Eros + 10K potentiometer on output?

keto · 5000

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Offline keto

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on: November 21, 2010, 02:11:40 PM
Would a 10K pot be too much load for the 4K output of the Eros? Are the outputs independent enough -- that is, of the ground plane, if there is one -- to permit such a modification? Thanks!

Tom Jones


Offline Paul Joppa

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Reply #1 on: November 21, 2010, 02:26:18 PM
I don't recommend less than 50K, though it will work. At 10K you'll see -1dB at 30Hz, -3dB at 15Hz, and the overall gain will be down 3dB as well.

You can make the bass deeper with a larger output capacitor, but the larger problem is that it will lack enough current capability to drive maximum output without distortion. You might need to be sure your cartridge has a low output, like 2-3mV maximum.

Paul Joppa


Offline keto

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Reply #2 on: November 21, 2010, 06:39:25 PM
Would it help at all to add a 10K:10K transformer to the picture, before the 10K pot (all of this would be in the phono stage chassis itself, so very short leads)?

Tom Jones


Offline Paul Joppa

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Reply #3 on: November 21, 2010, 08:16:29 PM
It would not make any difference, unless it was a crappy transformer which would make the situation worse.

Unless your cartridge has more than 4mV output, I'd say to go ahead and try it - maybe with an outboard clip-lead setup - and find out what you hear. The LF cutoff will reduce some rumble and probably tonearm resonances, so it's a balancing act - some good, some risky. See what you hear. To test the worst case, find a record that is recorded pretty "hot" - the overload problem will occur under the same conditions which stress the cartridge's tracking ability, making it difficult to separate them, but if a hot recording sounds good then you are in business!

Paul Joppa


Offline keto

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Reply #4 on: November 22, 2010, 03:09:49 AM
Thanks, I've been listening to the seduction with an outboard 10K Penny and Giles pot, and liking the sound. Will also experiment soon with 50K:600 mic transformers before the 10K pot. But I like the idea of just putting the 10K pot "inboard" and taking the outputs directly to the paramounts. Will report back...

Tom Jones


Offline Grainger49

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Reply #5 on: November 22, 2010, 06:00:26 AM
   .  .  .    But I like the idea of just putting the 10K pot "inboard" and taking the outputs directly to the Paramounts. Will report back...

The smaller the signal the poorer it travels.  Possibly the pot could be at the Paramounts.  You are not going a great distance.  So it may not matter.