The Dynaco Tube Audio Forum

Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Dynaco VTA tube amp kits, all Tubes4hifi.com products and all Dynakitparts.com products


    Volume control

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    johns2462

    Posts : 4
    Join date : 2011-10-05

    Volume control

    Post by johns2462 on Wed Oct 05, 2011 9:59 am

    Hello to the group,

    This is my first posting and I would like to say that I find this to be a very informative site. Although I have searched a little I cant find info on a volume control. Could anyone point me to a schematic or pictures/description on how to add a volume control to my oem configured ST-70? by necessity the pot will be on the rear left corner.

    Thanks in advance. John

    ramon68

    Posts : 87
    Join date : 2009-04-12
    Age : 76
    Location : naples fl

    Re: Volume control

    Post by ramon68 on Wed Oct 05, 2011 10:11 am

    Endler audio attenuators have been mentioned on this website. I haven't used them but someone will probably chime in with first hand info.
    Google Endler audio.

    Luddite

    Posts : 235
    Join date : 2009-02-04
    Age : 66
    Location : Texas

    Re: Volume control

    Post by Luddite on Wed Oct 05, 2011 10:32 am

    You could probably mount Bob Latino's attenuator on the rear left corner if need be. Be cautious, though, that's close to the choke and might be susceptible to picking up AC hum. Here's the link:

    http://www.tubes4hifi.com/bob.htm

    Best Regards,
    Charlie

    Bob Latino
    Admin

    Posts : 2411
    Join date : 2008-11-26
    Location : Massachusetts

    Re: Volume control

    Post by Bob Latino on Wed Oct 05, 2011 11:09 am

    Hi,

    There is information about the VTA stepped attenuator kit to add to your ST-70 at the forum link below. The attenuator was designed to replace the unused stereo/mono switch when using the VTA driver board. You can also use it with a stock ST-70. There is no reason why it could not be placed anywhere else on the amp as long as you are willing to drill a 1/4 inch hole in the chassis to mount the attenuator. Link below ..

    Stepped attenuator link on the Dynaco Tube Audio Forum

    Bob

    j4570

    Posts : 141
    Join date : 2010-08-30

    Re: Volume control

    Post by j4570 on Wed Oct 05, 2011 1:34 pm

    I have the attenuator Bob/Roy sell installed on my ST70 and like it a lot.

    baddog1946

    Posts : 304
    Join date : 2010-02-03
    Location : Costa Rica

    Re: Volume control

    Post by baddog1946 on Thu Oct 06, 2011 7:43 am

    Hi:
    I have both the volume control that Bob sells and the Scott Endler models. I am currently using the volume control kit Bob sells mounted as he suggests in the unused stereo/mono switch location.
    This is a very convenient location on the front of the amp and its easy to see the setting mounted on the front of the chassis.
    The Endler attenuators (100K)I am using are not the mountable types and I use them to attenuate my CD when I use it.
    These must be connected as close to the amp output as possible so I plug them into a 2 way RCA jack on the output jacks on the amp first and use cables from there.
    This works fine and noticeably better than being mounted at the other end of the cables. Both work fine. The Endler models are 24 point attenuators and have a slightly finer adjustment but the model Bob sells is more convenient with only one control knob and they have plenty of adjustment.
    I believe Endler has stereo models as well but I am not familiar with them.
    All in all if it is just for the amp volume control I can recommend using Bob's model for convenience and the tidy way it mounts on the chassis without making any holes in it and it works great.
    Baddog1946

    Bob Latino
    Admin

    Posts : 2411
    Join date : 2008-11-26
    Location : Massachusetts

    Re: Volume control

    Post by Bob Latino on Thu Oct 06, 2011 8:36 am

    The Endler stereo attenuator is also $100, while the VTA stepped attenuators for the ST-70/ST-120 are $50. The Endler attenuator is also larger than the VTA attenuator and I do not think it will fit into the stereo/mono slot. The Endler attenuator could be mounted somewhere else on the amp where there is space IF you drill a mounting hole.

    Bob

    johns2462

    Posts : 4
    Join date : 2011-10-05

    Re: Volume control

    Post by johns2462 on Thu Oct 06, 2011 8:46 am

    A sincere thanks to everyone for offering all this info. I think I need to explain my goals a little better. I use two ST-70 amps for four speakers. I would like to adjust the channels independently and I have seen many vintage amps with "level" controls to do just this. What I envisioned was useing a power cord with an inline fuse and installing a ganged pot in the old fuse location. FYI I just cant bring myself to drill holes in my amps. I do not have the knowlege to figure this out myself but I thought for sure someone must have done so along the way. Also I posted another question if anyone could offer thier opinion on that subject rabbit

    John

    Luddite

    Posts : 235
    Join date : 2009-02-04
    Age : 66
    Location : Texas

    Re: Volume control

    Post by Luddite on Thu Oct 06, 2011 10:38 am

    johns2462 wrote:A sincere thanks to everyone for offering all this info. I think I need to explain my goals a little better. I use two ST-70 amps for four speakers. I would like to adjust the channels independently and I have seen many vintage amps with "level" controls to do just this. What I envisioned was useing a power cord with an inline fuse and installing a ganged pot in the old fuse location. FYI I just cant bring myself to drill holes in my amps. I do not have the knowlege to figure this out myself but I thought for sure someone must have done so along the way. Also I posted another question if anyone could offer thier opinion on that subject rabbit

    John

    Why not just remove the stereo/mono switches and install the attenuators in place of them?

    Best Regards,
    Charlie

    j4570

    Posts : 141
    Join date : 2010-08-30

    Re: Volume control

    Post by j4570 on Thu Oct 06, 2011 8:51 pm

    Are you saying you want to adjust the left and right channels independently?

    If so, some sort of passive preamp with left/right adjustment might be in order.

    willieher

    Posts : 8
    Join date : 2009-04-19
    Age : 63
    Location : Ohio

    Re: Volume control

    Post by willieher on Tue Oct 11, 2011 11:32 am

    Hi Charley, If your not using the bias pot holes I have posted here a pic of my
    ST-70 rebuild using these holes to mount 2 Black Beauty pots one for left and the other for rite volume. These pots are no longer prodused but they do make a Blue Velvet pot.
    If this is an option for you, the space is there and I have no problem adjusting the volume.

    Willie...

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