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    SP6-PAS3-Z Kit

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    fromans4

    Posts : 14
    Join date : 2010-04-11
    Age : 55
    Location : Petaluma, CA

    SP6-PAS3-Z Kit

    Post by fromans4 on Sat May 01, 2010 1:12 am

    I have a Dynaco PAS3 and I am interested in the SP6-PAS3-Z Kit. But I have a couple of questions:

    1. I am very much into my vinyl and I use a few different cartridges on my turntable. To get the best results from these cartridges I need to be able to adjust the phono input loading. Is this possible when using this kit and if so how difficult would it be?

    2. I would like to retain the use of my tone controls if possible but I would also like to be able to bypass them for optimum signal path. Can defeatable tone controls be added to this design? Or maybe a modular tone control circuit can be added after the outputs so they don't effect the circuit design?

    Any help would be appreciated.

    Thanks,
    Brent

    tubes4hifi
    Admin

    Posts : 1291
    Join date : 2008-11-30

    PAS3-Z mod

    Post by tubes4hifi on Sat May 01, 2010 11:31 pm

    the PCB isn't set up for variable loading but that would certainly be easy to do, either internally or externally, for example adding a DIP socket near the input on the PCB or wiring the phono input in parallel to another pair of RCA jacks and inserting the particle load you need.
    The circuit isn't set up to use tone controls, so those would also have to be added, either externally or squeezed into the chassis somehow (along with another power transformer.
    It's possible sometime in the future months I may modify the circuit to do this, but it's an additional cost of around $100 to add tone controls. I've had a few customers add external tone controls hooked up into the tape loop.

    fromans4

    Posts : 14
    Join date : 2010-04-11
    Age : 55
    Location : Petaluma, CA

    Re: SP6-PAS3-Z Kit

    Post by fromans4 on Sun May 02, 2010 3:52 am

    the PCB isn't set up for variable loading but that would certainly be easy to do, either internally or externally, for example adding a DIP socket near the input on the PCB or wiring the phono input in parallel to another pair of RCA jacks and inserting the particle load you need.

    I was thinking of installing a selector switch where the blend switch used to be, seeings that I have already removed it. I would need to know which resistor in the origonal circuit is associated to the phono load so I could install this switch in the correct location.

    It's possible sometime in the future months I may modify the circuit to do this, but it's an additional cost of around $100 to add tone controls.

    If this option is going to be available relatively soon I would definately be willing to pay for it.

    BTW - There is an option for the SP8 preamp kit to upgrade the coupling capacitors and resistors, is this option applicable to the SP6-PAS3-Z kit? If not could a simmilar upgrade be spec'd so the user could purchase and install the propper components themselves?

    Thanks so much for your help,
    Brent

    fromans4

    Posts : 14
    Join date : 2010-04-11
    Age : 55
    Location : Petaluma, CA

    Re: SP6-PAS3-Z Kit

    Post by fromans4 on Sat May 08, 2010 11:05 pm

    Bump - Any ideas about the questions I raised in the last post?

    Sorry for the bump, but it looked like this thread got lost.

    Thanks,

    Corona

    Posts : 32
    Join date : 2010-03-11

    Re: SP6-PAS3-Z Kit

    Post by Corona on Sun May 09, 2010 1:54 am

    fromans4 wrote:Bump - Any ideas about the questions I raised in the last post?

    Sorry for the bump, but it looked like this thread got lost.

    Thanks,
    Roy is on vacation till the 16th I think.

    tubes4hifi
    Admin

    Posts : 1291
    Join date : 2008-11-30

    PAS3-Z phono loading

    Post by tubes4hifi on Wed May 19, 2010 11:22 am

    Hi Brent,
    OK, I'm back from vacation. The phono loading resistor on the PAS3-Z mod is the same as any phono preamp, it's the input resistor to ground (in this case R110) which is 99% of the time in all preamps a 47K resistor. This would normally only be changed if you were using a MC cartridge rather than a MM cartridge. I wouldn't recommend running wires back and forth between the input jack and/or the PCB right at the phono input since this signal gets multiplied 10,000 times and a microvolt of noise would totally wipe out your input signal.
    Not sure why you would want to change the resistance there, but the way to do it is either right on the PCB or right on the RCA jack. Most hi-end preamps put several resistor combinations right on the PCB and use a DIP switch to select the one used, or the latest technique is to add another RCA jack right next to the phono input jack and then plug in a jack with the correct resistor/capacitive load that you want to use.
    Roy www.tubes4hifi.com info@tubes4hifi.com

    fromans4

    Posts : 14
    Join date : 2010-04-11
    Age : 55
    Location : Petaluma, CA

    Re: SP6-PAS3-Z Kit

    Post by fromans4 on Sun May 23, 2010 5:28 am

    Hey Roy, I just ordered the SP6-PAS3-Z kit from your site. I will need a set of 12AU7's a 12X4 and a balance pot. I just got a set of 12AX7's to replace tubes I thought may be bad so I don't need those. I didn't see any way to order specific tubes or the balance pot from your web site. Could you PM me with the info I need to order these parts.

    Thanks,

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