Stereo Audio Power Amplifier (Home Use)

Above, a recently completed piece.  It is built on one of two identical NOS cabinets that I pulled from a Milford CT basement some years ago.  Aside from the unusual enclosure, this is the same “iPod” stereo amplifier that I have built before; see here and here for other examples.

The meter (0-30V DC) is a bias meter for the output tubes.  The switch below selects left, right, or off position.  This will help alert the user as to an appropriate time to replace the output tubes.  The circuit is very simple: RCA jacks on the back feed a 100K dual-pot, then on to a 6SL7 (one half per channel) and then to a single 6L6 per channel.

Inside the cabinet are a very large EDCOR power transformer, two paper-wrapped output transformers, a choke, and a whole bunch of filter caps. Rectifier is a 5U4 and filaments are AC.  Electronically it is nothing special but visually it is one of my favorite pieces yet.

Audio Anthology: Collected Hi-Fi articles from AUDIO ENGINEERING in the 1940s

PS dot com reader Paul R. was kind enough to send us a scan of “Audio Anthology,” (ed. C.G. McProud) a 124pp softcover published in 1950.  “Audio Anthology” (hf. ‘AA’) is a collection of project-construction articles aimed at hi-fi (rather than pro audio) enthusiasts.  All of the material had been previously published in Audio Engineering magazine during its first four years of publication (1947 -1950).  See here, here, here, here, here, and here for previous 1940’s AUDIO ENGINEERING MAGAZINE coverage on PreservationSound. 

Above, an interesting boost-EQ stage that could be helpful in an instrument or mic amplifier.  Can any of our helpful readers advise which caps or resistors in this circuit could be modified (and within what range) to alter the turnover frequency of the two filters at work here?  I am guessing that the answer is: all four caps that follow the input DC blocking cap… which would basically get us back to this piece, which i swore i would never build again…

Above, the most complicated tube amp I have ever seen.  Kinda feel like Shadow Hills Engineering must have come across this image at some point.  Dynamic noise suppressor, phono pre, two eq controls, visual feedback of high and low frequency drive, variable metering, tons of input switching… talk about the kitchen sink.  This project is organized around the very interesting 6AS7G dual-triode power amplifier tube: basically two 2A3s in one glass envelope with a 6V heater supply.  This is potentially some useful information, especially when you consider that a 6As7G is only about $13 from AES (priced out 2A3s lately?). I think that there could be a unique new guitar amplifier in the works soon…

My lord.  At least they didn’t try to thrown in an AM/FM tuner.  Follow the link at the end of the this post for schematics and parts lists for some 6AS7G amplifiers.

‘Audio Anthology Vol 1’ is available at Amazon dot com.

FOLLOW THE LINK BELOW for 6AS7G project schematics…

Continue reading Audio Anthology: Collected Hi-Fi articles from AUDIO ENGINEERING in the 1940s

Out-of-print Book Report: “Making 4-Track Music,” John Peel (TRACK pub., 1987)

Download a seven-page scan of some interesting hardware on offer in “Making 4-Track Music,” Track Publishing 1987:

DOWNLOAD: 4trackMusic_JohnPeel

Includes advertisements for Yamaha MT2X, DX100, and RX17 drum machine; Akai MG614 four-track machine, Tascam Porta2 4-track, Fostex 160, the Boss Micro-Rack series (RDD-20 delay, RPS-10 pitch shifter, RCL-10 compressor, RRV-10 reverb, plus a ton more), and KORG’s multieffects.




First-things-first: I have no idea if the ‘John Peel’ to whom this book is credited is the John Peel, he of legendary status as a DJ and taste-maker for an entire generation of rock and pop music.  There is nothing whatsoever in this 98pp paperback volume (found in a Manchester OXFAM back in the early 00’s)  that offers any indication pro or con.  A third option would seem to be the ghostwriter scenario.  Anyhow.  “Making 4-Track Music” (h.f. “M4TM”) is an A5-sized paperback that attempts to introduce readers to the equipment and processes of using 4-track recorders.

The 4-track recorder, for those unfamiliar, is a category of product first introduced by the TASCAM corporation in 1979 with their model 144.

The 1979 TASCAM 144.  Bruce Springsteen recorded his greatest album on this small plastic machine, believe-it-or-not.  (Image source)

TASCAM already dominated the home-recording market with their 3440 1/4″ open reel tape recorder and the associated mixer-units that were marketed alongside it.   These systems had a rather high cost of entry, though: they cost much more than a good used car.  The 144 brought the basic concept of multi-track audio recording and mixing to a far lower price-point by using consumer cassette tape rather than 1/4″ open reel tape as the recording media, and by combining the audio-recording device and the audio-mixing apparatus into one single item.  This made for a much more affordable system and it also made for easier use: no wires to hook up, no redundant or unnecessary features.  Just the basic technology needed to record a performance and then add 3 additional performances in perfect synchronization while retaining the ability to control relative volumes and treatments of each track.   With a creative user, the 4-track machine is capable of much more, but this is the basic concept.

“M4TM” covers all of this, and more; there is an explanation of the various recording and mixing features that the consumer would encounter in the marketplace, plus good treatment of the various types of additional processing equipment that a 4-track owner might like: digital time-based effects (delay, etc), compressors, gates, EQs., etc.

The aesthetics/art of making recordings is not really considered at all; there is a lot of talk about money, costs, (e.g., KORG’s above-depicted rainmaking) and the improved ‘recording quality’ that such expenditures can deliver but no mention of improving the presentation of songs and sonic ideas via any of this technology.  Here’s a typical passage:


As someone who’s work is largely based on the commercial recording studio that I own and operate, I find it rather… alarming/offensive that the prime benefit of making a recording in a pro studio is the sound-quality, to extent that this benefit could be completely undone by several generations of tape-duplication.  Jesus.  I like to hope that I give my clients something more than a good signal-noise ratio and even frequency response.  The passage above kind of makes it seem like it’s the EQUIPMENT in a studio that is doing the work, rather than the engineer…   is this how most musicians feel about studios?  Is this how I used to feel about studios, when I was 4-tracking at home at age 19?

(me at home, age 19: via Tascam Porta 03, Boss Micro -Rack effects): 07 The End

Furthermore, M4TM does not even entertain the aesthetic or artistic possibilities of all of this ‘4-track’ equipment.  Rather, the emphasis is very much on ‘making-a-demo’ en route to possibly getting a ‘record deal,’ and all that this will entail (presumably the “Riches and Fame” for which you will have KORG to thank).   The idea of possibly creating a compelling piece of artwork with this equipment is simply absent.

I wonder when this changed.  By the time I started recording heavily on a four 4-track machine, a mere 8 years later (1995), musicians like Bill Callahan (aka SMOG) and Jeff Mangum (aka Neutral Milk Hotel) were already getting attention specifically as masters of 4-track recording.  These guys did not appear too interested in making a ‘real record’ in a ‘pro studio.’  The 4-track medium, with its attendant tape hiss, awkward usage once you went past four tracks, and total absence of any sort of editing ability, was a huge part of the artwork that they created.  Artwork that has truly endured.

(image source)

I went to see Jeff Mangum perform last week here in CT.  He did a solo set at the Shubert Theatre in New Haven.    Jeff Mangum has not released a major album of his own in 13 years.  The Shubert was nearly sold-out to it’s 1591 capacity.

(image source)

Have a listen (above) to “Naomi” from Neutral Milk Hotel’s 1996 4-track masterpiece “On Avery Island.”  Would these songs have been rendered any more compelling had they been tracked and mixed in a studio?  I think we all know the answer to that…  Ultimately, though, what Mangum’s solo-acoustic-gtr-and-voice performance at the Shubert last week demonstrated to me was more the fact that it probably honestly didn’t matter how he had made those seminal recordings: the songs themselves are so good and his voice and affect are so well-wrought that their properties can impress regardless of the presentation.

Perhaps I am reading into this all too much…perhaps my ideas and taste are a bit ‘off’ and therefore I have ‘niche’ values.  Mangum seems, to me, to be a very straightforward singer/songwriter.. but perhaps my appreciation for artists like Jeff Mangum simply indicates that I have ‘weird’ taste, that I am out-of-step with ‘mainstream’ values…  Goggle seems to think so.   Here’s what you will see if you play a Neutral Milk Hotel song on Youtube:

Is your significant-other cheating on you?  Maybe you need to lose those glasses: improve yr appeal?  Fuck it, man, you’re a GEEK.  Face it.  Geek geek geek.  Date another geek.

I am so confused.

1987/2012:  Maybe our John Peel simply wrote “M4TM” in a lost era, simple as that… an era when there still was a vigorous economic basis for the music-recording-industry and therefore the idea of recording music as INDUSTRY rather than EXPLOIT was still the dominant theme.   It’s also interesting to consider that around the time of the first Neutral Milk Hotel album we also saw the introduction of Tape Op magazine, the first (that I am aware of…) widely-distributed publication that embraced the ethos of home-recording as a serious art form.   And all of this happened just-in-time for the introduction of the first affordable DAWs (e.g., Pro Tools LE), which completely changed both the technique and the aesthetics of audio recording forever.  You still need to be able to write a good song though.  That much hasn’t changed.

 Previous 4-track coverage on PS dot com:

Fostex recorders of the 1980s

Musician Magazine 1976-1999

Out-of-print Book Report: “Professional Rock And Roll” (1967)

Download a six-page excerpt regarding ‘the sound system’ from “Professional Rock And Roll” (Ed. Herbert Wise, Collier, 1967):

DOWNLOAD: Professional_Rock_And_Roll_Excerpt

Very much along the lines of “Electric Rock” (1971)  and “Starting Your Own Band” (1980), “Professional Rock And Roll” (h.f. “PRR”) is especially interesting in that it was published a mere three years after The Beatles appeared on Ed Sullivan, an event which is widely considered to have marked the beginning of The Sixties Rock Era.  In such a short span of time, enough of an industry and codified set of working-practices seems to have formed around young teen-oriented electric-guitar-based groups to have resulted in the large paperback that I now hold in my hand.

“PRR” parses the idea of what it takes to be a ‘professional rock and roll band’ in some interesting ways.  There is the chapter on PA equipment, with the various above-illustrated items discussed (BTW, I still regularly find most of these items at the estates+fleas, so points to the author for accuracy), as well as a chapter each on Electric Guitars and Keyboards.

Above: the three types of Electric guitar: ‘Early,’ ‘Solid Body,’ and ‘With Accessories.’

Above: The Rock Organ Player

We also get chapters on putting a band together, chords, songwriting, lead-singing, hitting-the-road, and managers/agents/publishers.  Somewhat more surprising is the in-depth chapter on how to locate and buy stage-clothing and the chapter on light-shows.

I think it’s somewhat interesting to learn how important the idea of visual-accompaniment-to-music was in those early years of the Rock industry.  We’ve been told so often how MTV changed the visual/sonic balance of musical-signification so drastically, to such varied effect as manufacturers’ increasing the size of their logos on equipment (E.G., Zildjian Cymbals) and even the barring of rock-stardom to homely female performers (I.E., the Janis-Joplin-wouldn’t-have-made-it-today assertion).   I can’t really say that this changes the argument, but it’s worth consideration.

“PRR” also has a number of charming anachronisms, such as the diagram above.  The authors felt it necessary to explain how a group should properly stage their gear on BOTH of the common types of stages: the theatre-type stage (band faces the audience) and, of course, the round stage.  Wow.  Were rock-shows on round-stages really that common in 1967?  I’ve performed probably a thousand shows since the early 1990s, in venues as small as basements and as big as 10,000+ festivals, and never once on a round stage with the audience on all sides.  Crazy.

Perhaps the most interesting thing about “PRR” is the subject that it totally omits: there is nothing offered on the subject of recording.  Not demo recording, not studio recording.  No mention.  Also lacking is a chapter on promotion and publicity.  To most musical groups today, these seem to be the central issues that occupy most of their energy:  thanks to all of the incredible, affordable audio-recording equipment and software we have now, recording and composing music have effectively become the same task; they are inseperble activities.  Likewise, the public promotion, marketing, and branding of a musical project can now begin as soon as the first track is mixed down.

*Is there a similar book to “PRR” published for the modern musical era?

*If a high-school age band were today to study and implement the ideas in “PRR,” could they generate a 1968-type garage-rock group?

*Did anyone reading this purchase “PRR” as a young musician?  Did you find it helpful?

Next up in this series: “Making Four Track Music,” John Peel, 1987.

The Tascam Series 40 tape machines of the 1980s

Download the complete twelve-page Tascam Series 40 catalog, c. 1984:

DOWNLOAD: Tascam40series1984

Products covered, with extensive text, specs, and photos, include: Tascam 42 1/4″ stereo tape machine, Tascam 44 four-track 1/4″ tape machine, and Tascam 48 1/2″ eight-track tape machine.

above: Tascam’s various data recorders of the early eighties. 21-track 1/2″ anyone?

Tascam helped create the category of ‘home-recording-studio’ in the 1970s with their 4-track reel to reel machines.  The 3440, Teac 3340, and Tascam 40-4 and 80-8 tape machines were the backbone of thousands of home studios and project studios.  This line-up was improved in the 1980s with the introduction of the Series 40.  The Tascam 42, 44, and 48 tape machines offered better performance than the older models, plus standard features such as balanced i/o, varispeed, and confidence monitoring (IE, they are all three-head decks).  The battleship-grey finish of the series 40 lets you know that these are commercial/industrial machines, and the 70/80 lb weight reinforces that idea.   (N.B. – Tascam also offered a series 50 with even better specs; i have no direct experience with these machines tho…)

The Tascam 48

Many years ago I inherited a couple dozen pro reel-to-reel machines from a media company that had updated to DAT.  Otari 50/50s, Tascam 22s and 32s, Technics 1500s, etc…  The best unit of the bunch was a Tascam 44.   The operational characteristics and sonics of that machine were incredible.  It is long gone now, like all the others, sacrificed to pay-the-rent in late 90’s Williamsburg.   It’s one of the few studio pieces that I really regret selling.  I don’t think I would ever go back to analog tape as a working production format, but as an effect of sorts analog tape has a quality that nothing else can deliver.  Just yesterday I was in the studio with E’s Marantz dual-cassette deck, bouncing some submixes onto a Type 1 Sony cassette and then back into Pro Tools, trying to get just the right amount of high and low end breakup.  I got it right after about ten attempts with different level settings.  A three-head machine would have been very useful in that situation… especially one with varispeed.

Anyone still using a Tascam 44 or 48 for music production?  Drop a line and let us know…

Martin Electric Guitars of the late 1970s

Download the four-page c. 1979 Martin Electric Guitars catalog:

DOWNLOAD: MartinElectricGuitars1979

Models covered, with text, specs, and photos, include: Martin E-18 electric guitar, EM-18 electric w/upgraded electronics, and EB-18 electric bass.

The 1979 Martin EM-18

With their entry in the ‘Hippie Sandwich’ runoff of the late 1970s (see: here, here, and here, to name a few), Martin got into the solidbody electric guitar fray for a few years.  I have never played one of these; anyone?

One example currently on GBase for $1.5k.

The Williamson Amp, part one

The original Williamson hi-fi amplifier schematic as published in “Wireless World” magazine (UK) May 1947.  

The Williamson amplifier is considered one of the earliest hi-fidelity audio amplifier designs.  It is certainly one of the most popular audio circuits ever developed for DIY’rs.  Without fail I seem to turn up at least one home-brewed Williamson every year at the local estates+fleas.  A PS Dot Com reader from the UK sent us the original articles from “Wireless World” as published in 1947.   I have yet to build a pair of these myself, and the idea of starting ‘from the top,’ as it were, with the original design, is appealing.  A few things to note: check out the provision to balance the driver stage, and separate bias level and balance controls for the output stage.  Also: check out R25: the formula for determining the feedback loop resistor.  I wish every schematic included this notation.   NB: the ‘L63’ valve is simply a 6J5 – aka, one half of a 6SN7.  the ‘U52’ rectifier is a 5U4 or equivalent.  ‘KT66’ is a better-performing 6L6; feel free to use 6L6 or 5881 if necessary.

UPDATED: The Very Early Magnecord SD-1 Wire Recorder

Courtesy of PS dot com reader H. Layer come these images of his Magnecord SD-1 wire recorder.  Magnecord ran a respectable second to Ampex in the development and proliferation of professional audio-tape recorders in the Unites States in the 1940s and 1950s.  You can find a tremendous amount of information regarding the various Magnecord tape machines on (you might want to start here), as well as many recent recordings that I have made with my Magnecord PT6 machines.  Anyhow, it is a small but important footnote in Magnecord history that their first attempt at a recording device was not a tape recorder but instead a wire recorder.  H. Layer relates the following:

“Years ago I acquired Magnecord’s only wire recorder, the SD-1.  After considerable research, I found out that Russ Tinkham (Ed: one of the four founders of Magnecord INC) was retired and living quite close to me …he was delighted to see the SD-1 after many decades and we became good friends. Photo of my SD-1 attached.”

SD-1 aspect fixed_B_100LAbove: helpful reader Art Scifrin provides come additional information concerning the SD-1.

Low-Budget Ribbon Mic Listening Session

In several of my previous posts I have expressed my love for the humble Ribbon Microphone.  Ribbon mics were invented in the early 1920s and they have remained pretty much the same in the majority of cases.  They remain one of the simplest ways that sound pressure can be reliably changed to an electrical signal.  When I started recording music in the early 90s, ribbon mics were not very popular.  Classic models like the RCA 44 and RCA 77 were still often used in major studios, but home recordists and smaller studios with some budget were much more likely to use Neumann and AKG condensers and the classic Shure and Sennheiser dynamic mics.   Aside from the Beyerdynamic ribbons (and the elusive Fostex ribbons) there just weren’t any new ribbon mics readily available.  At some point in the early 2000s this situation changed dramatically and there are now a good variety of new ribbon mics available at all points in the pricing spectrum, from $60 up to several thousands dollars.  I regularly use a variety of mid-and-upper-range ribbons in the studio, and I have also found myself in possession of a few of the cheap ‘budget’ ribbons currently on the market.  In this previous post, I went so far as to replace the output transformer in the $69 MXL R40 with a better ($23) transformer and the results seemed promising.  Anyways…  seemed like it might be a good idea to do a quick test and find out just how the el-cheapo ribbon mics compare with a thousand-dollar unit.  Cos you never know until you try…

In the image above, you can see (CW from upper left): the $1,300 Royer 121, the $59 Nady RSM-4 (n.b.: now $79), the $92 MXL R40 ($69+ $23 for an EDCOR output transformer) and the $220 Shinybox 2.   We set up all four mics on shockmounts in a cluster about 8 feet in front of a drum kit at Gold Coast Recorders.  The kit was a sixites Ludwig 22/16/12 with a 14×5 wood snare; cymbals are dark sixties Zildjians and the heads on the drums were all fresh.

Above: preamp gains required to deliver equal levels off each of the four mics:  Royer is at 6.5, Fathead II is at 7, MXL is at 6, and Nady is at 7.

Each mic went direct into an identical Sytek mic preamp and then right into the Lynx Aurora convertor.  No other processing was used.  Mic preamp gains were set to show the same level in pro tools.  Tim Walsh, a fine drummer and recordist, delivered a compelling drum performance and then we listened to the results.   This is obviously not a scientific test, and you might not even be personally inclined to use a mono ribbon mic as a front mic on a drum kit; that being said, a drum kit produces the most dynamic range and the greatest range of frequencies of any instrument, so it seems like a good way to get a quick handle on what one mic sounds like versus another mic.

Here are the audio files.  They are MP3s, but you can still get a pretty good sense of the sound.  Try to listen with good headphones or a system with real low-end; you will hear tremendous differences.

Royer 121: Royer_121

Fathead II:Fathead_II

MXL R40 with EDCOR Transformer: MXL_R40_w_edcorTrans

Nady RSM4: Nady_RSM4

Out thoughts were as follows:

Royer 121: Sound is tight.  Low end seems understated.  The kick drum barely activated the sub in the GCR control room.  Seems like some low end is not being reproduced.  On the plus side, this mic brought out the body of the snare best.  The snare felt much more three-dimensional.  There was a good overall balance of kick, snare and hat.  The noise floor was very low, barely over the noise floor of the (very quiet) preamp and convertor.

Fathead II: HUGE sub-bass.  Exaggerated, in fact.  The low end that you hear here was not present in the room when we made this recording. That being said, it sounded good.   Somehow this mic is adding a ton of very low end.  The high end is also slightly hyped – the cymbals have more shimmer.  The snare seems to have no body – the snares themselves are prominent but the tone of the shell is missing.  The toms sound much more prominent and present with this mic.  Noise-wise, it is pretty quiet, although there is a very very slight hum – sounds like 60hz.

MXL R40 w/ EDCOR transformer: Much more bass response than the Royer, although this sub-bass is deeper in pitch and less prominent in level than the Fathead II produced.  The kick feels very present and in-your-face; the rest of the kit feels like it’s on a slightly different plane further back.  Noise-wise this mic was the best: it is absolutely dead quiet.

Nady RSM4: This seemed to split the difference between the Royer and the MXL.  The Nady puts the cymbals much more forward then the other mics.  Noise-wise this mic was by far the worst, with a prominent 180 hz hum present.

Listen closely and draw your own conclusions.  My takeaway: the modded MXL R40 is gaining a permanent place in the studio mic locker, along side ribbons costing as much as 20x its modest price.  And I am not going to be putting the Royer on any source that needs to deliver real low-end in a mix.

You can buy all of these mics online at a variety of retailers.  I purchased my Royer at Vintage King, the Fathead II came from Sonic Circus, the Nady and the MXL were both purchased from Musician’s Friend.  FYI I have no idea if these places offer the lowest price or not.