Upgrading speaker posts on VTA ST70

brizey

brizey

New Member
Hi everybody. I picked up a beautiful VTA ST-70 that was assembled by a lady named Sue in 2013 (signed in the chassis). It is set up to accommodate 8ohm speakers only.

I want to hook it up to a pair of Klipsch Fortes which are 4ohm.

Anybody know what I'd have to do to upgrade this on the amp?

Thanks,
Brian
 
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are you looking to have both impedance available, or just change the 8 ohm output to 4 ohm but keep the existing hardware?
 
Wow! Fast replies! Thanks! I was really hasty with that post. I cracked it open and I see that I can just swap the 8ohm lead from the transformer with the 4ohm lead. Looks easy. I guess I should not have shot from the hip like that. Thanks.

I do have a question. This amp is of unknown provenance, it came with a quad of EL34s that were obviously not original How can I I tell if this was originally wired up for 6L6 or EL34 type tubes?
 
If the output transformers are marked A470, its meant to use an EL34.

so far as I know though all versions of the ST-70 were meant to run an EL34
 
The VTA ST-70 is quite a bit beefier than the older ST-70. It can run quite a few other tubes than just EL-34 from what I recall about the one I had. I was running 6550's, I believe.
 
Doesn't the original ST-70 have screw terminals on the back for 4 and 8 ohm taps already? There shouldn't be a need to rewire anything, ya?
I put the speaker post's VTA sells on my VTA ST-70 aired for 8 and 4 ohm.
 
avguytx said:
The VTA ST-70 is quite a bit beefier than the older ST-70. It can run quite a few other tubes than just EL-34 from what I recall about the one I had. I was running 6550's, I believe.
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There are twondifferent power transformers used on the Dynaco ST-70's.
The earlier versions had the smaller transformer. The later versions have the bigger transformers and can use KT-88's and 6550's as far as I know.
I found using KT-88's just didn't sound quite right to me. Probably because
The amp is optimized for EL-34 types? :dunno:
 
BlueVUMeters said:
Aren't all Forte's rated at nominal 8 ohms?
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Early original Fortes with round terminal cups ware "marked" as 4ohm. The later version of Forte 1 with a square terminal cup were "marked" 8ohm. I don't know if there was any difference between those versions electronically though. I have 2 sets of early version and I always ran them on 4ohm taps of my equipment.
 
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