[amb]

 
Quote:

Thanks. I take it that when you say they will have the same (large) adjustment simply means that wiring the attenuators in this way will not make the volume steps any smaller.

When either one is at maximum setting, the other one would work like a "normal" one-attenuator setup.  But if one is set lower, then the other one has less range to "work with" so to speak.  I am not sure if that's what you have in mind, but neither one would be a "fine adjustment".
 
Quote:

 
It did it on all channels... solve the problem by putting a 100 ohm resistor between the output and ground and probing the drop across that, not sure why it mattered but it fixed it, I guess that was able to lower whatever no-load oscillations were occuring

What are you using as the output wiring from the board to the jack (or are you probing on the board itself)?  What wiring is on your meter's probe leads?  Maybe there is significant capacitance or inductance.

 

[chronomitch]

Quote:

When either one is at maximum setting, the other one would work like a "normal" one-attenuator setup.  But if one is set lower, then the other one has less range to "work with" so to speak.  I am not sure if that's what you have in mind, but neither one would be a "fine adjustment".

I understand. What I'm going for here is a variable pre-attenuation circuit. I thought the easiest way to do that would be to just add a second attenuator. I suppose I could simply just add in resistors as described at http://www.goldpt.com/mods.html, but I will be using several different sources which will have various output levels. In other words, I need the pre-attenuation to be variable.
 
I have seen some interesting designs which involve mounting attenuators on the input jacks of amplifiers, but I thought I could get the same effect by putting in another attenuator in the volume control section.

 

[amb]

A diagram would be helpful here.  The cascaded pots you described is the first arrangement in the illustration below, and both pots could attenuate down to -∞ dB.
 
I added a second, alternative configuration.  In this setup the first pot will have only up to -6dB of attenuation (assuming the same value pots), while the second one can attenuate down to -∞ dB.
 

 

[chronomitch]

Quote:

A diagram would be helpful here.  The cascaded pots you described is the first arrangement in the illustration below, and both pots could attenuate down to -∞ dB.
 
I added a second, alternative configuration.  In this setup the first pot will have only up to -6dB of attenuation (assuming the same value pots), while the second one can attenuate down to -∞ dB.
 

I'm planning on using the setup in the first illustration. The main problem I am trying to combat here is that the beginning attenuation steps of most stepped volume attenuators are too large, especially when running with a hot source. I tend to like listening to music at lower volume levels, so it is difficult for me to find a good step (it is either too soft or too loud). This problem is further complicated due to the fact that I want to use multiple sources which will run at different output levels.
 
If I use a second attenuator, I can start it at the maximum volume level (i.e. no attenuation), and then back it down a notch or two. Since the upper steps of the attenuator are smaller, this will allow me to get to the right volume level. In other words, I will be able to attenuate the volume in smaller decibel steps.

 

[dude_500]

Quote:

What are you using as the output wiring from the board to the jack (or are you probing on the board itself)?  What wiring is on your meter's probe leads?  Maybe there is significant capacitance or inductance.

The hookup wire in the amp to the jack is about 8" of generic copper hookup wire, I think 18 gauge. Regardless, I'm testing it right at the board with generic multimeter probes. I've never had issues with this meter, not sure what's up with it... but regardless I got the problem solved with the 100ohm loading

 

[amb]

chronomitch, as I said, the top attenuator in the second diagram only has a 6dB range, so each "step" will have very fine adjustment.  You use the bottom attenuator to set a basic volume, then fine tune using the top one.

 

[chronomitch]

Quote:

chronomitch, as I said, the top attenuator in the second diagram only has a 6dB range, so each "step" will have very fine adjustment.  You use the bottom attenuator to set a basic volume, then fine tune using the top one.

Unfortunately, I doubt 6dB will be enough. My current M3 amp uses a gain of 5, and even with some Rothwell in-line RCA attenuators (-6dB), I usually don't move the stepped attenuator much past 9 o'clock.

 

[Beefy]

Quote:

I have two Goldpoint stepped attenuators that I am planning to wire in series for my beta22 volume control. They are rated as 10k, so I'm guessing doing this will result in an overall 20k resistance. This should still be fine, right?
 
I will be using the amplifier with a number of different sources, so I want to have a good amount of play in the volume control. In other words, I plan to use one control just to get the volume in a decent range and the other for fine tuning.

A possible alternative......
 
Set up the attenuators as per AMB's second picture, with both attenuators in series. But instead of two 10k models, use a 50k as the first attenuator and a 5k or 10k as the second. With a 5k as the second attenuator you can get ~21dB of range from the first attenuator, with a 10k you could get ~15dB.

 

[digger945]

why not just use the first attenuator as a 2 wire shunt. That would give you the ability to kill as much signal as you like, with no added resistance directly between input and the second attenuator. I'm sure some of them would overlap, but that's 529 possible combinations(ignoring the zero positions)

 

[Beefy]

I can imagine that it would get confusing trying to use it that way. If you have two set up such that the first in series is fine control, and the second is coarse, it is much easier to understand how to get a good level.

 

[chronomitch]

Ok. I'm pretty confused by this point, so I'm taking AMB's suggestion and providing some pictures. Please note that I only have two GoldPoint attenuators, and they are both 10k.
 
This is a diagram of the inputs/outputs of the attenuators and the epsilon 22 board with no wiring. Only one channel (right) is shown.

 
This next picture shows how I am planning to wire the attenuators. As I understand it, this should allow both attenuators to attenuate down to negative infinity.

 
And yes, I know my drawing skills are crappy.

 

[digger945]

The way amb described would probably work best, as the way I put it would halve your effective overall max value to 5k if you're using 2 of the 10k attenuators.
Do let us know how it works out for you. Below is a diagram to explain what I had in mind. It would give the ability to shunt a lot of the signal to ground, but I don't think it would work very good.
Each click to turn the volume down on the first pot will alter the input impedance of the amp.

 
Edited to reflect amb's correction in post #2773 below.

 

[amb]

 
Quote:

Originally Posted by chronomitch /img/forum/go_quote.gif
 
This is a diagram of the inputs/outputs of the attenuators and the epsilon 22 board with no wiring. Only one channel (right) is shown.

 

Your ε22 volume pot connector pin assignment does not match the board.

 
Quote:

The way amb described would probably work best, as the way I put it would halve your effective overall max value to 5k if you're using 2 of the 10k attenuators.
Do let us know how it works out for you. Below is a diagram to explain what I had in mind. It would give the ability to shunt a lot of the signal to ground, but I don't think it would work very good.
Each click to turn the volume down on the first pot will alter the input impedance of the amp.

 
This scheme will short circuit the source's output to ground when the first attenuator is turned down to minimum.  Not a good thing!  Also, that first attenuator shunts the signal to ground, but its effect is completely determined by the output impedance of the source.  If the source has very low output impedance (e.g., a few ohms), then most of the adjustment range of the first attenuator will have little or no effect until the first (minimum) click or two.

 

[chronomitch]

Quote:

Your ε22 volume pot connector pin assignment does not match the board.

I know. I just did it from memory.

 

[digger945]

Quote:

 

 
 
This scheme will short circuit the source's output to ground when the first attenuator is turned down to minimum.  Not a good thing! 

Whoops. I fixed it.
 
I tried to just change the url link thing, if that's possible, so that quoted posts would reflect the changes, but it didn't work. I'm not even sure it's possible.