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Old 18th September 2009, 08:53 PM   #2301
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I urbano63 well done !

how many Km of internal signal wire ?

perdonami non ho resistito!
usa anche un alberino di prolunga per il pot, tenendo i cavi corti puoi anche evitare i coassiali che hanno un'elevata capacita e metti il phono vicino agli ingressi
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Old 18th September 2009, 10:00 PM   #2302
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Hi Salas,
after the RIAA there is a JC-2 preamp kit that tubeshunter is selling on eBay.
I have no hum after your help, and i like how the RIAA sound.
Now perhaps because of long coaxial cable and/or because the JC-2 i lost a little bit of detail.
I tested the RIAA connected directly at my headphone amp before.

Ricardo your work is very good

Ciao nicoch,
how many Km of internal signal wire ? if i measure all the cable some meters. There is about 50 cm for the phono in, and less for each of the other 4 input.
But there is about 1 mt of coax cable between the pot and pre input.
This is a first test ... Yes i doubt and I can optimize the layout.
The cable capacitance used is about 280 pF/mt
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Old 18th September 2009, 10:10 PM   #2303
RCruz is offline RCruz  Switzerland
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Luca

What type of coax are you using ?
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Old 18th September 2009, 11:15 PM   #2304
iko is offline iko  Canada
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Very nice Ricardo, I'm glad you found the problem!
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Old 18th September 2009, 11:17 PM   #2305
Salas is offline Salas  Greece
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Quote:
Originally Posted by urbano63 View Post
Hi Salas,
after the RIAA there is a JC-2 preamp kit that tubeshunter is selling on eBay.
I have no hum after your help, and i like how the RIAA sound.
Now perhaps because of long coaxial cable and/or because the JC-2 i lost a little bit of detail.
I tested the RIAA connected directly at my headphone amp before.
Very well. Headphones is a very revealing test. Keep it as a benchmark, and try to reach the detail level against it the more you can. I am glad that you liked it. Happy listening!

P.S. Remind me, what is your TT comprised off?
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Old 18th September 2009, 11:23 PM   #2306
Salas is offline Salas  Greece
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Quote:
Originally Posted by RCruz View Post
The offending zener was replaced and now there is no more "woosh"... both channels sound the same with a very low ripple at full volume...
That was an easy one, the usual suspect did it.

I wonder why nobody can get TC compensated zeners in stock. Microsemi has some of the best. Keep it up with 1000uF good zener filter caps guys, its safer, and try to always get the glass encapsulated ones (usually red with a black stripe) even if 500mW. The black plastic ones suck. Very erratic.
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Old 18th September 2009, 11:56 PM   #2307
iko is offline iko  Canada
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I actually wonder if the tempco ones are lower noise, but I never looked into it. For diy purposes is a bit too crazy, but a low noise voltage reference can be had with a ccs and resistor.
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Old 19th September 2009, 12:03 AM   #2308
Salas is offline Salas  Greece
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We do that if needed (if with crap zeners at hand only) but a tempco zener would be low impedance too. If you remember there was a guy in the low voltage regulator thread that had access to some ESA lab tempco zeners and informed us that they are down to one led noise. Now to reach 36V with leds you will need 17-20. The resistor can be a good compromise, but it will be in the kOhm range. A good enough zener and a good 1000-2200uF cap can do enough of a decent job at least.
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Old 19th September 2009, 12:34 AM   #2309
iko is offline iko  Canada
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Yes, I remember now, I also recall that they were very difficult to find. OK, so the search for very low noise voltage references begins This should be old news for the big guys, right?
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Old 19th September 2009, 12:36 AM   #2310
Salas is offline Salas  Greece
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Sure.
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