New volume pot killed my sound

I've got an Audio Note Oto (push-pull valve integrated) with a Border Patrol power supply going through Klipsch La Scalas. It sounded great, but not long ago the volume pot started acting up - lots of crackling and hissing.

I spoke to Audio Note, who were very helpful. Unfortunately, the pot for this amp is no longer made, so they recommended a Noble pot as the only one which would fit - apparently, the original Oto pot is a funny size.

Anyway, bought the Noble and had it fitted. Oh dear. I went from clear, lively, open sound that was a joy to listen to, to (relatively) dull, thick sound. No joy at all.

Has anyone else had a similar experience and managed to rectify things?

 

Yup, I replaced my cheapo chinese pot with a blue amps and it was never the same again. I gave it a few months but if anything it got worse. I even fitted a cheapo ohmeg from CPC and that was an improvement. Ive sorted it now, I did the psuedo shunt mod and its fantastic. For the cost of a couple a resistors and abit of soldering its well worth it. You could also try a stepped attenuator, theres a few on feebay but www.hifi-collective.co.uk have started selling them for similar money. Id def give the shunt mod a try first.

 

That was my impression of the noble pot aswell, i have now gone to the pseudo shunt idea, useing Vishay resistors.

 

whats a pseudo shunt mod?

could someone tell me in noddy language? - also do you need a special vol control, or does it just help?

ta!!

Chris

 

nb my pre currently has an alps pot, a 'blue' I think.

Whats a lot better?

 

Cheers chaps, the advice is much appreciated. Good to hear I'm not the only one unhappy with the Noble. Listening to sludge instead of music was really getting me down.

The pseudo shunt mod sounds good. Unfortunately, I'm electrically/electronically ignorant and have no idea how to achieve this.

Could you tell me where to find details of this mod, please, so I can pass them on to my amp repair man?

 

Pseudo shunt, you have a resistor direct inline with the input, the volume pot is used as a potential divider to ground. The signal only passes thru the resistor.

Busy at the mo, will try and search for a diagram later.

 

Try this very comprehensive site re shunted pots
http://www.siteswithstyle.com/VoltS...Pure_Shunt.html

Something like this

 

Its also worth mentioning that the pot is connected the opposite way round when doing the shunt mod. What was the earth becomes in/out via a resistor. The wiper (the middle pin) and what was the input pin are then wired to earth.

 

Sorry for the size of the pic. Anyway Pin 1 was input, Pin 2 is the wiper and Pin 4 (3 on Alps) was the ground. Ignore Pin 3 on that diagram its unique to panasonic pots.

 

whats the advantage of the modification?

Cheers!
chris

 

The pot is taken out of the path, the job is done by two resistors such as Vishays. TBH Im currently using humble carbon resistors till I get something more 'audio'. The pot becomes a divider to ground as Penance says. It was all the rage over on WAD forum, a few even prefer it to shunt resistors. I like it alot.

 

hiya

I understand a stepped attenuator - covered in little resistors of different sizes..

Its just the rest Im struggling with!!

Severe noddy/big ears language needed here for me hehe

 

A log pot has a number of short-comings such as potential differences between the tracks and general wear and tear over time degrading the sound. Some also think they can be quite noisy and colour the sound. A stepped attenuator of a shunt variety gets round this by only having 2 resistors in the line at anyone time thus potentially giving a much 'cleaner' sound. The shunt mod to a pot has a similar effect, 2 resistors are only in the line, the pot, now grounded to earth acts as the shunt thus not needing a series of resistors. The quality of resistors is paramount and they must be matched as close as poss............I think.

 

I see.

So there is no advantage of doing a shunt mod if you intend to try a resistor-covered volume pot like a goldring or similar.

 

The stepped attenuators arent pots, theyre 12 or 24 position switches, what your doing is selecting a resistor value. The mod is well worth a try coz its so cheap and many prefer the shunt mod. Horses for coarses. Id try it before spending cash on a attenuator.

 

Is this 'shunt mod' just the equivelant of using an attenuated interconnect?

(which sounded shit in my setup)

 

No, all an attenuator does is lower the signal to the volume pot.

With a volume pot the signal goes through it, whether attenuated or not.

When shunted the volume goes through a resistor and nothing else. The volume changes because of the change in resistance to ground.

 

Strangely, though an attenuated interconnect killed the music when used between my pre/power amps, it works very well between the phono amp and pre-amp.