ADAGIO from Dr. Bora Jagodics

[alex mm]

New year, new build,in progress, tone correction preamplifier with 12AX7EH schematic ADAGIO from Dr.Bora Jagodics (R.I.P.) . Second build this year .....
Regards,
Alex

 

[alex mm]

pictures ..... 🙂

 

[kissabout2002]

Hi "alex mm", I am been impressed by the schematic of your build so I put it on a simulator specially for the tone control, I built so far many tone control so I was curious, here the result.( 1st/2nd pic.) I think some adjustment are necessary because the target of a good tone control is have the audio taper potentiometers to get rather flat response when they are set halfway between maximum and minimum around 0 dB and you can see the Adagio is far away from it also there is really no one curve response flat in the middle of the plot and a lot of roll-off frequency.
A good tone stack control should work like this ( Pic 3 & 4 ).
I build many tone control from the RCA schematic and so on but the one really achieve all goals I found in this website Practical Tone Controls.
Ltspice simulator work very well with tone control circuit, I recently built the 3 tone control propose in the website and the result is outstanding and as you can see simulation and real test are very close. ( Pic 5,6,7 )
Now I think the Adagio because can be used as a pre-amp without tone control or with tone control cannot really achieve a good performance because the first stage is not a cathode follower so with hight output impedance is very difficult but I think that some adjustment on the value of the component can just give some improvement. All the best

 

[alex mm]

Hi Kissabout 2002 ,
Thanks for your toughs , simulation, schematic . I will reconsider schematic, and I will try, some changes, in values of components to see how it works . This board it's a prototype and I agree for modified version. I'm not so good in theoretical things, I'm a hobbyist . Pictures from 2010 of first built tone correction. 🙂
Regards,
Alex

 

[jazbo8]

Posts moved from the Pictures Thread, please note that discussion of a specific build should be conducted in its own thread, and not in the Sticky thread.

 

[Ketje]

I think there is an error in the schematic 🙁
Mona

 

[Mosquito]

Hi "alex mm", I am been impressed by the schematic of your build so I put it on a simulator specially for the tone control, I built so far many tone control so I was curious, here the result.

Hi, missing in Your sim: 100K, from V1b plate to V1a cathode.

 

[kissabout2002]

Thanks Mosquito corrected...🙂, much better response

 

[PRR]

> I think there is an error in the schematic

Either way works, and could be "correct".

 

[Ketje]

You are right, but it felt wrong letting the current of one tube infuence the other. After all the original circuit is even better if tubes behave.The current in the first triode is better defined with it's an independent cathode resistor.
Mona

 

[alex mm]

Hi all ,
Transformer, mechanical adapted to PCB, it's shielded electrostatic and magnetic . Power supply, and timer, work fine, also muting, and by pass relay .
Tomorrow will test with tubes in circuit. 🙂
Regards,
Alex

 

[alex mm]

Tone correction preamplifier at final step. It's working, was tested, and now has new enclosure . More pic's tomorrow . 😀

 

[alex mm]

And inside pictures ....😀

 

[thealphonso]

Very nice work and PCB. Do you have the Gerber files for the PCB?
Also, I sent you a PM couple of days ago.
Thanks!

 

[alex mm]

Thanks, but gerbers are not available right now . Just 5 PCB was made by factory . Now I have rev.3.0 🙂
Regards,
Alex

 

[alex mm]

I try to build, a new tone correction, same schematic but new rev.3 PCB optimized tracks . Good quality components :Alps blue velvet pot's , Vishay propylene capacitors, 1% metalised resistors, shielded toroidal transformer (electrostatic and magnetic ) and selected highgrade 12 AX EH tubes.🙂
Regards,
Alex

 

[Machina]

Great work Alex mm