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    Signal path/discription

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    CNCfan

    Posts : 29
    Join date : 2018-08-13
    Age : 70
    Location : Houston Texas

    Signal path/discription

    Post by CNCfan on Tue Oct 09, 2018 1:21 am

    I have been looking for something that follows the signal path through the ST70 and describes what each part
    in the path does.  So far I am not having much luck or I am overlooking the obvious.

    Does anyone know of a document that does what I am looking for.

    Reason for my interest other than just being interested in picking up a little more understanding of how the St70 works.

    Keep reading if you want to waste a few more minutes, above is what I'm mainly interested in.


    I have another amp on the way I grabbed off of ebay. (wife is not gonna be happy) The output has EL84's, that and looking at the output transformers I do not expect the output wattage to be much above 20 watts. The output transformers look to be much smaller than what the ST70 has.  Wild guess on my part form the little reading I could find about the amp. The B+ voltage on the schematic is 275 volts.  

    Not looking for a boom box and much rather have a nice sound vice LOUD.  Crossed my mind I could replace the current transformers with the ones same one the ST70 uses.  Then I read a little more and looks like I would have to replace the EL84's with something else.

    Might be putting the cart before the horse as I do not that the amp in hand. Once I get it it may sound good enough for my intended use.

    It is an old  Guild New Englander which I find is not well thought of.   Reason I bought is was for the
    old time looking front control face.  Looks a bit steampunk and thought it would be a good project to see what I could come up with.
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    Peter W.

    Posts : 933
    Join date : 2016-08-07
    Location : Melrose Park, PA

    Re: Signal path/discription

    Post by Peter W. on Tue Oct 09, 2018 8:30 am

    CNCfan wrote:I have been looking for something that follows the signal path through the ST70 and describes what each part
    in the path does.  So far I am not having much luck or I am overlooking the obvious.

    Does anyone know of a document that does what I am looking for.

    Read page 1 (Description) of the original manual. That gives a pretty good description of the circuit and what it does.  Also: http://www.oestex.com/tubes/williamson.htm     With the understanding that Acrosound was the precursor of Dynaco.  

    Reason for my interest other than just being interested in picking up a little more understanding of how the St70 works.

    Keep reading if you want to waste a few more minutes, above is what I'm mainly interested in.


    I have another amp on the way I grabbed off of ebay. (wife is not gonna be happy) The output has EL84's, that and looking at the output transformers I do not expect the output wattage to be much above 20 watts. The output transformers look to be much smaller than what the ST70 has.  Wild guess on my part form the little reading I could find about the amp. The B+ voltage on the schematic is 275 volts.  

    At the the bleeding edge of melt-down the EL84 in PP might make 18 watts a pair downhill with a tail-wind. The Dynaco SCA 35 and ST 35 are excellent examples of EL84-based amps.

    Not looking for a boom box and much rather have a nice sound vice LOUD.  Crossed my mind I could replace the current transformers with the ones same one the ST70 uses.  Then I read a little more and looks like I would have to replace the EL84's with something else.

    Might be putting the cart before the horse as I do not that the amp in hand. Once I get it it may sound good enough for my intended use.

    It is an old  Guild New Englander which I find is not well thought of.   Reason I bought is was for the
    old time looking front control face.  Looks a bit steampunk and thought it would be a good project to see what I could come up with.

    The weakness of that unit (and design) are the anemic output transformers. What is interesting is that there is a center-channel set-up. I guess that will explain the larger OPT between the two small ones. Now, you are dividing the 35 watts or so by three - so you will not get loud unless you look for very efficient speakers. But it is an unusual design and might be a real giggle to set  up. You have the possibility of a quite-wide sound-stage with this unit.

    Enjoy!
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    CNCfan

    Posts : 29
    Join date : 2018-08-13
    Age : 70
    Location : Houston Texas

    Re: Signal path/discription

    Post by CNCfan on Tue Oct 09, 2018 1:50 pm

    Thanks for the info links Peter.

    I guess my overlooking the obvious was a bit of an understatement.


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