pucho812

« Last Edit: September 13, 2019, 01:24:07 AM by pucho812 »
You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is.


gyraf

Re: neve portico discussion and drawn schematics
« Reply #1 on: September 12, 2019, 03:40:15 AM »
I wonder how they keep the core from being permanently magnetized in the long run..?

I've replaced/reshuffled several output transformer cores in our PV76's that had become heavily magnetic because of DC from failing driving transistors, so I don't like where this is going..

/Jakob E.
..note to self: don't let Harman run your company..

mjrippe

Re: neve portico discussion and drawn schematics
« Reply #2 on: September 12, 2019, 11:48:46 AM »
Just run the Han-D-Mag over it every time you do your tape heads...

But seriously, thanks for sharing this.  I didn't know it had been reverse-engineered and they give an excellent in-depth description.

squarewave

Re: neve portico discussion and drawn schematics
« Reply #3 on: September 12, 2019, 12:01:01 PM »
Nice circuit. Basic CFIA with clever gain trim. It would be interesting to see the spectrum of the "silk" control to see precisely what sort of harmonics are generated but at least it's not a silly hack. It looks like a very solid and yet relatively simple circuit. For the price it's a nice preamp.

L´Andratté

Re: neve portico discussion and drawn schematics
« Reply #4 on: September 12, 2019, 04:52:11 PM »
Yes, interesting preamp!
While the silk section is the clou, I am especially surprised by the preamp topology, which is tagged as "benchmark"(mid eighties mic pre using the lovely 2sb797 transistors. From all preamps I have built diy-caveman style that is the only one sounding pristine).
PS I think portico was already posted here a not too long time ago...
Strictly amateur since 1973...

Re: neve portico discussion and drawn schematics
« Reply #5 on: September 13, 2019, 07:47:54 AM »
Spent a hour and redrawn schematic in to  much understandable view.

Re: neve portico discussion and drawn schematics
« Reply #6 on: September 13, 2019, 08:03:37 AM »
Thanks for redrawing 👍

gyraf

Re: neve portico discussion and drawn schematics
« Reply #7 on: September 13, 2019, 10:15:09 AM »
Could you re-upload to /technical documents section?
..note to self: don't let Harman run your company..

Re: neve portico discussion and drawn schematics
« Reply #8 on: September 13, 2019, 10:26:23 AM »
Could you re-upload to /technical documents section?
under Rupert Neve folder? Is it legal?)

ruffrecords

Re: neve portico discussion and drawn schematics
« Reply #9 on: September 13, 2019, 05:24:06 PM »
under Rupert Neve folder? Is it legal?)

It is perfectly legal. The device is on sale so anything in it is  public domain unless protected by patent or registered design.  A hand drawn schematic  derived from the product itself is quite legal.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'


squarewave

Re: neve portico discussion and drawn schematics
« Reply #10 on: September 13, 2019, 08:54:10 PM »
Agreed, I think that is indeed legal. What would almost certainly not be legal would be hosting / serving a copyrighted schematic such as one draw by and copyrighted by Neve (even one willfully provided by Neve). In that case, it is a copyrighted work just like a book.

In theory, you could look at a copyrighted schematic, understand it in your head, burn it and then redraw your own version from memory. But in this case it could be difficult to prove that you did not actually just look at it and do a simple transposition.

PRR

Re: neve portico discussion and drawn schematics
« Reply #11 on: September 14, 2019, 01:54:40 AM »
Circuits can't be copyright.

Circuit drawings are always copyright.

A mechanical copy (Xerox) is infringment.

A re-draw is a New Work and has its own copyright, not infringing.

Circuit details may be under Patent. You can re-draw these. You may not assemble the circuit without patent infringement; however broad leeway exists for "study and experimentation", so you typically don't get in trouble until you make a lot for sale. (Maybe if you gave them away in vast quantity.)

I am not a lawyer. Don't trust any legal opinion you haven't paid dearly for, from an expert who has also sized-up the other side. Even if you are right, if the other side is rich, they win.


L´Andratté

Re: neve portico discussion and drawn schematics
« Reply #13 on: September 15, 2019, 07:10:59 AM »
I would be interested in the transistor type and transformer type.

The working principle of the preamp is wonderfully explained by P.Baxandall here:
https://tinyurl.com/yxj4gfvg

PS: Since secondaries are connected 2*2 (ser./par.) maybe a similar transformer behaviour can be achieved with a transformer with only three (EA2503) or even two secondary windings?
« Last Edit: September 15, 2019, 07:15:08 AM by L´Andratté »
Strictly amateur since 1973...

squarewave

Re: neve portico discussion and drawn schematics
« Reply #14 on: September 15, 2019, 09:14:24 AM »
The working principle of the preamp is wonderfully explained by P.Baxandall here:
Warning: That link is 23 MB.

PS: Circuit in question is described on page 307.
« Last Edit: September 15, 2019, 09:18:30 AM by squarewave »

abbey road d enfer

Re: neve portico discussion and drawn schematics
« Reply #15 on: September 16, 2019, 02:04:38 AM »
I would be interested in the transistor type
Apparently 2SB797, that is now unobtainium)

Quote
The working principle of the preamp is wonderfully explained by P.Baxandall here:
https://tinyurl.com/yxj4gfvg
It's a very common architecture, and rather basic. It has been improved in two sequences: first replacing the single transitors with Szlikai pairs (two complementary transistors), and second applying voltage NFB to the transistors (typical Cohen topology). A lot of progress has been made since the 70's.

Quote
Since secondaries are connected 2*2 (ser./par.) maybe a similar transformer behaviour can be achieved with a transformer with only three (EA2503) or even two secondary windings?
Indeed; I routinely used quadfilar xfmr's in this application. Check the Lars Lundahl website (LL5402). Different implementation, though.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

Re: neve portico discussion and drawn schematics
« Reply #16 on: September 16, 2019, 06:05:22 AM »
Apparently 2SB797, that is now unobtainium)

Are you thinking of the 2SB737 maybe?  Manufactured by Rohm, TO-92 device having circa 2 ohm Rbb and beta up to about 500?
Doesn't matter much as they're extinct these days too 😀
I don't think the Neve uses them though whichever you meant, I'm sure it's a pair of current production surface mount devices in that device.  I'd be surprised if not.

L´Andratté

Re: neve portico discussion and drawn schematics
« Reply #17 on: September 16, 2019, 07:58:43 AM »
I think it is a misunderstanding. I had mentioned the 2sb737 in post #4 as being used in the old Benchmark design (yes 797 is the AD-chip or the Boeing ;D).  Hard to imagine that would be used in a current product, though.
There is no transistor specified on the copied Neve schematic...
Strictly amateur since 1973...

abbey road d enfer

Re: neve portico discussion and drawn schematics
« Reply #18 on: September 16, 2019, 05:13:49 PM »
Are you thinking of the 2SB737 maybe?  Manufactured by Rohm, TO-92 device having circa 2 ohm Rbb and beta up to about 500?
Doesn't matter much as they're extinct these days too 😀
I don't think the Neve uses them though whichever you meant, I'm sure it's a pair of current production surface mount devices in that device.  I'd be surprised if not.
Indeed, it's a misunderstanding. I shorted two neuronal connections.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

clintrubber

Re: neve portico discussion and drawn schematics
« Reply #19 on: September 17, 2019, 07:08:14 AM »
Nice circuit. Basic CFIA with clever gain trim. It would be interesting to see the spectrum of the "silk" control to see precisely what sort of harmonics are generated but at least it's not a silly hack. It looks like a very solid and yet relatively simple circuit. For the price it's a nice preamp.

Would indeed be nice to see the changes in spectrum.
For the time being there's the info below, from the manual:


TOTAL HARMONIC DISTORTION AND NOISE
@ 1kHz, +20dBu output level, no load. Better than 0.0025%
@ 20Hz, +20dBu output level, no load. 0.025% Typical (2nd and 3rd harmonic)

TOTAL HARMONIC DISTORTION AND NOISE WITH SILK ENGAGED
TEXTURE @ min
@ 100Hz, +20dBu input level, no load 0.015%, mostly 3rd harmonic (typical)
TEXTURE @ max
@ 100Hz, +20dBu input level, no load 2%, mostly 2rd harmonic (typical)



I haven't heard it, but understood from 511-reviews it's indeed a change, but remains subtle.

Bye


 

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