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Tape deck preamps

Discussion in 'Preamps / Channel Strips' started by Eriksmusicproduction, Dec 3, 2005.

  1. Eriksmusicproduction

    Eriksmusicproduction Active Member

    I have recently begun upgrading my studio with some better preamps (seventh circle) and converters (ISA428 card) and for some reason my 30 year old teac 2-track recorder has escaped my eye untill now.

    It is an A-7300, I think was one of Teac's (before tascam) earlier attempts at a semi-pro recorder. Anyway it has 4 transformer balanced mic preamps in it which I thought might not sound all that bad.

    My reasoning is that with transformers (opened the unit up but there is no brand name stamped on them, they are small cylinder types about 3/4" round and maybe 1 1/4" tall) and a rather large power supply (don't know the rail voltage yet) they are probably capable of quite nice sound.

    I did some quick tests the other day and compared to my fw1884 and isa428 they seem to be closer in quality to the 428. definately better than the fw1884, although it is hard to know untill I do some actual tracking with them. Their noise level is quite low.

    Anybody used machines like this for their preamps? If they work out well I will install some dedicated output jacks bypassing the output stages and mixer section.

    Also does anybody know if I might get better sound by installing some output transformers as well? They only have transformers on the input side.

    Thanks
     
  2. Calgary

    Calgary Active Member

    Wow. That's interesting and somewhat suprising... Great info. :cool:
     
  3. Kev

    Kev Well-Known Member

    possibly

    but it will depend on the nature of the drive section of the preamp
    just adding a trafo won't make magic

    it's probably safe to say that most of the whatever seems to happen at the step up and gain stage
    and some output sections can be very very clean even with a trafo

    getting the correct interface between your output and DAW input is more important than just using a trafo
    8)
    but it should be noted that using a trafo could be the way to go


    start with a simple small 1:1 like the OEP
    then try the larger heavier 1:1 units from a surplus pile
    or
    look to units from JLM, Sowter, Jensen ... Tim may sell you a spare to suit, from his Seventh Circle kits
     
  4. achille

    achille Active Member

    I have an old TEAC 3340 and I like the sound of the mic pre, it's not harsh like many preamp today.
     
  5. CoyoteTrax

    CoyoteTrax Well-Known Member

    I don't have an anser to contribute as far as modding your circuits with an output tranny.

    But I did want to say that I've always Loved the TEAC analog sound. Their circuits are fantastic and are what really made Tascam a usable product to begin with. Tight, accurate, thick, and a little creamy. Extremely musical and useable, with or without an output tranny.
     
  6. RemyRAD

    RemyRAD Well-Known Member

    One of the reasons you may like that preamp is because it is an old-fashioned "discrete" unit. That is one that is strictly made from transistors and not integrated circuit chips. That's why people like API, NEVE, etc.. Personally I think they sound distinctively like all Japanese stuff does. Japanese sounds like Japanese sounds like Japanese, to me. But yeah, the sweet sound of discrete circuits is undeniable.

    The transformers in the Teac are crap! Good transformers sound good, crap transformers sound like.... You know.

    I had an old pair of Auditronics consoles (501s from Memphis Tennessee). One had their own transformers for the microphone preamps, the other had Dean Jensen Transformers for the microphone preamps and the difference was like good religion versus bad religion. Need I say more?

    But remember, Transformers are our friends and provide free gain. That is to say if your input transformer has a 150 ohm input for the microphone and the output is 15,000 ohms to go into the preamplifier, it has a winding of 1:10 and therefore also provides 10 DB of free gain! That way your preamplifier does not have to work quite so hard as far as amplification goes and therefore also quieter. They also provide electrical isolation because the input windings and the output windings are not physically connected to each other but are both wound around an iron or nickel core and the signal is "inductively" transferred between one set of windings to the other. Cool huh?

    When making live recordings at any venue, I prefer transformer isolated splitters to active splitters because of the electrical isolation properties inherent in Transformers. Those type of transformers are unity gain with an input to output turns ratio of 1: 1 and therefore provide no gain and no loss (except for the inherent distortion within the transformer itself)

    I hope you did not get too wound up by my answer?

    Trans-girl
    Remy Ann David
    Maybe now you know why I'm so RAD?
    Now don't read into that too much because I don't know you yet! Maybe after a few drinks and a few dates.....?
     
  7. Kev

    Kev Well-Known Member

    yes
    Son of Grand
    I still have pair of these
    one good one
    and one for spare parts
     
  8. Eriksmusicproduction

    Eriksmusicproduction Active Member

    Just wanted to update everyone.

    I tracked my band a couple of weeks ago and ended up using the teac on 2 stereo overheads. Holy crap does it sound good, when the signal is low (or the pad engaged) it is very uncolored, but on loud signals however it clips the signal in a way that makes the track come to life.

    The enlarged clipping looks like a scallop, it isn't clipped evenly across the top of the signal, instead it starts clipping the signal and cuts more severely untill it stops, almost have to draw a picture. The clipped profile kind-of looks like one of those ski ramps for ski jumping competition only without the last raised lip.

    Is this a characteristic of the transformers clipping or something further down the line?

    I'm so pleased with it I'm going to permanently wire in the xlr's and maybe even put 2 diff transformers in 2 of the channels for more versatility.
     

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