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Acorn 411 (early SSL) channelstrip?

Discussion in 'Pro Audio Equipment' started by flextone, Feb 18, 2012.

  1. flextone

    flextone Active Member


    I've been offered two Acorn CF411 channels. These were built by SSL founder Colin Sanders, right before he started working on the SSL 4000B.

    From small acorns… « SSL XLogic Blog

    This all sounds very promising, but sadly I can't demo them and there is absolutely no information online. Even a guy I spoke to at SSL said he has one on his desk at work but never actually heard it. These are extremely rare so this is a long shot, but has anybody ever worked with these?

  2. RemyRAD

    RemyRAD Well-Known Member

    If it's a similar microphone preamp to the SSL 4000 E, I think it's crap. It's a transformer into a 5534 IC chip with a couple of output buffer transistors. The guy at SSL has one on his desk because it is a paperweight which is what they are really good for. That's why it's on his desk. That's why he's never actually heard it. There is no reason to listen to or record with a paperweight. But if you know what you are doing like Bob Clearmountain, it'll make hits for you.

    Not an SSL fan.
    Mx. Remy Ann David
  3. flextone

    flextone Active Member

    I guess it would be similar to the 4000A and B which came right after it. The compressors are supposedly mono versions of the famous ssl bus compressor. I don't intend to use these as mic preamps btw, maybe occasionally. I'm looking at them as channel strips for line level, for tracking keyboards, samplers etc.

    The guy at SSL has no schematics and has no idea about how to get them to work. Besides, why would he? He has enough ssl hardware already. I doubt he records and mixes music for a living, he is employed by ssl... and he never heard one since only about 50 were ever made.

    I respect the fact that you're not an ssl fan, but isn't it plausible that these are great channel strips with that ssl comp/expander and a 70s "british" eq?
  4. RemyRAD

    RemyRAD Well-Known Member

    Oh sure. It's not really horrible. I was never all that impressed with their microphone preamp in those earlier consoles. They really weren't any different than my Auditronics 501 from Memphis Tennessee. And as nearly the same as the later IC chip Neve's, with their own specialized Transformers which made them sound different from the SSL's. Still though, 5534 IC chips were the basis of those preamps. They were not discrete transistorized ones like the API or earlier Neve's. Nevertheless, they still offered plenty of headroom and low distortion. Which actually makes them easier to upgrade with the ability to swap out different IC chips that sound considerably different from each other. That in comparison to specialized all transistor operational amplifiers with a nonstandard form factor and pin out. You can't just plug different chips into a console that never had chips before. So in that way, you are kind of locked in to whatever operational amplifiers were designed for that particular unit. The Neve's had a little more interchangeability between their discrete transistor operational amplifiers and the IC chip/output buffer transistor operational amplifiers. You could swap the BA 438/440 transistor units with the BA 638/640 newer IC chip variants and vice versa. And of course, their equalization was quite comprehensive on the SSL along with their dynamics processing on each channel strip. So you really shouldn't have that much trouble finding somebody that could make your modules operational again. And I really don't think that while their equalizers were cool that they actually provided that " British EQ" sound. That title belongs more to the Neve's than any other. Those earlier equalizers like I have were ferrite core inductor equalizers that were stupidly simple with broad ranging Q on the selectable mid-band frequencies. The high and low frequency portion were simply shelving with a switchable and selectable frequency high pass filter. So that British EQ sound was more due to the design concept along with those ringing inductors and broad bell shaped curves. The SSL's are little more like George Massenburg's parametric's in their sound and function. Ain't nothing British about that sound. But hey, it's still cool what you have.

    Enjoy them, please.
    Mx. Remy Ann David
  5. flextone

    flextone Active Member

    I'm still not sure I'm getting them. I can't find anybody who can give me an opinion, they're just too rare. And I hate buying stuff without auditioning, my budget isn't large. They look great, the seller says they sound great (of course), and they do have historical value. But I need something I can work with.

    They're already operational btw...

    Thanks Remy
  6. RemyRAD

    RemyRAD Well-Known Member

    What do you mean you can't find anybody who can give you an opinion? I already have. As you showed and indicated it's a predecessor to the 4000 A which is the predecessor to the 4000 E. So to extrapolate that difference, I can go back through my history with consoles, lots of consoles. The way in which the 4000 A microphone preamp probably differed from the 4000 E microphone preamp, was the introduction of the Signetics 5534 IC chip op amp. Previous to that and most likely in the 4000 A, were most likely a product earlier available IC chips such as the Harris 910 that was utilized in the MCI JH 400 console when first introduced in the mid-1970s. Or it could have been a National Semiconductor LM 709 such as what was used in the first release of the Auditronics 501. The later iteration of the 501 utilized that new 5534 thingy. I have looked at the schematics of the 4000 E and the modules up close. So it's an adequate sounding microphone preamp. A bitchin' equalizer, relying on gyrator IC chip with sweep a bull frequency selection and Q. And a dynamic section not necessarily known for its beauty but more for its color. And of course, in the right hands, they sound great. The question is... is this a wise purchase for you?

    I really don't think it is. And I'll tell you why... as you said, they are too rare. And as you indicated, you need something you can work with. This obviously does not make this a wise choice for just those reasons alone. Something that's better known and just as prolific as SSL, is out there. Channel strips from SSL 4000/5000/6000/8000/9000's are all readily available. What you are trying to decide about is whether to purchase an antique car by a company that only existed for a short while, a long time ago. So retrofitting and customization may also be necessary to make these devices viable. If you're good with a soldering iron, I'd say go for it. If you need to be up and running and need something that works now, look into something that was actually known to sound good like old API and Neve. If you want all of that other special gobbledygook on one channel strip, go for those other models of SSL. That's assuming you are going after a channel strip? And that's where those API Lunch Box gizmos make a lot of sense for a guy like you. You can mix and match, buy and sell, nearly fabricate a couple of channels of Channel strips i.e. API 512/550 B/miniature mixer thingy, etc.. I mean if you get the really cheap, it would be a cool collectors item. We all have plenty of old audio stuff we can't necessarily use anymore that we keep strictly for the cool factor like my original Altec M. 21 tube condenser microphone, my original issue SHURE 55 looks so wide it looks like the front grill on a 53 Buick, Ampex AG 354, etc. Still usable, all of them but I don't use them anymore. They still work if I want them to. Anybody interested in a pair of Altec 1567's with the VU meters? How about a nine band, all transistor, ferrite core inductor Sphere console EQ? I think I still have a couple of API 312 cards lying around?

    I love dark Bavarian wheat beer
    Mx. Remy Ann David
  7. flextone

    flextone Active Member

    Well, you make several good points no doubt. However, the modules ARE 1) cheap. less than half the price of one API 500 series preamp for two of these strips 2) they're already good to go from a working recording rig, connected to xlr's and come with schematics. Only need PSU. 3) as I said, I won't be running microphones through them, only line level.

    Basically it's between these and starting a Danner rack with two eq's and twp compressors, like my other post indicates. This solution will however be more expensive, but still cheaper than a lunchbox :)
  8. flextone

    flextone Active Member

    So you're basically saying that they probably sound good (adequate preamp, bitchin' eq and the famous ssl comp) but I'll need to do a lot diy to get them up and running? In that case they seem like a great buy, seeing that they are already plug&play.

    Anybody else wants to chime in?
  9. RemyRAD

    RemyRAD Well-Known Member

    Yup, that's exactly what I'm saying. While I don't think it's one of those fabulous microphone preamp's it's still quite good and has recorded many, many, many hits with those. You just won't be able to as successfully overdrive those microphone preamps as one can with all discrete transistor microphone preamps to obtain a certain characteristic advantage. But they are clean and they have more than adequate headroom. And then you get all of the other cool stuff. Your basic challenge will merely be obtaining the correct edge connectors & proper schematics. We'll have numerous inputs and outputs along with patch points. Knowing that already, you may want to have a simple 1/4 inch TRS patchbay to contend with all of these numerous inputs and outputs.

    I know you're going to like these
    MX Remy Ann David
  10. flextone

    flextone Active Member

    Finally some encouraging words, thanks :)

    Again, I don't need any connector, the strips are already fitted with xlr in and out, so they're good to go. Just need to solder the psu cable. And the seller has the original schematics. He bought the whole console from colin sanders in 1972 in england.
  11. RemyRAD

    RemyRAD Well-Known Member

    Well that all sounds uber cool. Instead of soldering a power supply directly to the units, I would highly recommend pursuing a 4 or 5 pin XLR so that you can merrily plug into the power supply. And those connectors are frequently utilized just look at some of the products of BAE (British Audio Engineering formally Brent Averill Enterprises). He utilizes that connector on the back of his preamps to the power supply. It makes for quicker swap outs and troubleshooting when necessary and does less damage. So cool that your guy purchased that entire early desk. Totally awesome. History I never actually looked into since I was not a huge SSL user. Their later digital consoles, not the earlier analog desks.

    This is very intriguing
    MX Remy Ann David
  12. flextone

    flextone Active Member

    Well, I've decided not to buy the Acorn modules...

    Seemed like too much of a risk. I've emailed people all over the world, SSL tech people as well as an engineer who actually worked on that desk. All the answers I received contained the following claim "should be a great buy, if only for the historical value". Historical value is nice but as I said, I need stuff I can work with and although this was (and is) a great offer at a great price, I don't have money to gamble with. Hope I didn't make a mistake.

    I decided to start building a rack of vintage german broadcasting modules. Bought two BFE bke3 compressors and planning on adding a pair of eq's and possibly a mic pre.

    Remy, how do I implement your recommendation for an xlr psu? I planning on building the JLM audio kit or the Fivefish kit.
  13. RemyRAD

    RemyRAD Well-Known Member

    That all depends on what you need in your power supplies for your rack? Generally most anything that has a class A/B output such as API/Jensen, Hardy and others require ± 15 V of at least 3 amps. Some circuits will require ± 24 volts. And then there is the Phantom power supply issue of +48 Volts. Depending upon your primary voltage requirements, a 5 pin XLR can do the trick. Pin 1 should be ground. Then pins 2 & 3 can be your primary ± supply. Leaving pin 4 or, 5 for +48 V phantom. 6 pin XLR's can also be acquired should you need a combination of ± 15, 24 & 48 V though things are going to get rather tight which will require some expert soldering & heat shrink tubing just to be safe. On most video equipment, only +12 V DC is required which is on a 4 pin XLR where pin 1 is ground and pin 4 carries the +12 V. One should want to obtain a power supply or build one up that includes a transformer with secondary taps of output voltages higher than you will need. It is then bridge rectified, filtered with some large electrolytic capacitors and then fed into a pair of ± voltage regulators to produce a clean and regulated ± 15 and/or 24 V. And the ± 24 can be utilized to create the +48 V necessary for Phantom power. Though you could find it above 50 V which will require a +48 V regulator for the Phantom which is always a good idea. 3.9 K ohm, ± .1 or .5 accuracy metal film resistors will be required to distribute your +48 V phantom supply two pins 2 & 3 of each XLR microphone input. Then that will be referenced to ground on pin 1 along with the shield.

    It's also a good idea to have your power supply in a separate metal utility box and keep it at least 6 feet away from your active electronics.

    Das ist gute mit der deuthcha' gobbledygook.
    Mx. Remy Ann David
  14. flextone

    flextone Active Member


    Complicated stuff. If I should keep the PSU so far away from active electronics, why do I see racks with a built in PSU? Is it just PSU's with transformers that supply phantom 48V that need to stay in such a safe distance? I don't need 48V at the moment, and the german broadcast stuff require 24V.

    I'm looking at these on ebay for example:

    BICC VERO GK60 Monovolt Netzteil Netzgerät 24V 2,5A Modul | eBay

    VERO Studionetzteil PK 100 Monovolt Netzteil 24V/4A | eBay

    I saw the exact same psu in a rack full of Neumann eq's, only in a photo though. I would prefer an external box but those are cheap.

    I'm not german :)

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