AMEK Big MOD ... need help please.

[gjuodenas]

Hi,

I have just finished a very extensive rebuild and modification of an Amek big console with automation in Nashville TN. The console has 44 Big 1 modules, 4 big 2 modules and 1 big 3 module and an extensive patchbay.


When I got through with the project, the client was overjoyed with the sound and functionality. I could probably spend an entire day discussing this console and the modifications. Along the way, I also had to repair a lot of modules. If you would like, you can send me a private e-mail with direct questions and I will do my best to answer them.

The Amek big is being used with a RADAR 2. After tracks are cut, the entire project is transferred to a computer.

I started out by eliminating all of the automation circuitry. It was not very well implemented because digital noise got into the analog circuitry in numerous places.

I then modified the input modules so that the entire eq and the channel access point could be switched into the recording chain and not just the mids as in the stock console.

I also modified the aux sends so that all 8 could be switched into the record path or the mix path and could be chosen to be pre or post fader.
]In the master module, I beefed up the caps, changed talkback so you could talk into all 8 aux sends, put in switches for each pair of aux sends so that you can send them the stereo mix and and still be able to send more of individual channels.

I had to replace caps in huge numbers. I found a lot of dead coupling caps and even more distressing I found large numbers of coupling caps that were "1/2 dead" attenuating the signal somewhat and probably not in a linear fashion.

I also replaced the whimpy switching power supply with beefy analog supplies. I also found that the TRS jacks on the back of the console were intermittent. They required cleaning and some would just not make the normals.

With all of these issues, the console ended up sounding great. As I understand it, Rupert Neve had a hand in the design of the analog circuitry.

[Matt Syson]

Hi
All desks over say 10 years old should have the caps replaced so that would be an improvement.
Increasing the value of the caps used on the mix buss amplifiers would also help a bit.
The automation noise is aproaching the general background noise and was better than the ADATs which were the big digital thing at that time. If the automation noise is noticable then there is something wrong elsewhere although there may have been a bit of a burble when actually storing or recalling settings.
I doubt Rupert had much if anything to do with the BIG although he was in the building.
Matt S

[Long_Shaded_Eye]

Thanks for all those answers.
Yep recaping seems to be a good point to start ... but ALL caps need to be changed ? And for the master section if I choose bigger value capps how bigger should be the value ?
I wait & see for some more answers but anyway I will PM you Gjuodenas... Thanks for this. In terms of functionnality this console is perfect for what I do, it's just the sound that I wish to improve (some people say it's crap, lack of headroom and not very punchy but believe as a first real console , outside of the box stuff, it's great and my mixes sound far better).

Any other idea please ? For cleaning the console , what kind of product should I use please ?
THANKS.
/Nick.

ps: If I where in the US I would have contacted a tech to do this job for me ... but in France I think it would be harder to find a good tech for this kind of console... so I prefer to do it myself lol

[Matt Syson]

Hi
It is all the electrolytic caps that need doing.
The ones that I had in mind for increasing are actually already 1000 uF so to begin with just recap the whole thing. You could add some film caps in parallel with electrolytics which would add a bit of sparkle, I would go for those in the Big 3 first.
Headroom is only an issue if you are not aware of what you are doing, yes people always want more but this was a reasonable priced desk. The inserts are at +4dB and unbalanced send so limiting the headroom to 18dB, this is pretty common for music desks.
These desks were designed by Mr Langley. (Hence, BIG by Langley).
Matt S

[gjuodenas]

There are numerous examples of the digital noise getting into the audio on an automated BIG console. The one example that really stands out is the direct radiation of noise from the CPU card into the master module (Big 3). Some brilliant engineer put the CPU card directly under the master module. I cured this problem by cutting a piece of sheet steel into a pattern that would allow me to place it between the CPU card and the master module. I then covered the plate in an insulator to prevent shorts. I then ran a stout wire from the console body to this plate. This solution greatly reduced the digital noise in the master section.

The noise also dropped when I replaced the switching power supply with analog supplies.

[Matt Syson]

Hi
Having comissioned several hundred AMEK big desks, no one made any reference to any digital noise.
The switch mode supplies, with the benefit of hindsight, were a mistake. The standard supplies, apart from running a bit warm, were fine. You would have had 2 for a 44 channel, so would not run so warm.
Lots of screening could have been fitted and increased the price significantly but then they were a mid priced desk with a lot of functions and thee are many thousands of them out there.
Could you produce a desk with so many functions for as much in America, built by Americans rather than cheap labour exploited overseas.
Matt S

[gjuodenas]

The answer is no, this desk could not have been built in the US at the pricepoint it sold for. I hope no one has assumed I am trashing this desk. It is a very good sounding analog console. I think however, the functionality was overdesigned for the pricepoint requiring some compromises.

For instance, the PCB lands and pads are very very thin in some areas. Even with many years of experience in console mods and using professional desoldering tools, some lands got lifted when replacing caps and had to be replaced by jumpers. Some of the caps are on the small side (voltage and value rating) because there is no space available for larger components, there is a lot cramed into a small space.

[Matt Syson]

Hi
Ah the luxury of having a choice of op amps and VCAs 14 - 16 years later! None of the ones mentioned by Jim were available then.
I don't know who decided the depth of the boards but more space would have helped.
Back to switch mode supplies. AMEK never made any themselves. Over several years 3 manufacturers made units which were all found wanting in a combination of ultimate reliability, universal input voltage and super quiet noise free outputs. Different aspects on each of the units. A pair of 850 linear units on a BIG 44 is absolutely fine. One on a 28 gets a bit warm but is still fine if you don't abuse it.
The bigger 'American' made modules for the MPS15 was let down by cheapskates not using thermal compound or pads for the rectifiers or power transistors, all of about 10 cents worth! VDR and inrush limiters would help a lot too. They are also a pig to pull apart for repair.
Matt S

[gjuodenas]

Jim,
I am thrilled by the idea of more skills, where do I go to buy some? I would be glad to trade my old skills in on new ones. I wonder if my old ones have any trade in value.

[Long_Shaded_Eye]

PEACE lol

Hello everyone & thanks much for the time you give.
Mine desk is a Big28 , but for the PSU part I don't think I can change anything (for a noob like me it can be a real risk I think ... for the desk and perhaps even for me).

Bettween all thoses modes ... what would you do first please ? Recapping the Big3 ? Recapping the Big1 modules ? Changing the op amp & mic pre chips ? This last thing can bring a great improvement to the pre ?


THANKS AGAIN for sharing your skills... any of you.
Respect.
/Nick.

[Matt Syson]

Hi
Assuming it has not been recapped in the last 2 or 3 years, do this first. Start with the Big 3 and the stuff in it's area, then chanels. Swapping chips may make some difference but until it is recapped it is like polishing your car which has done 400,000 miles without an oil or plug change. When recapping add some film types (which will have to be on the solder side of the boards).
Matt S

[Long_Shaded_Eye]

Hello Matt & thanks for all this infos
Ok so let's go for recapping Big3 ... I will try this in a week or two.
By "adding film caps" you mean add another cap or just instead of the standard cap put a film one? Please what do they add to the sound ?

THANKS AGAIN.
/NicK.

[Matt Syson]

Hi
You need to keep the electrolytic capacitors (100, 220 or 1000uF) as originally fitted as they are needed to couple low, mid and high frequencies from one amplifier stage to the next. Jim Williams and others suggest that in ADDITION to the electrolytic, that you put a 'polyester or polypropylene film' type capacitor of 0.1 or 0.22 uF (perhaps bigger) in parallel with the electrolytic. This is to retain the very high frequency coupling as electrolytics have various 'dips' in their response. Since the BIG does not have holes in the board for extra capacitors they would need to be put on the solder side of the board. Maybe Jim or others would be prepared to share suggestions of which size / type of film cap should be used with a particular make and value of electrolytic for the 'best' sonics. This would take a few hours of work to compile!
There are suggestions that increasing the capacitance from where there was a 100uF to 220 uF will improve LF performance I doubt there is a lot of merit in doing this to a BIG as generally the values are sufficient for the impedances involved. There may be the occasional place where they could be usefully increased but probably not worth worrying about at the moment.
If you can get a 2,200 uf cap to fit in position C36 and C37 on the big 3 then there may be some improvement in LF during times when ALL channels are routed.
This only needs to be a 6V3 rated component as normally there is only millivolts of DC across it. There are better ways of achieving this coupling but it is getting a bit 'creative' and there is not a lot of space. I believe that Jim would suggest shorting out the capacitor and changing the mix op amp type. Simply shorting it out would actually work anyway but there would be a click of some magnutude when selecting channels to the stereo buss. This should only be small and it may not bother you anyway. Simply put a 'short' on the cap without removing it and see what happens. If you don't like it then remove the short.
Matt S

[stevep]

Originally Posted by Matt Syson

Hi
Ah the luxury of having a choice of op amps and VCAs 14 - 16 years later! None of the ones mentioned by Jim were available then.
I don't know who decided the depth of the boards but more space would have helped.
Back to switch mode supplies. AMEK never made any themselves. Over several years 3 manufacturers made units which were all found wanting in a combination of ultimate reliability, universal input voltage and super quiet noise free outputs. Different aspects on each of the units. A pair of 850 linear units on a BIG 44 is absolutely fine. One on a 28 gets a bit warm but is still fine if you don't abuse it.
The bigger 'American' made modules for the MPS15 was let down by cheapskates not using thermal compound or pads for the rectifiers or power transistors, all of about 10 cents worth! VDR and inrush limiters would help a lot too. They are also a pig to pull apart for repair.Matt S

The audio and GML PSUs (3 of them 8 total PSUs) for my APC1000 have International Power IP15s they just slide in the Amek rack mount chassis .

Super easy to RnR

The only problem is there around 100Lbs each




peace,


steve

[TonyBelmont]

Send it to Coleman Rogers... His Amek BIG center section mod is great!

[Jay Kahrs]

Originally Posted by gjuodenas

Hi,

I have just finished a very extensive rebuild and modification of an Amek big console with automation in Nashville TN. The console has 44 Big 1 modules, 4 big 2 modules and 1 big 3 module and an extensive patchbay.


When I got through with the project, the client was overjoyed with the sound and functionality. I could probably spend an entire day discussing this console and the modifications. Along the way, I also had to repair a lot of modules. If you would like, you can send me a private e-mail with direct questions and I will do my best to answer them.

The Amek big is being used with a RADAR 2. After tracks are cut, the entire project is transferred to a computer.

I started out by eliminating all of the automation circuitry. It was not very well implemented because digital noise got into the analog circuitry in numerous places.

I then modified the input modules so that the entire eq and the channel access point could be switched into the recording chain and not just the mids as in the stock console.

I also modified the aux sends so that all 8 could be switched into the record path or the mix path and could be chosen to be pre or post fader.
]In the master module, I beefed up the caps, changed talkback so you could talk into all 8 aux sends, put in switches for each pair of aux sends so that you can send them the stereo mix and and still be able to send more of individual channels.

I had to replace caps in huge numbers. I found a lot of dead coupling caps and even more distressing I found large numbers of coupling caps that were "1/2 dead" attenuating the signal somewhat and probably not in a linear fashion.

I also replaced the whimpy switching power supply with beefy analog supplies. I also found that the TRS jacks on the back of the console were intermittent. They required cleaning and some would just not make the normals.

With all of these issues, the console ended up sounding great.

You turned one of those into a "REAL" desk!!!



Gnarly!

[Matt Syson]

Well a recap was due so that would get it back to it's original condition and the jacks are routine maintenance. Apart from maybe a dB or two worse noise figures (compared to a linear type) there is nothing wrong with the supply, they are plenty beefy enough. The rest are mods to suit a different customer.
Matt S

[Long_Shaded_Eye]

Thansk all for your nice advices
I will check my board closer and see if I feel I can do it. If I don't think I will send it to a tech (then I'll have to find a GOOD tech here in France) who can do it for me.


THANKS MUCH AGAIN, all of you.
/Nick

[haryy]

Originally Posted by Jim Williams

I've rebuilt many of these and have never lifted a plated through hole or circuit trace. These should look like new when redone, if not, more skills, please.

I've also pulled every TL07X opamp and the SSM2017 mic pre chips too. I use TI THS, National 617X series and the LT135X series, all much more open and less noise. I'll use the BB INA217, that1510 or a AD SSM2019 mic pre chips. Many power supply bypass caps were installed with the usual poly film bypass caps on the signal electrolytics. The VCA's are all changed to that 2180A's, this lowers the dirt levels. The EQ gets very high voltage polyprop film and foil caps.
The circuit traces are thin and small, this leads to a thin and small sound, especially with the high current opamps. These pcb's were laid out in a cad program with 12 mil routes as a default, Grahm L. should have widend them. Use some beefy linear power supplies as AMEK supplies were always designed to fail.

Jim Williams
Audio Upgrades

Hi Jim, i know it's been a long time but we just bought an Amek Big 28 and i'm interested in a few modifications. In the case of switching the vca's to 2180A's, do we have to add anything else or is it a direct replacement as the ssm2019 mic pre chip? Thanks in advance.

[nosebleedaudio]

Originally Posted by haryy

Hi Jim, i know it's been a long time but we just bought an Amek Big 28 and i'm interested in a few modifications. In the case of switching the vca's to 2180A's, do we have to add anything else or is it a direct replacement as the ssm2019 mic pre chip? Thanks in advance.

I would go with the 2181a, IF you have the trim pots already..

[haryy]

Thanks nosebleed audio i was aware of that better replacement but i don't have any equipment on board, and i want to do the simple stuff myself before i call our tech for any heavy duties.

JIM as always you're been very helpful and straight to the point! As a final question, do you have any suggestions for the master "Big 3" strip and the "Big 1" Tape Returns?

ps. Our board came with an amek mps20 power supply. Is that a good one? (i feel it is because the board sounds more than ok and i don't believe it's a switching model because it does heat a lot)

[haryy]

Thank you very much Jim! I'm going to try the ssm2019/that2180a first and i'll see for the rest.. Thanks again for giving invaluable info to everybody!!

[haryy]

I did some tests and found out that the insert returns of the BIG, sound absolutely fine to my ears. So, i won't "mess" with the master section or the vca because the "problem" seems to be the tape return input. (Mic pre chips are going to be changed soon)
But, when i use the insert returns with half inserted trs jacks, noise starts to build up after 8-9 tracks. This is not coming from a channel only, it builds up gradually. Do i have a cure for this? Should i look into unbalancing all my cables returning from the sound cards?
Thanks in advance

[haryy]

Anyone?

[Farmerbrown2200]

Anyone know of mods to the Big 1 module "mix to buss" signal path that involves adding 2 x 47kohm resistors? Also seems to involve removal of R39 . This mod is on channels 1-24 only...


Thanks if you can help answer this riddle. Waiting on original service manuals to help but they have not materialized from the original seller in TO...

Cheers

A

[Matt Syson]

Hi
If you are using half inserted jacks into inserts and getting noise, wire it up properly (unbalanced) rather than having connectors half out.
The MPS20 was a switchmode unit (I am pretty sure) using a number of individual modules.
NOT made by AMEK directly and get too warm for it's supposed rated output.
Matt S

[haryy]

Thanks for the info Matt. In fact everything unbalanced on the board produces noise and everything balanced is dead quiet, and i really like the sound of insert returns (unbalanced). Less circuitry i guess! I really don't know what to look for first. Balancing the returns? How?

[haryy]

Just updating for other interested "big" users. I decided to use the console only as a front end and decided to upgrade all mic pres with SSM2019 chips (instead of stock 2017) which was also the cheapest choice of three sugested. The sound changed in a 'BIG' way (haha). I think that this updated the line amp also (i'm not sure about this). A direct comparison between a 2017 and a 2019 module proved to have a huge difference.
A blanket was off the sound which got MUCH clearer in the mids and highs. But the big bottom of the 2017 was lost and it could dissapoint someone especially in the bass/bd/toms department. But you can leave some modules for this purpose. I didn't because i was very happy with the clear and neutral sound i got (miles from clinical, though) so i left all 28 modules with the new chips. Hope this is helpfull for any potential modders out there.
I included a clip of a test recording i made with my band, to check out for yourselves (drums). All tracks pass through Amek's mic/line pres and have a hair of (amek) subtractive eq to various freqs commited to tape. No effects. No comps. No gates. No edits. Fabfilter limiter on the daw master.
- Bass drum: ev868->Amek mic pre/eq->mackie 400f ad
- Mono kit/bd: M-audio sputnik->Ua solo 610->Amek line pre/eq->mackie 400f ad
- Snare top: Rode nt5->Daking mic pre one->Amek line pre/eq->mackie 400f ad
- Snare bottom: Telefunken Ak47 (hypercardioid)->Amek mic pre/eq->mackie 400f ad
- Tom: Audix d4->Amek mic pre/eq->mackie 400f ad
- Ftom: Senheizer md421->Amek mic pre/eq->mackie 400f ad
- Overs: Audio Technica AT4040-> Chandler Tg-2->Amek line pre/eq->mackie 400f ad
- Rooms: Akg c2000b->Bae 1073mp->Amek line pre/eq->mackie 400f ad