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Insanely cheap stepped attenuator? (Crazy Eddie style) - Page 3

post #31 of 33
Yup, just as our good friend Steve says, you guys should never use the "shunt pot" configuration to get a volume control for a balanced amp. Only limit yourself to a 4-deck one or annoying yourself with separate left and right volume controls. It's much better to pay more money so you can avoid any association with a perfectly valid technique, just because some people believe it has benefits that it doesn't.
post #32 of 33
Quote:
Originally Posted by Fitz View Post
Yup, just as our good friend Steve says, you guys should never use the "shunt pot" configuration to get a volume control for a balanced amp. Only limit yourself to a 4-deck one or annoying yourself with separate left and right volume controls. It's much better to pay more money so you can avoid any association with a perfectly valid technique, just because some people believe it has benefits that it doesn't.
There's a little more to think about beside just the signal path mythology when deciding whether or not to use a balanced shunt attenuator.

If you use relatively small value series resistors in order to avoid high output impedance and throwing away a bunch of gain, then the taper gets screwed up and your range is significantly more limited, i.e. you'll be reaching maximum volume in the lower end of the rotation. And since this is a stepped attenuator, level adjustment will be much more coarse, and you ultimately end up with far fewer useful steps.

You can achieve a much greater range if your series resistors are on the same order as the pot. But now you have a much higher output impedance (as far as I can see, it's only offered in 50k and 100k versions) and you're throwing away a bunch of gain because even with the volume turned all the way up, you're still attenuating the signal by about 10dB.

So you have to weigh those two considerations against one knob versus two.

k
post #33 of 33
Thread Starter 
Ok, so I got the el cheapo stepper last week and put it in my zero. I've tried typing out the long version of the story a couple times but I kept losing my train of thought so I gave up each time. It was a bit of a pain with no pins attached. Keeping the small leads attached to the pot while soldering it to the board made for some interesting expletives. The output jack would not work right after I did it so I thought I screwed something up and spent an hour messing with it and using a lot more solder than I would like any one to see. I had to mess with the jack to get the left channel to work so I had to quit before I played the hammer game.

Today, I sat down again to take a look at my zero and try to find a replacement output jack for it. That was much easier than expected so I ordered two just to make it worth the cost of shipping. So after last weeks frustrations I decided I'd hook it up and see if I might be able to fiddle with it when I'm not ready to pummel it to death and get it working. So I plug it in and whammo! It just works. Just like normal. No missing channel. wth... It just figures, I spend the money on the part and it starts working fine. I hate Murphy.

Well, I can't be too ticked, I only spent about $10 on the replacement jacks w/shipping. Actually, I'm not ticked at all anymore. I can't believe this thing is a zero. I can't believe a volume pot can make so much of a difference. Definitely worth the $10 for the attenuator. I highly recommend anyone who has either modded their zero or is planning on it to swap out the crappy stock pot and throw one of the gigawork steppers in.

Now to fix the optical input and do something about that annoying switching relay. The clicking is drving me nuts.
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