GC Preamp Suggestions

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#421
In my PCB i skipped the rail-to-rail cap. because it would't fit 100% good on the PCB anyway i think. That cap. could be soldered directly to the socketpins from under (Wima MKS3, RM=7.5mm fits very good there) or perhaps a SMD cap. inside the socket in some way.
 
#422
This is just really a bump to see, if we are all still alive.

May i suggest that a poll is conducted, to see IF the group buy does get under way, we have decided on a design that everyone is happy with. As i think the designs are all pretty much finished.

Other threads for the power supply, etc could be started and discussed there.

This may get the groupbuy idea rolling again.




EDIT, Wrote pole instead of poll, lol
 
#425
re input pot

Question: With the diff pics of PCB

I may be wrong but:

I do not see a trace going to signal ground from the input to pot.

In other words there is not a voltage divider setup on the input
just a variable series resistance from In to to +input of Opamp.

It looks like only 2 connections to each pot.
 
#428
n00beR said:
May i suggest that a poll is conducted, to see IF the group buy does get under way, we have decided on a design that everyone is happy with. As i think the designs are all pretty much finished.
Click to expand...

I dont think there is any shortage of people interested and I think that once an actualy GB is posted there will be big interest......but there doesn't seem to be someone to do all the organising of the GB :xeye:
 
#429
Hi n00beR

I believe this one is yours then.
Personally I don't mind whether there is a pot on the PCB or not.
 

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#433
GeWa said:
Still no volunteer? :crying:
Click to expand...


My original intention when starting this thread was to have a group buy at the end. I haven't had any time latley to do anything as ambitios as a group by as I am crazy busy at work :dead: but if we can wait a few weeks I probably could be coerced into conducting one. We should definately conduct the poll to see what design we like...I still have a few changes of my own to offer....soon.

G.
 
#434
signal ground

I am a real beginner so please excuse my simple question.

I notice on a couple of these cool PCB designs that the signal ground is seperate on the circuit from power ground.

My question is do the SG and PG currents ever come together at any point?

If they do come together is it off the PCB at some star ground say at the PS?

Thanks,
Russ
 
#437
Gcollier said:

Input Buffer: BUF634
Gainstage: OPA637
Click to expand...

I realize you corrected yourself on the order of the chips, I haven't read the whole thread, so forgive me if this has already been mentioned:

What about running say an AD8610 as an input unity gain amp, then the OPA637, followed by the BUF634?

In general the AD8610 wouldn't be useful, but if you were running off of a relatively low quality source, the low input bias current may be a good thing?

Just thinking out loud....


EDIT:...bad idea afterall. AD8610 has a higher input current, so it would actually be harder to drive than the 637....
 
#440
robselina said:


Yea, it was a bad thought anyway wince the 637 has lower input bias current!


:cannotbe:
Click to expand...



I tested a range of pretty common opamps in a group listening session..we were all in agreement that the OPA627 sounded best in my design. The 637 had a level of crispness to it that almost sounded artificial. I didn't try the 8610/20. Also as I said earlier I removed the cap in the feedback loop of the opa627, it didn't seem to help any.

G.
 
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