Hello all. This is certainly the most informative DIY audio site I have came across and have been reading various topics for weeks now.
I have an idea for a HQ phono preamplifier with balanced input and SE output. I have read many great reports about balanced phono preamplifiers and this makes me exciting to try it.
Recently studied some op-amps and the Burr-Brown OPA2604 looks like a good candidate.
I am aware that not many enthusiasts are keen on using op-amps but I take a different view. The high PSRR is one of the first attractive features. Dual packages (or even quad) the second, etc.
I would like to toy with a 3 stage balanced setup using passive RIAA networks and maybe round it off with a tube buffer.
Gain of around 60dB is the goal and SNR of 60dB or more would be nice.
Lets embrace this wonderful technology called INTEGRATED CIRCUITS!
I believe Graham Slee uses op-amps in their phono preamplifiers.
Cheers
BIEP BIEP
I have an idea for a HQ phono preamplifier with balanced input and SE output. I have read many great reports about balanced phono preamplifiers and this makes me exciting to try it.
Recently studied some op-amps and the Burr-Brown OPA2604 looks like a good candidate.
I am aware that not many enthusiasts are keen on using op-amps but I take a different view. The high PSRR is one of the first attractive features. Dual packages (or even quad) the second, etc.
I would like to toy with a 3 stage balanced setup using passive RIAA networks and maybe round it off with a tube buffer.
Gain of around 60dB is the goal and SNR of 60dB or more would be nice.
Lets embrace this wonderful technology called INTEGRATED CIRCUITS!
I believe Graham Slee uses op-amps in their phono preamplifiers.
Cheers
BIEP BIEP
"the Burr-Brown OPA2604 looks like a good candidate."
Why? High noise and high distortion (forget the datasheet) make it
less than suitable for a phonostage front-end. About its only interesting feature is its very wide supply voltage range.
"The high PSRR is one of the first attractive features."
I wouldn't call 80dB particularly high.
"Gain of around 60dB is the goal and SNR of 60dB or more would be nice. "
The first 60dB indicates you want to make an MC pre, right? The second 60dB isn't very ambitious. Try to aim at 75-80dB to make life, and the project's result, more interesting.
Consider a low noise instrumentation amplifier like the SSM2019
or INA103.
You'll find these in quite a few commercial microphone and moving coil preamps. They are natively differential-in and have noise performance close to what's attainable with integrated devices.
If you really want to throw standard opamps at a differential input, then have a look at the AD797 and LT1028.
If you want to go discrete, then FETs like the 2SK369 apply. There's a neat example
here.
Why? High noise and high distortion (forget the datasheet) make it
less than suitable for a phonostage front-end. About its only interesting feature is its very wide supply voltage range.
"The high PSRR is one of the first attractive features."
I wouldn't call 80dB particularly high.
"Gain of around 60dB is the goal and SNR of 60dB or more would be nice. "
The first 60dB indicates you want to make an MC pre, right? The second 60dB isn't very ambitious. Try to aim at 75-80dB to make life, and the project's result, more interesting.
Consider a low noise instrumentation amplifier like the SSM2019
or INA103.
You'll find these in quite a few commercial microphone and moving coil preamps. They are natively differential-in and have noise performance close to what's attainable with integrated devices.
If you really want to throw standard opamps at a differential input, then have a look at the AD797 and LT1028.
If you want to go discrete, then FETs like the 2SK369 apply. There's a neat example
here.
Phono stage; balanced
I own two balanced Phono stages;
one is DIY and uses the DACT Phono board ( Danish Audio Connect ) which is superb; it's only a matter of fabbing a box + power supply; single ended input + balanced output
The DACT board uses surface mount components + is very accurate to the RIAA curve. Easilly adjustable for gain + capacitance with internal dipswitches
The other is the B.A.T. VP10SE; which is not DIY, has the choice of Balanced or single ended input, but only balanced output
Using Balanced cable ( XLR's ) greatly reduces the noise floor compared to SE, in a Phono stage, in my experience
Good luck with your project!
The Electric Gypsy
I own two balanced Phono stages;
one is DIY and uses the DACT Phono board ( Danish Audio Connect ) which is superb; it's only a matter of fabbing a box + power supply; single ended input + balanced output
The DACT board uses surface mount components + is very accurate to the RIAA curve. Easilly adjustable for gain + capacitance with internal dipswitches
The other is the B.A.T. VP10SE; which is not DIY, has the choice of Balanced or single ended input, but only balanced output
Using Balanced cable ( XLR's ) greatly reduces the noise floor compared to SE, in a Phono stage, in my experience
Good luck with your project!
The Electric Gypsy
Don't forget differential input has 3dB worse noise compared to single ended input,
http://www.diyaudio.com/forums/showthread.php?postid=1354996#post1354996
If you use nice 100% covered shielded cabling, I don't see much that can be left to be canceled by balanced cabling
Have fun, Hannes
http://www.diyaudio.com/forums/showthread.php?postid=1354996#post1354996
If you use nice 100% covered shielded cabling, I don't see much that can be left to be canceled by balanced cabling
Have fun, Hannes
Balanced vs. Single ended input
Using a balanced input on the B.A.T. , compared to a single-ended input, results in a significant drop in background noise + an increase in detail
This is particularly noticeable with low-output moving coil cartridges
I have 2 Phono cables that are identical but for their RCA/XLR terminations ( ie: same length, type + manufacturer ) and A/B'ing these the XLR setup is immediately noticeable as the better ( and quieter ! ) of the two
GW
Using a balanced input on the B.A.T. , compared to a single-ended input, results in a significant drop in background noise + an increase in detail
This is particularly noticeable with low-output moving coil cartridges
I have 2 Phono cables that are identical but for their RCA/XLR terminations ( ie: same length, type + manufacturer ) and A/B'ing these the XLR setup is immediately noticeable as the better ( and quieter ! ) of the two
GW
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.