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Old 22nd February 2009, 09:32 PM   #1131
Salas is offline Salas  Greece
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Johnm:

I recommend you to try resilient washers between 103R and Rega headshell. You would have to slightly readjust the VTA non the less.
Unfortunately I haven't got this underside photoed, but if you look on early pages you can see some pictures of the technique when the Riaa was in testing phase with batteries. In general, a U shaped thick copper peripheral buss bar is used, and the input grounds are soldered at its respective open ends. The output RCA grounds are tied together and with one thick wire they go at U bottom. The output coaxial cables are shield one end soldered only on the common output RCAs GND. The whole thing progresses symmetrically from open ends to end of U, stage by stage, grounding to the buss. Valve construction technique in short. Silver content solder is used. I always listen to better analysis, fluidity, calmness and stage VS any PCB, if the p2p is careful. Less soldering points, no thin traces, direct paths, can't lose. Not for the fainthearted though, and it takes practice. I thank my valve background for that. Big plus is rapid prototyping also, last but not least. The recommended 36.5V shunt has been pointed out and posted many times, but since you seem a bit lost as a late comer, here it is 4U again.
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Old 22nd February 2009, 09:36 PM   #1132
Salas is offline Salas  Greece
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Quote:
Originally posted by RCruz
Hi Salas

Yes, your answer was determinant... I will order some FT3 soon.

Now I understand that rload is system dependent. It is affected by the choice of C3, VTA, cart down preassure, cabling... I believe there is a sweet spot somewhere.... I changed from 39k to 680r and the sound was muffled.. now with 1k82 it is singing... but I know it can be better...must keep searching.

BTW Where did you get the 680u BGNx ?

Ricardo
You will again search for best Rload when you change parts quality most likely. But you will be in the ballpark after this search phase.

I cannibalized some other reg for the BG. I don't think its easy to find any more.
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Old 22nd February 2009, 11:05 PM   #1133
johnm is offline johnm  United Kingdom
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Thanks for that Salas - I did search back through the forums, but backwards.... of course I was on the page BEFORE the schematic when you replied haha! That looks great, and I seem to have many of the parts already - the audio Gods must be on my side today

I'll get some perf board and start building next weekend fingers crossed.

Thanks again for the help.

- John
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Old 22nd February 2009, 11:12 PM   #1134
Salas is offline Salas  Greece
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You are welcome. Good luck.
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Old 23rd February 2009, 01:29 AM   #1135
iko is offline iko  Canada
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salas, nicely done!!!

I too will build another version with careful attention to details, as the prototype sounds so great, no I can go ahead with a final version.
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Old 23rd February 2009, 04:50 AM   #1136
iko is offline iko  Canada
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For what it's worth, attached is the regulator schematic that has shown both in simulation, and in practice, the best regulation. I have tried all of the different variations in this thread, and have tried the sulzer, and jung regulator as well.

This attached schematic I have built a few hours ago, and the oscilloscope trace on the most sensitive setting, 5mV/div, showed a straight line, just a tiny bit thicker than when the scope is set on GND. This is as close I've got to DC, ever. It seems stable. There are more details about the things I've experimented with, such as different opamps, different driver instead of the darlington, but this configuration showed here was best. As far as the sound goes... that I don't know. Somebody else with more experienced ears should test it.
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Old 23rd February 2009, 04:54 AM   #1137
iko is offline iko  Canada
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Lower trace is scope set on GND, upper trace is the regulator output, scope set on AC, 5mV/div.
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Old 23rd February 2009, 10:07 AM   #1138
Salas is offline Salas  Greece
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Looks OK. But under some threshold, the scope will just show nice lines and it is difficult to evaluate small gains.
You will need FFT. Here is the FFT of the pictured phono, fed with DL160 nominal 1.6mV 1kHz. The 50Hz peak is the total hum. Good for such a small box with an non shielded transformer inside, and just p2p. That -107dB 100Hz edge might be the ripple residual or just random noise floor grass. Also that 16kHz -105dB peak might be interference from some TV scan frequency.
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Old 23rd February 2009, 01:12 PM   #1139
RCruz is offline RCruz  Switzerland
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Quote:
Originally posted by salas


You will again search for best Rload when you change parts quality most likely. But you will be in the ballpark after this search phase.

I cannibalized some other reg for the BG. I don't think its easy to find any more.
Hi Salas

With the 1k82 rload, the riaa is really singing ... I will try 2k21 just to be sure but I believe I am quite near the über setting.

now I would like to bypass the output caps and you suggested 0.047u PIO.... as I do not have any left, I would like to try other caps ... I have some ERO KP 1832 3000pF and some 4700pf styroflex... Can I use these caps or should I buy some 0.047u as per your indications? (My output caps are 4.7uF mundorfs MKP).

Is there a rule for these bypasses ? Should I use 1/10 of the original value or 1/100 ?

Regards

Ricardo

PS Just ordered some 0.1u Teflon CCCP caps just like yours for the Riaa circuit.

Thank you so much for the precious help... The Riaa is starting to sound as big as my superhyper CD53.
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Old 23rd February 2009, 01:17 PM   #1140
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Quote:
Originally posted by RCruz
The Riaa is starting to sound as big as my superhyper CD53.
I will never use digital source

Ops.. only in my car
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