Does the volume control effect sound quality?

We've done a lot of mods on Dynaco equipment over the years in fact that is how we got started back in the 70s. The volume control on the older PAS-3 was always a problem. Eventually we had some custom switches made up so we could install a stepped control in the unit.

The impedance of the control is important. The stock control on the original PAS-3 was 250K. If you install a larger value it will mess with the 12AX7 at the input of the circuit as the volume control and the input capacitance of the tube interact (Miller Effect). However if you go below 100k don't expect any bass out of the phono section!

IOW you do have to choose the value carefully. BTW it will not matter how nice the control is if these parameters are not observed- the same electrical rules apply to the best controls as the do to the cheapest.

Agreed! :)

I know we aren't supposed to be off topic here but is the Pope Catholic?? IOW, yes.

Georgelofi, we've done a lot of experiments with controls and I find that I can't agree with your regarding relays. Universally they were inferior to a good quality rotary stepped switch. However, switches are quite variable so I can see good relays being better than some switches. But if you have higher quality switches the relays don't stand a chance.

From what I understand of light-activated devices, one would have to be quite careful in doing a substitution in the case of this preamp! The light activated devices I have seen can cover a pretty wide range of resistances- the higher values, even if a better device, will still introduce coloration that an inexpensive control of the right value wont have due to the Miller Effect issue. IOW things are getting dicy if the control is able to exceed 250K.

Almost all rotary switches have a stiff disc wiper made out of a different material to the springier metal that the leaf/leaves are made out of.

'Almost all' *but not* all. I can think of several off the top of my head that use similar metals and some of those are not even 'high end' parts.

This is for a control going in a PAS-3 or similar circuit. If the values are not observed there will be a price paid in the form of bandwidth.

Phd, you are correct. Start with the right value. Only then do you switch things up, if you will pardon the expression :), with better quality.

Dracule1, both. First, the site commits a web 1.0 error, that of endless rant/scrolling. Second, many of the conclusions don't seem to arise in a scientific manner, instead are based on deductions without understanding of the math behind them that is at play in each instance.

I'm with dave on this one.

However if you are just replacing the stock part, you can find replacements that will sound better for under $30.00.

Is this an older preamp? If so, you may have bigger fish to fry as far as the sound goes. All the older ones need new filter caps in order to work right.

OTOH if you are really trying to push the performance, it is possible without going completely nuts and many of the updates/mods are more important than the volume control. It does not make a lot of sense to install an expensive volume control unless you are also planning or already have these updates!

Funny, the original poster is absent on this thread. My comments have been directed to the issues raised in his post.

To that effect, George, I think you are mistaken- this was indeed about the Dynaco PAS-3 and the installation of a replacement volume control.

I don't think anyone on this thread has denied that the volume control makes a difference. However there are engineering principles in play and they are such that if ignored, the result could be that a $4.00 volume control from Radio Shack can sound better than the best light-activated volume control system available.

There are plenty of other situations where that is likely not the case. IOW this cannot be taken out of context- the parameters of the surrounding circuits cannot be ignored. So if a light activated device is to be used, it would have to be one that is designed for the circuit.

That website is terrible!