Justin & Jerry's Hifi Blog

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Originally Posted by jandl100

Hmm, I seem to recall there is an internal jumper.
Just looked in the manual I got with my new DAC and it doesn't mention it at all!

Mine came with the vc only set to adjust headphone volume, but that's fine for me with my new shitty Schiit Saga preamp.

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Yup , I remember reading somewhere that there's internal jumpers too .

Quote:

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Originally Posted by jandl100

Hmm, I seem to recall there is an internal jumper.

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Nor does mine.

It us very easy to see what to do, though. Follow the volume pot lead to the back of the casing by the tube/solid state RCA output sockets. You will see two jumpers, one for each channel. Move both forward one pin. So they end up on pins 1 & 2, then a & b. They should be on 2 & 3, then b & c now for headphone volume control.

I tried the Sylvania Gold Band 5670. You wanna be using a Western Electric 396A was my fairly rapid conclusion. That really is a good valve.

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Originally Posted by jandl100

I got a pair of Reflektor 6n3 valves arrived this afternoon Jervalves today (only need one for the 01A but they were sold in pairs).
Anyone with one of these DACs like to try my spare one?

Grant - did my valves turn up ok?

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Valves arrived this afternoon Jerry, thanks.. Good ginger biscuits those; i see you never left me any :D
will give them a go soon.:cheers:

Great.
I mentioned that I had two Raytheon valves and included one in the pack I sent to you.
I tried the one I kept in my new DAC-01A and it wasn't at all happy! Sounded faint and skewed. :scratch:
So don't worry if yours is the same.

Will watch it then. Try other 2 first

The one problem with the valve output stage is that the HT voltage is only 75V, it is regulated which is good but it really could do with being higher to get the best out of any valve. The actual voltage across the valve is only 62V which only exacerbates the problem.

As it is only a buffer and is at a high signal level the regulation isn't necessary, so I removed it and simplified the filtering to achieve 90V across the valve.

:)

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Originally Posted by Firebottle

The one problem with the valve output stage is that the HT voltage is only 75V, it is regulated which is good but it really could do with being higher to get the best out of any valve. The actual voltage across the valve is only 62V which only exacerbates the problem.

As it is only a buffer and is at a high signal level the regulation isn't necessary, so I removed it and simplified the filtering to achieve 90V across the valve.

:)

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Yes but your a genius [emoji3]. You dont have a pic of the jumper change to bring the vc into play?

I'll get the top off and take a pic.

OK here is the pic. The jumpers are on the rear positions of the 3 pin headers, as so:

http://i67.tinypic.com/11a8yyq.jpg

So the jumpers are on 1-2 and a-b to give volume control on all functions.

oh, nice pic. thanks Alan...:)