Lookking for a BJT or JFET single supply inverting buffer

[maouna]

hello . i am looking for a bjt or jfet based inverting buffer running from about single supply. it will be used after a transistor based tone control to restore 180 degrees phase shift.i could just use an opamp but tone control is based on discrete parts and i would like to preserve the idea.

 

[Mooly]

Try designing your own. This is in keeping with the Radford design you are working on. See how good you can make it

 

[djoffe]

What input impedance would you like? Output impedance? Signal Swing capability?

 

[sarathssca]

hello . i am looking for a bjt or jfet based inverting buffer running from about single supply. it will be used after a transistor based tone control to restore 180 degrees phase shift.i could just use an opamp but tone control is based on discrete parts and i would like to preserve the idea.

Hi Maouna,

Could you please share the details of your tone control circuit ..
I am also looking for a tone control stage preamp ..

 

[maouna]

Thanks Mooly,i am testing some circuits in LTspice,i will post tommorow.

Djoffe ,input impedance at least 27K,swing capabillity at least 2V peak ,single power supply around 60V,bjt or jfet based or a combination of both.

Hi Maouna,

Could you please share the details of your tone control circuit ..
I am also looking for a tone control stage preamp ..

This is the line stage of radford zd22 figure 12 page 15 here on the pdf

http://www.acousticpsychos.com/Files/Radford-HD250-ZD22-int-sm.pdf

i will ommit final stage based on TS12,TS13 and will connect an inverting buffer because tone control has 180 degrees phase shift.

 

[djoffe]

The existing TS12/TS13 stage on page 15 has a gain of about 4700/820+1=6.73.

So, an inverting stage will need the same gain...or, you could sandwich the inverting stage in series with R112 if it has gain=1.

Which way to do you want to go?

 

[maouna]

The existing TS12/TS13 stage on page 15 has a gain of about 4700/820+1=6.73.

So, an inverting stage will need the same gain...or, you could sandwich the inverting stage in series with R112 if it has gain=1.

Which way to do you want to go?

I will omit this stage (line output amplifier TS12/TS13) and replace it with an inverting buffer with a gain of 1. I think there is already enough gain from the first stage(line input amplifier TS7/TS8)

Played in ltspice with two inverting buffers a jfet one and a bjt one. the bjt is used at radford tone control section but i configured it for 0db gain. the jfet based has a wide bandwith (maybe i could use a low pass filter at input).

I would like your comments and suggestions.

 

[djoffe]

You might like what I've whipped up...2nd harmonic is about 150 dB below the 1 kHz fundamental. (2 V peak into 10 K Ohms)...design not gone over with a fine toothed comb, but performance is pretty good.

Your Vout1 buffer has 2nd harmonic down about 91 dB...
Your Vout buffer has 2nd harmonic around -97...

 

[maouna]

You might like what I've whipped up...2nd harmonic is about 150 dB below the 1 kHz fundamental. (2 V peak into 10 K Ohms)...design not gone over with a fine toothed comb, but performance is pretty good.

Your Vout1 buffer has 2nd harmonic down about 91 dB...
Your Vout buffer has 2nd harmonic around -97...

it counts lot of parts.i have to design two of them on the same pcb with the rest section (line input amp and tone control).. something with 2 or 3 jfets or bjts would be ideal.

 

[djoffe]

I did quick sims on both of your designs...they were pretty good....certainly low enough distortion that they should work just fine...my contribution was just running down a thought experiment on how good things could be made given a bit more complexity.

Of course, you could even go simpler than the two examples you present...but that balance and trade-off is something that you are best set to judge...evaluating those trade-offs is part of what makes the subject so interesting and challenging!