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Old 3rd August 2010, 08:34 PM   #4311
Salas is offline Salas  Greece
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Quote:
Originally Posted by nicoch46 View Post
HI Salas, the R-core work fine ? sound better ?
Yes works fine. Its somewhat smoother and bolder. Mainly it allowed very low field for using just one box medium size with 61dB gain in that.
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Old 3rd August 2010, 09:03 PM   #4312
RCruz is offline RCruz  Switzerland
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Originally Posted by Salas View Post

Even with such measures always at least one channel will pick 5-10dB mains on FFT. Don't know if not if there was a steel sub box too. Me I don't mind a -90dB or -80dB single hum band even on my 95dB speakers, I know it will pick up probably when in the rack with the TT cables coming in near other mains feeds and equipment anyway. But FFT is your friend, just don't carve the box design in stone before you got all your parts and you are sure about the Riaa PCBs are dead quiet also, leave slack for changing your practices before final assembly. Low noise-high gain, is a bugger.
Hi Salas

What do you mean by "90dB or -80dB single hum band" ?

In my recent evolution I got hum to be lower than riaa amp Shhhhh... And this noise can only be heard at full output without signal.

Just rearranged the riaa layout to minimize loop area... look at the pdf

It is better than ever but still sensible to the "opening the lid" effect.

I guess I now I am ready to go fullfilm again

BTW.... very nice build.... I guess this is for the DL103R right ?
Attached Files
File Type: pdf DL160 48dB Loop area Mod.pdf (17.6 KB, 53 views)

Last edited by RCruz; 3rd August 2010 at 09:09 PM.
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Old 3rd August 2010, 11:14 PM   #4313
Salas is offline Salas  Greece
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Say the LF noise is at -110dB to -100dB relative to 0dB=1VRMS output depending on gain and psu etc. and then you got a mains 50Hz or 60Hz hum band picked up by a field or a loop in the box or outside and that pokes at -90dB.

The lid must be always closed in a phono.

Yes that build is the test LowMc with C0G RIAA caps, the rest are generic and Russian parts. Its so smooth and dynamic you would not guess it can be made better. Yeah, you bet, we know it can.
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Old 4th August 2010, 12:42 AM   #4314
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Salas,
Is there a particular Idss for Q7 that would be best? Same with Q6. I have hundreds of each. I hit the jack pot for LED's, and these type of fets. Just down the road from my house is BD Enterprise, a smaller version of Mouser. I bought the last of the sk170's from him. Either alot of people are building this phono riaa or there is another project going on at DIY audio. He claims to have had a run on them recently from this site.
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Old 4th August 2010, 09:01 AM   #4315
RCruz is offline RCruz  Switzerland
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after my last rearrangement of force and gnd lines in the riaa board I got ultra low noise and high freq detail is enhanced but overall equilibrium seems to be on the light side. Can this be because I used thinner wire in the new connections ?
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Old 4th August 2010, 09:56 AM   #4316
Salas is offline Salas  Greece
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Its you cleaned grunge.
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Old 4th August 2010, 10:13 AM   #4317
Salas is offline Salas  Greece
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Originally Posted by SGregory View Post
Salas,
Is there a particular Idss for Q7 that would be best? Same with Q6. I have hundreds of each. I hit the jack pot for LED's, and these type of fets. Just down the road from my house is BD Enterprise, a smaller version of Mouser. I bought the last of the sk170's from him. Either alot of people are building this phono riaa or there is another project going on at DIY audio. He claims to have had a run on them recently from this site.
Q7 is 2N5459, Q6 is BC550C in yours. 5-6mA for Q7 is OK for the LEDs.

Not many are building this, its the Pearl II and DCB1 Blue probably these days.
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Old 4th August 2010, 10:22 AM   #4318
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Ok, i'll put together a pair of 5.5 mA 2n5458 of Q7 and I will just match Q6.
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Old 4th August 2010, 10:43 PM   #4319
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As I was not happy with the subjectively "thin" presentation, I went further and placed another gnd wire from the CCS leds to star GND, separating these from input GND.

Noticed gains in spaciousness as well as a more full presentation (lost the thin sound).

Is there any instrument that can measure magnetic fields... if there is not a commercial unit available, it should be easy to build right ?

My next mod will be to return to fullfilm shunt. Just found two 10u Audyn cap MKP that are much smaller than the obbligato so I guess it will reduce loop area.
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Old 4th August 2010, 11:16 PM   #4320
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If you want a qualatative measurement you can make a coil of magnet wire and hook it up to an o-scope probe. There are instruments that measure it against a calibration but I would think they would be expensive.
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