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Old 7th April 2013, 03:23 PM   #411
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Quote:
Originally Posted by ahaja View Post
Ideal value is 1596R - instead of 1k62.
You cannot change it to other value because you change RIAA.
K
A 110K ohm in parallel with the 1K62 will give you very close to 1K596 (1K596448). That should be close enough.
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Old 16th June 2013, 10:45 AM   #412
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I've build this project and it does sound wonderfull. However I'm struggling to get rid of the humm.
Even more strange...when I mount the PCB in the alu tube, the humm increases.

Any suggestions where I could start looking?

Played with various grounding points for the grounding cable of the turntable and got the hum down but there is stull an audible hum when listening to vinyl.

Thx
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Old 18th June 2013, 05:53 PM   #413
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For the TT ground, I used an insulated speaker post that does NOT touch the chassis.

The chassis is connected to earth/safety ground through one of the PCB standoffs. You must use a metal standoff for this.

The speaker post is connected to power supply common on the RIAA circuit board, not the chassis.

I have no hum at all.
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Old 21st June 2013, 02:23 PM   #414
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Well...This IS how I've connected the grounding.

I'm in the dark as to where I need to look next
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Old 28th June 2013, 03:20 PM   #415
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Does the preamp humm without source connected? Maybe try different interconnects?
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Old 28th June 2013, 04:08 PM   #416
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I've disconnected the amp bd from the PWR supply and made a copper casing for the amp. I've checked the output voltage and its clean.
When disconnecting the input I just get a bit of noise (no hum). When I connect the turntable I get a 100hz hum. That is strange to me because I would expect a 50hz hum when the turntable is picking up mains hum.
i use a SME20 / SME-V with Ortofon Rohman

When I disconnect the ground wires from the turntable, I get a bit more hum, but that is 50Hz hum.

100Hz hum would indicate a power supply / after rectification issue but the voltages are OK and I cant see any hum on the output with my scope.
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Old 28th June 2013, 06:30 PM   #417
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Unrelated quiestion:

Does the phono section work with a step up transformer?
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Old 28th June 2013, 07:19 PM   #418
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I see no reason why it shoudn't. The only thing that could be changing the interface to the phono is the much larger output impedance of the stepup.
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Old 10th July 2013, 01:10 PM   #419
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Furher to my humm issue. Today i connected my phono board to alkiline batteries (2x10 AA) = 15-0-15V. There was no hum what so ever.

Question now is: Would this be a ground loop issue or a power supply issue?
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Old 6th August 2013, 06:25 PM   #420
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Does anyone know the deviation from RIAA equalization for this stage?
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