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Old 3rd August 2003, 08:48 PM   #1
Nuuk is offline Nuuk  United Kingdom
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Default Another buffer conversion

Well it took me longer than I expected but today I listened to my GC with a buffer and LPF.

And I am quite impressed at the sound, on first audition a clear improvement over the basic IGC.

The buffer that I used is contructed around an OPA627 and you can read full details HERE

A big thank you to Pedja Rogic for help and encouragement with the project!

BTW - I forgot to put it on the site but the LPF consists of a 695R carbon film resistor and 6N8nF polystyrene cap.
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Old 3rd August 2003, 11:20 PM   #2
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Hi,

Quote:
And I am quite impressed at the sound, on first audition a clear improvement over the basic IGC.
Quite predictable really...now get the real magic and use a valve for a buffer...

Cheers,
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Old 4th August 2003, 07:20 AM   #3
moamps is offline moamps  Croatia
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Default Re: Another buffer conversion

Quote:
Originally posted by Nuuk
[And I am quite impressed at the sound, on first audition a clear improvement over the basic IGC.
Hi,
nice work. Something more about OPAMP PS?

But, you have one more step to do.

Quote:
Originally posted by fdegrove
now get the real magic and use a valve for a buffer...

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Old 4th August 2003, 07:21 AM   #4
Nuuk is offline Nuuk  United Kingdom
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Quote:
Quite predictable really...now get the real magic and use a valve for a buffer
That's the plan Frank.

Another reason I wanted to do the OPA627 buffer was that I feel it much easier for less experienced constructors to try that type of buffer than dive straight in with a valve buffer!

And the important thing is to hear the difference the buffer makes, which will help confirm the idea that it is worth doing the valve buffer.
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Old 4th August 2003, 07:57 AM   #5
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Quote:
Originally posted by fdegrove
Quite predictable really...now get the real magic and use a valve for a buffer...
How 'bout some of these babies?
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Old 4th August 2003, 08:07 AM   #6
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Default WHAT??? NO HEATERS?

Hi,

Here's the minimum requirement:

Cheers,
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Old 4th August 2003, 09:10 AM   #7
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Quote:
Originally posted by Nuuk


That's the plan Frank.

Another reason I wanted to do the OPA627 buffer was that I feel it much easier for less experienced constructors to try that type of buffer than dive straight in with a valve buffer!

And the important thing is to hear the difference the buffer makes, which will help confirm the idea that it is worth doing the valve buffer.
Good on ya Nick. We have another convert!!!!

You've got the general idea... when Pedja decided to go the jfet route I did not pooh pooh the idea. While an IC would be my last option, then at least I reckon you chose a good chip. Expensive but quite good. I would have thought Pedja's jfet approach just as easy? But now we at least know it can work with IC as well.

If I was to recommend a less expensive chip, I'd say OPA-134 could work nicely as well. In fact, if you had an IC socket, you could go and get a whole bunch of UGS ICs and listen to the lot. In fact it occurs to me this would be a good tool to audition different ICs.

I read you audition comments on your web site with great interest. IC or not, would you still describe the plusses, that we would expect to be there?

And sure enough your description is right in the ball-park as to what you'd expect. In fact spot on!

It might be worth pointing out just how important that LPF is, in fact no Gainclone should be without it IMHO.

But it is the buffer that makes the LPF possible!

Also, this is a good way for new kids on the block to cut their teeth on tubes. Use 6922 or equavalents, and you don't need any lethal voltages... so now go for broke and show us what you come up with!

Joe R.
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Old 4th August 2003, 09:23 AM   #8
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very nice nuuk, please tell us about your power supply for the qpa627....
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Old 4th August 2003, 09:35 AM   #9
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Joe Rasmussen wrote:

Quote:
But it is the buffer that makes the LPF possible!
I don't know how you come to this conclusion. Adding an LPF without input buffer is just a question of dimensioning.

See my post #15 within the following thread:

Gainclone...No gain, YES pain.

Regards

Charles
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Old 4th August 2003, 09:36 AM   #10
Luke is offline Luke  New Zealand
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Quote:
But it is the buffer that makes the LPF possible!
Hi Joe,

I would have thought the LPF would work with out the buffer?
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