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Old 7th November 2005, 09:15 PM   #21
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Quote:
Originally posted by carlosfm


Why don't you put the chip on the bottom side and use single layer, as you said?
Don't bother too much about a ground plane, specially around the signal pins, it creates capacitance.
Also, if you rotate the bypass caps by 90º (side by side) you will get the electrolythics much closer.
Your use of V+ for heatsinking is correct. But even then, the SMD chip gets quite warm.
You have space on that board for some poplyprop output dc coupling caps. These are optional. If you have input coupling caps on the power amp, no caps on the pre. Or vice-versa.

PS: Just before I hit 'submit' I've noticed that you are using that chip as a normal op-amp.
It won't work.
Have you seen my schematic?
You need a way to fine-tune DC-offset, that circuit I made also deals with the input dc-offset.
Otherwise you would have to use input dc-coupling caps to protect the volume pot.
Then you will muck up the performance of the pre by over-capping.
Carlos, I thought that only applied if you are using current output?
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Old 7th November 2005, 10:14 PM   #22
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Quote:
Originally posted by Gcollier
Carlos, I thought that only applied if you are using current output?
Huh?
This is a current-feedback op-amp.
Different animal.
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Old 8th November 2005, 06:42 PM   #23
sklimek is offline sklimek  United States
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Default Eagle file...

Hi Gcollier, thank you for posting your .brd file. I spotted a ground ‘air wire’ at end of V+ & V-. Are you using a jumper wire here or wiring in underneath the board?

Forgive me if I am not spotting the obvious.

Stan
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Old 8th November 2005, 07:02 PM   #24
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Default Re: Eagle file...

Quote:
Originally posted by sklimek
Hi Gcollier, thank you for posting your .brd file. I spotted a ground ‘air wire’ at end of V+ & V-. Are you using a jumper wire here or wiring in underneath the board?

Forgive me if I am not spotting the obvious.

Stan

Stan,

You have a keen eye...but that is not an error. I named both grounds for V+ and V- the same...there is no physical connection between them...hence the 'air wire'. If you want you can easily jumper between the two, the best place is probably between the two big filter caps. If you check with a multimeter you will see that you have 0V between the two grounds...as it should be.



G.
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Old 8th November 2005, 07:07 PM   #25
sklimek is offline sklimek  United States
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O.K., I dig...

Thanx

Stan
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Old 9th November 2005, 12:05 PM   #26
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What is the lowest gain setting for the ad815 without lowering sound quality?
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Old 9th November 2005, 01:06 PM   #27
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Quote:
Originally posted by jaudio
What is the lowest gain setting for the ad815 without lowering sound quality?
It can be used as a buffer, but always with a resistor (with the recommended value) on the feedback loop.
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Old 9th November 2005, 04:59 PM   #28
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Quote:
Originally posted by carlosfm


It can be used as a buffer, but always with a resistor (with the recommended value) on the feedback loop.

Carlos,

Did you ever experiment any further into methods for reducing the DC offset?? Also for what reason did you choose the 7809 regulator...do you really need 9V to null the offset???

Any help would be appreciated...also maybe we should move this discussion to another thread...as it is a bit off topic.

Thanks

G.
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Old 9th November 2005, 06:53 PM   #29
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Quote:
Originally posted by Gcollier
Did you ever experiment any further into methods for reducing the DC offset??
Everything I tried is on my tread, and also on another one where I started (link on the first post).
I didn't use servos, I didn't want to.

Quote:
Originally posted by Gcollier
Also for what reason did you choose the 7809 regulator...do you really need 9V to null the offset???
That's a small 78L09.
Well, as the regulated PSU is around +/-15V it didn't seem very wise to use a 5V reg.
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Old 9th November 2005, 07:31 PM   #30
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Quote:
Originally posted by carlosfm


That's a small 78L09.
Well, as the regulated PSU is around +/-15V it didn't seem very wise to use a 5V reg.

I hadn't thought of that...it's a good enough reason for me!

I can't wait to try this out! I may research a bit for some different techniques to control the offset, but I will definately try out the regulator idea too. Gotta love the pinout on the 815, why can't BB follow Analogs example!

Thanks Again.

G.
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