Motown Direct Amplifier-inspired Preamp?

[ruffrecords]

FWIW
Pucho's link doesn't work for me either. It resolves to "mown", which obviously isn't a URL.

That's on a Mac, using Brave (Chrome based).

Didn't work for me either so I just copied it and pasted it to a new tab and then it did work.

Cheers

Ian

 

[untune]

Fascinated by the developments so far; there does appear to be an issue with that video link so here it is again (thanks pucho for providing this, I've never seen it!)



And it also highlights something I left out from my notes: according to Bob Ohlsson, John Windt was afaik the man who worked with Mike to actually build the equipment in the Motown workshop. If he can still be contacted then he may have a lot of insight.

I might start putting feelers out to Bob Ohlsson and Ed Wolfrum to see if they might be willing to contribute any knowledge

Cheers!
Lee

 

[untune]

Also, not sure if this will be any use but it might offer some clues to the rest of the unit; the MC-30 power amp section of the original

Lost... and (quite unexpectedly) found: "The Sound of Young America"

 

[pucho812]

Sorry guys,

You have to copy and paste the link as typed. I see if you click on it, it does not work. If you copy and paste it, it does.

Still learning the new format and how to do links correctly. If you click on take 2 here, then you are good to go. it was just tested on my machine.

Also John Wyndt is still alive and I just talked with him last month. He shared a lot of the same info to the brain trust.

take 2

 

[pucho812]

Also, not sure if this will be any use but it might offer some clues to the rest of the unit; the MC-30 power amp section of the original

Lost... and (quite unexpectedly) found: "The Sound of Young America"

the mc-3 would have driven the single duplex monitor speaker they had for the guitar players.

 

[jacomart]

The link in Pucho's last posts explains a lot of things. The inputs had a hidden preset trimmer, set by on eof the techs. There was an input dedicated to "acoustic" guitar and one to bass, but in addition it seems each player had its designated input with their designated guitar and role.

Basically a pre-mix? That is, they created an external group (as was then done on the big consoles of the 80s) because the mixers of the time perhaps did not have enough inputs to manage the balance between the various instruments in a better way?

Cheers
JM

 

[untune]

Sorry guys,

You have to copy and paste the link as typed. I see if you click on it, it does not work. If you copy and paste it, it does.

Still learning the new format and how to do links correctly. If you click on take 2 here, then you are good to go. it was just tested on my machine.

Also John Wyndt is still alive and I just talked with him last month. He shared a lot of the same info to the brain trust.

take 2

It's great that John is still around! I watched that entire video you posted this afternoon and it was fascinating, it seems to me that if anyone can put to bed the speculation and tell us what is really under the hood, then it's him. I've tried searching round for contact details but can't find any—are you still in touch with him, do you think he might be willing to weigh in on the discussion?

 

[ruffrecords]

Basically a pre-mix? That is, they created an external group (as was then done on the big consoles of the 80s) because the mixers of the time perhaps did not have enough inputs to manage the balance between the various instruments in a better way?

Cheers
JM

The explanation I heard was that each guitar player used his guitar volume control to adjust the level so it stayed out of the red on his VU. This produced five separate outputs to the console, one for each guitar. The five knobs on the front of the DI amp allowed the guitarists to make their own monitor mix to hear via the built in speaker. So in today's terminology, five inputs from guitars and five outputs to the console plus a local monitor mix.

Cheers

Ian

 

[abbey road d enfer]

Yes. I didn't make clear that there were "600 ohm +4dB" outputs for each signal.
But that's what made me wonder about the actual tube complement of the unit.

 

[ruffrecords]

Yes. I didn't make clear that there were "600 ohm +4dB" outputs for each signal.
But that's what made me wonder about the actual tube complement of the unit.

Me too; I cannot see them using five 6V6 tubes for line drivers. More likely 12AU7 push pull or even 6SN7 push pull.

ACME claim to have built theirs from 'an original 1960s schematic' but they don't say of what.

Cheers

Ian

 

[untune]

I read a social media post somewhere that mentioned Mike McLean working with Acme with the circuit in around 2016, and that they used his original diagrams from the 1960s. I guess he held onto them, unless the Motown museum may have kept some documentation. I am also guessing that they will have made some modifications in order to suit the expectations of a modern consumer—i.e that 'tube grit' and saturation etc etc might take precedence over the straight, efficient, clean gain of the original. This could explain why the tube compliment seems a bit off, or why there's one preamp tube more you would expect for the job. Without knowing the construction of the original to compare it, it's going to throw up more questions—I do think if we could get in touch with John Windt he might be able to clarify what was in it, even if we don't know exactly how it went together. The fact he revealed in the video about the trim pot hidden behind the monitor mixer knob was, as far as I know, unknown prior to then.

In the meantime I've carried on reading around. A throwaway comment that Bob Ohlsson made somewhere else mentioned that "Mike would find a way to do it often borrowing from motion picture post production technology" which could give a clue. However, he could be referring here to a story in which Mike built a device to detect tape splices.

I've found a lot of old Langevin catalogs from the early-mid 60s and they did offer a fair few plug-in preamplifier modules that could potentially have been borrowed from. One of these contains a single 6V6, but with a 65J7 ahead of it (model 102) and others contained a 12AX7 and a 12BH7, another (AM-138 I think) contained a 12AX7 and 2x 6V6 in p-p, but also had an interchangable input panel to suit different amplification tasks. Some of these had an additional 12AX7 for low/hi Z mics or crystal pickups etc. Also had a tube rectifier though.

I'll attached the catalogue link here in case it's of interest https://www.technicalaudio.com/pdf/Langevin/Langevin_Catalog_1963.pdf

Cheers

 

[abbey road d enfer]

ACME claim to have built theirs from 'an original 1960s schematic' but they don't say of what.

Since the ACME thingy is a single channel mic preamp, it bears little resemblance with a 5-channel DI, except being designed/sanctified by Mike McLean.
Rein Narma has designed many pieces of electronic equipment, but they don't necessarily derive from the Fairchild 670.

 

[ruffrecords]

Since the ACME thingy is a single channel mic preamp, it bears little resemblance with a 5-channel DI, except being designed/sanctified by Mike McLean.

I think it is quite clear they expect you to think it is a single channel version of the original 5 channel DI.

Rein Narma has designed many pieces of electronic equipment, but they don't necessarily derive from the Fairchild 670.

Indeed, smoke and mirrors play a significant part in many of these 'vintage' new designs. The only true route to understanding would be to obtain a copy of the schematic or at least get Mike McClean to explain it to us. Anyone have his contact details?

Cheers

Ian

 

[untune]

Indeed, smoke and mirrors play a significant part in many of these 'vintage' new designs. The only true route to understanding would be to obtain a copy of the schematic or at least get Mike McClean to explain it to us. Anyone have his contact details?

Cheers

Ian

Hi Ian

Unfortunately Mike passed away in November last year. I do think it would be good to preserve his designs but we don't know if Acme have any claim to them.

After watching the video of the AES talk that Pucho provided earlier in the thread, it became clear that John Windt is probably the most knowledgable person given that he worked in the Motown shop alongside Mike and built the amplifier with him. Pucho did mention that he had been in contact with him a month ago and hopefully he will be able to give us a lead; I've tried to track down some contact info but have not found much other than that he is based in Culver City, CA. Failing that I'm considering firing an email to the Motown Museum to see if there's a chance they've kept any records.

Cheers
Lee

 

[ruffrecords]

Sounds like a plan. Anyone on the US side of the pond able to pop down to the studio and persuade them to allow the insides (and particularly the tube compliment) to be photographed?

Cheers

ian

 

[abbey road d enfer]

I think it is quite clear they expect you to think it is a single channel version of the original 5 channel DI.

Expecting anyone to believe a mic pre is one fifth of a multiple DI is so far fetched it can only come from the wretched ming of a mktg guy. But it may work; that's the desperating truth of this world.

 

[ruffrecords]

Expecting anyone to believe a mic pre is one fifth of a multiple DI is so far fetched it can only come from the wretched ming of a mktg guy. But it may work; that's the desperating truth of this world.

Again I think it is pitched as a fifth of the Motown PLUS a handy mic pre stage but nonetheless there is certainly the heavy footed mark of marketing about the whole thing.

Cheers

Ian

 

[emrr]

Funny, a friend owned the Motown 1567A for awhile, acquired it with no knowledge or advert, and it arrived with a Motown inventory badge affixed. He talked with Bob O who verified it seemed legit. He had trouble selling it, I think no one believed it.

 

[untune]

Again I think it is pitched as a fifth of the Motown PLUS a handy mic pre stage but nonetheless there is certainly the heavy footed mark of marketing about the whole thing.

Cheers

Ian

Absolutely. I reckon, even with the pedigree, you might struggle justifying almost 2 grand for a DI box!

Funny, a friend owned the Motown 1567A for awhile, acquired it with no knowledge or advert, and it arrived with a Motown inventory badge affixed. He talked with Bob O who verified it seemed legit. He had trouble selling it, I think no one believed it.

I guess this happens quite a lot, must be almost impossible to prove. I caught a video while doing research last week of a guy in LA who thought he had James Jamerson's Ampeg head/cab, as Jamerson's name was sprayed on the side of the cab. Jamerson's son didn't believe the head was legit, however Dennis Coffey told a story of how they used to have haulage companies who would ship musician's equipment around LA to different sessions, and they would stencil/spray the names on them for storage. The style of the stencil matched the one on Coffey's Fender amp, but that was as close to they got to 'proof' of legitimacy!

 

[jacomart]

I bet George Petersen knows a lot of Motown secrets ... his email address is in this article about some Motown secrets (who knows if it's still valid) but I think his LinkedIn is ok and I hope he is too.

Cheers
JM