UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > General Vintage Technology > Components and Circuits

Notices

Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

Closed Thread
 
Thread Tools
Old 27th Jul 2020, 12:34 pm   #61
mhennessy
Dekatron
 
Join Date: Jul 2007
Location: Evesham, Worcestershire, UK.
Posts: 4,241
Default Re: Very low noise op amp recommendations?

Here's another list, which include both voltage and current noise. From Self's "Small Signal Audio Design". Shows that the AD797 might well have less noise voltage than an NE5534, but more current noise. It's also astonishingly expensive.

Mark
Attached Thumbnails
Click image for larger version

Name:	Op-amp noise.jpg
Views:	104
Size:	48.1 KB
ID:	211968  
mhennessy is offline  
Old 27th Jul 2020, 12:43 pm   #62
Craig Sawyers
Dekatron
 
Craig Sawyers's Avatar
 
Join Date: Nov 2010
Location: Oxford, UK.
Posts: 4,941
Default Re: Very low noise op amp recommendations?

Noise specs of opamps is a tricksy thing. I had not come across the MAX4016, so I had a shufty. The mid band voltage noise is better than the AD797 by 1.27 times, so a useful 2dB quieter for low Z sources.

But the 1/f corner frequency (for both Vn and in) for the MAX4016 is around 200Hz, which is rather high for an RIAA stage, even for a MC cartridge. The in is much too high for a MM.

The AD797 is still the best choice for low resistance sources with a vn 1/f corner at sub 10Hz.

Craig
Craig Sawyers is online now  
Old 27th Jul 2020, 12:47 pm   #63
bikerhifinut
Octode
 
Join Date: Nov 2013
Location: Penrith, Cumbria, UK
Posts: 1,993
Default Re: Very low noise op amp recommendations?

Quote:
Originally Posted by mhennessy View Post
Quote:
Originally Posted by bikerhifinut View Post
Sorry I couldn't split the circuit out of the PDF document. Its proably the portable device I am using.
A
Here you go, with annotations...

Mark
Brilliant Mark thanks!
For those interested they are less than a tenner if you look around and it does work, however if memory serves me right, the EQ isn't optimal according to the knowledgable on the site.
If you haven't got the parts in the toybox then I reckon that's not a bad price considering it includes the PCB.
As before though, you may want to use something more suitable in the EQ than ceramics, the electrolytic couplers I'd say were more down to choice. And you might want to put a small extra amplification stage in after it if it turned out to be a bit weedy for the amp in use. That's simple enough with another op amp.

A.
bikerhifinut is offline  
Old 27th Jul 2020, 12:55 pm   #64
mhennessy
Dekatron
 
Join Date: Jul 2007
Location: Evesham, Worcestershire, UK.
Posts: 4,241
Default Re: Very low noise op amp recommendations?

The MAX4016 isn't really an audio op-amp. Much as it might work if you don't mind +/-5V supplies, it's really intended for much wider bandwidth stuff. Where it might be useful, however, might be as a headphone amp for 32 ohm headphones, where the 125mA output current and low operating voltage is useful. However, there are more appropriate choices...

SMD only. Not sure I'd risk putting one on an SO-8 to DIL adaptor board, given the extremely wide bandwidth.
mhennessy is offline  
Old 27th Jul 2020, 1:37 pm   #65
bikerhifinut
Octode
 
Join Date: Nov 2013
Location: Penrith, Cumbria, UK
Posts: 1,993
Default Re: Very low noise op amp recommendations?

The AD797 rang a bell and I am sure (I have lost the magazine and DIY supplement) Hi Fi World a few years back published a circuit for a DIY MC stage.
It was a standard design as I remember and the MC signal was boosted using the AD797 in the first stage. As I remember it the description was to the effect that the AD797 although expensive was the only device with a low enough noise for boosting a 200uV signal.
bearing in mind the wallet emptying prices of even fairly modest (by MC standards) cartridges I guess the £25 cost of a couple of AD797 is relatively insignificant.
Interesting insight into the current and voltage noise differences between MM and MC and explains why the 5534 is actually a better choice than an AD797 for MM and vice versa.
As my pension doesn't stretch as far as it did 5 years ago (flat rate no inflation rises grrrrrr), when my Ortofon Quintet went belly up, I reverted to MM and given that I'm not using bargain basement transducers, I'm very very impressed with the current crop of quality cartridges, to wit the Ortofon 2M jobs and latterly I got an AT VM95 for use in the other turntable in my collection and with one of the more refined stylus options that's been a very pleasant thing. This is whats piqued my interest in solid state MM amps.

A.
bikerhifinut is offline  
Old 27th Jul 2020, 1:56 pm   #66
saddlestone-man
Hexode
 
Join Date: Mar 2009
Location: Cirencester, Gloucestershire, UK.
Posts: 391
Default Re: Very low noise op amp recommendations?

Looking back to what I wrote in Sprat (issue 121, Winter 2004) I did some subjective tests on what the noise generated by these different op-amps sounded like. The context of the tests was that in a typical direct conversion receiver there was a single, high gain audio stage in front of the power amp, and so noise in the audio path could be very noticeable. Constructors often used a 741 or a TL071 because they had one handy and I thought this might be restricting the performance they were getting from their receivers.

All the op-amps were pin-for-pin compatible with the 741, and I used a socket, so that I could swap them out very easily.

Here's what I wrote:
================================================== ==
Subjective tests
I did some subjective tests on some of the op-amps with a simple inverting op-amp circuit. With a voltage gain of 10 (20dB) the difference between a 741 and an OP27 (Very Low noise category, similar to the NE5534) was difficult to discern. I tried an AD797 and no noise could be heard at all.

With a gain of 100 (40dB) a 741 is definitely noticeably “hissy”; the TL071 was quieter (but by not as much as I expected), the OP07 and OP27 much quieter again, and I still couldn’t hear any noise from the AD797.

At 1000 (60dB) voltage gain, the relative order was the same, and the AD797 was still absolutely silent. In fact I had to check several times that it was powered.
================================================== ====

Note that the subjective noise was dependent on the gain of the stage.

In my experience the AD797 was superb. You get what you pay for, and it's not that expensive on eBay (if you can trust the ultimate source). Could you fit sockets to you board, use say NE5534s initially and get someone to treat you to an AD797 upgrade for Christmas?

best regards .. Stef
saddlestone-man is offline  
Old 27th Jul 2020, 1:58 pm   #67
ajgriff
Nonode
 
ajgriff's Avatar
 
Join Date: May 2004
Location: Halifax, West Yorkshire, UK.
Posts: 2,583
Default Re: Very low noise op amp recommendations?

You don't need esoteric and expensive op-amps to make a low noise MC head amplifier either. Jelly bean 2N4403 transistors (3 per channel) will do the job nicely when used with a couple of ordinary op-amps, according to Douglas Self anyway. 'Self on Audio' refers.

Alan
ajgriff is online now  
Old 27th Jul 2020, 2:10 pm   #68
Craig Sawyers
Dekatron
 
Craig Sawyers's Avatar
 
Join Date: Nov 2010
Location: Oxford, UK.
Posts: 4,941
Default Re: Very low noise op amp recommendations?

Even the AD797 is tricky to tame. It is sensitive to layout and decoupling in a way much more so than a 5534 or 5532.

Craig
Craig Sawyers is online now  
Old 27th Jul 2020, 2:12 pm   #69
mhennessy
Dekatron
 
Join Date: Jul 2007
Location: Evesham, Worcestershire, UK.
Posts: 4,241
Default Re: Very low noise op amp recommendations?

Quote:
Originally Posted by saddlestone-man View Post
In my experience the AD797 was superb. You get what you pay for, and it's not that expensive on eBay (if you can trust the ultimate source). Could you fit sockets to you board, use say NE5534s initially and get someone to treat you to an AD797 upgrade for Christmas?
So much depends on the surrounding components - with badly chosen resistors, for example, the thermal noise they generate can swamp the noise from the op-amp. Can you recall the details of your test circuit?

I would never buy an expensive audio IC from eBay. Re-labeling machines are widespread, and fake semiconductors are a real problem - even the major suppliers have occasionally been caught out. This is especially so for the types audiophiles are interested in - a lot of people doing "op-amp rolling" are not especially technical, and won't be trying them in demanding circuits like phono pre-amps. As such, they will hear the sound quality differences they've been told to expect, irrespective of the actual silicon inside the package. Easy money for the forgers...
mhennessy is offline  
Old 27th Jul 2020, 3:07 pm   #70
Craig Sawyers
Dekatron
 
Craig Sawyers's Avatar
 
Join Date: Nov 2010
Location: Oxford, UK.
Posts: 4,941
Default Re: Very low noise op amp recommendations?

Quote:
Originally Posted by ajgriff View Post
You don't need esoteric and expensive op-amps to make a low noise MC head amplifier either. Jelly bean 2N4403 transistors (3 per channel) will do the job nicely when used with a couple of ordinary op-amps, according to Douglas Self anyway. 'Self on Audio' refers.

Alan
It is certainly true that in 1980 2N4403's produced a voltage noise of ~0.9nV/rootHz at Ic of 10mA and 1nV/rootHz at 1mA. The old datasheet had Vn and In as a function of frequency, and a set of noise contours (contours of constant NF).

Three 2N4403 in parallel would have been about 0.5nV/root Hz. That is the Johnson noise generated by a 15 ohm resistor.

The current On-Semi data is NF as a function of frequency and NF as a function of source resistance. These are essentially sections through the noise contours, and suggest doing a side by side comparison that the spec of the current 2N4403 is at least as good as the 1980 ones.

Note that three in parallel is still noisier than the coil resistance of many moving coil cartridges (which are in the range 2 ohms to 14 ohms, with only one I know of that is higher, the DL103 with 40 ohms).

The all time best transistor for this work was the late and very lamented Rohm 2SB737, which had an rbb' of 2 ohms, with a single transistor producing 0.3nV/rootHz at 10mA, equivalent to a resistor of 5.5 ohms. Three in parallel would have been equivalent to 3 ohms and dealt perfectly with all low resistance moving coils. It, and other useful low noise transistors from different manufacturers were dropped when CD ripped the beating heart from vinyl records and the market collapsed for ultra low voltage noise transistors.

None of this is relevant to moving magnet cartridges, where the 5534A reigns supreme.

Craig
Craig Sawyers is online now  
Old 27th Jul 2020, 3:35 pm   #71
ajgriff
Nonode
 
ajgriff's Avatar
 
Join Date: May 2004
Location: Halifax, West Yorkshire, UK.
Posts: 2,583
Default Re: Very low noise op amp recommendations?

Quote:
Originally Posted by Craig Sawyers View Post
None of this is relevant to moving magnet cartridges, where the 5534A reigns supreme.
Not relevant to MM as you say. I only mentioned it because Andy made reference to using the AD797 for MC head amps in post #66.

Alan
ajgriff is online now  
Old 27th Jul 2020, 4:16 pm   #72
Craig Sawyers
Dekatron
 
Craig Sawyers's Avatar
 
Join Date: Nov 2010
Location: Oxford, UK.
Posts: 4,941
Default Re: Very low noise op amp recommendations?

You can of course parallel AD797's, provided you are that way inclined, have deep enough pockets, and can keep them stable in that configuration
Craig Sawyers is online now  
Old 27th Jul 2020, 4:38 pm   #73
Radio Wrangler
Moderator
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,799
Default Re: Very low noise op amp recommendations?

The noise figure of transistors is also dependent on the reactance of the presented source, so inductance and capacitance should for completeness be taken into account, but for audio frequencies and the sort of inductances of moving coil cartridges a purely resistive analysis isn't far off the money.

The best tool for visualising what is going on are noise contours and gain contours on a Smith chart, and you only get this sort of data presentation for RF devices.

You see that the source Z for best noise figure is often a long way from that for best gain.

If you don't have much gain, the noise contribution of the next stage may be significant and the analysis of noise figures in concatenated stages is what Friis' equation is about.

You can take a transistor and solve its noise parameters to find the source impedance for its optimum signal to noise behaviour. Once you know the source impedance your actual source presents you can then work out how many of the transistor's ideal source values in parallel would be needed to make up the actual cartridge's presented impedance. So now you know how many transistors you need in parallel. Simple diligence, no rocket scientists were harmed in the calculation. Good design involves making sure current sharing is fair. Some designers got this far and then spoiled the whole thing saving a few passive components. Sometimes you earn more about human idiocy than about transistors.

I understand that studio mixing desk designers still hold a memorial wake for the passing of the 2SB737. Rohm saw it only as a small motor drive transistor, and everyone was going to MOS or IGBTs for motors. It was the best game in town for inputs from moving coil studio microphones.

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is online now  
Old 27th Jul 2020, 4:39 pm   #74
Radio Wrangler
Moderator
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,799
Default Re: Very low noise op amp recommendations?

Quote:
Originally Posted by Craig Sawyers View Post
You can of course parallel AD797's, provided you are that way inclined, have deep enough pockets, and can keep them stable in that configuration
That's three 'AND-IF's" needed to coincide!

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is online now  
Old 27th Jul 2020, 5:55 pm   #75
bikerhifinut
Octode
 
Join Date: Nov 2013
Location: Penrith, Cumbria, UK
Posts: 1,993
Default Re: Very low noise op amp recommendations?

I think we can make some sort of conclusion here.
That the 5534 and to a slightly lesser extent the dual 5532 is pretty much as good as you practically need for a MM disc stage, in terms of device noise etc.
It gets muddier when we look at MC amps but I think for most of us here that's not particularly important, my own practical solution is a pair of ortofon T5 step up transformers (made I believe by Sony way back in the distant past) for matching any MC cartridge that may have fallen into my hands into a standard MM stage. There are side issues here and back when my main cartridge was an Ortofon MC I always felt the best overall balance of performance was a nifty and not too expensive commercial disc stage using silicon. Very low hiss levels.
And more matching permutations than you'll ever need, I personally found that MC cartridges don't seem all that fussy on resistance and capacitance loading compared to MM. 'nuff said.

So we have a nice cheap op amp that pretty much does it all, metal film 1% resistors are pennies these days so there's no excuse not to use them in a phono stage and the only grey areas are probably around the capacitors in the EQ network and for me that mostly hinges around how close you want to get to the "ideal" and if 5% parts do the job and make your feet tap to the music that'll be my benchmark. If you are particularly sensitive to slight deviations from the ideal then there are 1% capacitors if your wallets well stuffed. The text books are full of tweaks and ways to improve capacitor tolerance, I can never remember the maths so always end up with a book in front of me!
A.
bikerhifinut is offline  
Old 27th Jul 2020, 6:02 pm   #76
mhennessy
Dekatron
 
Join Date: Jul 2007
Location: Evesham, Worcestershire, UK.
Posts: 4,241
Default Re: Very low noise op amp recommendations?

Yup - that's a good conclusion. It's good that we've saved you a bit of money and, more importantly, hopefully saved you getting caught on the DIY audio merry-go-round!

If you haven't already got one, those cheap Chinese component testers are likely good enough for measuring caps. It's probably more important to match between channels than to hit the absolute values. Given how cheap polyester caps are, you could probably afford to buy a couple of packs of 10 with a 10% tolerance in order to get a pair of samples that are close to the required value. For example, the Self version requires 50n - you're bound to get two of those from a bag of 47n caps, and the rest can be used in lots of other projects. They've be fine for rail decoupling, for example
mhennessy is offline  
Old 27th Jul 2020, 6:27 pm   #77
saddlestone-man
Hexode
 
Join Date: Mar 2009
Location: Cirencester, Gloucestershire, UK.
Posts: 391
Default Re: Very low noise op amp recommendations?

Note that the ultra low noise op-amp in the table attached to post 58 is the MAX4106, not the MAX4016.

Strange how things haven't got any better, ie quieter, in the intervening 16 years since I built the table (and I guess the AD797 wasn't new even then).

best regards ... Stef
saddlestone-man is offline  
Old 27th Jul 2020, 7:17 pm   #78
mhennessy
Dekatron
 
Join Date: Jul 2007
Location: Evesham, Worcestershire, UK.
Posts: 4,241
Default Re: Very low noise op amp recommendations?

Oops - naughty Craig, and naughty me for not going back to the post he referred to! Still, an easy mistake to make

Having said that, I don't think I'd say much different - it's a low voltage, high speed part not really intended for audio. And it looks like it's no longer available.
mhennessy is offline  
Old 27th Jul 2020, 8:42 pm   #79
Craig Sawyers
Dekatron
 
Craig Sawyers's Avatar
 
Join Date: Nov 2010
Location: Oxford, UK.
Posts: 4,941
Default Re: Very low noise op amp recommendations?

Peter Baxandall published an excellent letter to follow up on Stanely Lipschitz's seminal paper on RIAA networks.

What Baxandall did was pick RIAA values which were all standard values, and switchable gain in 10dB increments to boot, attached.

With errors in component value to the theoretically correct ones of less than 0.6%. The only thing that he did that was in vogue at the time was the 20Hz 6dB first order cut, which needs taking out.

Craig
Attached Files
File Type: pdf Baxandall RIAA.pdf (800.2 KB, 103 views)
Craig Sawyers is online now  
Old 27th Jul 2020, 9:16 pm   #80
lesmw0sec
Octode
 
Join Date: Jul 2009
Location: Carmel, Llannerchymedd, Anglesey, UK.
Posts: 1,498
Default Re: Very low noise op amp recommendations?

Quote:
Originally Posted by ajgriff View Post
You don't need esoteric and expensive op-amps to make a low noise MC head amplifier either. Jelly bean 2N4403 transistors (3 per channel) will do the job nicely when used with a couple of ordinary op-amps, according to Douglas Self anyway. 'Self on Audio' refers.

Alan
You can also achieve good results with a hybrid arrangement. Ages ago, I designed a mic. amplifier which used the best (at the time LM301) IC. I incorporated a single low noise transistor stage at the front end and included it within the overall feedback loop. This had the effect of getting rid of the noise due to the two IC inputs by effectively reducing the IC contribution by around 10 dB. It achieved a noise figure around 1dB of the theoretical. It would have been impossible to achieve the same with just the LM301.
lesmw0sec is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 1:16 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.