LCR phono stage

This the layout of the pcb

Walter
 

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I believe that this is not a valid test. Because there is a RIAA network.
And there isn't any reason to do this.
If you look on previous posts I sent a real test lab on the inductors only where is possible to see the tech. specs.
And you can see the resonace frequency.


Walter
 
Some photo of the earlier protos with Tango original stuff
The first was alla Tango:
step up 999
interstage NP206 ( or 11107)
EQ-2L
intestage NP 206 (11107)

tube EC8010 and EC8020
In attach the frquency answer ( balanced out)

Then
A my Junior pcb circuit with EQ-2L and the frequency response


And the frequency response of proto of Shishido circuit always with Tango EQ-2L and TFK E88CC ( and CCA, same results)




The results are fine in alla cases.

The sound is , of course, different for each typology but always fine

Walter

Hello Walter,

For the design where you used the all-Tango approach (step up 999, interstage NP206, ( or 11107) EQ-2L, and interstage NP 206 (11107), could you please advise how you terminated the LCR network so it sees the required 600 ohm impedance load?

Did you terminate the output of the EQ-2L LCR network in a 600 ohm resistance, or did you terminate the secondary winding of the NP-206 step-up transformer after the LCR network with a resistive load, so that the reflected impedance from the NP-206 to the EQ-2L would be 600 ohms?

Thanks & Regards,

Bruce
 
Hi

I terminated the EQ-2L it with 600 ohm resistor and a trafo with a 600:10k ratio to get a better gain.
In both case the results are good.
Then I did some other dozen of tests with different termination but those were the best.

The problem is the Tango original are scarce to find and expensive.
Now I am trying with full Sowter stuff; the results are interesting.

Walter
 
Hi Walter,

Thanks very much for the quick reply!

I understand that you terminated the output of the Tango LCR network with a 600 ohm resistor.

-Did you also terminate the secondary of the 600:10K step-up transformer after the LCR network, as well as terminating the output of the LCR network with the 600 ohm resistor? If you did, what value terminating resistor did you use on the secondary of the 600:10K step-up transformer?

-Or did you just terminate the output of the LCR network with the 600 ohm resistor, and leave the secondary of the step-up transformer unterminated?

-Did you also try to leave the LCR network unterminated (without the 600 ohm resistor), and to only terminate the secondary of the 600:10K step-up transformer? This would rely upon the termination impedance at the secondary to be reflected back to the primary of the transformer, and the output of the LCR network.

-With the all-Tango line-up that you used, which terminating approach of the LCR network and/or the 600-10K step-up transformer gave you the best performance in terms of the RIAA accuracy, and overall gain?

Thanks very much for your guidance here!

Best Regards,

Bruce
 
Hi

1- the step up trafo was terminated with 10k but I tested other value around
2- I never leave the step up unterminated, I mean with a proper resistor or some similar value.
3- with step up I removed the 600 ohn resistor on the end of LCR network
4- I can say, after my test, that some differences exists but with a proper sequence of tests and some trimming you can get a good freq. answer with both systems.
I have the proper test set to check the performances and this help a lot.
The only thing is the max acceptance in input of LCR phono stage ( I mean the complete circuit) that is not so high but enough in the 100% of cases.

Then with the differents step I have done some listening tests with my friend that own 105 pcs of MC cartridges, all at the highest level.
In both cases the sound was very good in general; with a step up, probably due an higher gain, the perception of dynamic was better.
Also with the configuration with two ECC8020 / channel was very fine; but this tube costs like a good ring for your wife!!!

I found the E280F very fine but not so simple to use with a interstge trafos.


I hope the answers will be fine for you


Walter
 
I have used 6j52p, e810f and 6j9p-e in best pentode mode as first stage, enough gain into LCR no need step up after, they sound better than triode strapped mode in this setup, my interstage is ll1660 at 4.5:1, LCR are Silk 600 and Allnic 600.
 
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Hi Walter,

Yes, this was very, very helpful!

I am using a pair of D3As in each channel of my LCR phono preamp. I could not even consider the use of the ECC8020, due to their cost and lack of availability. If I did purchase them, my wife would give me back her wedding ring!

It appears that your approach of terminating the 600 ohm LCR network is identical to what I am planning on doing here; leave the output of the LCR network unterminated, but terminate the secondary of the step-up transformer after the LCR network with a value of resistance that will reflect 600 ohms back to the output of the LCR network.

That value of terminating resistance on the secondary of the step-up transformer may of course not necessarily be 10K ohms, due to the DCR of the transformer, and a few other variables. The optimum value may have to be determined by actual test. But did you indeed find that the 10K terminating resistor you used provided the most accurate RIAA curve, and the most gain from the circuit?

Thanks & Best Regards,

Bruce
 
I have two phono, one with best pentode (tried 6j9p-e/6j52p/philips sq e810f) and LL1660 into Acoustic-dimension LCR (Allnic OEM), another ec8010 with bartola gyrator hybrid mu-follower into Silk LCR (with 33uf auricap xo), no major difference btw them, same second stage 6e6p-dr in triode mode.
 
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