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    too much gain?

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    buschfsu

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    too much gain? Empty too much gain?

    Post by buschfsu on Thu Mar 07, 2019 7:36 pm

    hi all,  i have an st70 with new 120v power iron and choke, original speaker iron and 6u8 preamp tube converters.  the thing sounds awesome.  my only issue is that my outlaw reciever (rr2150) cant be turned up past 1 or its verrrry loud.  it feels like the unit is putting out too much gain.  could it be reduced in the preamp section?  (flying guess watch out)  reducing the cathode resistors on the pentode half of the 7199?


    Last edited by buschfsu on Thu Mar 07, 2019 11:36 pm; edited 1 time in total
    corndog71
    corndog71

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    too much gain? Empty Re: too much gain?

    Post by corndog71 on Thu Mar 07, 2019 8:00 pm

    I just looked up the RR2150's preamp output impedance and it runs between 880 to 1100 ohms. Which I would think would be ok. You may need to add an attenuator to the ST70 inputs.
    Peter W.
    Peter W.

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    Location : Melrose Park, PA

    too much gain? Empty Re: too much gain?

    Post by Peter W. on Fri Mar 08, 2019 8:04 am

    buschfsu wrote:hi all,  i have an st70 with new 120v power iron and choke, original speaker iron and 6u8 preamp tube converters.  the thing sounds awesome.  my only issue is that my outlaw reciever (rr2150) cant be turned up past 1 or its verrrry loud.  it feels like the unit is putting out too much gain.  could it be reduced in the preamp section?  (flying guess watch out)  reducing the cathode resistors on the pentode half of the 7199?

    Are you working with the correct output jacks?

    You want to be on PRE OUT.

    Just checking.
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    buschfsu

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    Post by buschfsu on Fri Mar 08, 2019 10:39 am

    yes there are only rcas for pre out and power in so the later wouldnt result in any sound at all. did double check though thanks.

    so would a simple L pad be appropriate or is there a better solution at the input of the st70?
    Peter W.
    Peter W.

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    Post by Peter W. on Fri Mar 08, 2019 10:53 am

    buschfsu wrote:yes there are only rcas for pre out and power in so the later wouldnt result in any sound at all.  did double check though thanks.

    so would a simple L pad be appropriate or is there a better solution at the input of the st70?

    I am thinking that Outlaw may have used a linear taper pot on their VC - something that, as it is their design on both ends, may have some benefit to that design. Back in the day, that would have been called and EPL loop (External Processor Loop). And a linear-taper pot would explain why you are getting such a sharp gain - as the idea is NOT to drive another amp, but to insert some level of processing into the circuit. Were it to drive another amp, then the use of a logarithmic VC would be typical.

    I am not sure how to advise you to do this. Do you want to set the output from the Pre on max, then trim with the L-Pad (so as to get proper transient response)? Do the specifications give you the V-out from the Pre at max? If more than 2V or so, then yes, you will probably want it at max, controlled down-line. Operative term is "probably".

    Let me puzzle on this a bit to see if I can discern a good response -
    Peter W.
    Peter W.

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    too much gain? Empty Re: too much gain?

    Post by Peter W. on Fri Mar 08, 2019 12:12 pm

    OK - after looking at various Kluge-like options, you could insert one of these:

    https://www.mouser.com/Passive-Components/Potentiometers-Trimmers-Rheostats/Potentiometers/_/N-9q0yp?P=1z0yqrwZ1y8ziurZ1y92ddvZ1yhozxtZ1yzotm4Z1yzekiwZ1yzekiqZ1yzvm31  

    Which would involve either creating an outboard box and adding a set of patch-cords, or finding space in a fairly tight chassis, or adding the VC option from VTA - best in my opinion based on what you have. And, if you used the tape-out on the Outlaw, this would also work nicely.

    Or, get a pre-amp for the VTA, feeding it from the Tape Out on the Outlaw.
    This would allow you to retain the amp in the receiver for other speakers if you so choose. And, you could leave the VC on the Outlaw at zero gain so as not to load the amp if no speakers are connected- never a good thing.

    Enjoy!


    Last edited by Peter W. on Fri Mar 08, 2019 12:18 pm; edited 1 time in total (Reason for editing : added another random thought.)
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    buschfsu

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    too much gain? Empty Re: too much gain?

    Post by buschfsu on Sat Mar 09, 2019 12:26 am

    thanks! i dont want to loose the volume control with the remote on the outlaw so ill try the l pad and post back the result

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