The Lonely Amek M3000

This is where we talk about testing, measuring and repairing things. Sometimes we have to repair the equipment we use to test, measure and repair other things. It's an endless cycle of fixing the broken things we need to fix other broken things.
gettestudios
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Re: The Lonely Amek M3000

Post by gettestudios » Wed Jun 18, 2014 12:32 am

Brian, I removed the schematic out of professional courtesy to GL.

Just an update, Console has been completely rewired and is back on its stand. Doing the final touches on the frame and will begin the process on the modules.....

Another update is the console has been confirmed to be the Amazon console.

ricardo
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Re: The Lonely Amek M3000

Post by ricardo » Wed Jun 18, 2014 7:53 pm

gettestudios wrote:After years of researching the "Opamp" looking at reviews as well as listening to the deferences between types, brands etc. I have settled on one.
The LME49860.
Before you go mad on OPA rolling, have a really good read of ...

Kingston on GroupDIY had an excellent thread on what is REALLY important for noise & THD; opamps and local decoupling of rails, some questions

http://www.groupdiy.com/index.php?topic=37307.80

Many true gurus chime in. It proves how OPA rolling takes a VERY poor second place to correct earthing, layout & decoupling. It’s a long thread but read the whole thing from #41 to find pearls of wisdom.

What you get is critically dependent on how good the AMEK decoupling, layout & earthing system is. VERY few people can do this properly. JR is one of them though I'm sure he's ROTFL :D
The console currently uses at an exclusive level, NE5534N/NE5532N.(schematics show TL072's)
Also look carefully at where some idiot .. I mean (pseudo) guru has substituted 5532 for TL072. There's usually some good reason for TL072 .. probably to do with bias current. The best replacement for TL07x is OPAx134.

Note it comes out better than practically all the uber OPAs in Kingston's thread though its spec suggests otherwise. The reason is it is probably the least fussy of the 'modern' OPAs to dodgy decoupling, earthing bla bla. It also has VERY high immunity to RFI.

Da uber OPAs may do better in simple test circuits, but OPAx134 & 553x will often outperform them in complex systems like big mixers.

Also watch bias currents. 553x are npn input with loadsa Ib. Good makers use this to ensure electrolytics are nicely polarised. FET OPAs like TL07x have zilch & many of da uber OPAs have evil Ib cancelling.

Unlike JR, I think the important faults are the ones the customer notices and complains about. :D That's cos I was a real DBLT guru in my previous life. Clicks are verbotten on Broadcast Desks. (There's even a test spec based on a BBC PPM) So I will happily put evil electrolytics (nicely polarised) in the signal path. :o

There's NO evidence that paralleling electrolytics with Golden Pinnae films gives ANY advantage, audible or otherwise.
EQ, I have drooled and studied the SSL and VR EQ's for some time.
EQs, like compressors & limiters, are very personal. If you like it, dun change it.

Take care of the pots, especially any Reverse-Log ones ... unless you have a branch of Ye Olde Unobtainium Shoppe nearby.
MicPre is centered on a Sowter 4057 transformer, transistor and a single IC. Needless to say, since i am expanding to 48 ch, i do not even want to know how much it would cost to have these custom made. I am leaning toward a L1538 based mic pre (still costly) but am open here, ideas and suggestions. I want a clean pre that has little color and handles low end well.
Don't knock da old transformer designs.

Though I will never design another one, they do certain things that are nearly impossible with modern stuff .. in particular practical RFI immunity & 'The Phantom menace' Main practical CONs are $$$, size & weight. Performance wise, a THAT solution can have 1dB NF while the best I've done with a transformer is 1.6dB. Frequency Response is also difficult to get from DC to zillion MHz .. which is why some appear to have better LF cos it is often lumpy and with a bit of 3rd harm. too.

The various THAT solutions are hard to beat for 'clean'
Only change is, U1.1A, U4.1A, U6.1A, U8.1A was originally a TDA1034, I am showing it as a TL072, and i also removed the 33pF comp cap.
Du...uh! TDA1034 is an early name for NE5534. It is a single OPA compensated for 3x gain (hence the 33p for unity gain). TL072 is a dual OPA.
______________

If you want to 'improve' a historical desk from a competent manufacturer, the good mods are those the maker did in later examples. There will be good reason for them.

eg I'd love to see one of Jo Wuttke's last Schoeps mike circuits to see what he changed and what he kept.

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JR.
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Re: The Lonely Amek M3000

Post by JR. » Wed Jun 18, 2014 10:31 pm

ricardo wrote:
Unlike JR, I think the important faults are the ones the customer notices and complains about. :D That's cos I was a real DBLT guru in my previous life. Clicks are verbotten on Broadcast Desks. (There's even a test spec based on a BBC PPM) So I will happily put evil electrolytics (nicely polarised) in the signal path. :o
JR is responsive to customer (and dealer, and rep) complaints. Service would even send some difficult customers to me... (even years after I was no longer working at Peavey) :lol:

Take care of the pots, especially any Reverse-Log ones ... unless you have a branch of Ye Olde Unobtainium Shoppe nearby.
+1... I used several custom pots that are surely unobtanium now.

The various THAT solutions are hard to beat for 'clean'

If you want to 'improve' a historical desk from a competent manufacturer, the good mods are those the maker did in later examples. There will be good reason for them.

eg I'd love to see one of Jo Wuttke's last Schoeps mike circuits to see what he changed and what he kept.
+1 look at later documentation. Like I said earlier in this thread I would like to send all my first builds into deep space,,, I was very disappointed that I never got to incorporate the several improvements I made to my last big desk in the lab, but I got my ass kicked in the market by Mackie's 8 bus. :oops: Apples and oranges but the customer is always right even when horribly wrong. :D

JR

gettestudios
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Re: The Lonely Amek M3000

Post by gettestudios » Thu Jun 19, 2014 9:43 am

Thank you both JR and Ricardo... Your replies have always been informative.

Much like how Jr views his earlier console designs, I view my earlier posts both in this thread and in the "the ultimate...". Over the course of the last few years, I have gained some incredible insight and experience in the field of analog audio design that has changed allot of the views I have expressed earlier.

The Amek M3000, is a restore project that I have no intention of changing anything. Unless a part has failed that has become obsolete, AKA the 202 VCA's, reed relays, etc...

As to the Later Mods to the original design, ricardo had mentioned.That to is ironically present in this console, It not only contains the very first modules ever built, it also contains the very last modules ever built.... Crazy.... Originally was loaded with 28 channels, when Amek decided to end the production of the M3000, they contacted Amazon, to so if they wanted any of the left over parts... So the last 8 channels where built, using the latest Schematics, with the final remaining parts.... talk about Full circle! :D

The 5532's are stable in the EQ slots replacing the TL072's However, I do not know if a OPA2134 Upgrade would yield enough to justify an upgrade. May have to run an AP test to see what changes if any and of course, an A/B test. But I would not expect any real change......

If you are more interested in the process taken so far in the restoring of the console, you can go here.

http://recording.org/index.php?threads/ ... 000.54489/

Joel

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JR.
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Re: The Lonely Amek M3000

Post by JR. » Thu Jun 19, 2014 11:50 am

gettestudios wrote:Thank you both JR and Ricardo... Your replies have always been informative.
===

The 5532's are stable in the EQ slots replacing the TL072's However, I do not know if a OPA2134 Upgrade would yield enough to justify an upgrade. May have to run an AP test to see what changes if any and of course, an A/B test. But I would not expect any real change......
5532 is a unity gain stable dual OA, the 5534 is externally compensated so 5532 should be stable in place of TL072, issues are extra PS current consumption and higher input bias current, due to bipolar opamp input.

I often used 07x on internal circuit nodes that did not have to drive the outside world, or heavy loads (like a bunch of aux sends in parallel.)

I would not expect a huge difference using OPA 2134. With consoles it is pretty easy to mod one channel and null against unmodified channel to see how much difference the mod makes.
If you are more interested in the process taken so far in the restoring of the console, you can go here.

http://recording.org/index.php?threads/ ... 000.54489/

Joel
This weekend I'm restoring my lawnmower..

JR

ricardo
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Re: The Lonely Amek M3000

Post by ricardo » Sat Jun 21, 2014 1:44 am

JR. wrote:5532 is a unity gain stable dual OA, the 5534 is externally compensated so 5532 should be stable in place of TL072, issues are extra PS current consumption and higher input bias current, due to bipolar opamp input.

I often used 07x on internal circuit nodes that did not have to drive the outside world, or heavy loads (like a bunch of aux sends in parallel.)

I would not expect a huge difference using OPA 2134.
Ditto to all that including the reasons for use of TL07x

If the 5532 replacement for TL072 was via AMEK, its should be OK. I was referring to naive replacement by unqualified Golden Pinnae pseudo gurus.

Some of my own designs would benefit from OPAx134 over TL07x. Better THD in some cases .. eg voltage followers. TL07x also has really icky overload behaviour in some LF EQs which I 'cured' with some even ickier diodes. :o

I had some cheapo designs which were TL07x inside .. 553x on stuff which saw the outside world in da days when this would make a cost difference.

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