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SVT to run 8 ohms "mod"?

Discussion in 'Amps and Cabs [BG]' started by Timi, Aug 20, 2007.

  1. I have done a search and found countless threads about running SVT's at 8 ohms, technically it works but you shouldn't ect......

    What I am wanting to know, is it theoretically possible to "mod" an SVT to run at 8 ohms? By "mod", I assume a new transformer would have to be made with 2, 4 and 8 ohm taps, or does anyone know if any of the various tube SVT's over the years have had 8 ohm taps that just werent connected to anything?

    Has anyone had this done?
  2. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    I know of no such.

    Yes, it would require a new transformer. It is certainly perfectly possible theoretically, that sort of thing is common.

    A new transformer would very probably also make a difference in the sound. I know that in the transfer process to Viet/china the transformer was an issue. The sound and performance were not there for the early samples.

    There is also the possibility that there is no "room" inside the transformer for the extra turns. While the extra turns would not occupy much space, the termination and wire exit may occupy too much space. Otherwise I don't know why it would not have been done.

    Originally, it was probably not done because the existing speakers would not handle 330W in a 4-10 configuration, which is how the 32 ohm speakers would be configured to get 8 ohms. Possibly later it was decided not to "mess with success". That was certainly the case with the SLM versions, since the original transformer was made by the original manufacturer.

    In any case, it has not been done to my knowledge.
  3. Yeah I've read that the originals were meant to be used with two 8x10's, but you could use it for smaller situations with one, so the only options were 2 or 4 ohms.

    Seems silly that the SVT-2 (original and pro) and SVT-CL have kept this feature while changing so many others.....

    Interesting issue you brought up regarding the space the extra windings would take, I didn't think of that.
  4. I've recently aquired a 200w 4x6550 amp with taps for 4, 8 and 16.
    Seems strange to me - as most 60's era stuff I've seen has taps for 8 or 16 ohms - or 5 and 20ohms.
    I've never seen another all-tube amp from that era go as low as the SVT into 2 ohms.
    Anyone wanna correct me?
  5. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    The SVT did it primarily (I think) due to power issues and low end. It took a lot of 10" speakers to handle the 330W and do it at the low end. That means lower impedance with their choices.

    They chose 32 ohm speakers so that they could be parallelled, as opposed to some series parallel "mess". Then, to get higher impedances, they would have needed 64 ohm speakers.....

    I would NOT be surprised if there was some "now they need to buy OUR speakers" action as well.... 4 ohm speakers were not quite as common then, the 8 and 16 you mention were more so.

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