Audio Historians - REDD/RCA/Langevin/RFT Lorentz/WSW

[emrr]

It's important to remember many of the old limiters, when first introduced, were intended to replace the existing program amplifier if possible.  In a self-contained console, maybe not possible, but a rack install with a control surface, sure.  Then you get to the 1950's with the General Electric and Collins consoles, and a plug in comp module that DID replace the plug in PGM module.  Said module the basis of Gates redesign for the Stalevel. 

 

[ruffrecords]

There is an archive of all the old BBC schematics going back to the 1930s. When I find it I will let you know.

Cheers

Ian

 

[matriachamplification]

Noted on all posts. Thank you.

We are of course going to rack all Tube Compressors as Doug suggested. And the BCC LIM 2 is an ideal build. Will begin disecting this soon

The other build we had looked into but was informed it was a huge undertaking is the 1959 Ikegami-Tushin Limiter Inspired by the RCA BA6A. Below is the original post I found the information from. I have connected with the builder SK who was a bass player in a blues band in Chicago prior to moving back to Japan.

Any thoughts on this Tube Compressor?

http://www.preservationsound.com/2015/01/

 

[boji]

Thanks Winston and Ian, enjoying these links!

 

[emrr]

The other build we had looked into but was informed it was a huge undertaking is the 1959 Ikegami-Tushin Limiter Inspired by the RCA BA6A. Below is the original post I found the information from. I have connected with the builder SK who was a bass player in a blues band in Chicago prior to moving back to Japan.

Any thoughts on this Tube Compressor?

http://www.preservationsound.com/2015/01/

The first stage preamp isn't needed.  Looks pretty typical otherwise. 

 

[Dreams]

reviewed Langevin AM4 console literature, could find no mention of panning,
yet had one when restoring an AM4 some time back.

Pan pots were introduced very late in that board's run, on the AM-411A(S). Pan pot took the place of the solo button extremely conveniently at the top of the module

This catalog and an old ebay (or something) listing is the only place I've ever seen em though:

http://lcweb2.loc.gov/master/mbrs/recording_preservation/manuals/Taber%20Langevin%20(MCA%20Technology)%20(catalog).pdf

 

[ruffrecords]

Likewise, the Helios EQ was not based on REDD but was just a Pultec circuit scaled up 2.5 times in impedance but with less insertion loss.

When I was designing my version of the REDD EQ, I was struck by its similarities with the the Helios 69 EQ rather than with the Pultec. I even began a thread here suggesting  Swettenham's experience in the service dept at Abbey Road gave him the inspiration for the Helios EQ.

However, you point about the REDD EQ originally being a pair of frequency selective T pads each with 6dB of insertion loss (one for each band) and later versions combining both bands into one T pad gave me further food for thought. You see, T pads were used in the REDD because the EQ itself was balanced. But both the Pultec and the Helios unbalance the signal before feeding it to the passive EQ. SInce you can ow follow it with a relatively high impedance gain make up amplifier, you do not have to manage its output impedance as the REDD EQ had to; instead you can throw away the right hand arm of the T and just use an L pad as the basis pof the EQ. Both the Pultec and the Helios use L pads so in that sense they are similar. But both the EQP1A and the MEQ5 use a pair of cascade L pads whereas the Helios has just one. Furthermore, the Pultec bass boost is capacitive but the Helio is inductive and I suspect the REDD was too although the Helios is resonant and the REDD is not. Also the Helios 10KHz boost/cut is identical to to the REDD. The Helios mid offers all the EMI brilliance plug in frequencies and more and offers both boost and cut like the brilliance plug-in whereas the Pultec only offers cut and a different set of frequencies. Swettenham appears to have compromised on the mid cut to make it simpler which leads to the cut Q being several times higher than the boost EQ unlike the REDD brilliance plug-in where boost and cut Q are identical.

Overall, although Swettenham was no doubt familiar with the Pultec, I think the Helios design owes more to REDD than any other EQ.

Cheers

Ian

 

[ruffrecords]

I forgot to address this bit:

REDD EQ did not manage the output impedance per se.  This is a common misconception.  Signal from EQ's, or faders or... whatever,  was always fed into a bridging high impedance load. 

Can I ask how you know this? P.S thanks for the Old BBC radio Broadcasting etc link - that was the one I was thinking of.

Cheers

Ian

 

[Winston OBoogie]

Can I ask how you know this? P.S thanks for the Old BBC radio Broadcasting etc link - that was the one I was thinking of.

It's in the manuals written by Len Page when describing the equipment:
'The circuitry is not intended to be "closed off" by 200 ohms'  are his words.

I began collecting the EMI documentation decades ago.  I acquired some via talking to an ex EMI colleague of Len Page, who then contacted Len for me and asked questions etc.  Abbey Road were also not so secretive or as guarded about the info back then as no one else was really interested in it so, some documentation came my way directly from there.

More info came from various other sources that had had equipment at some time. 

Before the existing REDD.51 was found and Brian Gibson (ex Abbey Road technician) began restoring it etc., I also provided Brian Kehew and Kevin with all the various EQ curves for the 'Pop' and 'Classic' EQ's for the 'Recording The Beatles' book as they had no curves or plots whatsoever at that point.  I'm one of the folks credited in the back of the book for providing technical help if that helps convince that I'm not making this up 

Basically, I've been collecting and had much of this info so long, that a good deal of it is engrained in memory. 
Some of the manuals you can find online came via me.  Certainly the little one for the REDD.47 amp did, as well as the basic REDD. 37 desk manual. 
I haven't posted desk blueprints though as there was basically so much of it. 

No one really cared for the longest time anyway since most assumed the Beatles used V72's and that was it.

However, for me, collecting the info was a hobby until about 10 years ago.

 

[Winston OBoogie]

P.S.  The only info I got from Len that turned out I was wrong on, was down to a misunderstanding.

After looking at the blueprints for the REDD.37 which mentioned the REDD.51 desks and the use of REDD.47 amps, I had asked "how many REDD.51 desks were made?"

Len's answer was "there were two, and one went to Milan".

I assumed for the longest time that this meant that two desks total were made and that one of those two went to Milan.
What he actually meant was, "there were two" made for Abbey Road, plus "and one went to Milan".

This was solved years later when Kevin and Brian got the info from, I believe,  Ken Townsend that both Studio 2 and Studio 3 had had REDD.51's installed.
I think it was Kevin who finally twigged while the 3 of us were driving in Brian's car what exactly Len had meant.

We/he needed/wanted to reconcile what Len had said to me all those years before, with what was the solid known information. 

So, on any earlier than 2005 or so online statement by me that there was only 1 REDD.51 desk at Abbey Road, mea culpa. 

 

[ruffrecords]

It's in the manuals written by Len Page when describing the equipment:
'The circuitry is not meant to be "closed off" by 200 ohms'  are his words.

I began collecting the EMI documentation decades ago.  I acquired some via talking to an ex EMI colleague of Len Page, who then contacted Len for me and asked questions etc.  Abbey Road were also not so secretive or as guarded about the info back then as no one else was really interested in it so, some came via a source there.

More from various other sources that had had equipment at some time. 

Before the existing REDD.51 was found and Brian Gibson (ex Abbey Road technician) began restoring it etc., I also provided Brian Kehew and Kevin with all the various EQ curves for the 'Pop' and 'Classic' EQ's for the 'Recording The Beatles' book as they had no curves or plots whatsoever at that point.  I'm one of the folks credited in the back of the book for providing technical help if that helps convince that I'm not making this up 

I wasn't for a moment suggesting you were. I am the one who is basically making this up as I go along from whatever info I can pick up on line - which is basically sod all - and I couldn't work out how you could possibly know so much - I mean we were both less than 10 years old when this all happened. I had not realised you had a significant repository of real info. Super cool. When this Covid thing is over maybe I could come see you and get a serious coke tech fix?

Cheers

Ian

 

[Squeaky]

At some point it seems that sharing old recording equipment schematics and information (to the very few who are probably still interested) must be a good way to go for those who have such information? Keeps that information alive and part of recording history? I mean, business cases relating to the information must be harder and harder to establish as time goes on? And in any event, who are the rightful heirs to such information and is the information even proprietary?

Probably a bit idealistic of me. Who knows, maybe, like the resurgence of vinyl, there will be a resurgence in the manufacture of discrete consoles? (Reminds me of the saying: how do you make a small fortune out of a winery? Start with a large fortune).

I can think of nothing worse than information being lost (e.g. hard copies of files and drawings literally thrown out) just because someone wanted to keep that information to themselves (for no reason other than they could).

Pretty obvious, although probably not really often though about, but as long as the lights stay on, everything that is published on this website (any website for that matter) can be probably seen as history being written (for all the good or ill that might entail).

 

[Squeaky]

I get the feeling that there might be individuals (in business) out there that are inclined to overstep their bound. Someone I talked to was warned off repairing certain audio equipment, which just seems ridiculous. However, I'm ill-educated as to acceptable conduct amongst pro audio design and manufacture business-persons, and I have never been part of the industry.

It is always a good idea to try and avoid pissing off old friends (particularly if like me you didn't have that many to start with - not crying poor, I prefer it that way).

All the best.

Nick

 

[matriachamplification]

All amazing stuff to learn. Tonight I will start breaking up these conversations and hopefully by Monday I will have something somewhat cohesive on the website. No promises though

We have to thank @Heikki for suggesting the BBC LIM/2 Valve Compressor. It is added to our build plans and the website with the wife and kids already organizing BBC research documents. Thanks again.

However, I'm ill-educated as to acceptable conduct amongst pro audio design and manufacture business-persons, and I have never been part of the industry.

Squeaky brings up a good point here. The Canadian Fair Use Act allows us to use materials without written or credit for the purposes of education, research and study. However, I am a puriest and prefer permission prior to commiting anything to paper.

We are also very interested in preserving content but have only just begun considering the best possible approach to make this happen.

I beleive SSL may have built a design from Gyrafs DIY builds. Not positive but someone had mentioned something similar to me at some point. 

Thanks again! My family and I are enjoying this thread.

Wall

 

[emrr]

Bunch off drama queens out there building some of that gear.
I don't miss coming in contact with some of them.
Again, some of them.  There are certainly folks that don't get involved in the drama.

Generally, it's the ones who are insecure about their technical abilities that will be the most secretive and dramatic.

And you'd be surprised - or maybe not - with how many folks out there building gear have no real right to be doing so and calling foul, since they have practically zero idea what they're doing themselves.

I personally know enough to know I don't know enough.

But walking down a typical AES show isle, I've certainly felt, at times, like a lot of folks there have less competence than some on here who just build  stuff as a hobby.

AND:  there is absolutely that faction of folks who lurk on here and then take whatever info and, suddenly, they're  selling gear.

Yes and yes and yes. 

Then there's the hoarder/collector aspect, anyone dealing with vintage gear or info has to encounter them, and it has many of the hallmarks of doing a drug deal, you're never quite sure what the currency is going to be for 'the goods'.  It's often not about money, even though it requires a lot of it, as point of entry.  Large money changing hands for rare paper means that paper doesn't get shared.  Sometimes you can only trade some very specific unicorn for another unicorn, and otherwise there is no price.  It's maddening, and expensive, and frequently impossible.    If you do it much, you're vested, then you need to recoup costs!  Copying and sharing info is labor time too! 

 

[Heikki]

We have to thank @Heikki for suggesting the BBC LIM/2 Valve Compressor. It is added to our build plans and the website with the wife and kids already organizing BBC research documents. Thanks again.

I sent the full manual of BBC LIM/2, LIM/5 and LIM/6 to admin here at groupdiy to add to the tech docs. The file size is too large for me to add them. In LIM/5 & LIM/6 the basic design stays pretty much the same except sidechain uses 12AT7 tubes, gain reduction stage EF92 tubes and additional 12AT7 amplifier stages are added after gain reduction stage.

 

[matriachamplification]

I sent the full manual of BBC LIM/2, LIM/5 and LIM/6 to admin here at groupdiy to add to the tech docs. The file size is too large for me to add them.

That was very thoughtful, thank you. We will keep a look out for them to be added.

Some of the information I have cost me in real dollars too.

Then there's the hoarder/collector aspect, anyone dealing with vintage gear or info has to encounter them, and it has many of the hallmarks of doing a drug deal, you're never quite sure what the currency is going to be for 'the goods'. 

This raises a question I really hadn't considered. Given we live with internet information is obviously much more readily accessible.

Are there any repairs or rebuilds on gear you couldn't find schematics to or intersting adventures finding them?

I think this is a fairly interesting subject. I know I shopped for gear in the Penny Papers for decades. 

 

[ruffrecords]

So, if Dick Swettenham joined EMI in 1951 and was there for 5 years, he would have left EMI long before any of these later EQ's (other than the standard treble and bass desk controls) were around the studios.  The earliest being the REDD.37's 'Pop' eq of 1958, and then the 'Brilliance'. box of 1962. 

I'm absolutely open to other evidence but, as of yet, I just don't see it. 

Note **

"MTS 884/1162 Pol. Finish Light Grey Cell. Enam" is EMI's spiffy new grey colour documented for use on panels and, I think it must be an internal number as I've yet to find a match in any old British colour charts.  Maybe someone else knows otherwise?  I'd love to find out

The key seems to be when Swettenham left EMI. I cannot piock him up at Olypic untill the eraly 60s so if he left EMI isn say '56 where did he go next?

Cheers

Ian

 

[matriachamplification]

The key seems to be when Swettenham left EMI. I cannot piock him up at Olypic untill the eraly 60s so if he left EMI isn say '56 where did he go next?

Cheers

Ian

This is where we are actually figuring out some particulars. I have some form of a timeline going already but a lot of it is based on blog posts and scattered information. We have connected with Helios and are just getting back to Crispin to dissucss.

I understand there was a statment made either while at EMI or shortly there after from Sweetenham stating "I can do it better.". I had assumed it was while at EMI discussing a console being built for something.

I will review notes and see if there is a connection to my thought pattern.

 

[emrr]

Are there any repairs or rebuilds on gear you couldn't find schematics to or intersting adventures finding them?

Lots of things I've never found schematics or manuals for, many/most of which I've drawn out myself.  Dozens of things I drew myself years before the schematic finally surfaced.