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Chosing the correct Alps ?K value?

post #1 of 8
10/14/05 at 8:41pm
Thread Starter 
I'm considering swapping out my DACT for an Alps and have the opportunity to hand pick the value for my application.

The amp is a HeadAmp Reference, the source a Musical Fidelity Tri-Vista 21. The MF TV has an output impedance of 50ohm and is tube driven.

If it was SS a 10:1 ratio would mean a 5K Alps, 500 not existing and all But tubes might not like that value too much so maybe a 10K?

My understanding is that I want the lowest value that will play nice to keep noise and RFI down. So 5K, 10K, 20K, the defacto 50K or the Alps recommended 100K?

Figured I'd start in the amp forum but this might be a DIY question in the end.
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post #2 of 8
10/14/05 at 11:07pm
What did Justin say?
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post #3 of 8
10/15/05 at 8:35am
Thread Starter 
Don't know. I haven't asked him. I bug him enough about this mod I'm sure he's ready to shoot me

The real people to ask would be MF but they have no email that I can find. The other Tri-Vista amp/pre/int are 220K but that seems high for a source that claims to be able to push 5W.

I can say that the Tri-Vista does play nice with the Senn 650 directly connected. Since my Reference is on route to Justin, my Dynahi is in BC and my RudiStor ships out today... This truly is a source first house

Part of the problem is resale, an Alps loaded, 5K input imp, unity gain, single ended Reference won't sell very easily even if it is ideal for a lot of applications.
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post #4 of 8
10/15/05 at 1:30pm
i'd go with 100k.

afaik with tubes, the higher the impedance they see, the better. the pot is likely to be the first component in series after rca input, right?

50ohms is a bit on the low side though, are you sure your mf tv does not have a transformer coupled output?
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post #5 of 8
10/15/05 at 1:52pm
Thread Starter 
No idea, just regergitating what is listed on the web site.

All I can tell you is there are 2 tubes per channel and a claim of 50ohm output. Seems like a reasonable value, using the Senn 650 directly I am listening at -24dB using trim pot in PatchMix to achieve 70dB output, the same value the A324 gives and its all SS.
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post #6 of 8
10/15/05 at 2:53pm

pardon the bad english - i got this out in a hurry.
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post #7 of 8
10/15/05 at 3:02pm
update:

after looking through the 5703 datasheets and based on the lack of output transformers, i'm willing to gamble that the tubes simply serve as some intermediate form of amplification (or tone control perhaps?) - a la' pmillett hybrid. the final stage before output is likely some form of ss buffer stage.

hence i think you should be able to use any alps pot value without problems. hope that helps.
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post #8 of 8
10/15/05 at 4:47pm
Thread Starter 
Good to know. I guess a 5K would be a good start... or I can just stick to my original plan and just mod the gain. Lots of time to think it over still.

All of this being mute if Justin only stocks 50K
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