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Converting discrete op-amp into chip?

PostPosted: 19 Aug 2014, 15:50
by LooseCannon
Hey guys,

I want to make a version of the Boss OD3 with an IC opamp instead of the discrete opamp gain stage.

But since the OD3 opamp uses Jfets and most chips use BJT i'm not sure how to do this conversion.

Any ideas?

Here's the schematic:

Re: Converting discrete op-amp into chip?

PostPosted: 20 Aug 2014, 20:57
by EddieTavares
The first section of that circuit (Q8, Q10, Q11, Q13, Q14... above in the picture) is almost the discrete version of the first stage of TS8 so put all the components in a protoboard and try it and compare that with the original circuit. Sure the result would be a little bit different in comparison with the original circuit

Re: Converting discrete op-amp into chip?

PostPosted: 21 Aug 2014, 04:13
by LooseCannon
Did you mean the TS808? Because i'm not familiar with the TS8.

Thanks

Re: Converting discrete op-amp into chip?

PostPosted: 21 Aug 2014, 13:25
by EddieTavares
It's not exactly the same.

Re: Converting discrete op-amp into chip?

PostPosted: 21 Aug 2014, 14:08
by LooseCannon
Do you have a schematic of the TS8? I can't seem to find one.

Re: Converting discrete op-amp into chip?

PostPosted: 21 Aug 2014, 14:32
by EddieTavares
So, read this very good article about:
http://www.electrosmash.com/tube-screamer-analysis


This is the ts8 circuit.
Image

What you have to consider is replace the "clipping amp".

Re: Converting discrete op-amp into chip?

PostPosted: 21 Aug 2014, 15:02
by LooseCannon
Thanks.

So this is just the standard TS9\TS808 schematic i'm familiar with. Do you refer to the TS808 as the TS8?

Re: Converting discrete op-amp into chip?

PostPosted: 23 Aug 2014, 07:06
by LooseCannon
So I think i'm starting to figure it out.

Looking again at the OD3 schematic- Q13, Q14 and Q1 form the op amp, before that there is a notch filter (R34, R35, R48).

Q8 is the input buffer and Q9 is used for switching.

So what is the purpose of Q10??