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    Pas 3 no bass with phono - Help!

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    hrudu90

    Posts : 26
    Join date : 2011-01-02

    Pas 3 no bass with phono - Help!

    Post by hrudu90 on Sun Nov 08, 2015 12:45 pm

    I have a Dyna Pas 3 pre-amp, restored,  hooked up to a VTA St70 or a Dyna ST70 and it sounds fantastic with CD or tuner.
    Now with a turntable it sounds good but no bass coming out at all. All tubes are still original.

    I tried with a different Pre-amp hooked to the same system and the bass is 'normal'
    So I am thinking something is wrong with the phono section in the Pas 3.

    Maybe replace the tubes in the Pas 3?

    Please help.
    Thanks
    Gin

    peterh

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    Join date : 2012-12-25
    Location : gothenburg, sweden

    Re: Pas 3 no bass with phono - Help!

    Post by peterh on Sun Nov 08, 2015 1:33 pm

    What is done by "restored" ?
    Changing to lower resistance volume control could do exactly this..

    modifying the selector wrongly could also make the above ( since the RIAA configuration is part
    of the selector )


    PeterCapo

    Posts : 380
    Join date : 2008-12-05

    Re: Pas 3 no bass with phono - Help!

    Post by PeterCapo on Sun Nov 08, 2015 3:23 pm

    Does not sound like a problem with the tubes. Like peterh said, what was the nature and extent of the restoration work that was done?

    hrudu90

    Posts : 26
    Join date : 2011-01-02

    Re: Pas 3 no bass with phono - Help!

    Post by hrudu90 on Sun Nov 08, 2015 10:29 pm

    The pas-3 was recapped only; everything else is still original.
    Here is the pic before:

    hrudu90

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    Join date : 2011-01-02

    Re: Pas 3 no bass with phono - Help!

    Post by hrudu90 on Sun Nov 08, 2015 10:29 pm

    And here is the pic after:

    j beede

    Posts : 316
    Join date : 2011-02-07
    Location : California

    Re: Pas 3 no bass with phono - Help!

    Post by j beede on Sun Nov 08, 2015 11:07 pm

    Did the phono input work properly prior to recapping? Keep in mind that a MC pickup likes to see an input resistance in the lower ranges. If you run a MM cartridge with a numerically small resistive load it may sound bass shy.

    MontanaWay

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    Join date : 2014-02-06
    Age : 58
    Location : Cameron, Montana

    Re: Pas 3 no bass with phono - Help!

    Post by MontanaWay on Mon Nov 09, 2015 9:41 pm

    that is one of the cleanest original PAS3's I have ever seen!
    I noticed on your 'modded' photo, you seem to be a capacitor short on the right hand pots?...I only see one yellow axial.......or is that just my imagination......

    PeterCapo

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    Join date : 2008-12-05

    Re: Pas 3 no bass with phono - Help!

    Post by PeterCapo on Mon Nov 09, 2015 9:48 pm

    That might be it.

    hrudu90

    Posts : 26
    Join date : 2011-01-02

    Re: Pas 3 no bass with phono - Help!

    Post by hrudu90 on Mon Nov 09, 2015 10:15 pm

    Oh Oh, that is it!
    No, I am not sure, will open it and take a look weekend.

    You don't see anything unusual on the phono board? No?

    BTW, the sound is great when playing through CDP or tuner.

    Thanks for now.

    MontanaWay

    Posts : 767
    Join date : 2014-02-06
    Age : 58
    Location : Cameron, Montana

    Re: Pas 3 no bass with phono - Help!

    Post by MontanaWay on Mon Nov 09, 2015 11:07 pm

    hrudu90 wrote:Oh Oh, that is it!
    No, I am not sure, will open it and take a look weekend.

    You don't see anything unusual on the phono board? No?

    BTW, the sound is great when playing through CDP or tuner.

    Thanks for now.

    well I know there need to be two capacitors there, so yes, that may just as well be it.
    Phono preamps are more 'sensitive' for one of the better words, so you may get away with a missing capacitor with CD & tuner, but perhaps not a phono preamp.

    daveshel

    Posts : 148
    Join date : 2011-11-06
    Location : Tucson AZ USA

    Re: Pas 3 no bass with phono - Help!

    Post by daveshel on Tue Nov 10, 2015 2:56 pm

    I don't think so. That cap is in the tone control circuits, and those circuits would have no way of differentiating between a line level signal from CD and a signal that was brought to line level by the phono preamp. The problem is in the phono stage. Looks like you still have the original RIAA components on the selector switch - I'd suspect those.

    hrudu90

    Posts : 26
    Join date : 2011-01-02

    Re: Pas 3 no bass with phono - Help!

    Post by hrudu90 on Sat Nov 14, 2015 12:16 am

    daveshel wrote:I don't think so. That cap is in the tone control circuits, and those circuits would have no way of differentiating between a line level signal from CD and a signal that was brought to line level by the phono preamp. The problem is in the phono stage. Looks like you still have the original RIAA components on the selector switch - I'd suspect those.

    dave, which components are the RIAA?
    Do they need to be replaced as well, just like other caps?

    Thank you


    ~~~

    GP49

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    Re: Pas 3 no bass with phono - Help!

    Post by GP49 on Sat Nov 14, 2015 9:13 pm

    Two questions: What phono cartridge are you using?

    Is there anything else connected to the PAS when you are testing the phono, other than the tube amplifiers you mention?

    hrudu90

    Posts : 26
    Join date : 2011-01-02

    Re: Pas 3 no bass with phono - Help!

    Post by hrudu90 on Sun Nov 15, 2015 12:39 am

    GP49 wrote:Two questions:  What phono cartridge are you using?

    Is there anything else connected to the PAS when you are testing the phono, other than the tube amplifiers you mention?

    I am using the Audio-Technica AT95 and the Denon DL110.
    The cd player and the Dyna FM tuner are connected to the PAS 3 as well.


    ~~~

    daveshel

    Posts : 148
    Join date : 2011-11-06
    Location : Tucson AZ USA

    Re: Pas 3 no bass with phono - Help!

    Post by daveshel on Mon Nov 16, 2015 1:00 pm

    hrudu90 wrote:
    daveshel wrote:I don't think so. That cap is in the tone control circuits, and those circuits would have no way of differentiating between a line level signal from CD and a signal that was brought to line level by the phono preamp. The problem is in the phono stage. Looks like you still have the original RIAA components on the selector switch - I'd suspect those.

    dave, which components are the RIAA?
    Do they need to be replaced as well, just like other caps?

    Thank you


    ~~~
    I believe they are on the middle wafer of the selector switch.

    GP49

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    Re: Pas 3 no bass with phono - Help!

    Post by GP49 on Mon Nov 16, 2015 7:29 pm

    Seldom do the RIAA components need replacing (unless you are changing the circuitry...the original provided for switching among RIAA phono, NAB tape and flat response), and if you do, you may find they're hard to get if you want to duplicate the stock PAS circuit because they are close-tolerance parts.  Any old garden variety parts will inevitably result in inaccurate RIAA.

    The cartridges would seem to be a good match. Associated equipment you mention should not have any effect. What many times does roll off the bass on a PAS phono is a cassette deck or other line-level solid state equipment...this includes computer line stages...connected to the TAPE OUT.

    Dale Stevens

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    Age : 67
    Location : Loris, SC

    Re: Pas 3 no bass with phono - Help!

    Post by Dale Stevens on Mon Nov 23, 2015 5:59 pm

    Gin, are you still there?? what did you find? Dale

    hrudu90

    Posts : 26
    Join date : 2011-01-02

    Re: Pas 3 no bass with phono - Help!

    Post by hrudu90 on Tue Nov 24, 2015 1:09 am

    Dale, Someone over there at AK suggested to clean the switch and I did clean the switch and I really can hear some improvement! Not bad, but I am still thinking it could be much better than that for sure.The highs and mids are amazing. And some one else suggested to replace the noisy resistors and move RIAA caps to the board but it would be waaayyy over my head! So for now I just enjoy them the way they are. Evil or Very Mad
    So if you guys have any ideas, let me know.
    Thank you for asking.
    Here you go

    Dynaco in the morning. cheers
    Gin

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