

[n_maher]

I tried it two ways. On one, I floated the ground which didn't work well and produced the exceptionally loud buzzing sound but did allow for some audio signal to pass through (albeit not volume controlled) and when I tried tying the input ground to pin1 on XLRs I get no audio. So neither seems correct.

Should I be doing something else? I currently have the IG of the two boards tied together, which seemed like the logical thing to do.