completed chipamp pre

[Russ White]

Here is my latest preamp with headphone amp.

Pics to follow.

 

[Russ White]

and another....

 

[Russ White]

The preamp part is my FreeBird design.

It is a simple stereo opa726 circuit which looks like this...

 

[Russ White]

The headphone amp part is two of my single channel YardBird design which is a opa637 and a buf634 running at 3X gain. Stability is achieved by adding a 5pf cap from opamp out to -IN.

The BUF634P is byassed with a 500R resistor which yields very good results.

 

[Russ White]

Finally the PS is a simple LM7812/LM7912 regulated supply. It looks like this....

 

[DcibeL]

Looks good. Is this the board that you plan to offer as a group buy in the future? I am still contemplating whether I should build your design or Nuuk's JFET buffer preamp. It's a thinker I tell you.

 

[Russ White]

Looks good. Is this the board that you plan to offer as a group buy in the future? I am still contemplating whether I should build your design or Nuuk's JFET buffer preamp. It's a thinker I tell you.

Yes, i plan to produc both the YardBird and the FreeBird designs. And I can tell you they drive GCs very well.


I have tested it now with inverting/non-inverting and Mauro's Ref design.

I am quite pleased with the outcome.... but please feel free to build one yourself and be the judge.

I will send a FreeBird and a pair of YardBirds to the first Member in the US or Canada who commits to build them in the next couple of weeks to evaluate.

Cheers!
Russ

 

[Russ White]

The offer is for PCBs alone of course.

 

[Russ White]

I really do not want to exclude those outside of the US or Canada, so I guess if it costs me less then a couple of bucks to ship anywhere is OK.

 

[tobias_svensk]

Hello Russ! Man! you must be the top poster of the last couple of months

Nice work Russ, it must feel nice to have build it all by yourself (and not like myself wich seems to go backwards )

But one warning, to much computertime can get you to read things sdrawkcab

It is a simple stereo opa726 circuit......

 

[maf_au]

I really do not want to exclude those outside of the US or Canada, so I guess if it costs me less then a couple of bucks to ship anywhere is OK.

Hey Russ, I'd do it, but I couldn't promise it for at least a month, I've got a BrianGT LM4780 and Mauro to build first... I'm thinking preamps, but holding off while I learn how things tick, and catch up on what I've already started...

For a standard preamp, I'd just need something like your freebird, a decent pot and input selector switches?

Michael

 

[DcibeL]

I'd do it, but I am waiting at least 2 weeks to have all the nessisary parts here. Plus the only thing I have to compare it with is my current reciever, a big NAD T770 5.1 deal.

I am building Mauro's amp, but with not having any other preamp to connect to this amp, I really wouldn't be able to say if it's better or worse than any of the other preamp options.

 

[Russ White]

Hello Russ! Man! you must be the top poster of the last couple of months

Nice work Russ, it must feel nice to have build it all by yourself (and not like myself wich seems to go backwards )

But one warning, to much computertime can get you to read things sdrawkcab

That's too funny Tobias. I can't believe I did that.

Of course it is a opa627.

 

[Russ White]

Hey Russ, I'd do it, but I couldn't promise it for at least a month, I've got a BrianGT LM4780 and Mauro to build first... I'm thinking preamps, but holding off while I learn how things tick, and catch up on what I've already started...

For a standard preamp, I'd just need something like your freebird, a decent pot and input selector switches?

Michael

Yep, that would work fine.

A simple rotary type switch for selector works fine. Nuuk has a great how-to on his site.

Ok, So you get the boards. I will send them sometime early next week. Just email me your address again if you would.

Cheers!
Russ

 

[Russ White]

I'd do it, but I am waiting at least 2 weeks to have all the nessisary parts here. Plus the only thing I have to compare it with is my current reciever, a big NAD T770 5.1 deal.

I am building Mauro's amp, but with not having any other preamp to connect to this amp, I really wouldn't be able to say if it's better or worse than any of the other preamp options.

DcibeL, I am in a generous mood, So I will send you a FreeBird/PS too. Please send email your address and it will be on its way.

I know you will not have anything to compare it to, but you need to start someplace.

Now, off to etch and drill....

Cheers!
Russ

 

[VT67]

Russ, is there any chance you can etch a Freebird board for me?
I'm following the varous threads with BUF634/OPA627 preamp designs for some time now and I'm eager to build me one of those things to hear how they sound.

Regards

 

[Russ White]

Ok GeWa, I have a PS and FreeBird coming to you too. But thats it. I now have plenty to keep me busy. The offer is now closed.

GeWa email me your address is you would please.

Cheers!
Russ

 

[DcibeL]

DcibeL, I am in a generous mood, So I will send you a FreeBird/PS too. Please send email your address and it will be on its way.

Wow, that was unexpected. Thanks so much.

 

[maf_au]

Yep, that would work fine.

A simple rotary type switch for selector works fine. Nuuk has a great how-to on his site.

Ok, So you get the boards. I will send them sometime early next week. Just email me your address again if you would.

Cheers!
Russ

Thanks Russ!

I think I'll just run the pot for this one. I'll drop you an email about component values, I might as well get all the parts for the Mauro and this together.

Michael

 

[DcibeL]

I'd hate to be a bother, but could you post a schematic for these boards so that we can know component values? Thanks again.