Jensen JT 34K DX for shishido LCR phono?

[WFCkeyman]

Hello!
Since the Tango MCT 999 is no longer make, I want use Jensen JT 34K DX for substitution. Would it be possible? Any drawbacks?

Thanks!

 

[waltube]

I have a type made for me from Sowter exactly the same of 999.

In attach the freq. response of the three ratios.
I built a step up with the possibility to change the load on secondary to trim the reflected impedance

If interested write me.

Walter

 

[analog_sa]

That Jensen has extremely high transforming ratio which is fine only for very low output cartridges. Do you need so much gain?

The 20Hz response is unacceptable for me and is a side effect of the extreme gain.

 

[waltube]

In some cses is better to have more gain ( and the right reflected impedance) on trafo instead on phono circuit.
The s/n will be better

Walter

 

[analog_sa]

Only if you assume that S/N is the most important parameter. Someone considering a passive, tube, LCR correction has clearly other priorities.

 

[waltube]

No I think you are in error.
The s/n is one of the most important aspect in a phono circuit
The s/n is strictly related to the type of tube used, the quality of power supply mainly.
Then the use of an high impedance riaa network
In this case with a passive riaa the s/n can be, in theory, less than active riaa (on the feedback loop) .

I have made one and the results are very good if you use some type of tubes.
The 6922/E88CC can be a reasonble tube for phono but the gain is not high.

Walter

 

[euro21]

600R LCR has about -15..20dB "gain" at 1kHz.

If you use first stage with 30dB gain, LCR with -15dB at 1kHz, and second stage with -at least- 25dB, the "overall" gain is about 40dB. This is at the "low limit".

Better option is 30dB gain, LCR, 30dB gain.

 

[soulmerchant]

Hi Walter

E88CC has lots of gain if you cascode it. It is in fact an excellent valve/tube for RIAA in the right circuit.

Hope you are well in Rome these days.

Ian

 

[waltube]

The problem is the Zout of the first circuit because the LCR has not an high impedance.
In fact you can read a great value of coupling cap.
LCR 600 means that it has 600 ohm of impedance.
In this way you loose more signal from the standard -20dB and this is not a good idea because you have to re-amplify it again with more gain.
I have in my lab the EQ and I left in an angle the proto of riaa with some good results but not perfect as I want.

Walter

Ian, in Rome we are fine with not a big numbers of people with Corona but in the north there are problems, there are better numbers but not yet very fine.
Thx for interest

 

[euro21]

E88CC has lots of gain if you cascode it. It is in fact an excellent valve/tube for RIAA in the right circuit.

Right, even with 40..45dB gain.

But this schematic is a mu follower, with a little over 28dB gain.