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    #31
    Originally posted by KC9UDX
    Now here's the funny thing:. I put the better 6SL7 in the Lowrey, and vibrato came back to life. But, I lost the portamentoness in the Glide. And, got a big pop on and both triggering and releasing the glide. So I put the weak tube back in and vibrato works again, but the Glide returned to proper operation. Go figure. So the tube socket was probably oxidised. It's funny how components age. If I had to use the good tube, I'd have a resistor she probably capacitor to replace, too. But all the old components work together.
    That is quite strange – not the tube socket being dirty, but definitely the glide problem being introduced by the new tube. I'd wonder if the new tube has some fault that was not detected on the tester. You could try another strong 6SL7 (perhaps one from the filter-amp section).


    Originally posted by KC9UDX
    Speaking of 6SL7, the book schematic shows the Quality Control amplifier tubes are 6SL7, but my organ in 12AX7. I originally assessed the year of manufacture early, probably 55 or 56. But I'm finding too many 1959 components lately, and the design change indicates the this is a later model.
    It definitely would be later than 1956 with the change to 12AX7, and of course the newer-marked parts. I have basically the opposite problem with my LS; the closest schematic I have is for the LSB, which already changes to all-miniature tubes (except the 6V6s and the rectifier), while my LS uses all 6SN7 and 6SL7 on the Quality Control chassis (plus two 6X8s). I'm still looking for a proper LS schematic. One funny thing is that "6SL7" is stamped into the quality control chassis above all tubes, including the 6X8s and 6SN7s!

    I wonder if there is a date stamped anywhere inside your SS. On my LS, there is a stamp in at least two places saying "NOV 6 1957". But my FL (from 1960 based on tube dates) does not have any stamps, at least that I've found.


    Originally posted by KC9UDX
    Like you, I have only found references to a Lowrey, and sometimes a DSO or DSO-1. Gary has a ton of knowledge and for all I know, he knows something everyone else doesn't. But I don't know what a Novachord is capable of, and I've seen people perfectly duplicate the sound on Lowrey organs.
    The Novachord can produce very beautiful and distinctive sounds, but I don't believe any of them are the right sort for Lucy. I will explain why I think so, while also explaining the function of the instrument in modest detail, since it is rather interesting. The Novachord is divider-based – the earliest divider-based instrument that I know of – but those dividers produce asymmetric waves instead of squarewaves. Looking at the circuit and listening to the sounds, their shape is probably sawtooth-like, but rounded, hence without as much high-frequency content as proper sawteeth. All of the Novachord's sounds are rather mellow, regardless of filter settings. I don't believe it can produce a bright harpsichord-like tone, nor affect such a tone with the appropriate kind of volume envelope, considering what I am about to explain with the control circuitry.

    It uses electro-mechanical vibrato oscillators – 6 of them, each controlling 2 adjacent master oscillators, in order to avoid all notes modulating in phase with one another, and to have slightly different vibrato rates between notes, making for a chorus-like vibrato effect notably richer than typical divider instruments. But really the most remarkable feature of the Novachord is that each key has its own "control" circuit, which imparts a volume envelope on that key's tone. This envelope can be anywhere from a very brief percussive one with near-instantaneous attack and quick decay to silence, to a slowly-attacking and fully sustained tone. In fact, these envelopes are basically of the "ADSR" type made popular in later solid-state synthesizers, though the individual parameters cannot be controlled separately. I don't think you can get a harpsichord-like envelope, because no setting has the combination of instantaneous attack, slow decay, and zero "sustain" level. Whereas this is exactly what you get from playing a Lowrey in long sustain mode with staccato technique. Anyway, if you're interested, more detailed info on the Novachord can be found in Electronic Musical Instruments by S.K. Lewer (published 1948), which I have scanned and uploaded here: http://crasno.ca/articles/doc/EMI_SKLewer_1948.pdf

    Here are some good example of the Novachord's sounds:
    https://www.youtube.com/watch?v=dMEuibX4c04
    https://www.youtube.com/watch?v=TwxmHZaYORc
    https://www.youtube.com/watch?v=Rm3RBAZChrQ


    Originally posted by KC9UDX
    I wonder what difference those different filters make for this sound.
    For the Harpsichord, no difference, because only the string amplifier is used, which effects no filtering at all. I will explain further down. The difference would be in the flute tone, which uses those low-frequency filters for sufficiently removing harmonics from the low-frequency collector groups.


    Originally posted by KC9UDX
    I also kind of want to drag an oscilloscope into my music studio to see what those filters are actually doing.
    I would like to do that some time also. But for the time being, I rely mostly on the description of the filter-amplifiers of an early transistor Lowrey (model H) provided in Richard Dorf's Electronic Musical Instruments, 3rd Edition (which I hope to scan and upload some day). He mentions that the circuit topology is similar to a phase-shift oscillator, but without enough gain to self-oscillate. He built a copy of the circuit and tested it. In his words:
    "Below 'resonance', transmission is flat. As the nominal turn-over frequency is approached, response begins to rise, reaching a well-defined peak and then sloping off sharply. The height of the peak depends entirely on the gain of the transistor as an amplifier, which depends in turn on the transistor and on the value of some convenient component such as the emitter resistor."

    Of course, we just replace "transistor" with "tube" and "emitter" with "cathode", and the description applies just fine to our tube Lowreys. The question then is how much higher the typical resonant peak level is as compared to the flat section of the transmission characteristic. Dorf reports 8dB higher with his arbitrary transistor and a 470Ω emitter resistor, and no peak at all with a 15kΩ resistor. Another thing to emphasize here is that although these filters may have a resonant peak, their response does not roll off sharply on both sides – only on the treble side, while the bass side may still have significant transmission. This explains the lack of any very "nasal" or "narrow-formant-range" voices on Lowrey organs.


    Originally posted by Lazlo
    This is a very good thread as finally we're starting to see some real exegesis of the workings of these old tube Lowreys.
    I agree, it's been quite interesting so far. You may also be interested to know that soon I hope to publish an article on my site about my Lowrey "Holiday" LS, which will go into more detail about the inner workings of tube Lowreys than any source I've found!


    Originally posted by Lazlo
    And, their value is becoming increasingly appreciated by other organist, usually Hammond ones, who are starting to see their worth (maybe the tube Thomases will be next).
    This seems a little bit true, but really just for those few models that are very well-known, such as the DSO and DSO-1. Where I am, in central Alberta Canada, their monetary value is still quite near the trash mark, it seems, considering I got both my LS and FL for free. This is after they had sat around in plain sight for years in a local music shop, and despite that the FL has some prestige bestowed by Garth Hudson. They could very easily have ended up in the trash if not for my interest. I am just lucky that nobody around here is "smart" enough to scrap them for tubes and associated parts for stupid guitar amp projects, etc.

    I also have some other tube organs, including two Hammond S-6 chord organs (purchased for a total cost of about $60), and two Conns: a 430 "Caprice" which is a spinet from 1960, and a Conn 811 "Classic" from 1958, which is a massive full-sized console built much in the pipe style, and requiring two Leslie 50C speaker cabinets to be heard. The "Caprice" sat for sale locally for about 5 years before I bought it. The 811 setup I received for a price about 0.8% of its original cost, adjusted for inflation. Yet, I think the Conns are also quite worthy of renewed interest, as they have some of the best voicings that I've heard (especially of the reeds & strings, and the flutes are very nice through the Leslies), and of course the benefit of individual oscillators. The 811 and others even have separate ranks of oscillators – the upper, lower, and pedal sections all have their own generator sections, and the pedals on the 811 are fully polyphonic!

    The tube Thomases that I know of are especially interesting in their economy and in some very unusual novelty-type features. For one, they use potentiometers in place of stop tabs, allowing continuous adjustment of voicing and vibrato. The oscillators are very few in number, being Hartleys that share 2 to 4 adjacent keys (much like the "organ" section of Hammond chord organs), and their outputs are taken on both "flute" and "complex tone" (i.e. string/reed) buses, also like the "organ" section of Hammond chord organs (but also as done by Conn and others). Model H has a percussion system that is repetitive – if one key is held, and another is pressed, the percussion is triggered again, which is very unusual. Even more unusual is the ability to adjust attack and decay lengths of the percussive envelope with front-panel potentiometers. Also, the model GS-1 has a built-in 4-speed record player! The model J is a chord organ with 120 buttons arranged like a typical accordion, unlike Hammond's buttons which are not.

    I have never seen any Thomas tube organs in person, nor seen any for sale locally, nor have I found any recordings online. I would love to find one some day, fix it up, and play it. Do you have any other comments about them, Lazlo? I'd be interested to hear, especially if you own, or have owned one.


    Originally posted by Lazlo
    As for Lucy in the Sky... its registration is somewhere between an Oboe with Guitar, long sustain. But studio EQ is going to affect the exact timbre. But non Lowrey players' obsession with this short musical figure is mind boggling, as there's so much more to the instrument than Paul McCartney's brief time spent playing it.
    I agree that it is mind-boggling, given so much more interesting use can be made of these instruments. One of my favorite examples of what can be done with a DSO-1: https://www.youtube.com/watch?v=SzV16Blgq24

    Soon, I hope to make some proper recordings featuring my LS and FL. Still looking for a pedalboard for the FL, but otherwise it is working well now.


    Originally posted by Lazlo
    As for the Harpsichord tab, this should sound like a full, harmonic-heavy registration and is generally used when going for a full-organ exposition. It sounds best though with AOC, as do all the brighter registrations like Trumpet and Saxophone. Unfortunately the SS, FL and LS lack this feature. The AOC versions - SSO, FLO (and the church model CHO) are impossible to find these days.
    Well, I decided to really compare the Harpsichord tab on the FL and DSO schematics, to see firstly if there is any serious difference, and secondly if the tab is truly expected to be "full" and "harmonic-heavy" on the FL, considering it definitely sounds neither. To spoil the ending, it turns out there is a difference, and it may be significant enough to make the sound "full" and "harmonic-heavy" on the DSO even though it isn't on these earlier models!

    On the FL, the Harpsichord tab adds "8' Collector #1" and "4' Collector #1" together (through 330kΩ and 1.5MΩ respectively), reduces high frequencies with a 500pF capacitor to ground, then routes the signal to the non-resonant String amplifier. Those 8' and 4' collectors are formed by adding together the individual collector "groups", the signals of which are squarewaves. There are some capacitors in the summing network, but from what I can tell, they are sized to avoid coloring the sounds, while blocking the DC collector bias used for sustain, and facilitating the 8' shorting relay.

    Anyway, if we assume the 8' and 4' collectors have roughly the same signal levels, clearly much less 4' is added than what you'd expect from normal "staircasing" (i.e. 1/2 of the 8' amplitude), hence explaining why the resulting sound is too "hollow". (In fact, I would think that more 4' should be added than the usual for staircasing, to imitate the classic double-rank harpsichord sound.) The significant filtering effect of the 500pF capacitor explains the lack of brightness. This is very strange, and it really does suggest that Lowrey's designer(s) did not understand what a harpsichord sounds like when they made this circuit.

    On the DSO schematic (which is much better drawn, by the way), they call the combined collectors "voice collectors", and the way the groups are combined is virtually the same as on the FL. On the Harpsichord tab, the 8' and 4' voice collectors are added through 330kΩ and 1.5MΩ respectively, as before. However, rather than having 500pF to ground afterwards, there is no such capacitor, and both of the summing resistors have 500pF in parallel! This means the high frequencies are emphasized instead of reduced as in the FL, and I mean significantly – consider that the reactance of a 500pF capacitor is only about 160kΩ at 2kHz, completely overwhelming the 1.5MΩ resistor especially, and thus adding much more 4' than the FL's circuit does. So, the DSO's Harpsichord must sound much brighter, and could very well be described as "harmonic-heavy" and "full"! It might even be the Lucy sound, who knows...


    Originally posted by KC9UDX
    Until I learn what they're plated with, I don't want to get too carried away.
    It looks to me like they are silver-plated, based on the black tarnish, which I am guessing is silver sulfide. I've also found that they are quite difficult to fully clean up, but the best method I've found so far to clean them is to put cleaner on a thin piece of flexible and not-too-fibrous cardboard, then work that in between contacts. (A tongue depressor is probably too thick and won't conform enough to the curve of the spring.) Just squirting cleaner on them doesn't help much. I've also heard using an eraser can work well, so maybe I will try that. I have to re-clean some contacts of my LS before recording, anyway.

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      #32
      Thanks JQA. Looks like we can refer to you for any future tube Lowrey issues. With regard to the tube Thomas, it featured alot on the early soundtrack recordings of the great Italian film composer Piero Piccioni. Here's an excerpt from B movie The Tenth Victim. To hear it properly you can find the entire soundtrack on Lp and it may even be on Spotify. The Thomas sounds like a cross between a Lowrey and a Farfisa
      https://youtu.be/VSQq6YcNsh4

      Comment


        #33
        Originally posted by Lazlo View Post
        With regard to the tube Thomas, it featured alot on the early soundtrack recordings of the great Italian film composer Piero Piccioni. Here's an excerpt from B movie The Tenth Victim. To hear it properly you can find the entire soundtrack on Lp and it may even be on Spotify. The Thomas sounds like a cross between a Lowrey and a Farfisa
        https://youtu.be/VSQq6YcNsh4
        That is a really great sound, and I see what you mean – it sounds much like combo organs such as the Farfisa. Do you know which model was used? I do wonder if it is really a tube Thomas, since the shared-oscillator models (which I think were the vast majority) shouldn't be able to make such sounds. Especially the bright string-like tone sounds like there are multiple registers involved – at least two octaves from my hearing. All of the shared-oscillator tube Thomases described in the Electronic Organ Handbook only have one register (8'), because they do not have intramanual couplers, which would be very impractical to make with the shared-oscillator design.

        From what I understand, Thomas made some custom-built tube organs in the early 50s that were quite large and full-featured, but intended to be as pipe-like as possible. Also they are probably in the "least likely to be exported to Italy" category, due to their large size and made-to-order specs. The year of the film, 1965, means that domestic Italian transistor organs were already being made. If I had to bet, I would say it was some kind of Farfisa.

        Comment


          #34
          Point taken about the exportability of early Thomases. However, I own quite a few vinyl recordings of Piccioni's soundtracks from the mid 60s and before he switched to Hammond he was using these kinds of sounds, which are very close to a tube Lowrey on a string registration...i.e. sawtoothy and fizzy, but crucially quite woody and warm. One notices the woodiness on the lower tones. Farfisa had a much more brittle, typically transistorised tone which I'm not hearing here. Perez Prado managed a similar sound on the Latin smash Patricia... but again, who knows. Could be a tube Baldwin or Wurlitzer.

          I'm thinking it's a Thomas because I was once told I could meet Piccioni by a Roman friend who said. ".....and I'll see if I can let you have a go on his Thomas organ". But sadly he died not long after. It may have been a different model though.

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