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  • in reply to: Alice 828 Mixer #15470
    Ted Fletcher
    Keymaster

    I do indeed purport!
    The 828 was our most successful design… we sold hundreds of them with customers ranging from the Singapore Army to Wimbledon Tennis Club. It was the classic of its day, a simple 8-channel transformer input mixer with a very useful stereo limiter compressor on its output.
    There are many ‘gee-wizz’ stories about 828s; one of my favourites actually happened to me…. on a visit to Pinewood I was shown the brand new (as it was then) sound stage with its outrageous Neve mixer that required at least 3 operators, and in the centre on the script area was an 828…… they were doing the final mix for the Bond movie ‘Thunderball’ through it because they liked the limiters!

    As it happens, I do have all the circuit information for the 828 and I will send them to you on normal email tomorrow.

    Technically, the 828 was very interesting in hindsight…. the channel retained a transformer for the mic in; it was made for us by Dr Sowter. The channel amplifier was extremely simple with minimal feedback and running in class-A, and the mixing, very unusually, was passive! The result was a signal path with virtually no odd-order distortion (class-A and minimal feedback), the noise at the output was not great by modern standards, but was certainly good enough for professional studio use.
    With its very high input overload margin, the performance was perfect for speech applications and it became the preferred mixer for radio and television O/B use as well as being ideal for commercial production.

    The 828 was living proof of a number of ‘ground rules’ about quality sound reproduction…..
    Overload margin (headroom) is everything.
    Noise is relative.
    The unpleasantness of distortion has little to do with the numbers.
    And now after all these years, it was proof that low impulsive distortion sounds right!

    I designed the 828 with help from Steve Dove (this was actually before Barry Porter’s time with us at Alice.)
    You talk about ‘small format broadcast desk’…….. I think we invented it.
    :)

    in reply to: VC1 v2.02 No Input #15468
    Ted Fletcher
    Keymaster

    Sounds like you have a power supply problem…. seriously, if you are coming to Somerset, why not send me the unit and I will fix it?
    Fixed price £25 plus the cost of sending it back to you. I’m in Torquay.
    I’m happy to send you circuit diagrams…. I will send them by normal email.

    in reply to: P10 attack time #15462
    Ted Fletcher
    Keymaster

    Koen, thanks for your posting….. The attack and release times of the P10 are very definately ‘nominal’ (!) They vary hugely depending on the transient nature of the the signal. I’m sending you the circuit diagrams so that you can see the compound attack and release components….. the most important one being C26 (100nF) which sets the attack time depending on the slope of the transient detected, the setting of the attack control and the residual charge in the main capacitor underneath it.
    When I designed the P10 I had intended to be accurate about attacks and releases, but in practice in the studio the variation is huge, and the right way is to listen!
    Of course, piano is notoriously difficult to compress successfully, and again it depends on the touch of the player, and the type of music.
    I will send the circuit diagrams by regular email.

    in reply to: VC1 V3.02 Prototype #15428
    Ted Fletcher
    Keymaster

    The original ‘brick’ had the same transformer…. and there’s a story behind that! That transformer was originally designed as a ‘line matching’ transformer for line level audio. To most designers it is physically wastefully big to use as a mic transformer, but in a professional studio one often gets large audio signals that could send a smaller transformer into distortion. This ‘line’ transformer has winding tappings on it so that it can be configured to get the right impedances. It has a high permiability core using 90% mu-metal, and it is wound using a ‘bi-filar’ technique that makes for high efficiency, good frequency response and excellent common mode rejection….. in short, it’s a good mic transformer.
    But at the same time, the circuitry around the transformer has to be right too. The original ‘brick’ had a circuit that I developed for radio broadcast mixers; it uses integrated circuits, but spreads the gain requirements so that the maximum gain provided by any amplifier is less than 25dB, this eliminates transient distortions within the amplifiers; (an effect ignored by other manufacturers) making a warm and full sounding pre-amp.

    in reply to: tfpro p38 to new upgrade kit #15424
    Ted Fletcher
    Keymaster

    Hi Laurent, thanks for the message….. but I’m afraid it’s not possible to upgrade a standard P38 into a P38EX… the printed circuit layout is completely different to accomodate the changes. There are additional buffer amplifiers and components to allow the sidechain access, and modifications to the output stage to achieve the by-pass mixing.
    But, don’t forget that as you already have a P38, I can let you have a very good ‘trade-in’ allowance for a new P38EX.
    Please email me direct on [email protected] letting me know when you bought the P38 and where from, and It’s likely I can make you an offer you can’t refuse! :)

    in reply to: Slight Off-Topic: Question regarding mono Alice desk #15461
    Ted Fletcher
    Keymaster

    LOVE the picture of the transformers!
    Yes, that would figure….. we made some stuff for Westward Television at Derry Cross, Plymouth back in the early days. It must have been a mixer for an interview facility or something like that. I expect it still works well!

    in reply to: Slight Off-Topic: Question regarding mono Alice desk #15459
    Ted Fletcher
    Keymaster

    No, not really off topic…. this is what it’s all about!
    Wow, that’s a real old one! This was the SM series mixers that we made in 1969/70/71. I don’t really know where that one came from…. they were all ‘specials’ in those days; we used to tailor the design to suit the application.
    Interestingly, it has a PPM so it was probably for speech recording, but it’s odd that it has so many channels…. it’s a bit of a mystery.
    I will get Eric the Oracle to look at the pictures; Eric remembers every mixer we ever made (Eric was a founder member/director of the old Alice company).

    Regarding the design, I don’t have any circuits from that era, the designs were very simple with a discrete transistor mic amp and equaliser. Some of the early mixers had a single transistor emitter-follower stage after the fader….. but I can’t be any more helpful than that.

    I will report back when I know more. :)

    in reply to: Regarding the old SC2 #15456
    Ted Fletcher
    Keymaster

    Joseph, it’s unlikely that there’s anything wrong with the old SC2 V1.05 other than wear in the input gain pot…. that’s the most common cause of unequal gain in the channels. This was particularly so with the ‘Omeg’ pots used at the time (easy to identify…. take the knob off and look at the shaft, if it’s black plastic, it’s an ‘Omeg’.) Later units used ‘Alpha’ pots which are superior.
    It’s true that some LDR cells do deteriorate with time, but in the SC2 version 1.05 I remember we used a type of cell that is well sealed and I have not found one ‘aged’ yet.
    Back to gain shifts…. this is a constant problem with all 2-channel systems; the accuracy of the pot tracks has to be VERY good to meet a criterion of even plus or minus 1dB. The old ‘Omeg’ pots had backlash between the tracks and were notoriously poor in this respect.

    Yes, I do have stocks of the parts for the SC2, but not those input gain pots, we now use ‘Alpha’ pots and switches.

    in reply to: VC1 V3.02 Prototype #15426
    Ted Fletcher
    Keymaster

    Thanks for the post….. Wow, that’s an old one! I must admit I don’t remember it at all.
    I’m sorry, I don’t have any circuit information on those very early VC1 models, they did vary quite a bit, and only settled down at the VC1Qcs model when I changed from a conventional transformer input to the more rugged ‘cs’ version.
    I will have a rummage at the office on Monday, but I don’t hold out much hope. :(

    in reply to: Regarding the old SC2 #15457
    Ted Fletcher
    Keymaster

    There’s a lot more to this question than meets the eye (or ear).
    The attack circuitry of all my optical compressors operate by making high surge currents available through the LED; initially, with the older Joemeek circuits, this worked to overcome the very slow response time of the light-dependent resistors (the light cells). Nowadays, this is less important as I use a much faster reacting cell.
    The very early compressors used a little transistor array as the current drive, and in the earliest SC2 (the ones with a bevelled edge front panel) the power supply was only just capable of driving the required high currents, so the later compressors did sound just a little tighter because of an improved attack response.
    The release circuitry was always a ‘compound’ circuit responding quickly to transients, and more slowly to steady sounds ( this system is usually called ‘auto’ by other manufacturers). This arrangement never changed on the SC2 through all the variants, except on very late SC2.2 models where I think I shortened the release times generally.
    One of the ‘secrets’ of the SC2 sound was a little trick that I still use, to make the compressor release time actually shorten just before compression releases completely. This makes for a very odd looking release curve, but is great for compressing drums.
    So, to answer the question directly, yes, the old V1.05 still had a slightly ‘soggy’ power supply and is probably the most collectable SC2 nowadays. The later ones had a slightly ‘tighter’ sound due to the attack curve being more controlled.
    As a matter of interest, the new P38EX has settings that can duplicate the early SC2, but without the image shift that the early compressors were prone to suffer from.

    in reply to: TFPro P3 power supply #15423
    Ted Fletcher
    Keymaster

    Hi Simon, this comes under the same arrangement as any other gear of my design…. I’m happy to look at it, service it, fix it, for a fixed fee of £25 plus the cost of returning it. I can’t guarantee to get it sounding the same as the other one…. there were no design changes that could have caused the difference.
    If you would like me to look at it, pls send it to The Sound House.
    :)

    in reply to: P10 vs P110 #15442
    Ted Fletcher
    Keymaster

    Ru, the P10 was the one that came first…. I designed it as a dual channel ‘front end’ that could be linked for stereo operation.
    The P110 does use basically one half of the P10; it has a very slightly modified gain structure, altering the law of the input gain control, but the quality and performance are essentially the same.

    in reply to: Service VC1 Brick #15439
    Ted Fletcher
    Keymaster

    Hello Frank, the short answer is, I would not trust anyone with service on a ‘brick’! They are quite delicate and difficult to strip and re-assemble. The most sensible way is to send it to me at ‘The Sound House’. I have an arrangement where I repair/service any equipment of my original design for a fixed fee of £25 plus the cost of returning it to you.
    It sounds like there is a fault with the ‘comp 1’ setting. If you would like me to fix it, pack the unit well and send it to me.
    The address is:
    Ted Fletcher
    The Sound House
    Hunsdon Road
    Torquay TQ1 1QB
    UK
    And make sure that you note that it is equipment sent for servicing and quote the IPR number IP/0929/089/11 this will avoid problems with VAT and duty.
    Once I have the unit I will fix it and ask you to transfer £25 plus the cost of postage back…. all by paypal.
    BTW, this goes for any and all old Joemeek equipment as well as Alice mixers and early TFPRO equipment.

    in reply to: VC1 BRICK owners manule #15431
    Ted Fletcher
    Keymaster

    Hi Joseph, the gain difference on the two ‘bricks’ is quite understandable; I did alter the gain structure and so I’m not surprised that you have two that do not match exactly, but the quality will be the same, and it’s unlikely that there is a fault.
    I recall that the lower gain one is the earlier one; I did change the circuitry slightly to improve the linearity of the gain pot, it was quite a trick at that time to get the very high levels of gain swing on a single pot.
    I must advise NOT to let any regular equipment workshops loose on the ‘brick’, the mechanical construction is tricky and the circuitry is delicate…….. it’s a great example of the old saying ‘if it ain’t broke, don’t fix it!’

    Regarding comp 1 and 2, yes, these are effectively ‘slopes’, the switch alters the shape of the compression curve. Comp 1 gives a very gentle compression, while ‘2’ starts gently, but increases to a maximum of about 6 to 1. The curves are very non-linear and it’s that fact that gives a compression that is very close to the natural compression response of the human ear, completely unlike other compressors……. this was the whole ‘magic’ of my early optical compressors.

    in reply to: VC1 BRICK owners manule #15429
    Ted Fletcher
    Keymaster

    Jim, the ‘brick’ was the very first Joemeek VC1, I designed it in 1993 based on design thinking from work in both music recording and broadcasting. We made only about 55 of them, and now they are very rare…. mainly because a number of influential producers hang onto them to use on lead vocals on their records.
    Interestingly, I was discussing the ‘brick’ with my son (Guy, who is working on a new Knopfler album at British Grove) over Christmas; he uses one for his lead vocals.
    As for a handbook…. I don’t think there ever was one!
    However, the ‘front end’ was very similar to the first V3 versions of the VC1 and I have a handbook for that.
    If you would like to drop me an email direct ([email protected]) I will email you a pdf of it.

    As a matter of interest, I have re-created the exact mic amp structure including the same transformer and identical overload margins etc. in the new P110. :)

Viewing 15 posts - 436 through 450 (of 451 total)