The best phono preamp on op-amps?

[djaleksei]

Hi there! I'm new to these forums so maybe this question has been asked many times. I tried to search, but couldn't find the exact answer... I've been reading threads about phono preamps but still wandering which one is the best...

I don't care about the price of parts. I'm looking for a high quality preamp schematics. Which one of all phono preamps projects mentioned on this forum is the best in terms of sound quality, very low distortion and low noise for MM pickups?

The reason I'm asking this is because I'm planning to build an amp with line and phono inputs, and also be able to use the phono preamps that I'll include in this amplifier as a stand alone devices for recording....

Thanks.

[phn]

I'm not the one to answer this. But perhaps you should try rephrase the question. Here are lots of great stuff, but nothing "best." If it were that easy there would only be one audio manufacturer out there.

[richwalters]

Hi thzere....National Semi's website on the LM833 offers an application note for a general RIAA characteristic. In fact there are stacks of ic's suitable for this app, some noisier than others. For moving magnet pickups....the input level and impedances are way different. The simplest solution which Ortofon did with MM types was to supply step-up transformers to match moving coil input eq's. For lowest noise this was the best solution. keep working on it!

rich

[Carondimonio]

Originally posted by richwalters
Hi thzere....National Semi's website on the LM833 offers an application note for a general RIAA characteristic. In fact there are stacks of ic's suitable for this app, some noisier than others. For moving magnet pickups....the input level and impedances are way different. The simplest solution which Ortofon did with MM types was to supply step-up transformers to match moving coil input eq's. For lowest noise this was the best solution. keep working on it!

rich

Hi,

maybe I didn' t understood your post correctly, but a step-up transformer is used to match an MC cartridge (low output level, low impedance) to an MM phono input.

Cheers,

Bruno

[djaleksei]

I was looking into the Phonoclone and VSPS preamps, and also into many others like those that are included in application notes from different IC manufacturers. I suppose that not only the ICs are the ones that determinate the quality (noise, THD) but the feedback circuits, voltage supply and everything else... Am I correct?

I like the specs of the AD797, but how hard is to modify for example the VSPS or the Phonoclone circuit in order to be able to implement the 797? I like those two phono stages because they are simple, but how about the specs in terms of noise and THD? Thanks.

[Soundadvice]

The circuit on the lm833 data sheet seems to have alot going for it in comparison to the `one op amp types` normally found in most mixers,integrated amps,not to mention some other manufacturers data sheets ! I have not built this yet , but even for the not very mathematical amongst us the gain can easily be increased at the second stage,the only downside is that from the figues provided and the ones I calculated for a different first stage gain,it always seems to come up with-E96 values of resistors.Seems a good excuse to use the low noise :- very stable welwyn types ! Still if I am to assume correctly that you will be recording your own mixes ; 2 x rotel rq 970 bx (which can be picked up for arround £50 stirling S/H ) running into the mixers line input should give exellent results without the hastle of fabricating your own PCB`s !

Happy mixing !

from soundadvice !

P.S. my soldering is much better than my typing, I do much more of the former than the latter !

[peranders]

AD797, LT1028/LT1115 are three low noise opamps but if you not are going to use any MC pickups you will have many good opamps to choose from. The noise should be less then 10 nV/Hz.

Have you seen this datasheet for inspiration? In the datasheet you have two different kinds of RIAA amps.

http://www.linear.com/pc/productDeta...09,C1026,P1293

Datasheet here:
http://www.linear.com/pc/downloadDoc...26,P1293,D1612

[ran_ph]

Anybody tried this one?

http://www.rane.com/pdf/ps1sch.pdf

[richwalters]

Originally posted by ran_ph
Anybody tried this one?

http://www.rane.com/pdf/ps1sch.pdf

Hi there...........the o/p stage 2142...electronically balanced for console buss....it may object having one side grounded for single ended. On some chips the gain would go up by +6dB on grounding one side..
The rest looks bog standard.

ricxh

[AndrewT]

Hi,
I'm not going to give you the answer, I can't.
But my thoughts on what to look for.
1. Buffer on the input with a bit of gain (+6 to +10db) before anything gets done to equalise.
2. Split passive equalisation with buffer/gain blocks between stages.
3. Simple passive 75us roll off as last equalisation, achieves noise reduction and maintains single pole to infinity, well almost.
4. Lots of spare voltage overhead at the output buffer and in the intervening gain blocks. Oh and remember all caps have some inductance.
5. If diy find a way to measure your caps to 1% and match channels to 0.5%, resistors to 0.3% accuracy and matching.
regards Andrew T.