Contact us / F A Q

I cannot offer gratis technical support at this time.  For other inquiries you can reach me at Chris at PreservationSound dot com.


If you have some old audio item and want to know ‘what is it worth?,’  your best bet is to examine the ‘sold listings’ on eBay for similar items. That’s where I start,,,


If you want advice about how to do develop the skills necessary to scratch-build and repair tube-type audio equipment, I can’t offer any to you.  There are a great many people for whom this is just not-for.  It’s a frustrating, difficult, dangerous, and fairly expensive endeavor to train one’s self in.   On the other hand, you might take two years to get-to where I’ve gotten in over a decade.  I just don’t know, so I am not going to offer any advice on this subject.

That being said, I can share with you how I developed the skills that I have.  I was in a rock band that toured a lot.  We used big vintage Fender tube amps.  They would sometimes need servicing, and at the time (circa 2003) the tube amp repairmen we could find in NYC were expensive and/or unpleasant and/or incompetent.  We had a few bad experiences, so one day in Nashville I picked up an on-sale copy of Aspen Pittman’s “The Tube Amp Book” at Valley Arts for $15.  I figured it was worth a shot seeing if I could fix my own gear.  I read the book over and over again that tour.  When we got back, I bought a basket-case Tweed Gibson 50 watt amp on eBay for $120.  I had basic soldering skills (I had built a few science fair things and a PAIA theremin kit as a kid) but that was it.  I read a few blogs and it seemed like the Fender 5F2A Princeton was a useful amp that was a good ‘beginners’ project.  So I decided to use the chassis and as many other parts as I could salvage from the Gibson and make a 5F2A clone.  It took about a month, and it worked but it sounded fkkn awful. So I did it again, this time with a fresh Hammond aluminum box.  This one took about A YEAR.  It had a parasitic oscillation problem that literally took a year to figure out.  But once I squared it, it sounded pretty good!  So I built another one.  And another.  Now it was getting easier.

I moved on mic preamps.  I started with the RCA BA2C because it seemed simple.  I think I got lucky and I figured that out pretty quickly.  So then I started trying anything I could – Tremoluxes, phono pres, power amps, more mic pres, compressors, ETC, ETC, basically whatever I could make that did not require fancy custom-would transformers or inductors.  There were many successes and some very frustrating failures.   And all along, as I was making all this stuff (probably around 200 scratch-built pieces at this point), I was buying any and every cheap (under $30) old tube amp I could find and either fixing it up or parting it out if it was too effed.  Once I fought my way through a few hundred old chassis of every stripe, I had been exposed to pretty much every layout, wiring, mechanical, and related non-schematic quirk that actual trained designers used in the original tube audio era.

I bought decent tools, I use a temp-controlled Weller soldering iron, I have basic multimeters and a $300 scope and some decent basic audio test gear.  I use a solder-fume extractor and safety glasses whenever I work.  I buy most parts from Mouser, Antique Electronic Supply, EDCOR, and Jensen,  and most tools from MCM electronics.   I try not to read too much commentary online because the internet is simply not a reliable source of information; instead I bought hundreds, maybe thousands of old issues of Television and Radio Repair, AUDIO magazine, the AES Journal, etc., etc.  Primary-source documents, essentially.  The internet is, however, useful as a source of schematics, and I have downloaded and/or screen-captured just about every single tube-amp schematic I have ever seen – many thousands – I and I keep them all indexed on my macbook and always take the time to study every one of them looking for new (old) ways to do things.  I don’t fully understand all of them yet, but maybe I’ll get there someday.


Thanks and have a great day.

145 thoughts on “Contact us / F A Q”

  1. Had a reel to reel in high school/ recorded regularly off the TV( American Bandstand). Hooked up wires to the tv speakers and jacked this into the tape recorder. Still have the tapes/ brought the tape recorder to parties as a music source. I guess I was one of the first DJs.

  2. Hi,
    I’ve discovered on a fly market a “Brush Sound Mirror” reel to reel, probably a BK401.
    It seems to be in good state. I want to restore it as carefully as possible.
    My work should be more easy if I had some technical information about the machine.
    Do you think that I could find the user manual, service manual, schematics, etc… ?
    Where ?
    Thank you very much if you could help me to find sources of information.

    1. Hi Jamie. thanks for writing. as i explained in the article, the unit is simply a combination of the BA2 and the OP6. I don’t have a complete schematic drawn; but you really don’t need one… just join the input stage of the the BA2 (up to the output wiper of the volume pot) to the OP6 (from the grid of stage 2 on out). be sure to add a 1M resistor from the grid of stage 2 to ground; isolate this from the volume pot with a 1K resisitor. You can use the power supply from either unit;you should also use DC filament supply. Good luck. the piece sounds really awesome; it’s worth the effort.

      OH BTW also… since it is a 90DB gain preamp… there is SOME hum at high levels… so would recommend using the Jensen triple-sheilded inoput transformer rather than the basic 115 transfo that i used.


  3. how many IPS does the Fostex A-8 (8track) record I have tapes i want to digitze and all studios are asking me what speed it was recorded at.

  4. Have an interesting horn, not sure if it came from gramophone (cast), or logging horn. Thank You I will send pics if you give the go ahead

  5. Hi,

    I just came across your terrific site while trying to find some information about an old microphone. I have an Electro-Voice model 664 serial number 181415. I’m trying to buy a desk stand for it. Apparently something called the stud size changed in 1968. If I have the pre-1968 version then I can use a 418 base. Otherwise, I need the 419. These are not cheap. They’re running between 75 and 150 dollars on eBay, so I want to make the correct choice. Anyway, thanks in advance.

    Shawn Rosvold

    1. Hi shawn. I don’t have an idnex of EV serial numbers. Can anyone else help shawn out? I can tell you that in my life i have only see 3 different sizes of professional-mic thread-sizes, and couplers to adapt them all are still avail cheaply; try BSW, marketek, full compass, etc… good luck…

  6. I can’t believe a site like this exists! Older gear has fascinated me ever since I found a Foxx wah and Fender Bandmaster amp in a barn about 25 years ago. Old gear takes me to another era. Thank you so much for this site!!

  7. I have a pair of Bozak ls330a speakers that have a 1 and 2 on the back for speaker hookup. My question is which one would go to the + or – on the receiver or amp

    1. Mark: I have used the following technique in the past. You will need to visually see the actual speaker cone in order to do this. Attempt at your own risk.

      “An old trick is to take a 9V battery and connect it to the guitar speaker (9V won’t hurt the speaker if connected momentarily—–connect each pole “+” and “-” to the speaker connections—i have a 9V speaker clip with two alligator clips made up for this purpose) — the speaker will move In or Out—- the speaker connection that is connected to the “+” 9V battery pole, when the speaker moves Out (away from the magnet)— this is the Pos speaker connection.
      The same 9V battery trick can also be used to check if multipule speaker cabs have all their speakers connected “in phase”— connect speaker cable to cab and then connect 9V to the Tip and Sleeve connectors of the speaker cable plug—-see if all speakers are moving in the same direction—–then put the back panel of the 4×12 cab on and jam out…………………..gldtp99″

      1. I have used this idea with a 1.5 volt “D” cell & “C” cell also. If you cannot get access to the speaker cone itself, try taping a piece of tissue paper of some kind onto the front of the speaker grill. Then momentarily touch the positive side of the battery to the wire. You may have to do this several times to be able to see the tissue paper move, however when it moves “out” a little, you will see it, and there you have the + connection! Good luck!

  8. HI since 1983 I have. A recording studio, and its still my livin’ I workt for manny years with an DDA console, the sound is O K, bud now mi console is starting to make strange noises, and a lot of hiss, I wont to by a new one, but DDA is not longer available.
    A good friend of mine told me that the sound of an LOFT console is amaizing, so now I wont to by a LOFT CONSOLE, bud a. New one, my question is can you send me the link to a website, ore can you mail me something about a new LOFT console,
    A S A P , because now I can’t work, thank you

  9. Hi I’m Frank Santa.saludos from Barcelona, ​​I have some time here in my workshop a strange and beautiful machine that we know very little that comes from the EMI studios, a noise suppressor, full of good Brimar valves type 6060, Mullard logo 50’s ECC88-pin gold, Marconi EB91, EAA91 and several Mullard 0B2, transformers manufactured by EMI type RSA12B, RSA28C for years looking for information about this device works properly, so if it were possible to work with in the context of current recording studio if anyone has information about this I would appreciate knowing the make.
    Thank you very much for your time.
    Best regards. –
    Frank Santa.

  10. Hi Chris,

    Just wanted to say thanks for very interesting content on this website. I’m an audio student in Vancouver, Canada, and I’ve found your articles to be very relevant and often inspiring in my learning of the recording process. Thanks again!



    1. Rudy
      Have a Fairchid 641 Stereo cutter system with a VanEpps overhead
      carrier with a regulated Bodine Variable Pitch drive, a Fairchid 750-2
      turntable (33,45), Fairchild console stand. The 641 system (Serial #2) was retired in 1983, in great working order. Have Lp album pressings to
      attest to its perfomance. It is in storage and was never replaced.

      would be interested in talking with anyone –

  11. I’m the original owner of a pair of JBL L45 Flair speaker systems & would like to sell them at a fair price directly to someone who would appreciate them.
    The aluminum speaker frams are intact. The foam, as with all of them, has disintergrate but I had them covered with auto speaker material.
    I’m in the Tampa, Fl area. My email address is

  12. Hi I have built your Marantz 7 preamp phono and line stage. The rest of my system is Marantz CD 10 Technics SP 10 MK2 with Jelco tonearm and Denon 304 with sowter step up transformers. My power amps are Western Electric 91a with 300b tubes, and speakers are Lowther PM7A in Mauhorn 1v horns. sounds very musical.
    Regards Peter.

    1. that is great Peter! I am about to start my second Marantz 7 phono pre now… once i get a couple of other things off the bench. c.

  13. I have an Kustom K-150-1 amp, serial #90905 and I need to replace the speakers in it. Does anyone know where I can find the proper specs for the speakers I need. I got it when I was trying to recover from a severe head injury in 1977 (used) and it has an immense amount of sentimental value to me and I want it to be “right”. I would really appreciate any help. Thanks.

  14. YIPPeeeeeeeeeeeee!!!! Hot Da@# Dog!!!! Finally!!!!….thankx a mil Chris
    WE are a ‘GO’ mission (scully 280 ct)

  15. I have a pair of 1970s Rola celestion G18z-200 i have no neef for if anyone is interested call me on 07952177920

  16. Buongiorno,
    sono in possesso di due diffusori “university Sound” modello “brillance” funzionanti.
    C’e’ qualcuno che può essere interessato? Quanto può essere il suo valore? A richiesta si invia foto degli stessi.
    Ringrazio per l’attenzione cordiali salutiù
    Morello Gian Mario

  17. Hi Chris, I thought I’d mention that I’ve been having trouble loading the pages. Seems a few weeks back the pics became very enlongnated. Loving the stuff your posting. I’m a Hammond organ nut. I wondered if you’d ever poked around with them?

    1. hi keith. thanks for letting me know. Yeah WordPress changed a bit recently re: file uploads, and it now seems to want to default to incorporating full size dimensions rather than default scaling the images to fit the wordpress column width. It sucks. I’ll try to be more diligent about this. on my Mac it looks fine, so i had not realized. so thanks i appreciate the feedback.

      I have two hammonds – an L101 and an A100. Both are tube/tonewheel organs, the A100 is a B3 with built-in speakers and reverb system, otherwise identical i believe. L101 is a ‘spinet’ model but it has this great psych-y effects board built in that makes it still a worthy contender. I’ve worked them a little bit, changed a few tubes, caps, switches, etc., but nothing major. They both work great and use them on most projects at Gold Coast. c.

  18. I have four Tannoy PA speakers, Model SD5 they are approx. 3ft long with an 18in. square bellmouth. I would like to know what age they are and if they have any value.

  19. In the mid 1960s (1963-1965) I purchased a Pilot Gerard phonograph Model #XKE 1000 Suitcase carrying design. I still have it in my possession and it is in excelent condition. I could not find this model on any of your web pages and Iam wondering if this products has value to a collector.
    Sincerely, Kurt Gottschalk

    1. I took one of these to college in 1965. My father bought it for me at Sam Goody in Manhattan. These were made at the same time that KLH Model 11 were selling like crazy- I think the Pilot was about $ 20.00 less. The KLH portable was a real classic and most of the other units that tried to capitalize on its success never achieved similar sales or status. Its almost impossible to come across The Pilot imitator these days but I doubt that will contribute to its value. For sentimental reasons a few of us — myself included — might wish to add it to their collections but I doubt any of us would pay much for it. Just like the case was in 1965– the KLH remains the one to acquire and collect. No one could do the speakers like Kloss

  20. Hey there,

    Big fan of your blog and your knowledge of all things old and audio. I was wondering if you did repairs? I have a Moog Parametric EQ that needs to be revitalized? The last guy didn’t have the proper testing instruments. Something you might be able to help me with? I’m located in Bridgeport.

    1. hi matt. i specialize in servicing vacuum tube-based equipment. I could prolly fix yr moog but i might not be the fastest or cheapest option. you can find plenty of dudes who can repair solid state stuff… many people around here use Audio Nexxus in milford for that sorta thing. See ya round town …. c.

      1. Thank you, Chris! I’ll give them a call. I also have an Altec 1567a with the transformer extender that could use some TLC. Do you have a good source for reasonably priced Altec transformers? What are your rates for repairs?

  21. Halo
    do you know what kind of tape the schaller echo reverb machine 2000 use.
    and where to get it.
    my tape is broken 🙁
    best regards

  22. I was looking for info on D-104 heads and found your page. I saw your collection of heads. I have a bullet shaped haed that’s designated as a “10C” and is a high inpedance crystal head in a bullet head. I’ll send a photo when I find it. Thanks for the info.


  23. I have 4 Altec 9849-8A speakers and want to know more about them, and how much they might bring on Craigslist. We got them from our local church sometime in the 80’s.
    They have a great sound and seem to be intact. Thank you. Roxie

    1. my $.02: start ’em at 85% of the average eBay sell price and then drop the price each week until they sell. Every market is different.

  24. Hello! Im thinking of buying a shure mic model 55s or 556s can or is it possible to have this repaired thank you.

    1. Hi Edwin. Anything is possible, but I would under no circumstances knowingly buy a non-functional 55 or 556 if you actually want it to work. If the transformer or switch is damaged, then yes it’s pretty easy to fix. in all likelihood, though, it is the actual element that is damaged, and repairing it would require retrofitting another modern element into the mic cavity. Costly, and also, it won’t be a 55 or 556 at that point!!! Save yr money and buy a working unit is my advice. Anyone else wanna chime in?

  25. I have a primo mic model UD863 with a bass rolloff switch marked 0-5-10 and a slide switch with 600ohms/50k ohms. this mic also has a metal case and mic stand adaptor combined. There seems to be a part # of 85892, but that may be just for the casing and adaptor, I really don’t know. It also has a Japan engraving on the case. Can anybody help me date and spec. this mic? thanks scott

  26. I have just purchased a 1970’s solid boby commitee guitar madr in USA, with original case. Model # 7628 Serial # 4-9136. The guitar is in near prestin condition, and the shows it’s age but still lock and the Gretch name on the case is still very readable. The pick gaurd is smoked brown. Question, was it a good buy, are a good investment?

  27. Hi there,

    Do you have any idea what console this might be? It’s from Byron Lee’s Dynamics Studio in Kingston, Jamaica, 1972. They had just sold their 4-bus MCI console to a certain Osbourne Ruddock and upgraded to 16-track to accommodate the Rolling Stones and other international talent. I believe the studio was loyal to MCI but I haven’t been able to identify this desk.

  28. Hi,
    I have been involved in audio as a youngster in the 50’s to today.
    Besides owning lots of early gear, much lost to a flood, I have much of the Audio Engineering and Audio Magazine early publication. I have had a few people interested in purchase to “cut up” and sell on ebay. I want to know if anyone has archived much of this great magazine for the public to use. Does anyone know of a site with back issues of Audio magazine from the late 40’s, 50’s, and 60’s ?
    If one can not be found, I may need to keep these magazines and someday post them on a web site.
    Any one with information about this, please leave me comments.

  29. See:


    Most of the better tech articles in Audio Engineering /Audio magazine were reprinted in seven Audio Anthology compilations, six of which were reprinted by Ed Dell’s Audio Amateur Press/OCSL organization.

    Anyone into vintage tube audio should have the full set, which are still available from a few sources new.

  30. I have personal experience using the GE BA-5A limiter. It has an audio delay line in the audio amplifier channel that uses two inductors and two capacitors that create a phase shift as the frequency increases. The side channel that develops the control voltage for gain reduction uses a low impedance voltage generator using a push-pull cathode follower into the rectifier tubes.This results in a faster attack time and because of the audio phase shift, the time constant circuit delays become negligible. The result is extremely fast attack. I love this limiter because it uses feed-back limiting as opposed to variable-mu and the sound is extremely “transparent”. It has a 10db compression range but it is enough for a final peak limiter when a good agc amplifier is used ahead of it.

  31. Hello, recently a roommate left me a 280 Scully 4-Track that I am assured runs good but just needs a missing pinch roller replaced. I’d be happy to let it go for a low price to anyone in the NYC area who’d like to pick it up. Please let me know if you have any feedback where I might reach out? Many thanks!

  32. I know that El Maya guitars were possible to buy in Germany during mid 1980’s and far as i know since the end of 1970’s, later they change the name in Solton but the guitar were the same at least during that time period, i have El Maya 1300 and it is much better than any of my Gibson, Fender and Jackson i own, anybody have any idea were i can maybe find some of those old El Maya guitars? somehow i get feeling that this might be the right place to ask, if not than sorry, thanks in advance and friendly regards from M.

  33. I am looking for any University Sound x-over schematics, but one in particular for a 3-way system I built in 1966. I recently opened the bass reflex box to replace original capacitor(s). What I found for components was (2) 60mfd caps soldered in series (2) L-Pads, and (1) University N-2B per speaker. That’s it! I am questioning the two 60mfd caps soldered in series. I’m not sure that, as a 19-year old, I really knew what I was doing. All paperwork is long gone. Worst case: I replace the caps wired as they are now.
    University Drivers: HF-206 Horn Tweeter, Diffusicone Eight Series 200 8″ Mid-Range, and C-12SW, adjustable response, dual voice-coil 12″ Woofer.
    Any and all help in my quest will be gladly appreciated. Thank-you. -Richard

  34. My father-in-law has a Pilot Hi-Fi Tower system. Model 4042683, s/n 665984. It has tags on the chasis MAG527. He is in need of a power supply complete with the circuit board that it mount on. Do you have any idea where a person one? We’re located in Phoenix, Az. if that of interest.

    Thanks for any help

  35. Love your site! I grew up with a pair of Medallion XII’s, paired with a Dual 1019 Turntable and a Bogen RT 6000 receiver. I currently have a pair of ca 1975 University “Laredo” cabinet speakers, in xlnt condition. I’m wondering what is the best forum in which to sell them, and what I might realistically expect to get for them. I’d be grateful for any advice. Thank you!

  36. I am looking to sell my late husbands disc recording equipment. Is there anyone out there that would be interested?

    1. Hello Mary,
      I would be interested. Do you have a list of gear you could forward to me via email?

  37. Hi,

    I’m trying to get some info on the Kenwood 31, 51 and 71 headphones so as to see the difference between the 3 of them and also their price when they were sold. What did one have more than the next. Why have 3 different headsets if all of them offered the same performance? Thanks for the info!

  38. I have a pair of PVC-4 Pilot speakers which i just acquired and am looking about getting an amp or stereo to power them and to use them. If any one can help me or lead me in the right direction that would be great. Thanks

  39. Hi, I’m Spanish so forgive me if my writing is not quite correct.
    Would need to know where I can buy a mic stand exactly this.
    thank you very much.

  40. Wondering the value of 2 Altec Lansing columns 1207B along with an Oliver PA-100x head all in excellent condition. I would put it all circa 1971-1972. Thanks!

  41. Hi I am looking for some plans or info on cabinets made that carried the RCA inscription in pencil dated 1935. They were 2-15″ front loaded horn “W” cabinets

  42. Hi Chris was wondering if you could help me i want to sell 2 recorders
    one is a TEAC 6010 SL Stereo Tape Deck…the other is a
    Magnecord 1028 -24
    both are in good condition and was wondering what i could get for them?
    I really would appreciate your help!
    Thanks Mike

    1. Hi Mike. Ebay “Sold” listings set the valuation for pretty much all sound equipment. Use that as a guide. That’s what I do. c.

  43. Hello, I am looking for Presto magnetic tape recorder SR11 transport and electronic schematics. I just bought the complete console and I want to refurbish to put it back in service to get the original sound.
    Can you help me to get the schematics?

    Thank you in advance,
    Kind regards,


  44. Would you know where I could get a transformer for a red knob Sunn Concert Bass amp?
    Thanks – Tim

  45. Thanks for all the great history on your site! Proud to say I just purchased an sp6. Can’t wait to learn more about it! Plan on using it for tracking .

    1. That’s great Jasen. Watch out for those push button switches. They need frequent cleaning. The board has phenomenal performance, you will be very happy. The noise floor is astonishingly low and there is a ton of headroom.

  46. Hey Chris, Loved the spring reverb suggestion using a headphone amp. Could you conceivably do a stereo version using Y cables or would it be best to use two separate headphone amps? Thx for the great insights. -Scott

  47. Hello
    I’m searching for information of Andy Lauren.
    I found a record with hand written title on a 7 ” acetate Reeves Soundcraft record.
    songs: Like a baby / Southern love.
    I can’t find a thing about him but that there are 2 singles.
    Andy Lauren with Jamie and The Domains 1965
    Alpine Records Cleveland Ohio
    R & R Teen
    1965 – Louisville at night /The story of my love
    1967 – Love me tender / High on a mountain 1967 – Issued with ps(whatever this means)
    Is there anybody who knows where I can find information.
    Joop The Netherlands

  48. I have two Presto Orange seal discs un-cut in the original box that stored 10. Is there anyone interested in buying them?

  49. I’m a little late to the party, but wanted to drop you a note to say, ” Thanks!” and keep up the good work. Enjoying your Instagram feed as well!

  50. Hello. I fully respect and appreciate the work that you have put into this site and your videos. It is hard to find others that are interested in vintage audio and recording. Thanks for all that you do.

  51. Hello,

    I have seen your video where you make a “simple” spring reverb unit with just an Samson S-amp headphone amp and a Accutronics springreverb tank. Great idea an great sound!
    Because i have the same Samson Headphone amp i would like to make my own reverb unit to.
    The output impedance of the S-amp is 100Ω per channel. What would be the best reverb tank (input and output impedance) to match with the S-amp. What did you use in your video?

    Kind regards!

    I v.d. Heide

  52. I discovered your website via your Facebook page.
    Heck, you even have reference to the dark/goth/scary Multiphone cylinder “jukebox” that scared me when I was about 4 years old at the Cliff House in San Francisco.
    I have literally been into records since I was 3 and was given my first Symphonic portable mono player.
    I love and collect / hoard old keyboards, home recording gear, pro recording gear, disc cutting equipment, tape recorders and focus on portable consumer music players (mostly stereo phonographs and reel to reel recorders) from the end of WWII to the beginning of digital. But I have my share of cassette, 8 track and more obscure format players and media as well.

  53. hello
    can you tell me what companies made 20 inch bell bakelite horns
    I know that music master made the wood 20 inch bell
    if not who might you be able to direct me to

  54. Having spent some time in Chanute, Kansas, home of Kustom amps, I was very interested in the Kustom amp articles you had. Only a few miles away, in Neosho, was an electric guitar factory known as Holman guitars. Holman eventually morphed into Wurlitzer guitars, including the cultish Gemini. Then they went belly up. I understand Kustom made some guitars for a short while, too, possibly borrowing from personnel and ideas from Holman.
    Love your site.

  55. Carlos Moura Distortionless EQ

    I have just programmed it into LTspice

    Insertion loss approx 16.5db
    Max Bass Boost +3db @ 40Hz
    The other controls do not do much.

  56. I have a set of horn type 15 inch P A speakers that I acquired years ago. The drivers are marked “University Loudspeakers”.and with the letters SA HF. The conections are marked L1 & L2. Can anyone tell me anything about them. I hooked them to a 4 ohm impedance amp, and they worked great. I think the L1 is the + connection. Am I right?

  57. I have been looking for the Pioneer T-shirt for quite some time and stumbled onto this site. Are there still these shirts available? I had this shirt a ton of years ago and would love to have it again. The “My Components are Pioneer” Best shirt. I will absolutely buy some of these.
    Thank you in advance

  58. Hi there !
    we shared a bit of correspondence about our PTP REDD47’s last year. I am really pleased with mine – I use ’em on nearly everything.

    I wondered reading some other posts whether you ever had any success with your experiments with Germanium mic pre’s ?? ( from the RCA Hobby articles )
    I have a stack of Germanium trannys and am looking for a nice simple Germanium mic pre to add to my set up.
    Cheers from Leeds, England,

  59. Hello, I am looking for a GE BA6 B remote mixer Schematics.
    Can you supply? Know a link to? At what cost?

    Kind regards

  60. hi
    if i want to build a stereo spring reverb , do u guys think that i should get one 2 spring tank and one 3 spring tank , or one long and one short ? to get a wider sound ….or ?
    thanks !

    1. if you get two different tanks it might be best to use it in mid/side. It may not matter at all though, I have no idea how consistent the tanks are, so two of the same model might not even match well. They are so cheap, why not buy a few and see how you like it?


    I wish I had seen this Wheatstone SP-8 sooner. Several months after the ebay listing above had closed, I stumbled upon it while looking for a TV-600 manual. I contacted the seller right away (an e-recycling center), and he informed me that the console was destroyed. The 24 mono/stereo modules in the console and a box of extra modules were used for scrap metal. He had also found the power supply, which was similarly destroyed. That type of shit makes me very sad. I guess it’s true – you snooze, you lose. In this case, everybody loses. RIP beautiful analog console…

  62. Hello, I ve just purchased a really neat EAA Quest 1600 which is mid 80’s … unfortunatly this mixer comes with no power supply, the factory as closed, everybody is now dead, and it’s a quite rare mixer, I can’t find any information on the voltage to feed it …
    As I m always linked to your website when I look for esoteric analog mixing gear, I m taking a chance to ask you if you would have any information about that mixer series, just anything that could give me a lead to make it work again. It appears to be a kind of french studer mixer which is actually the kind of stuff you don’t want to trash for a simple missing power supply 😀

    Thank you


    1. Hi Ed, I have no idea, but any professional studio tech should be able to handle this for you. It’s not that hard to figure out if u know what yr doing. If you don’t know any legit techs, call a couple of major studios in your area and ask for a reco. good luck.

  63. Looking at the Presto 40A, The 3-pin balanced input connector looks exactly like our Australian 240V mains sockets!!
    Without knowing the actual dimensions, I can’t say it actually is one, but it sure looks like it.

  64. Hello Chris,
    last month, I heard your radio program on WPKN and really enjoyed it. The theme was psychedelic folk.
    Are you going to do any more shows?

    1. Hi Guido, yes i certainly will do more – if you want to know when, follow me on instagram -thats where i post abt the shows. c.

  65. nice pics of the premier 88 .I have the original schematics from the 50’s.Please contact me if you would like a set.Thanks

  66. I have a dual M462B Parametric Equalizer and am looking to make or buy a power supply…anyone ?

  67. Hello!

    I am now trying to understand how the emi RS124 works and I’m not sure what exactly does the 6CG7. I know the first valve (6BC8) stage is an amplifier. Its output to the 6CG7 grid is only the AC component. But what exactly does the 6CG7? Is it only for less distorsion? Does it change the threshold voltage seen by the diodes??

    Thank you in advance!

    Best regards,


    Thank you in advance

    1. The 6CG7 is a balanced output amp. It’s a crucial part of the system. Correct that the CCG7 received the AC component of the 6BC8 plate. This is the basic nature of R/C coupled amplifiers.

  68. Hi
    I recently found a 78 audition album recorded by my father around the end of the 40’s or maybe early 50’s (this is my best guess). It has a metal alloy core and some of the surface material has flaked off over the years. I have a friend who was able to rescue some of the sound from the album despite it’s rather poor condition. I was thrilled, to say the least.
    I have been trying to find other information about the album itself as well as your company.
    Any info you could provide would be wonderful.
    My father passed 30 years ago, so this was a rare and priceless find for me and my family.
    Were early recordings such as this spared or destroyed over the years?
    Thanks in advance for anything you can tell me about this 🙂

  69. Just wonder if you have ever come across any info on a company called M P Engineering? Founded by Mirko Paneyko about 1936, located in Fairfield Conn. and in business until sometime in the sixties.
    Related companies: MP Concert Installations, M P Television, M P Audio Corp.
    They built and installed custom Hi Fi systems. Also built tape recorders, televisions ans phonographs.

    1. Hi Joe. Yes, I have. Too late, unfortunately. I bought one of his amps for $20 in 2011 and quickly sold it for not very much money, as I failed to ID it and I did not learn about him until early 2016.

  70. Excellent site…and thanks for the good comments on Tweed Audio Equipment.
    My Facebook page on Tweed Audio – The History .. is building nicely……anyone with information or positive comments ,please feel free to add.
    Pete Gillespie ex : Tweed Audio Kelso. Scotland.

  71. The metal tag you affix to your custom builds is so very retro / cool and substantial. Have you considered affixing it to the chassis with something other than screws? Copper pop rivets, or blind rivets maybe.

  72. Hello Chris, just wondering if you’ve ever come across a Marantz Model 9 Prototype. I recently picked one up. Its a very interesting piece and Im being told by many that it was one of Sidney’s developmental pieces that was used to test transformers. It has 8 tubes and not 7 like the production models that are missing V2. The V2 tube was omitted for production. There are many differences between mine and production models. It has no serial plate but the chassis is stamped #9-6. Ill include my email below if you would like images for the site Id be more than happy to share them. I really just wanted to see if you’ve ever come across one and if not, wanted to let you know that one exists!

  73. I’m still using a vintage Heil Sound HM1200 console in my home studio. I currently have one of the best vintage console techs in Nashville checking it out and refurbishing it for me. I noticed an article on vintage Heil stuff and it asked readers to drop a line if we’re still using any of the old gear. I think this thing is awesome and was recently approached about a matching Heil multicord stage snake (the only known example still surviving). I’m going to try and get the set together and I would love to have it written about or photographed!

  74. Hi. So I have a record dated from 1947 a Reverend Moyer, I believe the spelling says. And history on the record?


  76. I have a similar ADM mixer to your BC-5 sitting in my garage. Somehow I have only one power supply. I even have a schematic of the mixer, but there is no mention of the power supply voltage or current. I was looking online for a replacement power supply and the schematic did not mention specs. Can you advise me on where to look?

  77. hey i just got what i waited for a pair of completely restored altec 436b compressors
    the mods made : all pots are stepped resistor 20 steps all controls the units have a jack on the rear to link them one is master one is slave / 2 pots on rear so ast to be able to fine tune the tubes so they are matching i have pics how do i send them. i will also have very soon from the same tech 2 ea matched kt ue 100 custom made by david manley. i think they are the only 2 in the world. drip is making a modern version in a 2 ch package. i might have gotten older but i still have ears.lolololol. my gear list is the list of who is who.

  78. I have only recently become aware of the significance of Langevin gear (consoles in particular) during the mid 60s. My father, Donald Trauscht, was president of Langevin from 64-67. He was hired by the owner (Ed Swanson?) at the time to get the company out of the red and back to profitability, which he did. Unfortunately my dad passed away very recently, and he was largely unaware of the legacy of the gear that was manufactured and used during his watch. I am trying to learn more about it. Any insight you have or resources that you could point me to would be much appreciated.

  79. Chris (wimconcern), Been reviewing PS site for several days now. Long enough, I don’t remember how I found it. I do a lot of tube work(>30yrs.), mostly guit.amps. Oldest unit was a 1947 P.Amp conversion to mic and guit. solo performance unit. Re-engineer many units. Seen a lot of design errors that cause failures; try to not perpetrate the fault. Sait grad’86 in BrdcstElectnx. Music since’65, bands and sound from ’70’s. Been digging on your ol’data schemes and articles. Helluva treasure trove. Just wanted to drop you a note and let you know I’ve enjoyed rooting through articles and ‘lifting’ (read transcribe) the occasional circuit I don’t have in my extensive schema collection. My bible-w/blue AudioCyclopedia. Other religious texts include D.Davis sound books (2), and some ’40’s ham radio manuals, as well as Aspen and Gerard. Ham opr. since ’74; took electronics test on tube xmit/rcvr schema. Thar’s a lotta sites for arcane gear, but yours has the most personal touch. Btw, love the de/re-construct end of the bus., and built the quietest, most insane gain 12″combo (Williamson) using 5871’s (real Tung-Sol). Dad uses 5881’s in his fender silver-face BandMaster, though his hearing is going and he doesn’t enjoy playing as much. Anyway…….. thx, nikk

  80. I recently purchased a Kustom 150-8 model with a serial # 67944 wonder if you could tell me when this amplifier was made???? has 4/10″ speakers thanks

    1. Jerry, this may help. Get hold of the blue book of amps. They have listings in the back for many co.’s year to s/n. Good luck. thx, nikk

  81. Chris, I have a SHURE 51 mic and am using it for ham radio. I am trying to find the impedance switch as described in the manual. Would you know if it Is under the black plastic plate at the base of the mic?

    Thanks for any help you can offer.


    1. Mark, it is on the face of the mic just below the grille. It looks like a slotted screw. It is surrounded with text ” L M H” indicating the three impedance variations. it may require careful De Oxit spraying to function reliably. Good luck.

  82. I have a Garrard turntable with a sticker on it that says it is a Model RC-4, but the spindle is missing. Do you know if other Garrard spindles will work on it and can you refer me to a source for buying one?

  83. Hi I had a question for you I’m thinking of having a Ba2 clone preamp made with 6j7 tubes and I was wondering what your onion of this style pre is?

  84. hello,
    I just bought a Telefuken 15A tape recorder.
    I heard the motor is noisy , may be in platter, or motor.
    Is it can fix?
    please show me how.
    Thank you

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