E810F: RIAA circuits

[waltube]

Hi boys,

time ago on Audioreview forum (in Italy) I posted some circuits with E810F . The reason was a discussion about Thorsten riaa circuit.
In the following links there are some schematics.
1)http://www.audioreview.it/VB/attachm...8&d=1170688005
thti a variation on original circuit to drive the LCR Riaa with low impedence, for me the right solution; the tube in CF can be a 5687 or 7044, we can drive the Tango with about 250 ohm of impedance (same for the output).
2)http://www.audioreview.it/VB/attachm...6&d=1174938591
this a circuit that I build with a Srpp with E810F in triode connection.
The main results is the low impedence Riaa network so we can have a low attenuation (20,5 dB at 1KHz) and a very good S/N.
The gain is 33dB for the first stage, 20,5 db of atteunation due to riaa network, and again 33dB with the output, in total are about 46 dB, with a step up (for MC) of 26 dB (20 times) we can reach 72 dB (about 4000 times), it is good.
3)http://www.audioreview.it/VB/attachm...1&d=1174829030
at this link there are the two basic circuits I tested with E810F. Both are Srpp, in the left there is a complete triode configuration, on right, a pentode configuration (bottom tube)
4)http://www.audioreview.it/VB/attachm...2&d=1174829048
in this link there is a 1khz signal, 1 vout about the triode connection;
in this configuration the gain is 33dB (45 times) and the output impedance is 225 ohm; at 1 vout the disotortion is 0,1%. The current on each tube is 18mA.
5)http://www.audioreview.it/VB/attachm...3&d=1174829137
at this link there is the output voltage at 3v, the distortion is 0,3%, good.
6)http://www.audioreview.it/VB/attachm...4&d=1174830086
here there is a output signal at 1 volt for pentode circuit, the distortion is 0,5%. This has a gain of 250 (47dB) and output impedance of 1,3kohm; there is some noise because I build the citcuit on air. With the same consideration of above, the chain will have a gain of 86dB, too much!
At the end I preferred the first one.

Comments are welcome

Ciao

Walter

[Gordy]

Walter,

That site requires registration. My feeling is that people here will not want to work at registration in order to provide help to you.

Experience suggests that if you make it easy for people to see your circuits then they will be very happy to comment and discuss them with you.

You might want to consider posting your circuits here.

Kind regards,
Gordon

[dshortt9]

I agree. I have been designing an RIAA with the E810F but do not wish to register.

[Graeme]

Me too!!

(Have the tubes, calculator, and time...) Registration to view is just too much like local council measuring/charging for water supply.....now they want to tax toilets,,,,,,,,,there's two of us here with just two toilets.....hell!! I just cannot make a decision where to dump!!!!!

Graeme

ps : PC warning, PC warning, PC warning, PC warning........
NZ is an agriculturally-based country - there's twelve + sheep here for every-one population. A fart-tax has been suggested - imagine - little beaurocrats running around fields of contented cows/sheep capturing every discharge.........

Won't be happy re toilet tax until they include scales - with a photographic-based discount.....

Graeme

[waltube]

Just to understand.
I click on link I posted here and I can see the schematics, where is the problem?
Why the registration is a problem?

Other wise I will attach the files here.

1) http://www.multitask.it/e810f/1-riaa.JPG
2) http://www.multitask.it/e810f/2-e810friaa.jpg
3) http://www.multitask.it/e810f/3-e810f.jpg
4) http://www.multitask.it/e810f/4-1vout.jpg
5) http://www.multitask.it/e810f/5-3vout.jpg
6) http://www.multitask.it/e810f/pent-1KHz.jpg

The numbers are in same order of my post.
I hope this will be better

Bye

Walter

[dshortt9]

OK, I can see clearly now. Thanks!
I did not want to register because my Italian is not good and I might download a virus or something. The registration was in Italian.

[dshortt9]

LCR is good but expensive.

SRPP looks good.

Why not use the pentode SRPP as the first stage for a gain of 250 or 47db. Use SRPP triode as the second stage for another 33db. Do not use a stepup transformer.
The first stage would only amplify to about 100mv so distortion is lower.
Total gain is 80db or minus 20db at 1Khz is 60 db. Just about right.

[dshortt9]

What current are you running the tubes at? They seem to be around 12 to 15ma. The Gm would improve significantly at 20 or 30ma. Then noise, gain, and Rp would also be better.

[waltube]

The tubes running, in triode conf., with 18mA. I tested also more current but in this configuration they seems to run better.
I prefer the triode connection because I can reach a good S/N.
In addition, with a low impedance MC it is better to use a transformer step-up; this solution allow you to mantain a very good S/N with a chain amplification of about 4000 times (72 db) as mentioned. The risk, with the tubes, is to have a terrible "wind" noise if you have a high gain input stage connected directly to MC.
I always use a low impedance riaa network; the problems are the values of capacitors (they are big) , but the benefit on noise and low attenuation are great.

Bye

Walter