@arjen6t8 take a look at Wayne's post #2 here, or on my just finished preamp https://www.diyaudio.com/community/...ono-preamplifier-thoughts.414816/post-8036866
Suggestion is to get rid of that 50Hz and its harmonics for good.
Suggestion is to get rid of that 50Hz and its harmonics for good.
but OP27 is twice as expensive as FET-based OPA192, which is significantly better in all respects
Frankly I never looked at OPA192, so no clue.
Just now opened datasheet..... yes it is typical Jfet input. It is not at all "better in all respects" ! I would say it is typical comparison of Jfet and bipolar input opamps. OP 27 has observably lower voltage noise and particularly much better LF noise corner. All to be expected and also probably irrelevant as LF LP surface noise is huge.
For cost I would say OP27 is 1€ more expensive. OP27 exists in extreme grades that are really expensive and not needed. OP!192 2€, OP27 3€... Nothing even close to 627 at 30+€ or even 828 at 6 minimum.
You are very experienced guy Nick, I respect, than you also know that there are many bipolar and Jfet opamps that technically reach at least 10db better noise performance with real cartridge and in real circuit than LP surface noise. If talking THD, all of them will be many many times better than LP so its pointless to discuss.
I think we should let individual people chose their own best sounding opamps , when there is difference in perceived sound quality they should go for it. Technically I think all jfets with low V noise and all bipolars with low I noise will satisfy LP playback requirements... The rest is on listening... I refrain myself of recommending any opamp therefore, unless someone wants to use one that's completely wrong....
For me OP27 is private history as one of my first to play with, replacing 5534 in role and it was better, now I did it again 30 years later, and it is still good 🙂
Only thing I like to recommend to all is to go balanced (use dual opamps at same price as single or whatever, spend 4 euro more) and get very high CMRR and all 50 - 60 Hz garbage out, that's far more annoying than some white noise heard only when record is not played and only at extreme volumes....
but OP27 as bipolar has 0.4 pA/√Hz input noise current density vs 1.5 fA/√Hz of FET OPA192, or 270000 times worse. It is important for MM preamp with 0.5 H inductance (60 kOhms @ 20 kHz) cartridge input.
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Yes, but what is the benefit of that?
If ships sinks in 50m deep sea or in 10,000m deep sea, will it be 200 times worst? No, it is sunk well and all one can observe is open sea, no ship......
Once again link to OP27 based preamp in TT, MM cart connected, with motor running, one trace with needle in groove and other with arm in the air.... Min 10db difference everywhere in the spectrum of interest.
I do accept that I by far don't know everything, so please explain if there is some benefit of 270000 times less current noise in real phono preamp that one can actually hear while playing music., I would like to learn and I will follow advice.
If you are just proving numbers that has no real listening meaning, or listening to silence without LP, lets stop it here, I admit it is 270000 times better, you are right.
Cheers,
Drazen
If ships sinks in 50m deep sea or in 10,000m deep sea, will it be 200 times worst? No, it is sunk well and all one can observe is open sea, no ship......
Once again link to OP27 based preamp in TT, MM cart connected, with motor running, one trace with needle in groove and other with arm in the air.... Min 10db difference everywhere in the spectrum of interest.
I do accept that I by far don't know everything, so please explain if there is some benefit of 270000 times less current noise in real phono preamp that one can actually hear while playing music., I would like to learn and I will follow advice.
If you are just proving numbers that has no real listening meaning, or listening to silence without LP, lets stop it here, I admit it is 270000 times better, you are right.
Cheers,
Drazen
If you really want a moving-magnet phono preamplifier to produce less noise than the cartridge, also during the silence between records, you have to do something about the 0.5869 pA/√Hz of thermal noise current that the 47 kohm termination resistor injects at 20 degrees Celsius. Nick uses non-standard termination impedances for that, I use an electrically "cold" resistance (as its inventor named it in 1939, it's also known under several other names). When you only care about the total noise with a record playing, it's a non-issue.
Agree Marcel, that is to the point.
Even I don't listen silence and with normal 47k there is still no noise until pot is 3 o'clock , not playing, if I lower arm then it would blow my ears and windows out, noise wouldnt be an issue 🙂, And than it just some white noise, so what...
At some stage I will separately try synthesized cart loading, as EC recommended here, and OPA2828, both not for noise even that will technically improve, but to see if it sounds any better... But I'm in no rush to do it, sounds good as it is 🙂
Even I don't listen silence and with normal 47k there is still no noise until pot is 3 o'clock , not playing, if I lower arm then it would blow my ears and windows out, noise wouldnt be an issue 🙂, And than it just some white noise, so what...
At some stage I will separately try synthesized cart loading, as EC recommended here, and OPA2828, both not for noise even that will technically improve, but to see if it sounds any better... But I'm in no rush to do it, sounds good as it is 🙂
The guys who look for international VLF signals are fond of low-noise opamps like OP27, AD797 ...
http://www.vlf.it/easyloop/_easyloop.htm
http://www.vlf.it/easyloop/_easyloop.htm
with 75 Ohms antenna instead a 60 kOhms MM cartridge 
This is a perfect visualisation that better than completely adequate makes no sense. 👍
Hans
The AD797 is not low current-noise though. Its optimized for very low impedance sources.