New Volume Pot

[lilolee]

The volume pot on my amp (EAR859 13w SET) is getting a bit noisy so I thought I'd change it for a stepped attenuator. According to the schematics it is a 4k7 log.

So far I haven't been able to track any down. So how could I accomodate a different value without causing a loss of sound volume?

Cheers

Lilolee

 

[jam]

Lilolee

Are you confident it is 4.7k and not 47k?

Jam

 

[GRollins]

Lilolee,
I agree with Jam, 4.7k sounds low.
Have you tried cleaning the pot? Any electronics house will be happy to sell you some spray cleaner that will dissolve any grunge that might have crept into your pot.

Grey

 

[lilolee]

Here's the schematic

http://www.leehibbert.pwp.blueyonder.co.uk/ear859.jpg

It definately says 4k7 log.

BTW any advice about what components to change and where to put the bypass caps.

Thanks a huge amount

Lilolee

 

[tvi]

Theirs another (cleaner) schematic listing 4k7 at
http://joelist.free.fr/schematics/Thorsten collected oddities/


Is the value that critical?

Regards
James

 

[GRollins]

No, the value of the pot isn't that critical, but...
Keep in mind that your source is going to see a 4.7k load. That's pretty low, and some phono stages, tape decks, CD's etc. may have a hard time with it. I regard even 10-20k as on the low side for input impedance. 47k is a good compromise, although many pieces use 100k, or even 1M.
If you're using a source whose output is capacitor-coupled, you're almost certainly getting a *very* high rolloff in the bass.
Really, the only reason to have an input resistor that low is to reduce cable-related sonic problems. I'll leave that one up to you.
By all means, change values if you like. At that point in the circuit, there's plenty of lattitude. (Or leave it the same, if you want...)

Grey

 

[walton]

Pot Value

There was a pronting error on the original article that appeared in HFN - which had the schematic. The correct value for the pot if 47K.

 

[lilolee]

Thanks Walton. I've spoken to some other filks and they agree with you.

I suppose I should just open her up and have a look!!!

I was going to go for a Goldpoint stepper and they have 47k if memory serves.

Cheers all.

Now about those capacitors......