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Old 13th February 2014, 10:53 PM   #1
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So I plan to get one of the Goldpoint Min-V attenuators and am uncertain how to determine the correct value for the input impedance of the TSE?

From what I have read 25k, 50k or 100k would work but I don't want to have to guess. Is there a calculation I can use to work it out?

Thanks
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Old 16th February 2014, 03:48 PM   #2
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More reading makes me think 100k or 50k will be fine.

Volume pot for Simple SE

Though the above relates to the SSE my feeling is it would be applicable to the SE too.
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Old 16th February 2014, 04:22 PM   #3
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100K is what I use for my TSE. No problem so far.
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Old 16th February 2014, 05:06 PM   #4
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Thank you.
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Old 16th February 2014, 09:29 PM   #5
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I can't find it, but I swear I read a post at some point where George said a 100K pot would react with the miller capacitance of the 417A/5842 and roll-off high frequencies. I used to run 100K pot in front of my TSE, but changed to 10K after reading that post. The difference, at least for me in my setup, was substantial.

I'm not saying go with 10K as I don't know if your sources are capable of driving that. I went with 10K as my tube RIAA has no issue driving that and my other sources are solid state, and I plan on adding a Heretical at some point (published design is around a 10K pot).
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Old 16th February 2014, 10:17 PM   #6
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JP, I have an Emotiva XDA-2 as my preamp for CD/Computer but will need to include volume control for my Turntable. The RIAA I use is this one (actually it is the Phono1+ which for MM is basically the same as this one): Vista Audio - one step ahead.
Do you have any thoughts on how this might work?
Thanks.
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Old 16th February 2014, 10:52 PM   #7
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I found the post:

Simple SE volume pot value???

George says 50K is the upper limit on the TSE in that post. I can't find output impedance specs on your sources, but I'd be beyond surprised if they're not well below 1K, so a 10K pot should be fine (assuming reasonable cable quality and length). I'm not an expert in this area, so hopefully someone with more experience here will chime in.

Alternatively, if you've an existing attenuator that's higher, you can always parallel resistance with it. That's what I did as I've a 100K TKD 2P65CS, and at $700 USD today, there's no way I'd buy another one, so I paralleled 15K with it to bring it down to ~10K. I've read this will affect the accuracy, but I haven't noticed any meaningful difference in my setup.
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Old 16th February 2014, 11:58 PM   #8
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Hmm! Thanks for finding that.

I do have these options:

10K, 20K, 25K, 50K, 100K

Hoping George is watching and can chime in.
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Old 18th February 2014, 04:16 PM   #9
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Quote:
Though the above relates to the SSE my feeling is it would be applicable to the SE too.
The input impedance of the TSE is set by the resistor across the input. I used 131K in my boards since I have a few thousand of them. It is not the important factor.

The TSE uses a 5842 tube which has a slightly higher Miller capacitance than the 12AT7 in the SSE. I have noticed a measurable drop in high frequency response with a 100K pot set at mid range which is worse case with a typical low impedance source like a CD player. This may not be audible, but would be with a larger value like 250K or 1 Meg.

To avoid this use a 50K or lower pot. Anything below this will be fine, until you start to load down your source. Most anything solid state will work into 10 K or lower....things like Ipod's, phones and laptops have no problem with 100 ohms since they can drive headphones. A tube line or phono stage may like 25 or 50K.

Given that I can't find a spec on minimum acceptable load for your phono stage, I would say to choose the safest choice which would be 25K. You might choose 50K if you might build a tube preamp, or phono stage later on.
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Old 18th February 2014, 06:18 PM   #10
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George,

thank you for the informative input and suggestion.

I notice that the Goldpoint can be easily attenuated up or down with the placement of a resistor in the event I choose an unworkable version (which is unlikely).
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