828 MIXER Mk1 and Mk 2

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Home Forums Ask Ted 828 MIXER Mk1 and Mk 2

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  • #15303
    Ted FletcherTed Fletcher
    Keymaster

      The original Alice 828 mixer was derived from an earlier type…. the Alice AD62.
      In the early part of 1977 we decided to market a rugged but portable 8-channel mixer based on experience with the earlier lightweight type.
      The circuitry was very professional for its price…. the mic amp was particularly good, using a Sowter or Belclere transformer into a very sophisticated little amplifier. ( I now have a sketch of the circuit of the Mk 1 channel board available).
      We started selling the Mk 1 828 in July 1977 but rapidly altered the design of the mid EQ circuit as the very early few were unreliable; I incorporated an IC (!) amplifier stage and a discrete transistor tuned circuit which all worked very well.
      We sold the Mk1 828 until mid 1982 when we introduced the Mk2 with completely re-designed circuitry making use of modern IC types. (Circuits available).
      Under test, the distortion figures of the Mk 2 are better than the Mk 1, but actually, the sound of the Mk 1 is certainly sweeter….. but beware here…. the Mk 2 is still significantly superior to any present day ‘economy’ mixer.
      The main secret with all these things is overload margin; these old desks were built to specifications demanded by broadcast people for use in ‘outside broadcasts’ which could mean a rapid set-up in a muddy field with no run-through!
      Modern desks are designed so that the noise level is very low; inevitably this means that there is poor overload margin, so the thing sounds thin and nasty. These old 828s sound wonderful… and that’s why there are so many still in use by discerning engineers in spite of their extreme age!

      I have a complete handbook PDF for the Mk 2 now…… email me direct at ted@tfpro.com

      Don’t all rush at once, but I have now located a stock of the special input gain pot used on both Mk 1 and Mk 2 828s. :D

      #15909
      AvatarSteveAudio
      Participant

        Hey Ted,

        I do studio technical work in the Los Angeles area, and I had a client bring me an 828 that he really loves.

        Can I get schematics from you, that would be really helpful.

        Do you know where Steve Dove is today? We hung out back in ’83 when I was the L.A. tech support for Hill Audio, and AC/DC came through here; he was on the tour with them as sort of a tech support boffin; incredible guy, very friendly and helpful.

        Thanks in advance,

        Steve

        #15908
        Ted FletcherTed Fletcher
        Keymaster

          Hi Steve,
          Yes, email me at ted@tfpro.com and I will email all the circuits I have…… I have the full set for the Mk2, and a rough sketch of the Mk1 channel.
          Steve Dove is now living down in Florida….. I will let you have his email address on a return email.
          Forgive the clandestine approach but I have had all sorts of problems with scammers from Poland and Russia….. but I think I’m winning! :)

          #15907
          AvatarFizmo100
          Participant

            Are there any visual differences between the MKI and the MKII, or are all the changes at the circuitboard level? I adore these little desks – they are perhaps the best kept secret in the audio world… and long may that continue – just added an 8 channel desk to my 12 channel for a song on Ebay! 😆

            #15906
            Ted FletcherTed Fletcher
            Keymaster

              Just finished repairing a Mk1…… yes, by modern standards it actually performs well too!
              No there are no differences on the outside. On the inside, the channel circuit boards on the Mk 2 are rectangular; parallel top and bottom, on the Mk 1 they are angled. In performance the Mk 1 is slightly softer sounding. :)

              #15905
              AvatarWHoops
              Participant

                Ted Fletcher wrote:

                The original Alice 828 mixer was derived from an earlier type…. the Alice AD62.

                Don’t all rush at once, but I have now located a stock of the special input gain pot used on both Mk 1 and Mk 2 828s. :D

                Hi Ted,

                do you still have these Pots?

                I was checking in the schematics and the input gain pots seem to be different in the MK1 and the MK2, maybe I’m wrong but it seems that in MK1 the input gain pot is a 100k Rev Log but in the MK2 it uses a 22K Lin,

                is this right ?

                Thanks

                #15904
                Ted FletcherTed Fletcher
                Keymaster

                  Yes, that’s right, the circuit of the earlier Mk1 needed a reverse log pot…. and I still have a few of these!

                  The Mk 2 uses a 22K lin pot…. the circuit is quite different. Both mixers sound very good, mainly because of the high overload margins and the delightfully simple Baxandall EQ, but I actually prefer the sound of the Mk 1 although technically it is inferior…. the mic amp distortion is on the high side…. but it is ‘class A’ so the distortion is pleasantly harmonic. :)

                  (Apologies for my error on an earlier post….. saying that the gain pot was the same on both models!)

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