PI Audio

[h9361]

Then it will be best to use Dom?s through hole version, mine is surface mount
BTW, the original circuit is Mickstv design, not mine, I just did some mods to suit what I wanted.

cheers

Dear Mdtoday.
I want to use TL072 instead of your amp because it's low noise. Please see attached, do you think lm386 part is correct (especially emitter and collector of Q1).
Thank you.

[Teleno]

Sorry for my questions.
I can find JFET 2N3819 in my city. Do you think it's a good replacement for JFET PMBF4393?
Thank you

I would say you can basically use any N-JFET as long as its parameter "Gate-source cut-off voltage V(p)GS" is 2V above -Vcc. In this case above -3V (-5V + 2V). Otherwise the OpAmp output may not go low enough to turn it off completely when needed.
However, this parameter varies a lot between JFETs of the same type. Some manufacturers group then by ranges, otherwise you need to buy a few and manually measure them to select the good ones.

[h9361]

Then it will be best to use Dom’s through hole version, mine is surface mount
BTW, the original circuit is Mickstv design, not mine, I just did some mods to suit what I wanted.

cheers

Sorry for my questions.
I can find JFET 2N3819 in my city. Do you think it's a good replacement for JFET PMBF4393?
Thank you

[h9361]

Then it will be best to use Dom’s through hole version, mine is surface mount

cheers

OK. In this case, i can use BF256 for PMBF4393?

[Mdtoday]

Thank you, i hope you find an equivalent for BF4393. I want to assemble your schematic as through hole.

Then it will be best to use Dom’s through hole version, mine is surface mount
BTW, the original circuit is Mickstv design, not mine, I just did some mods to suit what I wanted.

cheers

[Mdtoday]

Yes, Please send me your version. thank you.

It is a surface mount version, not through hole.

I will post it here once I find it, it’s late atm

cheers

[h9361]

I have found the JFet input Opamps like the OPA1642 work best in this circuit but there are many others and it is not super critical, again I use what I have plenty of Texas Instruments and Analog Device stock for prototyping and testing, unless it’s something specific required, like low noise, low drift or offset etc, then once the circuit is proved, I may change to more suitable components.
Experiment, I think Dom even used an LM324, it is not an equivalent to OPA1642 but a lot cheaper if it works.

Thank you, i hope you find an equivalent for BF4393. I want to assemble your schematic as through hole.

[Mdtoday]

Is it possible to introduce me some equivalent amp for OPA1642?
Thanks

there are many and it is not critical, again I use what I have plenty of Texas Instruments and Analog Device stock of for prototyping and testing, unless it?s something specific required, then once the circuit is proved, I may change to more suitable components.
Experiment, I think Dom used an LM324, it is not an equivalent to OPA1642 but a lot cheaper if it works.

[Mdtoday]

Thanks dear Mdtoday.
Unfortunately, i can't find JFET PMBF4393 in my city. Can i use BF256B (for BF4393) and BC557C (for BC857C)?

The Bc857 is a sot23 smd package, the Bc557 Is through hole, it will be fine
Ill have to look at JFet BF256B specs, should be ok.

[h9361]

ok, now the link you posted is the through hole PCB version designed and posted by Dom.
I have not built that version. It should work although I also believe a capacitor was left off around the audio amp, it’s been a while , Dom posted a link to Gerber or artwork too I think from memory. Maybe other members have built Dom’s version and can verify.
My version is a surface mount pcb as per the link posted by Waltr.
If you want the Gerber for my SMD version I can post. It is verified and working.
BTW, the 120uF tantalum bypass capacitors around the opamps can be reduced down to 47 probably even 22 uF will be fine.
I used 120uf as I had a reel of them.

cheers

Is it possible to introduce me some equivalent amp for OPA1642?
Thanks

[h9361]

ok, now the link you posted is the through hole PCB version designed and posted by Dom.
I have not built that version. It should work although I also believe a capacitor was left off around the audio amp, it’s been a while , Dom posted a link to Gerber or artwork too I think from memory. Maybe other members have built Dom’s version and can verify.
My version is a surface mount pcb as per the link posted by Waltr.
If you want the Gerber for my SMD version I can post. It is verified and working.
BTW, the 120uF tantalum bypass capacitors around the opamps can be reduced down to 47 probably even 22 uF will be fine.
I used 120uf as I had a reel of them.

cheers

Yes, Please send me your version. thank you.

[Mdtoday]

Thanks.
Is it possible tell me its last version?
Is the link last version?

ok, now the link you posted is the through hole PCB version designed and posted by Dom.
I have not built that version. It should work although I also believe a capacitor was left off around the audio amp, it’s been a while , Dom posted a link to Gerber or artwork too I think from memory. Maybe other members have built Dom’s version and can verify.
My version is a surface mount pcb as per the link posted by Waltr.
If you want the Gerber for my SMD version I can post. It is verified and working.
BTW, the 120uF tantalum bypass capacitors around the opamps can be reduced down to 47 probably even 22 uF will be fine.
I used 120uf as I had a reel of them.

cheers

[h9361]

Sorry for late reply, directly after SAT stage is the place

cheers

Mdtoday

Thanks dear Mdtoday.
Unfortunately, i can't find JFET PMBF4393 in my city. Can i use BF256B (for BF4393) and BC557C (for BC857C)?

[Mdtoday]

Hello
Dear MDtoday.
Before everything, thank you for your excellent work.
I want to use your PCB on HH1. Can you guide me which point of HH1 should connect to input of your PCB?
Thanks.

Sorry for late reply, directly after SAT stage is the place

cheers

Mdtoday

[h9361]

IC8A is the integrator for the Hammerhead. The Audio schematic shows the circuit starting post integrator so I would think that after IC8A would be the point of connection.

Thanks.
Is it possible tell me its last version?
Is the link last version?