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    4 Speakers on a St70

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    Sled108

    Posts : 40
    Join date : 2010-02-03

    4 Speakers on a St70

    Post by Sled108 on Sun Jun 27, 2010 3:37 am

    So...What will I Fry by Running my ST70 into (4) 8 Ohm Bozaks? It really Sounds Marvelous. Much Nicer Bass now that I have (4) 8" B800BC's doing the work..

    erlingt

    Posts : 15
    Join date : 2010-06-23
    Location : Denmark

    Re: 4 Speakers on a St70

    Post by erlingt on Sun Jun 27, 2010 6:35 am

    4*8 Ohms speakers, is 2*8 Ohms in each channel. So you just connect them to the 4 Ohm connectors, and everything is OK.

    Sled108

    Posts : 40
    Join date : 2010-02-03

    Re: 4 Speakers on a St70

    Post by Sled108 on Sun Jul 04, 2010 11:58 pm

    No, I mean running 4 Speakers out of the 8 Ohm Outputs..

    Sal

    Posts : 223
    Join date : 2009-02-05
    Location : Central New Jersey Dynaco-ST70.com

    Re: 4 Speakers on a St70

    Post by Sal on Wed Jul 07, 2010 11:49 pm

    Why not connect them to the 4 ohm tap on the speaker terminals? Then it will be a non issue.

    Sal

    GP49

    Posts : 717
    Join date : 2009-04-30
    Location : East of the sun and west of the moon

    Re: 4 Speakers on a St70

    Post by GP49 on Thu Jul 08, 2010 12:42 am

    You won't blow up anything but two 8Ω speakers in parallel on each channel makes a 4Ω load, so why do you want to connect them to the 8Ω tap? All that will do is make for a non-ideal load to the output tubes, and lower output power.

    Sled108

    Posts : 40
    Join date : 2010-02-03

    Re: 4 Speakers on a St70

    Post by Sled108 on Fri Jul 09, 2010 10:35 pm

    I do not have 4 Ohm Taps on my 'ST70'... Only 8 Ohms...

    Bob Latino
    Admin

    Posts : 2373
    Join date : 2008-11-26
    Location : Massachusetts

    Re: 4 Speakers on a St70

    Post by Bob Latino on Sat Jul 10, 2010 7:44 am

    Sled108 wrote:I do not have 4 Ohm Taps on my 'ST70'... Only 8 Ohms...

    You probably DO have an 4 ohm tap for your output binding posts and it is probably INSIDE the amp. Open the amp up. If it is a stock A-470 output transformer or even a clone A-470 output transformer they have the same wire color coding as the original Dynaco A-470 output transformer as below.

    16 ohm > YELLOW wire
    8 ohm > ORANGE wire
    4 ohm > BROWN wire

    To set up your amp for a 4 ohm tap you just unsolder the ORANGE wire from the binding post on each channel and solder on the BROWN wire. Be sure to insulate the end of ORANGE wire that you just removed.

    Bob

    Sled108

    Posts : 40
    Join date : 2010-02-03

    Re: 4 Speakers on a St70

    Post by Sled108 on Sat Jul 10, 2010 8:40 pm

    Hi Bob, thanks for the reply...You've already seen my Not-So 'ST70' with the 6u10s...I've been trying to figure where to go with this since one of the A-470s has started running Hot...I now have a Pair of Edcor 60W 4.2K 8 Ohm OPTs ready to be Installed...But, I also have 8 JJ KT77s with Small Pins, and it could use a new set of Tube Sockets...That, and a very Hot running PT has me thinking...I can get an Edcor XPWR029 700V Ct, 50V, 6.3v Ct for $83...So, if I'm doing all this, maybe I can also upgrade to KT88s?

    Sled108

    Posts : 40
    Join date : 2010-02-03

    Re: 4 Speakers on a St70

    Post by Sled108 on Fri Jul 16, 2010 8:44 pm

    Thanks Bob...I just went for the Easy Fix as you Said....Swapped the 8 Ohms with the 4 Ohms in all of 5 minutes...It's Sounding Great now...After 25 years, this is the first time that I've Heard the 4 Ohm Taps, and it pretty much Sounds the Same on 4 Speakers...Thanks Again...
    I guess I'll put in the Edcors come Cooler Weather and maybe Re-think the KT88's..I've read they need -70V to Bias...

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