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Neve 10852 stereo line amp
Old 22nd November 2009
  #1
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spectrasound's Avatar
 
🎧 15 years
Neve 10852 stereo line amp

I just bought a Neve 10852 card that I'd like to use in a summing amp design. Does any one have, or know how to get, a schematic diagram for this card? It would help me immensely! Many thanks. Please feel free to PM

Jim McGee
[email protected]
Spectra Sound Solutions
Old 23rd November 2009
  #2
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Geoff_T's Avatar
 
🎧 15 years
Quote:
Originally Posted by spectrasound ➑️
I just bought a Neve 10852 card that I'd like to use in a summing amp design. Does any one have, or know how to get, a schematic diagram for this card? It would help me immensely! Many thanks. Please feel free to PM

Jim McGee
[email protected]
Spectra Sound Solutions
Hi

From memory, it's a line input quad buffer amp using the later Belclere transformer and 5534 ICs. Before you start, whatever you do will not sound like a vintage Neve and involves a lot of mods to make it do anything other than a buffer amp.

Old 23rd November 2009 | Show parent
  #3
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🎧 15 years
Beg to differ....

Geoff,

This IS a discreet card. Stereo line amps of some type. Dan Alexander said Class A.

No 5534 chips. I have seen the audio DA card you're talking about with the Belcleres and this is not it. This runs, I know, on 25 vdc rails and has a lot of headroom. It's got 2 large toroidial output transformers. each amp has 2 transistors (output stage?) on a heat sink.

Does any of this ring a bell? I need to find pinout & hopefully a connecting mate for this card. I'd be in heaven if i could find a schematic. I'm hoping to build an external summing box for my 16 balanced outputs from the ProTools rig... feeding my Ampex 440C (1/2").

Any help or leads would be greatly appreciated. Thanks!

Jim McGee
Old 23rd November 2009 | Show parent
  #4
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Geoff_T's Avatar
 
🎧 15 years
Quote:
Originally Posted by spectrasound ➑️
Geoff,

This IS a discreet card. Stereo line amps of some type. Dan Alexander said Class A.

No 5534 chips. I have seen the audio DA card you're talking about with the Belcleres and this is not it. This runs, I know, on 25 vdc rails and has a lot of headroom. It's got 2 large toroidial output transformers. each amp has 2 transistors (output stage?) on a heat sink.

Does any of this ring a bell? I need to find pinout & hopefully a connecting mate for this card. I'd be in heaven if i could find a schematic. I'm hoping to build an external summing box for my 16 balanced outputs from the ProTools rig... feeding my Ampex 440C (1/2").

Any help or leads would be greatly appreciated. Thanks!

Jim McGee
Hi Jim

I don't have a diagram for it so am going by memory plus the approximation of manufacture by the board number. I would love to see a photo of it because 8108 were 700 series boards which puts it more in the all IC era.

Are you really sure you have quoted the right board number?

One thing I can guarantee is that it may be discrete but it won't be class A.

Here's a thread on my site on the subject... they are part of a 5116 console.
- Neve 34136 chanel strip and 10852 amp card

Plus here is a diagram for it... wonderful thing a Goggle Search, it found these two items in seconds!

NEVE EV-10852

Old 24th November 2009 | Show parent
  #5
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spectrasound's Avatar
 
🎧 15 years
photo

Geoff,

Thanks for your quick reply. I'll try to email a photo. This is possibly a later issue. Your schematic said EV 10852 ISS 1. My board is EV 10852 ISS 5 SPC-BBT. I count 9 transistors on each amp. The schematic shows less. The ISS 1 photos show 3 output transistors, where my board has only 2 per amp.

Is the discreet circuit in the schematic that you sent call A? If not is it A/B?

I'll keep searching for the correct schematic.

Thanks so much.

Jim McGee
Old 24th November 2009 | Show parent
  #6
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mexicola's Avatar
 
🎧 10 years
The card is the line out amp from 51xx series channels.

Sorry I couldn't help you with the schematics, spectrasound.
Old 24th November 2009 | Show parent
  #7
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Geoff_T's Avatar
 
🎧 15 years
Quote:
Originally Posted by spectrasound ➑️
Geoff,

Thanks for your quick reply. I'll try to email a photo. This is possibly a later issue. Your schematic said EV 10852 ISS 1. My board is EV 10852 ISS 5 SPC-BBT. I count 9 transistors on each amp. The schematic shows less. The ISS 1 photos show 3 output transistors, where my board has only 2 per amp.

Is the discreet circuit in the schematic that you sent call A? If not is it A/B?

I'll keep searching for the correct schematic.

Thanks so much.

Jim McGee
Hi Jim

As I mentioned in my emailed reply, the first series boards were Neve's first foray into VMOS stages when VMOS was in its infancy. They found that the device on the negative side had different conduction properties to that on the positive side so they fitted two transistors in parallel. By the time your issue came along, there were matched devices available so there's one in the positive and one in the negative.

Mentions of Class A in this era are comical. Gentle wrist slap to Dan who should know better. The circuit is AB.

The whole point of this amplifier, and the 50 odd volt total power rail difference, was to drive greater than +26dBu output of the 1:1 toroidal transformer. The board also introduced a new system of grounding.

Old 24th November 2009 | Show parent
  #8
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spectrasound's Avatar
 
🎧 15 years
Thanks Geoff!

I think I'm straight on everything here. Thank you for your help. Final question...

You would or would not advise using this in a summing amp? Would I do better with a 1272?

Jim
Old 24th November 2009 | Show parent
  #9
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🎧 15 years
Also....to clarify my error

Dan Alexander did not proclaim this to be Class A.... but merely discreet. An uninformed friend said this was Class A.
Old 24th November 2009 | Show parent
  #10
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Geoff_T's Avatar
 
🎧 15 years
Quote:
Originally Posted by spectrasound ➑️
Dan Alexander did not proclaim this to be Class A.... but merely discreet. An uninformed friend said this was Class A.
Hi

Not that it really matters but this is your quote from earlier...

This IS a discreet card. Stereo line amps of some type. Dan Alexander said Class A.

Old 24th November 2009 | Show parent
  #11
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Geoff_T's Avatar
 
🎧 15 years
Quote:
Originally Posted by spectrasound ➑️
I think I'm straight on everything here. Thank you for your help. Final question...

You would or would not advise using this in a summing amp? Would I do better with a 1272?

Jim
Hi

It would be a whole lot easier.... this amp was never designed for that purpose though, if you were tenacious of hard work and studying, you could probably adapt it.

The dual supply rails are a bummer compared to single +24v, though.

Old 6th March 2014
  #12
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🎧 5 years
Bumping this - has anyone ever (in the history of humanity beyond neve) figured out what to do with these cards? many cold trails, but may be on to something...
Old 17th March 2014
  #13
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🎧 5 years
It's Alive!

Hi - I'm not sure if I should start a new thread for this, or simply continue this one.

I have a 10852 line amp card, and have been working with it as a test rig to explore DIY.

the first iteration, i used the mix inputs and a 15v power supply, and it worked nicely.

i decided to take things further as I learned more, and got a JLM AC/DC power supply to provide the correct +/- 25V power. I've also recapped the board, and am now using it as a virtual-earth gain make up amp for a very simple 8-channel stereo summing matrix. No pans, axes, just 4 channels, balanced hard left & right, using 10K resistors.

I'm currently working on lowering the noise floor, getting the grounding right, etc.

As an aside, I purchased Geoff's Technical Notes and have found them hugely helpful, and would recommend to anyone exploring DIY.

I'll note some observations and questions, which hopefully will be helpful to anyone else exploring this card. I'll put the questions in bold.

The card has separate connections for input & output return, which I take to mean ground/0 V reference, and if anyone could illuminate:

What's the best approach to grounding this card in a stand-alone DIY application?

Geoff mentioned in an earlier post that this console series (51-xx) introduced a new system of grounding, and a 'quasi-balanced' mix buss architecture - would love to hear more about this.

With only 4 inputs, the bus impedance is fairly high on the summing network. I'm taking the + sum to the non-inverting input, and the - sum to the inverting input, both of which feed differential transistors. It works, but the summing matrix is very susceptible to induced noise. I switched to screened cables inside the chassis from the matrix to the amp inputs, and it made a big difference. I thought that by using the VE inputs, the buss impedance would not be as important to bring down with a shunt resistor, so not using one currently.

Should I use a shunt resistor to lower the bus impedance to improve noise performance?

What would be the optimal input impedance for this amp?

Would a transformer at this stage provide any benefits? Perhaps a 10K/600r or variant.

The applications guide for this amplifier notes that when using the VE inputs, a certain resistor ( which doesn't match the issue number of my card) should be replaced with a wire link to improve noise performance. Any thoughts as to why?

Also, the make-up gain of the amplifier is determined by an external feed-on resistor. It seems that the circuit has a default value if nothing is connected here, and I haven't changed or added any values here.

If the feed-on resistor is a potentiometer/variable resistor, could this function as a gain control?

That's all for now - this little unit is quite fun & rewarding to play with, as a matched discrete amplifier and transformer combination. Sounds come alive in here, and since they seem to be around for currently reasonable money, it's been a good start for DIY playing. It seems that the rest of the console had its issues, but this component is quite flexible in what you can do with it, although I don't think trying to make a mic-pre from it makes much sense. Hope this info is helpful, I've learned a lot from this forum.
Old 21st March 2014
  #14
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🎧 15 years
Hi

Just flipping through the thread I believe the card is their bussing card which is an adapted virtual earth summing system.

You need to do a smidgen of research into virtual earth summing because you would not ask what the input impedance is, as you might for voltage summing, because (as the name implies) this is current summing... the impedance is virtual(ly) earth.

The achieved quazi-balanced bussing by having a resistor between the input and output 0v's... 10 ohms or thereabouts I think it was. so your mix input is into the inverting input of the mix amp and the end of that 10 ohm resistor.

I recall Neve R & D did a wonderful drawing of the ground paths of that mix system from the sending amp and through and around the aspects of that mix amp.

It certainly worked... and achieved noise and crosstalk figures 20db better than traditional vintage Neve voltage summing.

And no, it would not help to put a transformer in front of it...

Old 25th March 2014
  #15
Here for the gear
 
🎧 5 years
Thanks Geoff! I had a feeling that the impedance wouldn't really matter if I was using it as a virtual-earth amplifier, just wanted to confirm.

Made the suggested changes (wirelink replacing R8) and things are working well, sounding really nice.

Although I am currently feeding the balanced mix signals to the non-inverting and inverting inputs, rather than the input 0v. I'm still getting a low-level hum, and trying to figure out if I should connect the input & output returns to the power supply 0v or to chassis ground (or both, or neither)
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