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Old 22nd April 2005, 03:05 AM   #11
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Hi dsavitsk

Good point. Having never heard of the preamp, I went to the link and noticed US$395, so I had a perception it was meant to be up there.

Are the OPA637's really that exe and who's Warren Young when he's at home with his golden ear???

I'm sure I can get 637's for about A$15 i.e. ,US$12! - I'll be happy to pass some on.
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Old 22nd April 2005, 03:54 AM   #12
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The bugle actually sounds remarkably good for it's cheap parts. It is a pretty well thought out and balanced design, and better opamps would likely be wasted. Maybe not, though, and it might be worth tinkering a bit. I think if I were swapping out, the first thing I would try is the AD823. at only $5 for a dual, it is a pretty solid chip.

DigiKey lists the OPA637 at just over $18. I am not really an opamp guy, but if you know of a way to get them cheaper, you would make a lot of people very happy.

As for Warren Young, he has made many contributions to DIY audio, mostly head phone amp related. Search for Tangent here and at Head-Fi, or poke around his site. There is much to be found.

Oh, also, the Bugle uses the OPA2134, not the OPA2130, which, if you believe the descriptions at DigiKey, is a much lower noise opamp.

-d
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Old 22nd April 2005, 05:20 AM   #13
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Hi dsavitsk,

Once again I looked at the link given and it showed OPA2130's.

Frankly, I don't like the concept at all - it looks to be a hangover from the misplaced enthusiasm for wideband open loop active stages and passive eq from that moribund TIM dinosaur - an attempt to have constant NFB across the audio spectrum! Except it has substituted narrow OL chips.

I would ditch the passive eq and the second and third stages and wrap the whole RIAA eq around one really good chip like an OPA627 (for UGS) or if the noise still wasn't good enough, multiple matched FETs driving a OPA604. You could do worse than a LT1028 if you're OK with bipolar inputs.

ONE CHIP TO BUY (per channel)

But I didn't want to spoil Mantisory's day, but offer genuine suggestions based on science rather than wooly...

I'm still waiting on the OPA627/637 price. I'll post it. I have much experience with these in pre and power - where else can you get a monolithically matched FET cascode input stage WITH 50MHz GBW and 50V/us and 120 dBand 4.5nV ?
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Old 22nd April 2005, 05:43 AM   #14
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I see on the schematic where you are getting the 2130's, but here is a link to the build manual (http://www.vacutrace.com/pdf/bugle.pdf) which lists opa2134's. My guess is that most people building this design are not particularly experienced, and are thus looking at the parts list and not the schematic. Lots of people like this phono amp. It is easy and inexpensive to build, and at it's price point (for a commercial, or semi-commercial design) it has yet to be bettered so far as I know.

That said, if you can make a better design at this price point, I'd love to try it. The bugle has been the default super cheap phono stage for a while, so some new design concepts would be great. Post a schematic if you've got one.

-d
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Old 22nd April 2005, 07:41 AM   #15
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Hi dsavitsk,

Yes the OPA2134 is a world apart. But still noisy - does nobody notice this. Surface noise must be the reason. It's achilles heel is very poor +ve supply rejection so I would do this-


Now to jUst recall those time constants 3180uS,.... it's been awhile since I'ver done one.
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Old 22nd April 2005, 01:03 PM   #16
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Thanks for the input guys, but

Quote:
My guess is that most people building this design are not particularly experienced, and are thus looking at the parts list and not the schematic. Lots of people like this phono amp...
I think I may, sadly, fall into this category. I'd wish I could remember my electronics class from my Uni days, but that was a while ago - i don't even remember most of what i learned in physics
Anyway, I'll try to digest what you've all been saying and either try the 317/337 with my trafo, or figure out a good battery replacement scheme for the case i am building - this is a more 'practical' matter for which I don't need remedial help.
Mantisory
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Old 22nd April 2005, 01:22 PM   #17
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Quote:
Originally posted by mantisory
Thanks for the input guys, but



I think I may, sadly, fall into this category. I'd wish I could remember my electronics class from my Uni days, but that was a while ago - i don't even remember most of what i learned in physics
Anyway, I'll try to digest what you've all been saying and either try the 317/337 with my trafo, or figure out a good battery replacement scheme for the case i am building - this is a more 'practical' matter for which I don't need remedial help.
Mantisory
Hello there,
We need more info, pics of the new case, inside and outside, how much room left for the psu etc

The Butcher
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Old 22nd April 2005, 01:47 PM   #18
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not quite sure whatcha mean, chris...
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Old 22nd April 2005, 04:22 PM   #19
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The room available inside the case may be a determine factor of which way your PS will go that's what I meant.

The Butcher
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Old 22nd April 2005, 04:38 PM   #20
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i see...
well, i suppose there is actually quite a bit of room really and i am free to put in just about anything (next meet, i'll hopefully have it done and bring it along).
I think at this point i am a little confused and need to do some more studying before i make any decisions...i may just make an external battery pack and at some point 'upgrade' to a proper power supply...
Mantisory
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