An DIY Tube Mixer Project c.1954

TubeMixer_DIY_1954Today’s article scan, again via reader Bill W., was written by one John S. Carroll and originally appeared in RADIO & TELEVISION news in 1954.  It describes a four-into-one mixer based on a design spec’d by UTC.


1954_tube_mixer_rear1954_tube_mixer_bttmThere’s nothing terribly interesting about this particular circuit other than the output stage, which is push-pull and and is driven by a 3:1 interstage transformer which functions as both a phase inverter and provides a bit of additional voltage gain.

Output_stageI’ve never made a mic pre with a transformer phase inverter, but it could be very cool.  At Gold Coast Recorders one of the engineers’ favorite mic pre’s is a custom unit that I built based around an RCA 9362 cinema line amp (see earlier article here).  The 9362 is a push-pull output module, and it’s definitely a different sound – almost every tube mic pre made is single-ended.  Anyhow, at some point I will def build the circuit above into a mic pre.  Probably as soon as I find a pair of appropriate hi-fidelity (and shielded!) transformers for a buck.


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A DIY Broadcast Limiter Project circa 1955

1955_DIY_Limiter Courtesy of reader Bill W comes today’s scan of a much more complex tube limiter project.  Herbert Hartmann penned this 1955 article for RADIO & TELEVISION NEWS.


Similar in principle to the Altec 436/438 and the Gates Sta-Level, the Hartmann unit is a Vari-Mu design.  As the author points out, the release time spec’d here is too fast to allow for totally distortion-free low frequency response.  If you’ve ever messed around with an Altec tube compressor, you will know that there is a real ‘limit’ to how fast you can make the release before distortion and artifacts emerge.  This was one of the real advantages of those insanely complex contemporary Fairchild and GE mastering and/or broadcast compressors, btw:  through some really inventive (and expensive) designs, they overcome the timing issues inherent in simpler devices like the Altecs and Gates units.  Here’s the Hartman schematic:

1955_limiter_SchemComments and suggestions are welcome,,,

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A Simple One-Tube Compressor Circuit c.1953

1954_DIY_limiterReader Bill W recently sent us a few interesting ancient DIY audio projects that we had not seen before.  Today’s post is from RADIO-ELECTRONIC ENGINEERING and was written by one Ed C. Miller.

DOWNLOAD THE COMPLETE ARTICLE:Constant Output Broadcast Amplifier

The article details the operation and construction of the above-illustrated broadcast-remote mixer/amp, which includes a limiter.  While the overall unit is probably not something you’d want to ‘F’ with, the limiter component could be added to a DIY tube mic preamp (perhaps with a true-bypass switch).  One caveat: as the article warns, there are apparently ‘thumping’ artifacts inherent to this circuit, which was acceptable in its intended operation since it was designed for voice-frequency.

1954_limiter_SchemAnyhow, might be a fun project for a rainy day – build a pair of these into box with cheap 1:1 input transformers and simple line output stages?  Crush some room mics?  Anyone?

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The JVC 900 Digital Audio Mastering System of the early 1980s

JVC_1Download the complete sales materials for the circa 1982 JVC 900 series of digital-audio-mastering products:

DOWNLOAD: JVC_900_Digital_Audio_System

Products covered, with text, specs, and photos, include: the JVC AE-900V Digital Audio Editor, the DS-DM900 Digital Audio Mixer, the VP-900 Digital Audio Processor (AFAICT, a duplex stereo A/D, D/A), the TC-900V timecode unit, RM-900 remote, CR-850U 3/4″ ‘umatic’ tape machine, DS-FC901 Digital Interface Unit, DS-SU900 Sync unit, and BR-8600 1/2″ tape machine AKA a real expensive VCR.

JVC_digital_mastering_systemContributor Tom Fine told us, “this was a competitor to the Sony 1600 system.”  We’ve covered the early Sony units bit in the past (see here and here) – they were available early as 1978 – but I have never come across this JVC system before.  As Richard Hess writes in his very thorough blog,

JVC had a competing (with SONY  -ed) and incompatible mastering system called the DAS-90 and later the DAS-900. …The processor in the DAS-90 system was called (at least at one point) the BP-90 while the processor in the DAS-900 series was the VP-900. The first version (DAS-90) used 3/4″ U-Matic video cassettes while the second version (DAS-900) used either U-Matic of VHS video cassettes (the latter to obtain longer playing time). I have not been able to confirm if tapes made on the DAS-90 can play on the DAS-900 or not. Early input says they are compatible and should interchange.”

JVC_900_mixerBut damn look at this lil 4×2 digital mixer!  It’s like a lil baby SSL!  And this is an actual digital mixer, btw – it’s just styled to look/feel like an analogue desk.  Crazy.

Anyone out there still using this system for anything?  Thoughts?  Let us know!

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P/S Video Vol. 7: “A Single Tool Cuts A Clear Path”: Online Now

PSV007_titleFor the seventh installment of the Preservation Sound video series, we examine how an unplanned encounter with a highly unusual instrument can provide direction for a vibrant and idiosyncratic body of musical work.  Fans of modern music are likely to be familiar with duo Mates of State, who have released nine internationally-distributed albums over the past fourteen years.  Mates’ first three releases were nearly solely arranged around a traditional drum kit, the duo’s two voices, and a single other instrument: the circa 1971 Yamaha Electone YC45 Combo Organ.

I first heard Mates of State in a small Brooklyn venue circa 2002, and I was blown away by the raw, massive sound that was conjured up through such a minimal setup.  As the band explains in our program, their unusual sound was not the result of any strategic planning, but rather a willingness to embrace the tool that they happened to have available.  Mates’ relationship with the YC45 is an indelible example of the strength that can be found in limitations.  Watch the video featuring exclusive new in-studio performances now on Youtube.


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2nd live radio show this wk: D E E P 8 0 s : 11.20.14 : 2A-6A EST 89.5 FM

Deep80sHow y’all doin on this frosty morn.   Soooo,,,  I’m on the air again tonight/early manana.



WPKN 89.5 FM (Metro NYC area)

And live worldwide at

For this middle of the fkkn night edition of Preservation Sound Radio, my special guest will be legendary raconteur and record hoarder Dave Schneider.  D/S has selected the theme ‘D E E P   8 0 s’ and it’s all comin to you off the original wax.   It will be ‘rad’ etc.

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Live Radio Show * 11.18.14 * WPKN 89.5 FM * LINK TO LISTEN

WPKN_111814Update: this show has now aired, but it remains available to stream via this link.  Enjoy! C.

How y’all doing on this fine+chilly day.  Wanted to L Y K that we will have another live installment of Preservation Sound Radio today at 4PM -7PM  EST (that’s New York time, folks) on WPKN 89.5 FM. You can get the signal anywhere in the metro NYC area, and it will be streaming online at WPKN.ORG.

My guest today will be Ian S., proprietor of the fine record shoppe Records The Good Kind in Vernon CT.  For today’s show, Ian has selected the theme ’60’s Pop Psych,’ and we will be spinning the entire three -hr set from vinyl.  No surprise there I suppose.  Ian is twenty+years into the record business and will no doubt have some real gems for us.  Tune in,,,

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UTC “R” Series universal replacement transformers of the 1940s/50s

UTC_r58_transformer_boxWhile searching through my output transformer shelf for a suitable reverb-driver transformer for the basket-case Kalamazoo Reverb 12 I recently rehab’d, I was glad to find this ancient NOS UTC R-58.   Inside the box was a near-disintegrated wiring sheet for the entire UTC ‘R’ line.  If you find yourself with any of the following units, here is what you need to know to implement it in your piece.  Apologies for the poor condition of the paper, this is the best we got!  INCLUDES: UTC R-27, R-28, R-38, R-38A, R-59, R-60, R-58 output transformers, UTC R1, R2, R3, R4, R5, R11, R12, R13, and R54 power transformers; and UTC R23, R24, R25, R26, R27, R28, and R29 ‘varitap’ interstage and input transformers.


IMG IMG_0001

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The Olmsted AC Custom Microphone Preamp

AC_CustomA few months ago I detailed a new vacuum-tube mic preamp that I was designing for a client who was interested in the preamp sections of old 1960s tube reel-to-reel tape machines.  The Akai and Roberts reel-to-reels have circuitry that is largely derivative of the American Ampex machines of the same period, combining an EF86 front end with triode drivers.  Anyhow, click here to read my earlier article describing the development of the device.  I wanted to capture as much of the vibe of these classic prosumer machines but with a feature set and performance that would make the units suitable for use in a modern production environment.  And here are the results:

PreviewScreenSnapz001I tested the unit before delivery and was very happy with the results; you can see it here perched above the rack at our studio Gold Coast Recorders:


memoMy client is a highly experienced engineer who goes to work everyday behind a full-size API console in a studio with a Steinway and $100k of microphones; so when I got this feedback from him I was quite pleased.  If you would like your own, contact me via the link on the main page.  Pricing for 120v units are $2500 stereo, $1500 mono.

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Nxt Wknd : Nov15+16 : Annual Open Studio Event at the PS dot com shop

OpenStudio2014Above: a picture of a picture of a picture (via internet): take that Baudrillard

How y’all doing on this fine day,,, before I head off to the sad+moldy basements of lower Fairfield county to hunt for more piles of ancient electronic arcana for the 1000th consecutive Friday morning, I wanted to LYK about next weekend’s OPEN STUDIO event.

Located in the former American Fabrics building in Bridgeport’s far East side, Preservation Sound will open our doors to the public for this once-yearly event along with all the wonderful artists and craftspeople who occupy this circa 1900 factory.

It is free and open to all.

See all the details, get directions, etc, here.

The AmFab building, home to the studios of 30-40 artists, is only one of several large art-spaces in Bridgeport that is taking part in this event.  You can also visit The Nest and 305 Knowlton and a host of other venues on this weekend.  It’s fun and family-friendly and always a lively good-time.

I will be working in the shop(pe) through the weekend, probably on some sort of tube mic preamp that I am late in delivering to a customer, and also… SELLING… reams of stuff.

Because we’re moving.

And this is probably our last open-studio event for some time.

I’ve had two shops for a few years now and that’s just one-too-many.  So I’ve decided to consolidate and shut down this location.

I’ll be selling loads of LP records, musical gear, guitars, sound equipment, drums, and tubes tubes tubes tubes.  Tools, transformers, parts, you name it.

And no, I don’t have a list so pls don’t ask.  If I was that organized of a person I would sell the stuff on eBay at much higher prices.

Come on down, chat, and enjoy a complimentary beverage and/or rectangular piece of cheese.

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