Bugle PS

Hi all...
I have a bugle phono pre, currently using rechargeable 9V batteries, that'd i'd like to place inside an integrated amp i am building. I also have a dual 12V 2A transformer to use, and am wondering...should I use the transformer with a bridge rectifier (4 1N4007's or something), unregulated with smoothing Caps, or should i use the LM317/337 pair that I have to regulate it? I need +/- 15V to power the bugle (www.hagtech.com/bugle)
Thansk for your help
Mantisory
 

dhaen

diyAudio Moderator Emeritus
2002-06-10 12:01 pm
U.K.
www.keystrobe.co.uk
Ah, I didn't appreciate that you needed to use "in stock" parts ;)

What sticks out about their psu is the use of Schottky diodes as a bridge rect. That'll be much quieter than the 1N400X diodes, so is a must.
R2 and R12 form noise filtering too and should be incorporated.
As for regulator types, I don't think theirs are that special.
The other Schottky's are just "fussing" IMO.
 
Hi Mantisory,

You would do well to use the 317/337 set to 15V and 1N4002's up. The adjustable regs have much better performance than the fixed ones recommended so better to use what you have.

The OPA2130 (ugh) has very poor HF PSRR so it should benefit considerably. A discrete regulator using a pass transistor, current source and TL431, or LT 317/337 would be better. You can increase R2, R12 and increase R6,R9 to lighten loading.

Then save up for some better chips, those 2130's are noisy, low bW/SR. Try an shoehorn some OPA637 singles in and sit back and enjoy the relative silence and cleanness.
 
amplifierguru said:
Try an shoehorn some OPA637 singles in and sit back and enjoy the relative silence and cleanness.

Yes, that sounds like a great idea. Add $110 worth of opamps to your $50 phono stage.

If you are going to spend that kind of money, you might as well get a better phono stage. Short of a different circuit, there are plenty of other good opamps you can try that are much cheaper than the opa637.

-d
 
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
 
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 ?
 
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
 
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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Thanks for the input guys, but

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. :smash:
Mantisory
 
mantisory said:
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. :smash:
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:D
 
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