Digitally controlled preamp/headphone amp

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#221
Re: opamp sockets

doggy said:
Just a question; is it possible to use an opamp socket on the board so that you could easily use different flavours of opamps like; opa2228, lt1361,opa2134,ne5532an,etc.

cheers
doggy:drink:
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Not really, because the PCB is designed for SOIC opamps, not DIP. The reason is I wanted to get he best electrical contact on the PCB with really good opamps like the AD8620 and the OPA2227 with minimal lead inductance.

Cheers!
Russ
 
#230
hayenc said:
Russ/Brian,

Not even sure which thread to put this on. Have you looked at leaving out the input cap on the My Ref when the Kookabura is in front of it in a permanent install?

Just wondering before I try it.
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Hi Craig,

It should work fine under the following circumstances:

1) The source connected to the kookaburra has no DC
2) Or, if the source does have DC on output use an input cap to the kookaburra(1-2uf is fine).

The kookburra has no input cap on the PCB on purpose, as a good one would be too big to place on the PCB and keep it small.

The output of the kookaburra is not DC coupled, so the only DC on the kookburra would be very slight (tiny) offset from the opamps plus what ever is coming from the source. So you should be just fine.

What I would do is check the output of the kookaburra first when it is connected to your source with the source on and playing and the kookbura powered up. You should next to nothing when you put you DMM on the output and check for DC.

I do not have an input cap on the monoblocs which I use for my computer,as I have a kookaburra in front of them just as you propose, and I know the source has no DC.

You should be just fine, and it should sound very good! :yes: 🙂

Cheers!
Russ
 
#232
lazyfly said:
The $64,000 question for me is... what does this little iconic bird of ours do for Mauro's Rev_C musically?

Cheers
Kendal
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It does not take much to make the Mauro's amp sound good. 🙂 But I think having a good pre in front does help. The kookaburra does do a good job in that department. 🙂

I would say the most noticible change is lower noise and lower distortion because there is no volume pot(as far as the signal goes), I can't really explain my impressions, but if I had to choose just one word, it would be "clarity".

This pre way really not intended just for the MyREF though. I own a couple of power amps that have relatively low input impedance, and this preamp really makes those amps shine. 🙂

Cheers!
Russ
 
#233
So my question is:

I have a set of Pavel's "audio refiner" driver/buffer PCB's and want to use a Kook as the volume control. Can the Kook be configured withOUT the output buffer? IE... 0 Ohm jumpers?




PS- I have my beta Kookaburra complete and "hope" to transplant it into my Rev_C this week/end.
 
#234
rabstg said:
So my question is:

I have a set of Pavel's "audio refiner" driver/buffer PCB's and want to use a Kook as the volume control. Can the Kook be configured withOUT the output buffer? IE... 0 Ohm jumpers?




PS- I have my beta Kookaburra complete and "hope" to transplant it into my Rev_C this week/end.
Click to expand...


Sure you could do that.

You would simply use a small piece of wire, or a simple solder bridge accross three pads on both sides of the output opamp.

Look at the attached picture, the pads to bridge have a red line where you should solder. DO NOT SOLDER THE OTHER TWO PADS!!! 🙂

Be very careful that either:

A) you don't solder the power supply pads.
B) you carefully cut the PS traces to that opamp, in which case you could solder all four pads.

In either case you can omit C17,C18,C19,and C20, and of course IC3. 🙂

One are alternative is to simply omit all the same parts as above, and them run a wire from the PGA output to the output header pads on the bottom of the board. That way is pretty simple too.

Cheers.
Russ
 

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#235
Thanks Russ.

I realise the pre wasn't designed neccesarily with Mauro's circuit in mind but had to ask due to 2 conflicting issues. 1. I doubt my current setup could sound much better with regards to amplification... and to contradict that statement somewhat... 2. Part of this whole DIY thing is tweaking to the nth degree 😉

Thanks for the reply 😀

Cheers
Kendal
 
#237
Right no need to waste that opamp. 🙂 I would use it in the input buffer spot if you only have one, as in the beta test. The PG231 has low input impedance (which is not so good) while the opamp has very high imput impedance (which is very good).

In that case just use the opamp in the IC8 spot along with the caps in C25,C26,C27,and C28. After that just follow my previous instructions.

Cheers!
Russ
 
#239
Brian / Russ,

If I don't have paypal, can I pay via $$$ thru DHL to your address? I wrote you a mail thru your website but received no answer. I am most interested in the both the Kookaburra pre and the My Ref REVC amp. Thanks if I could a response.
 
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