Hah! This is da supa virtual reality Z servoed wid go faster stripes 😱
I haven't played with anything like this in this or the previous Millenium so I bow to Guru Self's facility wid da black magic.
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Mark Johnson, are you going to spend 20min and work out a nice 12dB/8ve JLH type 20Hz filter as in my #266 post? We would all be soo.oo grateful and Doug might even put it in his book 🙂
Please feel free to change the RIAA network itself for any of the 4 Lipshitz topologies. (with added pole to cancel the supersonic zero of course).
30dB & 40dB 1kHz gains would be nice ..
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Just in case some of you are baffled, this statement refers to applying load synthesis to a standard 5534A phono stage.
1) I'm finding that modern bias-current-compensated op amps (e.g. LME49720, OPA1612) always under-perform from a noise perspective with a real MM cart.
The NJM2068 "DD" (bipolar) is actually one of the quietest and a virtual tie with the FET input OPA2132 and OPA1642. The 5532 is also relatively quiet as is the NJM2114.
All of the later group out-perform the Ib-compensated group.
The OP27 may be the exception for an Ib-comp'd amp.
2) This whole argument against uA-level bias current in the cart is total BS. Bias current/cart effects is a non-issue.
3) The protection an input coupling capacitor might offer from an input stage fault, or the DC blocking it provides, is virtually zero at t=0 when the capacitor is effectively a dead short and the current is limited by the DCR of the cart. At turn-on or at the instant of a fault your cart is just as likely to get whacked by some transient if it has a series cap or not.
4) The input coupling capacitor is a noise source when op amp noise current flows outward on its way to the cart. You almost never see the added LF reactance in a model.
5) And while we're discussing phono inputs let's just completely and totally ignore the benefits of balanced cartridge to preamp interconnect something mic-level circuits and telephony have benefited from for a century. There is absolutely nothing to see here folks just move along....[/SARC]
And I forgot one:
6) To remove the dominate effect of warp HPF Side at a high fc. The original recording will have very little vertical modulation at low frequencies. Then use simple HP filters on L and R to remove the lateral LF garbage.
The NJM2068 "DD" (bipolar) is actually one of the quietest and a virtual tie with the FET input OPA2132 and OPA1642. The 5532 is also relatively quiet as is the NJM2114.
All of the later group out-perform the Ib-compensated group.
The OP27 may be the exception for an Ib-comp'd amp.
2) This whole argument against uA-level bias current in the cart is total BS. Bias current/cart effects is a non-issue.
3) The protection an input coupling capacitor might offer from an input stage fault, or the DC blocking it provides, is virtually zero at t=0 when the capacitor is effectively a dead short and the current is limited by the DCR of the cart. At turn-on or at the instant of a fault your cart is just as likely to get whacked by some transient if it has a series cap or not.
4) The input coupling capacitor is a noise source when op amp noise current flows outward on its way to the cart. You almost never see the added LF reactance in a model.
5) And while we're discussing phono inputs let's just completely and totally ignore the benefits of balanced cartridge to preamp interconnect something mic-level circuits and telephony have benefited from for a century. There is absolutely nothing to see here folks just move along....[/SARC]
And I forgot one:
6) To remove the dominate effect of warp HPF Side at a high fc. The original recording will have very little vertical modulation at low frequencies. Then use simple HP filters on L and R to remove the lateral LF garbage.
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One speculation I heard is that a small bias current could make the pick up more linear. It might be possible to measure this with a test record. Even if the record is well used the data should change. Who knows ?
One thing I noticed when using 3 paralell bipolar op amps was it changed the colour of the noise. Like a fool I didn't do a before and after test that I could show here. It could be it was just lower noise. My instinct is to think it could be more than just how much. If trying to give an idea the noise was more like a high grade pentode when compared with the white box versions ( 1/f ? rather than partition noise ). EF 86 for example. My pick up was Lyra with 5 ohms coils ( plus arm wire ). It was just a cheap MC33079 op amp, it had very good sound. The last op amp did the 3180/318 uS. The LF was tuned using 1K8 and 22uF ( 10 uF initial ) on stage 2. The DC offset was fine when the first stage to DC. I re-ran the tests recently with NE5532. It is a very similar sound which I find less good as time goes by. If it had sounded better I fancied trying a NE5534 with external input transistors. BC337-40 perhaps?
One trick seen in studios was to add low noise transistors to a 741 op amp and a current sink/source to the output. Some reasonable mic preamps were made this way. Although not as ideal as the 5534 version it worked. There is a chance a recording you treasure was made this way. SSL recording desks used NE5532, sometimes the signal went through 90 of them to quote Dave Mate the engineer. He did use other op amps when improving the SSL desks. I am told by John Deans his technician of old that the power supply design was critical as was being sure the op amps did not oscillate. I did check my 5532 for oscillation and did decouple as close to the op amp as I could. A mistake I might have made was using a mylar cap, a cheap ceramic might have been beter. Mine was 10 nF + to -. I had some high grade 10 uF rail to 0V close as I could. John tells me the drop in price of 5532 was due to SSL using so many as far as he knows they were the worlds largest user at the time of the price drop. I have no idea if that is true.
One trick seen in studios was to add low noise transistors to a 741 op amp and a current sink/source to the output. Some reasonable mic preamps were made this way. Although not as ideal as the 5534 version it worked. There is a chance a recording you treasure was made this way. SSL recording desks used NE5532, sometimes the signal went through 90 of them to quote Dave Mate the engineer. He did use other op amps when improving the SSL desks. I am told by John Deans his technician of old that the power supply design was critical as was being sure the op amps did not oscillate. I did check my 5532 for oscillation and did decouple as close to the op amp as I could. A mistake I might have made was using a mylar cap, a cheap ceramic might have been beter. Mine was 10 nF + to -. I had some high grade 10 uF rail to 0V close as I could. John tells me the drop in price of 5532 was due to SSL using so many as far as he knows they were the worlds largest user at the time of the price drop. I have no idea if that is true.
They actually used 5534s which is close enough. I count about 30 in an SSL 4K mixdown channel path alone. With the module having an inline architecture signals that are tracked go through about 30 on their way to the recorder and another 30 in the monitor path to the mix bus. Add about another 30 for the center section. The late Bob Pease and I discussed this back in 1993. The number I came up with is 92: Pro Audio Design Forum - 1992 Discussion with Bob Pease re Cascaded Op Amps
For a period of time SSL used Raytheon RC5534s which sucked. I changed out thousands of them in SSL desks back to NE5534s for customers which SSL paid for. Raytheon had a dirty analog process: SSL made it right.
If you're interested in SSL schematics I host some here: SSL Schematic and Drawings Index
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And there was me thinking Douglas was using a bit of artistic license when he said the signal goes through 'hundreds' of op-amps. Thanks for the links Wayne.
I see John every week. See how much more I can find out. If anyone if looking for a gifted engineer I think he is ready to jump ship.
Did you actually measure OP27 with a real cartridge Wayne?
I replaced OP27 in a commercial product with 5534 and got a dB or more improvement in real life noise IIRC. It was someone else's design.
Here is a conventional op amp I did try. It was noticably better than most if saying MC.
LT1115 - Ultra-Low Noise, Low Distortion, Audio Op Amp - Linear Technology
I find the DL110 an MC that genuinely can be all things to all men. If you have one tweak the gain. It really is important to give it 6 dB more than a standard MM. Noise is still very good if so.
LT1115 - Ultra-Low Noise, Low Distortion, Audio Op Amp - Linear Technology
I find the DL110 an MC that genuinely can be all things to all men. If you have one tweak the gain. It really is important to give it 6 dB more than a standard MM. Noise is still very good if so.
Nigel what would be the effect of 6dB more gain (in the headamp I assume)? Would it not just play louder, all things being equal?
Jan
Jan
That's right. It seems so subtle, I feel is helps to have the CD level and phono about the same. Maybe I fool myself?
Very nice to see that Douglas Self's 'dozens of opamps' or 'hundreds of opamps' in the signal path of a typical recording is not urban myth but in fact has merit i.e. the truth. All hail the mighty opamp.
I went for an interview at SSL once near Oxford, UK - I however wound up going in another direction career-wise. Pretty impressive place (1996)
Thanks for sharing 🙂
I live two miles away and know Dave. My favourite Dave Mate quote " There again I am only the designer so what do I know". Of all the people I met he is the one who does know.
No not fooling yourself, but in any serious comparison the level (and freq response) should be diligently matched! Otherwise, the loudest and/or the one with some bumbs will sound better....
Jan
So the '+6dB' may help you personally to better compare stuff, but it has nothing to do with the sound quality of that cartridge. The same happens with turning the volume control a bit further CW.
Jan
Jan
In my mind it's this way. Someone buys a DL110 which is neither typical MM nor MC output. They might be mildly dissapointed as it seems a bit puny compared with perhaps the Ortofon VMS 20EII they had before. This is something the newby could put right. Learn how to reset the gain of the preamp to be optimum ( taste of that person ). The dissapointment may come from the fact that the VMS is perhaps 10dB different in output. I made this mistake and was very surprised how resetting the levels made me feel it to be a vastly better pick up than I thought. Wheather I should know better is a good question. I felt that fine tuning the preamp to suit made me happier. Somehow turning the volume up wasn't quite the same thing. Maybe I like a bit of overload in the preamp? Where I felt the DL110 scored was the lowest hiss levels I have known whilst the more open sound of an MC. I think 1 mV suits it well.
Another interesting pick up is the Shure M44-7. If you take the trouble to make it a preamp it can sound very good in the fashion of the Decca London ( better in some ways ). The gain needs to be reduced on most preamps for this one. Neither the low stereo seppartion nor simple stylus type is obvious. Hiss levels must be about as good as it gets. I learnt this from the 44-78 used in the SME 5. A spare stylus for LP was around. The sound would surpass many MC's and suits the SME 5.
Another interesting pick up is the Shure M44-7. If you take the trouble to make it a preamp it can sound very good in the fashion of the Decca London ( better in some ways ). The gain needs to be reduced on most preamps for this one. Neither the low stereo seppartion nor simple stylus type is obvious. Hiss levels must be about as good as it gets. I learnt this from the 44-78 used in the SME 5. A spare stylus for LP was around. The sound would surpass many MC's and suits the SME 5.
Turning the vol control is the problem imo/ime.....ie ime, expect slightly differing sound according to the volume control position for typical carbon pots.
On live mixing desks, tweaking channel gain and channel fader position very slightly for same overall level can give 'sweet spot' sound, or 'nasty spot' sound.
Just sayin'.
Dan.
