Pultec Solid State Gain Stage (LANGish) Documents Updated

[ForthMonkey]

There is RGAIN.I want to get gain about 20-30dB.

 

[abbey road d enfer]

There is RGAIN.I want to get gain about 20-30dB.

If your circuit is still the one you posted earlier, you need the trimpot (unlabelled) to be about 15k for 30 dB gain. The way it is arranged the minimum gain is unity (0dB). If you want a better control range, e.g. 20-30 dB you make the trimmer 5k and put a 10k resistor in series. I think you should read about the gain formulae for the commonly used implementations of opamps. In that case: G= Rfb/R1

 

[joaquins]

In that case it won't affect your output impedance unless you go close to the open loop gain, when the OL output impedance of the opamp will start to take place... So, not, it does not affect the output impedance.

JS

 

[ForthMonkey]

I added final circuit to first post for now.What do you think?

 

[abbey road d enfer]

I added final circuit to first post for now.What do you think?

The input gain is now -6dB. The actual gain range of the output stage is 27 to 32dB. Is it what you want?
R3 is not connected properly. It should be in series with C9; it is now in parallels. also there should be another 470uF in series with R2.
You should make provision for a small cap across R6, for the risk of oscillation.
Finally, I don't see any decoupling caps on the schemo; don't you intend to add them?

 

[ForthMonkey]

The input gain is now -6dB. The actual gain range of the output stage is 27 to 32dB. Is it what you want?

Yes,it's what i want.I will use this with passive EQs.But i have to change RGAIN to 22K and R10 to 5K.I want a little bit wide gain range.

R3 is not connected properly. It should be in series with C9; it is now in parallels. also there should be another 470uF in series with R2.

I've used API Line Amp circuit.

http://danalexanderaudio.com/ApiInfo/api2520_02.jpg

You should make provision for a small cap across R6, for the risk of oscillation.

Yes,i will add 10-47p cap.

Finally, I don't see any decoupling caps on the schemo; don't you intend to add them?

I will add them,too.For now this circuit final design but without improvements.

I'll add circuit.

 

[abbey road d enfer]

R3 is not connected properly. It should be in series with C9; it is now in parallels. also there should be another 470uF in series with R2.

I've used API Line Amp circuit.

the parallels arrangement in the application note is valid only if a transformer is used.

 

[ForthMonkey]

I added two circuit.First one is simple with impedance balancing.Added all parts.

And transformer balanced version with 2520 I/O & 2503 out transformer.

Can you check two circuits? And tell me 2503 pinout for 600 ohm.

 

[ForthMonkey]

Now waiting for http://www.classicapi.com store.Checkout is Temporarily Disabled.

When i wait,can you tell me about 2503 out pins?How should i connect to to 600 ohm?

 

[ForthMonkey]

Added "IN" documents.

 

[ForthMonkey]

I think this is better...

 

[ForthMonkey]

For now everything is ok.What do you think about 2N2222?

 

[ForthMonkey]

Added PCB design.I will add self etch files,too.

 

[ForthMonkey]

All docs added.