| veteran |
Hello!
Some time ago I decided to build a pre-amp on new TI pga2310 chip (this one is theoretical better than cs3310 offered by Crystal). There was a few models and ideas of it, but the (maby) final version You can see od the pictures below :)
Pga2310 is controlled by Atmel ATMega chip via SPI transoptor-isoleted bus. There are two ways to controll the volume, mute, zcen... - rc5 ir pilot or Bourns digital encoder.
Few board was made for me and the Lukar forum, and they will be tested soon. Software for uP still need some improves, but it is working enough stable now :)
More infos (in Polish only) and pictures you can finde on my web page www.veteran.of.pl |
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| veteran |
| Here is the picture :) |
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| pro |
Very nice and interesting.
When do 'll be possible to have the site translated in a more affordable language?
No translator on the web for Polish language.
Saluti. |
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| MWP |
Woo.. using a Crystalfontz PLED/OLED display (i work for them).
Looks nice.
Oh... but how does it sound?? ;) |
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| Alien8 |
Hi veteran
Yours sure looks nice (AND compact)
Hopefully you find time to test them thoroughly soon (and post some results).
A few questions maybe :
I noticed you probably use 78/9xx style regulators for the analog supply. Can you measure what noise leeks through to the outputs ? Maybe a lower noise type could make a difference ?
And a more trivial thing : the specsheet says 10 mA quiescent current, but do you have an idea what would be the maximum current (probably at the +31.5 dB setting) into the 600 ohm load ?
You seem to have extra coolers on some of the regulators...
That would be a nice thing to know as I'm designing a similar one but with tl431 style regulators, which can't have that much current...
The 'woofer' is just the 2nd pga controller isn't it ? |
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| veteran |
->MWP
The sound is very neutral and op-amps inside the pga2310 works as a impedance buffer (with gain from -91.5 to 0dB).
->Alien8
I'm useing lm317/337 (+-15V) and I think that they are good enough for this aplication.
If you need more powerfull output use op-amp buffer. I don't recommend the 0 to +31.5dB scope. If you want to amplify the signal- use an external non inverting opamp (opa2604, opa1632...).
The second pga2310 is for a XLR but i'm useing it as a woofer driver. |
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| kafka |
Hi, actually I'm also workimg on a similar design. But in my preamp there will be a buffer before and after PGA2310. As a power supply there will by LM317 and 337 with TL431 as a reference. See in datasheets.
BTW This is a very interesting link I'm basing on. http://www.mhennessy.f9.co.uk
I'm sure I have seen some Mark's posts on this forum. |
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| Devil_H@ck |
Hehe, seems like everyone's making a pre with a pga2310. I'm planning to make one too after my JLH amps finished (it's been in the making for like 6 months now, I know, I'm slow).
I got a lot of idea's from that same url Kafka.
Here's some more idea's I will include that I haven't seen anywere else:
- Offset for left & right channel controlled with a digital potentiometer. Settings for all the inputs will be stored in the µcontroller.
- LCD backlight controlled by digital pot.
- Bit-banged I˛C output to interface with other DIY devices. Those devices have a µcontroller inside that decodes the signal and thus does things like turning on/off the device.
- Analog power supply will be made out of OPA548s (5A max output) and a REF3130 as a reference (0.2% accuracy, 15ppm/°C -> great isn't it :)). Digital power supply will be some standard stuff (LM317 or something), it's just for the µcontroller, an LCD (well, VFD in my case) and some addition chips.
- The power for the analog stuff (+12v, +15v, -12v, ....) will be shutdown when the preamp is in standby modus (with the enable pin of the OPA548 or a MOSFET in case that opamp isn't used).
- A clock with alarm function, etc. (standard on stuff you buy, but I haven't seen it yet in a DIY preamp).
- More things that I can't think of right now ;).
Ok, that might not be ground breaking and all that original, but it might give you some idea's. Remember who you got them from :p. |
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| Kay |
hello veteran,
nice pictures, but no Circuit? |
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| kafka |
| Hm... OPA548 is a good idea. I have few of them. The E/S pin is very interesting, but I have one problem. Will it be wrong if I disable + and -15 in PGA2310 and left digital +5?? |
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| Devil_H@ck |
| Hm, I have no idea actually. I don't think anything will go wrong, the thing just won't work, but that's probably what you intend to make it do when you cut the power to it ;). |
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| veteran |
->kafka
There wont be any problem if you leve +5V for digital section od pga2310.
If somebody would like to cut the power from pga2310 he can use a LM317/337 supply driven with a transistor (so you can controll it with TTL signals). |
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| GeWa |
Hi y'all
Just finished my prototype of the digital volume control unit. It's based on Elektor's "The Audio Link". I used a PGA2311 instead of the PGA2310. In the attached pic you can see it right beside my NIGC prototype.
Happy listening
Walter |
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| The_Hi_End |
| wow, GeWa, they both look very beautifull! how's the sound? |
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| GeWa |
The NIGC is a basic kit from BrianGT. It's playing for about two weeks now and I must say that it sounds surprisingly good. The toroid is the most expensive item of the whole amplifier, so value for money taken in to acount not bad at all. The digital volume control sounds better than my passive preamp (blue Alps pot) but I still didn't had the opportunity to do some extensive listening.
Attached a pic with the front view of the thing.
Happy listening
Walter |
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| GeWa |
Hi Pepepe
Very nice looking indeed. Were did you got the housing from?
Walter |
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| pepepe1 |
| old Sony CD player + handmade alluminium front. As cheap, as possible :) |
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| GeWa |
epepe1
Is that front realy handmade?
Excellent job my friend.
Walter |
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| kafka |
I have a problem with shut down in OPA548. It works as -15V supply. I take 2.5V reference from TL431 and OPA inverts it with gain = 6. It works good. But I can't shut it down. I used the circut from the datasheet with dual supply mode. The e/s pin is at the same potentian as negative rail, so it should be good, but output voltage changes then from -15 to -12 and I can give quite a lot currnet.
And another question. How can I shut down reg1117(3,3V)? Any idea? I feed it from 5V regulator which is enable all the time. |
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| Devil_H@ck |
You could use a MOSFET to cut the power to the REG1117.
Normally the E/S pin on the OPA548 should allow you to disable it. |
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| kafka |
| quote: | Originally posted by Devil_H@ck
Normally the E/S pin on the OPA548 should allow you to disable it. |
I know it should, but it don't. The rest of OPA548 works well, but they have negative rail tight GND and I can drive them from TTL levels. That one have positive rail at GND level and negative at -18V. |
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