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Old 22nd June 2010, 06:27 PM   #4001
Salas is offline Salas  Greece
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Quote:
Originally Posted by Franz Gysi View Post
As I wrote earlier: it is an often underestimated cartridge! Swiss public broadcast used this cartridges on their EMT's!

Just try the correct capacitive load together with your phono cables!

Something between 200 to 600pF in parallel to the input resistor and you can find the point where it begins to sing.

Correct mounting of the cartridge and adjustement of the tonearme are essentially, before testing the needed capacitive load.

Franz

/Edit: best caps for this task, imho: Styroflex.
There must be already 50-75pF of Miller (kept there thanks to the cascode), plus 150pF from TT cable. Extra capacitance additions must mind that residual.
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Old 22nd June 2010, 07:05 PM   #4002
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Quote:
There must be already 50-75pF of Miller (kept there thanks to the cascode), plus 150pF from TT cable. Extra capacitance additions must mind that residual.
Best practices:

Use a variable cap, one of this aircaped old radio caps. 0 to 500pF or 365pF.

Easy to search the optimal point by listening and then measuring the capacitance and replace by a fixed value.

Of course only for MM cartridges.

Franz
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Old 22nd June 2010, 07:21 PM   #4003
Salas is offline Salas  Greece
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Varying the ohmic load does a lot too. Has been discussed here before but here it is again http://www.tnt-audio.com/sorgenti/lo...magnets_e.html
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Old 23rd June 2010, 04:46 PM   #4004
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Hummmm

... eated up all my diy time in the last ten days. No time to build the Salas shunt regulator V1.2 psu.

Why?

I was still working on replacing a bottleneck in my audio chain: the active crossover.

And I had a longtime project, reported earlier in this thread:

Rod Elliott opamp based crossovers (P09) and two t-amps in two 3-way monoblock enclosures.

And, as I also reported here: hum problems.

So, I removed the t-amps. Working well.

I added the needed power up delay, shorting the outputs to ground.

Hummmmmm.

I tried all different kinds of grounding.

Till I began, to make a drawing of my whole audio chain, including the grounding connections.

This is the block schematics without ground connections. Just draw it by yourself and think about!

Click the image to open in full size.

Horror, a lot of ground loops! Why dont I have balanced cabling for a long time???

I tried bus grounding through my whole audio chain. No real success. Hum or buzz.

I realized, the main problems are:

- the point to connect the audio chains ground to safety earth
- splitting up the stereo chain into two mono-xover and then going to three stereo amps

O.K.

Different tries showed me, that the central grounding point should sit in the xover, not in the preamp.

I quickly made a MDF enclosure to include both channels xovers in one enclosure, together with one psu. I also added the two delay circuits.

Hum.

This time, I quickly identified the problem as an input loop problem, between the preamp and the xover. Simply disconnected the ground on one channel:

I finally got it.

Click the image to open in full size.

The enclosure is big enough to replace later the opamp circuit by a fine FET thing...

For me it was urgent to finish ONE project (soon), including enclosure (O.K., MDF is not perfect).

Soon, I can proceed to the V1.2 psu for the phono pre.

And later, one (first) Pass F5 (no MDF), to replace one of the t-amps.

But: next problem will arise: how can I drive 6 channels of F5's to drive my speakers? In winter season, it will be O.K, but in summer?

Franz

Last edited by Franz Gysi; 23rd June 2010 at 05:10 PM.
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Old 28th June 2010, 10:11 AM   #4005
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Default Riaa upgrade

@Rcruz

The last buy to upgrade RIAA:

Click the image to open in full size.

0.047uF / 1000VDC Obbligato teflon
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Old 28th June 2010, 12:58 PM   #4006
RCruz is offline RCruz  Switzerland
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Hi Merlin..... I am looking forward to read your comments on this upgrade
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Old 28th June 2010, 01:51 PM   #4007
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Ok Rcruz, I will let you know soon.
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Old 29th June 2010, 01:05 PM   #4008
Salas is offline Salas  Greece
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Quote:
Originally Posted by merlin el mago View Post
@Rcruz

The last buy to upgrade RIAA:

0.047uF / 1000VDC Obbligato teflon
Is that SCR Teflon & tin foil, or just Teflon?
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Old 29th June 2010, 03:51 PM   #4009
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Originally Posted by Salas View Post
Is that SCR Teflon & tin foil, or just Teflon?
Tin foil
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Old 29th June 2010, 03:55 PM   #4010
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Hi Merlin..... I am looking forward to read your comments on this upgrade
FS: 2 caps silver mica 47nF 500V news 16€00 special offer 8€00 each + paypal + shipping fees
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