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Old 7th November 2012, 09:47 PM   #7651
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This is really interesting :IMD - Something New
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Old 7th November 2012, 09:51 PM   #7652
FdW is offline FdW  Netherlands
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Originally Posted by Joachim Gerhard View Post
I do not know why but i get a lot of samples from a lot of companies. Maybe they think i have good ears ?
Or they hope you do not
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Old 7th November 2012, 09:57 PM   #7653
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Sure, i do not care. But testing a lot i do and i give back reports. I am consistently bad C:
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Old 8th November 2012, 06:24 PM   #7654
Mooly is online now Mooly  United Kingdom
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Many posts have been deleted at FdW's request (as they contain what could be misleading info) although this action should be seen as a one off.
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Old 8th November 2012, 06:27 PM   #7655
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Thank you so much for the prompt action Mooly
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Old 8th November 2012, 06:30 PM   #7656
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Your welcome
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Old 8th November 2012, 07:02 PM   #7657
FdW is offline FdW  Netherlands
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Many posts have been deleted at FdW's request (as they contain what could be misleading info) although this action should be seen as a one off.
Thanks Mooly
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Old 9th November 2012, 03:04 AM   #7658
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Today i got one channel of my transimpedance tube RIAA for ETF 2012 working.
This did not come easy. Design and build took me the better part of one year, on and off.
I have great help from a very experience friend but i ran into several problems that drove me crazy. First i had a problem with the current sources and then i got oscillation. That proved to be a grounding issue of the heater supply and chassis.
Anyway, it works. With near textbook values i get a response that is flat from 100Hz to 100kHz ( -3dB ), under 100Hz i have some loss in the bass. That can be tuned in, tomorrow. I use a self conducting cascode with cascoded depletion mosfets at the input and a mü follower at the output so i have tremendous gain, around x266 in the input and
33 in the output for a total of 8800. That amplifies 0,5mV P-P to 4,4V P-P. I use very high transconductance russian tubes at the input and an E188CC at the output. Output impedance is 140 Ohm and there is a volume control in the RIAA. Noise will be low enough for medium to high output MC. For low output MC i build a box with transformers. At the moment i have no desire to share the circuit diagram. I have simply too much to do plus the crazy Paradise project. I hope i can get it working before ETF on both channels.
Attached Images
File Type: jpg ETF Tube RIAA1.jpg (631.9 KB, 272 views)
File Type: jpg ETF Tube RIAA 2.jpg (603.6 KB, 265 views)
File Type: jpg ETF Tube RIAA 3.jpg (594.8 KB, 253 views)

Last edited by Joachim Gerhard; 9th November 2012 at 03:06 AM.
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Old 9th November 2012, 03:59 AM   #7659
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Lookin' good Joachim !

You must get to bed earlier though.
( that's what I'm told anyhow )

Best time to work; the wee hours...
...just switched off the iron.

Good luck with channel 'B'.

Cheers

Si.
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Old 9th November 2012, 09:05 PM   #7660
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I got the tube RIAA tuned. It spans 4 octaves from 20Hz to 200kHz ( -3dB ). I kept a small rolloff in the bass. I do not think it is a good idea to extent the deep bass response too much in a tube RIAA. High frequency extension is somewhat dependent on the volume control in the RIAA. Under worse case conditions ( potmeter in the middle position ) i still get 70kHz ( -3dB ). I put the amplification down by 6dB so it has now a maximum gain of x 4400. 1mV input give 4,4V output. The 1kHz square looks good with anti RIAA.
Photo later.
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