Simplistic NJFET RIAA - Page 27 - diyAudio
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Old 20th November 2008, 09:50 AM   #261
RCruz is offline RCruz  Switzerland
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Thank you Salas

You made it perfectly clear to me now.

Maybe I will use a 220uF BG on the output.... I really like BG sound.

Regards

Ricardo
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Old 20th November 2008, 11:49 AM   #262
massimo is offline massimo  Italy
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Kalimera, Kirie Salas!

Just one question about your shuntreg: why did you use such a beefy TO247 mosfet for the CCS and the parallel device? It's only 120 mA for the first one and much less for the second. Wasn't a TO220 mosfet (such as IRF9610) enough for this purpose?
(OK, OK, I know one possible answer: I picked up what was available in my drawer.....)

P.S. I like the idea of a P device for the shunt, while many others use N devices that amplify the noise.
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Old 20th November 2008, 02:50 PM   #263
Salas is online now Salas  Greece
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Beefy usually sounds...errr...beefy. Plus it will not create instability so easily as a very fast one, plus low Rds On (9610=3 Ohm, 9240=0.5 Ohm). In my initial concept explanation I talked about faster TO220 Mosfets too and that many devices will do. Open to experiments. Also we may run Amperes even if we feel like spending money and space on transformer and heatsinks. It will sound different maybe. Also 9240 has good availability.
As it is now, the sound opens very noticeably in dimensional scale, cleans up a lot, the focus of each instrument becomes very certain, and the overall musical detail gain is breathtaking.
The concept is easy, please experiment with Mosfet types and capacitor values and qualities as much as you can.
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Old 21st November 2008, 03:21 AM   #264
Salas is online now Salas  Greece
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One last thing. For those who are going to use RIAA versions requiring under 30V B+ better use 4.7k resistors for the current source BC560 instead of the 6.8k ones in the 37V B+ example. That way its current stays about the same level as in the example. Taken that the Vin is +6 to 8V up Vreg.

And a hint. Auricaps sound nicely warm and beefy at the final output coupling capacitor position in my RIAA. But that is a system match and preference area. You know all that.
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Old 21st November 2008, 04:37 AM   #265
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I had a look at the shunt regulator posted here, and I couldn't resist twiddling with it. Attached is my simulated take, with a fast pulsed load attached for testing.
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File Type: gif shunt2.gif (12.3 KB, 1359 views)
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Old 21st November 2008, 04:41 AM   #266
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Here are the simulation results. The regultor is fast, low impedance, and should be pretty low noise. Whys and wherefores will follow when I feel like writing them. In the meantime, dissect it into component functional blocks and think about it for a bit.
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File Type: gif sunt2_perf.gif (37.2 KB, 1280 views)
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Old 21st November 2008, 01:50 PM   #267
Salas is online now Salas  Greece
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Nice! Can you substitute BC560, BC550 & 2SK170, so we can do it in Europe easier too?
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Old 21st November 2008, 02:02 PM   #268
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Quote:
Originally posted by wrenchone
Here are the simulation results. The regultor is fast, low impedance, and should be pretty low noise. Whys and wherefores will follow when I feel like writing them. In the meantime, dissect it into component functional blocks and think about it for a bit.
Some friends are substituting adjustable shunt regulators for zeners in their microphones. Any thoughts? It's nice having one part for all voltages, no TC, much less noise, very low min current.
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Old 21st November 2008, 05:19 PM   #269
Thomo is offline Thomo  United Kingdom
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Today I finally found time to build this circuit. Unfortunately, I am not getting any sound output.

Being pretty noobish, I have a noobish question if you don't mind. I'd just like to check that I have the FET's and transistor the correct way round. Which pins on Q6 are tied together please? And is it pin 1 of Q3 (bc550) that connects to Q1?

Cheers, Lee.

(Confused as to why it won't work)
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Old 21st November 2008, 06:58 PM   #270
mikvous is offline mikvous  Greece
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Lee,
Which version are you trying.Don't worry we'll find it
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