Ultrasimple MM/MC RIAA preamp 2

[jackinnj]

Maison using N-1 topology:

An externally hosted image should be here but it was not working when we last tested it.

 

[nicoch58]

HI jackinnj

thanks for your fast and good work!

 

[nicoch58]

well I rebuilt the phono with mad k riaa (not perfect riaa value ), in my sistem sound more balanced ,I change the r load to 47k for open up a little more .

BUT but in this jfet phono the kind of component r/c are vey important , more of little riaa deviance !!!!!

I have change the good vishay mkp1847 with a mundorf s/o ,
with mkp the Cymbal are in the face with s/o too hidden/soft!

OK little difference are normal but so big


PS
I will try the jackinnj riaa

 

[jackinnj]

I will try the jackinnj riaa

It's found in Walt Jung's "Op Amp Applications Handbook" -- you can get individual chapters of the book on ADI's website. I just scaled the values.

 

[johnm]

Hi folks.

Have some SK170GR's arriving this week, so I can get started on this project at last

I have a Denon MC 103R but I don't think the gain in this circuit is enough to do it justice - anyone tried an MC with this pre? I might have to use my MM Goldring G1042 instead.

Just a little confused which schematic to use: Mad Ks, the original Pacific, or the Pacific with Tschrama's fine tuned RIAA? Which design - on paper at least - offers the closest adherence to the RIAA specification?

Many thanks,

- John

 

[nicoch58]

the mad_k are the better (idss-4-6ma)but with 103 you need more gain ,the Salas jfet are the best link

sorry 2sk170bl idss 7-7,5ma

use good component !

 

[audiodesign]

I suggest my design

http://www.audiodesignguide.com/Phono/pre-phono2.html

 

[nicoch58]

Sure !

but I can't see jfet

 

[johnm]

Cheers for the replies

Audiodesign - nice design, but a wee bit complicated (and expensive) for me at present. Will start with this Ultrasimple, then probably move to the Phonoclone next and then... well I'll take it a step at a time - lol!

Nicoch46 - Sorry do you mean I need to use the BL jfets? I thought it was the GR versions required for this design?

Thanks,

- John

 

[nicoch58]

Johnm with 103 you must use Salsas jfet ! for correct gain

the goldring have too much output 6,5mv saturate the jfet !

aka pacific work well with 1,6-3,5 mv HIMO

PS BL in pacific with 33r on surce lowered the 2HD a lot ,but I like it!

 

[MRupp]

I suggest my design

Thank you for sharing, very interesting design, especially since I have some D3A . One silly question: Could I leave out the cathode bypass caps or would I lose too much gain?

 

[nicoch58]

Johnm at last you need a stepup trafo ....denon or cinemag

 

[johnm]

I'm surprised that you say the MM Goldring G1042 isn't suitable for the Mad K Pacific pre? I thought the Goldring was a pretty standard MM cartridge, and the Mad K is designed for MM cartridges? Looks like the PAcific isn't suitable for my Goldring or Denon then

Is there anyway of lowering the gain of the Mad K so I can use the Goldring G1042? I can't afford step-up transformers for 103R just yet unfortunately...

What cartridges are people using - successfully - with the Pacific pre then?

Thanks,

- John

 

[nicoch58]

2] Each JFET has a gain of about 30dB, that's 60dB in total, but you loose 20dB in the RIAA nrework.. so expect a 1KHz gain of about 40dB, that would mean 5mV in, 500mV out.

I think 500mV would be too high, as the output JFET starts distortion to much beyond 300mV. Maybe you can get rid of some gain to keep the output below 300mV. Exchabnge the first 2.4K resisro with 1.2K, and put another 1.2K in series. This will halve the gain.

Thijs

this riaa have 300pf input ,not report here but have plus 100pf cable you think that is a MM stage ?

for me is a HO MC ,I use for dl-160 2mv

you can tray with 103 if amp+ speaker have gain......

If I remember well you for1042 you can play with rload...

 

[johnm]

Yeah it definately seems better suited to HO MC's I think. Thanks for the quote by Tschrama - I think I'll try halving the gain like he suggets.

I'll try the Denon 103R anyway - I already have the parts for the Pacific which is why I'm keen to make it work

Cheers,

- John

P.S. Like the record you are playing - see you keep abreast of the latest music

 

[nicoch58]

you must match the jfet for idss 4-6ma at 0,1%ma

+10v>meter(ma)>Drain
surce&gate to -
for 5minuti

 

[johnm]

Thanks for the info - I have 8 JFETS arriving so I hope 4 of them can be well matched when I test them - fingers crossed!!!

 

[Salas]

This is the original Pacific along with active step up for 2SK170GR. I attach it here if of any help.

 

[Salas]

I run a simulation and I see that 2SK170BL 7.5mA Idss IS usable, and to my opinion preferable. Because it gives 50dB instead of the 45dB with GRs, and keeps the Vds under 8V which is much better for the drain to gate leakage, else escalating at 11V that the GRs produce.
I would not change the original wiggly, somewhat brightening the mix RIAA, because without R source degeneration and no local Rd filtering surely it will sound thick with a flat RIAA. I am sure that it is finely tuned by ear and I can see the reasons. Of course I don't see the real reason why not making it as I did in my version with less THD, more gain, more headroom (7mv max input@20Hz), and accurate RIAA. Listening to the original and comparing for system tone matching and then converting it again to something updated if needed, is enough reason in DIY I guess. Nice to know.

 

[nicoch58]

HI Salas

fist you know that i put bl+33 in mad-K and I don't feel....but now I have supex....

I can try without resistor ?

little trouble why I have with idss4-24v-2k4 I have higth Vsd ??? 13,4v!!!


I try the pacific riaa mod with 470nf back to second jfet, sound very brigth !! MAd__ k much better in my system ,Mr Thorsten L ..touch....

forgot little active stepup ,nice