DIY Grammafoon Versterker circa 1939

Radio_expres_magazine_NetherlandsWe’ve covered some fairly obscure + forgotten audio publications here at PS dot com, but this one takes the taart. RADIO EXPRES was a Nederlands DIY radio/audio magazine published from 1932 through 1939, and perhaps longer.   Well, it was certainly published for the entire year 1939 (22) issues, since I’ve ended up with that pile of them here.  As is typical of ‘radio’ publications in the pre hi-fidelity era, the emphasis is much more on RF than AF, but I still managed to find a few interesting articles of possible use to y’all audio-folk.  First off:  this cute lil 4-watt Grammafoon Versterker (that’s a phonograph amplifier, btw):



The ‘Lampen,’ or ‘tubes’ used are an E99 high-gain triode input stage and an AL5 pentode output tube.  Interestingly, these are both 4V filament tubes.  The 4V filament is not seen in any US-manufacture audio tubes that I have ever come across.

Versterker_partsListThe article, penned by one J. L. Leistra, spans two issues of Radio Expres and it is very thorough.  It covers all of the theory involved in developing the circuit, and the second part gets into some pretty extensive detail regarding the feedback-based compensation filter.  It wraps up with fabrication, layout, and wiring instruction.  It’s all written in Dutch, btw.

Versterker_Tagboard Versterker_Chassis*************



EL5_schemThe only other really interesting audio-bit that I could discern was this 3pp exposition of the then- ‘neu’ Phillips EL5 (incorrectly indicated as an ‘FL5′ in the above image) 18-watt output pentode.  The EL5 seems like a tube worth exploring; it’s a high-power, 6.3v filamant audio output tube designed to run ona pretty low plate voltage (250- 275) for such a high powered tube.  Could be useful in some situations.  Anyone using EL5s?  Here’s the whole article for you to…. look at. (unless you read Dutch, of course).


I’ll leave off with a quick survey of the best part of this run of magazines: the incredible, world-envied graphic design that the Nederlands is still renowned for almost a century later.  Enjoy – c.

MastheadStoetsRadio Frequenta Bell_Telephone_Holland Sondisko Kristal_Microfoon ThermionLampen

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RCA 100 Series Broadcast Components of the 70s – complete tech info

RCA_BE100_faceYears ago I ‘lunchboxed’ one of those above-depicted RCA BE100 equalizer modules.  The RCA 100 series of the early 70s was the end-of-the-line for RCA’s pro audio gear.  The series consisted of the MI-141651 op amp, the BMM-100 Mixer (channel strip, aka MI-141550), BE-100 EQ (aka MI0141560), BA-101 and BA-103 preamps (also designated as MI-141501, MI-141503), BMM-110 Submaster module (aka MI-141570), and BIM-100 Isomix amplifier (aka MI-141520).

RCA_opampsSince I seem to be one of the few fools who has publicly admitted to spending time messing around with these things, I’ve gotten several requests over the years for the accompanying data and schematics. Well guess what. TIME HAS COME TODAY.  Download all of the tech date for all of these modules.



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Studio Outboard Gear Odds & Ends ’71- ’73

Urei_1176_1970Today: just a few things that caught my eye from ’71 -’73:  the ‘new’ black-cosmetic version of the Urei 1176, plus some odd bits from Soundcraftsmen and Sansui (I had no idea that they had made pro audio products), and another forgotten Quad-Eight rack device (see here for our earlier coverage of their very obscure reverb unit).  Also something called the ‘OP Reverberation’ …. anyone?  ,,,and a few unusual items from Martin.  Wrapping it up is the annoucement ad for the original API 525C, which has become one of my favorite compressors for vocals since we got one at Gold Coast Recorders.  If any of y’all are using the Martin or Quad-Eight kit, let us know!

Soundcraftsmen_RP10-12_1972Above: The Soundcraftsmen RP10-12 equalizer

Sansui_QSE_1_1971Above: The Sansui QSE-1 Quadraphonic Encoder

Quad-Eight_Filter_1972 Quad_Eight_1972Above: The Quad-Eight Variable Filter, Auto-Mix 23B compressor, EQ 312 channel EQ, and RV10 Reverb unitParasound_reverb_1971 Martin_Console_1972 MArtin_1972_2Above: the Martin SLM-1020B mixer, PEQ500 rackmount program EQ, and varispeed 3B tape machine speed controller.  API_525_1972

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From the laffs dep’t

FirefoxScreenSnapz001These helpful bros want to solve your excess-cable-length problems.

so much talk online

everybody an expert

who can I believe

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Kehinde Wiley documentary w/ our analog synth score

KH_EOGEarlier this year I had the chance to work with composer Nathan Halpern on director Jeff Dupre’s documentary “Kehinde Wiley: An Economy of Grace.”  Wiley is one of the most significant contemporary painters;  his work manages to accomplish many of the traditional functions of portraiture while intensely exploring issues of race, class, and hegemony.

You can view the entire program for free at this link (PBS dot org).

The 44-minute documentary won the short-form doc category at SXSW earlier this year, and had its broadcast television debut 9/5/14 on PBS.  You can get all the details here, and view the trailer at Vimeo.

Home_StudioThe score was made primarily using the minimal setup you see above here:  an Arturia mini-brute and a Korg MS20 with the oft-maligned but oh-so-versatile Line 6 POD Pro XT effects processor; my el-cheapo Alesis midi controller was also on-hand to operate various soft-synths since it can’t all be monophonic, all the time,,,,.  Drums were primarily recorded at the big room at Gold Coast Recorders.   If you’ve been reading this blog for a while and have ever wondered, ‘but what does he DOOOOOO with all that stuff?’, well, here’s your chance to find out.  I write a lot of music for television, but rarely is a project so near+dear to my heart, both musically and thematically.

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Bespoke Mic Preamp based on Akai/Roberts circuit

AC_Custom_front(Above: the prototypeakai_m-9_front) A client contacted me recently regarding his 1960’s Akai stereo tube tape machine.  Apparently there is a popular internet ‘meme’ based around the modification of these units (the same machine was marketed under both the Akai and Roberts brand names)Here’s an example of one of these DIY sites.  Handy types are encouraged to turn these stereo tape decks into four independent microphone preamps, and step-by-step instructions are available.  Anyhow, my client is an engineer at a busy commercial studio in Brooklyn NY and he had purchased one of these machines in order to have this mod performed.  After a look over the instructions and forum info, it was clear that these mods would present some challenges for use in a pro studio – especially as far as impedance and output level are concerned.  My advice was: leave the Akai alone!  And spend the money instead on a fresh build that utilized the most significant/interesting parts of this project, add a ton of useful add’l features, and pushes full +22 output level at 600 ohms.

Akai M7 Right Schematic _MOD_2_Preamps_In_OneAbove is the Akai preamp with the popular ‘Ron Childers’ modification notes added (I can’t seem to recall where I found this – if someone has an attribution link, pls LMK and I will add it).  I began the prototype by building it as you see here, taking the output from the cathode of V2B.  It was quickly apparent that the cathode of the 12AX7 was incapable of driving a 15K:600 output transformer to a high enough level.  The solution was to replace the entire V2A/V2B section with a 12Au7-based voltage amp plus cathode follower similar to this classic RCA design:


I repo’d the gain pot between the EF86 input stage and the first stage of the 12AU7, also adding a 1/4″ switching jack immediately ahead of the pot so that medium impedance (nominal 10K ohm) signals could be ‘directly injected’ into the 12Au7 stages (ideal for adding a little bit of gain and/or crunch to drum machines and synths).  Also as per my client’s request I added phantom power and my familiar variable output pad (see here and here for video).  The pad is fully bypass-able via the TPDT switch located directly above the pot.

AC_Custom_insideAbove: inside the completed prototype

At left of the image above is input transformer.  It’s a shielded unit as found in the ubiquitous Shure M67 ‘Mic Mixer’ that was sold in huge numbers for decades to churches, civic institutions, etc.


Many of the online Akai/Roberts discussions recommend using the 4 input transformers as-found in these units as donors for the ‘4 channel’ mod.  My client was significantly intrigued by this as to request the same thing.  Luckily I had a spare M67 in stock (these things are readily available in the $10 – $50 price range) and so I pulled a transformer from it.


Above: T. Walsh at Gold Coast Recorders

I was pretty suspicious about the quality of these Shure transformers; even though they spec’d out OK as far as measured frequency response, I would have been much more inclined to use my standard Jensen 115 input transformer as I do in 90% of units that I build.  I thought that the best thing to do was to really put the prototype unit through it’s paces.  T. Walsh, himself an Akai machine owner, was kind enough to come to Gold Coast Recorders where we spent 3 hours writing and recording an entire pop track using only the prototype preamp on every source: drum kit (a Telefunken tube mic, in front), vocals (can’t recall,,,) , acoustic guitars (U87), hi hat (460), percussion (Royer), and all synths and drum machines were likewise routed through the front-panel input of the unit.  I figured that if my client liked what he heard in the recording, he could make up his own mind regarding the suitability of the input transformer.   Here’s the track.  The lyrics are an homage to the Akai unit itself:




Anyhow, my client was happy with what he heard, so I proceeded to building the 2-channel unit that he had requested.  It is near completion and I will post a follow-up once it has been delivered.

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Olmsted BRDCSTR preamp used heavily on latest Sigur Ros album Kveikur

RackAbove: the BRDCSTR in Somers’ outboard rack, left side, third from bottom

ART_coverThanks to reader EL for reporting that Sigur Ros’ engineer Alex Somers made mention of his Olmsted ‘BRDCSTR’ preamp in the Sept 2013 issue of AudioTechnology magazine.  The context was a thorough piece written by Paul Tingen on the making of Sigur Ros seventh studio LP “Kveikur.”  According to Somers,             “When recording (Sigur Ros Vocalist) Jonsi, I used a Neumann U47… we mostly used a really cool preamp made by Preservation Sound.”

See below for the full text.

Alex_SomersBelow is the actual BRDCSTR that Somers purchased.  If you too would like one of these preamps for your outboard rack, drop us a line. And you don’t have to pay in Krona.


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Less But Better: The Braun TG-1000 Tape Recorder of 1970

Braun_TG_1000_!972_picIt’s very hard to find vintage BRAUN hi-fi gear in the states; i’ve seen some amazing BRAUN receivers in Canada, but they either were not sold here, or poorly distributed, because they just ain’t around.  Sporting a design aesthetic that would be popularized in the NAD, ADS,  and PROTON lines of the 80s, BRAUN kit owed it’s beautiful, so-far-ahead-of-its-time character to Dieter Rams.  Rams put his stamp on a huge range of goods for BRAUN; I once found a Rams-designed mini desk fan (!) that was shockingly valuable as a collectors item.  Anyhow, here’s a great synopsis of the career of a man who’s ideal could be summed up as Less But Better:  CLICK HERE.


Via Wikipedia, here are Rams’ ten principles off good design.  Enjoy.

  1. Is innovative – The possibilities for progression are not, by any means, exhausted. Technological development is always offering new opportunities for original designs. But imaginative design always develops in tandem with improving technology, and can never be an end in itself.
  2. Makes a product useful – A product is bought to be used. It has to satisfy not only functional, but also psychological and aesthetic criteria. Good design emphasizes the usefulness of a product whilst disregarding anything that could detract from it.
  3. Is aesthetic – The aesthetic quality of a product is integral to its usefulness because products are used every day and have an effect on people and their well-being. Only well-executed objects can be beautiful.
  4. Makes a product understandable – It clarifies the product’s structure. Better still, it can make the product clearly express its function by making use of the user’s intuition. At best, it is self-explanatory.
  5. Is unobtrusive – Products fulfilling a purpose are like tools. They are neither decorative objects nor works of art. Their design should therefore be both neutral and restrained, to leave room for the user’s self-expression.
  6. Is honest – It does not make a product appear more innovative, powerful or valuable than it really is. It does not attempt to manipulate the consumer with promises that cannot be kept.
  7. Is long-lasting – It avoids being fashionable and therefore never appears antiquated. Unlike fashionable design, it lasts many years – even in today’s throwaway society.
  8. Is thorough down to the last detail – Nothing must be arbitrary or left to chance. Care and accuracy in the design process show respect towards the consumer.
  9. Is environmentally friendly – Design makes an important contribution to the preservation of the environment. It conserves resources and minimizes physical and visual pollution throughout the lifecycle of the product.
  10. Is as little design as possible – Less, but better – because it concentrates on the essential aspects, and the products are not burdened with non-essentials. Back to purity, back to simplicity.
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RCA Solid State Audio Projects c. 1968

RCA_1968I’d never been particularly interested in learning solid state electronics.  There just didn’t seem much point; considering that you can buy a 4-channel Sytek mic preamp for $900, there just ain’t much to motivate anyone to DIY ss kit.  Tube stuff is another matter – it’s a different sound, and well-made ‘real’ high-plate-voltage, transformer i/0 tube gear is super-expensive.  So I learned to make the tube gear both for my own studio and as a way to make some add’l income by custom-building for other engineers.

All that being said, there is an undeniable appeal to be able to build something useful that doesn’t require a heater circuit and the attendant 60-cycle-hum battles that come from those hi-current windings.  Solid state is just easier, which is prolly why it has won-out in the world of consumer electronics, if not necessarily in the pro-audio world.  In my endless diggin for ancient tubes and transformers and bakelite meters I invariably come across stashes of ole germanium and silicon transistors, and I recently decided to take the plunge and try and cross this bridge once and for all.  Cos I can talk tubes and tube audio circuits up+down, but frankly I don’t know shit abt solid-state and maybe it’s time I learned.


The old RCA Tube Manuals have always been my primary source of information for my tube-audio builds and experiments.  The circuits that they recommend are the most solid, reliable, and practical that you will ever find.  I trust them implicitly.  And why not?  After all, this was the company that made the tubes themselves!  So when I decided to try and get into SS, I started with the RCA Solid-State Hobby Circuits Manual.  In the scan above you will find a mic preamp, a line-level compressor, and a fuzz pedal.  I’ll be building all three eventually and I will LYK how it goes.  In the meantime, if any of y’all beat me to it, drop us a line and report back,,,

RCA_SS_MicPre_Schem RCA_FuzzBox_1968_schematic RCA_SS_Comp_1968



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Rock Scene mag c. 1980 presents: The Connecticut Rock Report

RockSceneMag_Sept1980_coverDo YOU think Ted Nugent is sexxxy?

“ROCK SCENE” was a musician-oriented newsprint rag published out of Bethany CT from 1973 – 1982.  Now, Bethany is a sorta non-place just north of New Haven perhaps most notable for its Book Barn.   So the fact a new-wave/punk-loving magazine came out of here back in the day is pretty amazing.  NEways, I was flipping thru some cartons of old garbage at the Flea Mkt recently and I came across the 09/80 issue. Top story: CONNECTICUT ROCK REPORT.


Being a rocker in CT is kinda like being a (what) in (where).  So, CT rockers of ’80: we salute you.  You are our past, and our future.

Crayons_FlyingtigersAbove: The Crayons.  The Flying Tigers

PArt2Above: Lytes; Eyes; Fast Fingers (Ewwwww (-Ed)); Jett

Part3Above: Napi Brown; Toys; The Orange Group

Part4Above: The Simms Brothers Band; Frankincense & Myrrh; Back To Earth Band




BTW: some wonderful absolute fkkn nutcase, glob bless him, has scanned EVERY FKKN PAGE of EVERY FKKN ISSUE of ‘Rock Scene’ and you can waste a ton of  yr employer’s money by clicking this link

Posted in Connecticut Audio History | 3 Comments