Dynaco St-70 Help!
fire-stick
Posts: 4
hi there i just recieved a dynaco st-70 tube amp today the guy i got if from said he updated this amp. he added a SDS cap board and said its hooked up for trio mode? 16 watts per channel. should i leave it in trio mode or convert it back to original? and how do i do that? it still takes the 7199 input tubes so i do not know how he did the trio mode but i notice some of the output wires on the trannies are not hooked up? any info would be great. thanks fire-stick
Post edited by fire-stick on
Comments
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Hi Fire-Stick,
Welcome aboard. I have an ST-70 that I did a lot of work on. There are also several others ST70 owners in here.
You're talking about the triode mod. The amp's original design was "ultralinear". When you change it back to UL, you'll double up the power but lose that delicate touch of triode.
You really need to try both and decide which kind of sound you prefer. It also depends on how efficient your speakers are.
To convert back to UL, remove the 100 ohm reistors tied between pins 3 and 4 on each output tube socket. Then re-connect the UL taps from the transformers to pin 4 of each output tube socket. Make sure you connect each tap to the appropriate socket.
Do you know about discharging capacitors? This must be done before doing any work on the amp. Even when unplugged, the amp stores a lethal amount of capacitance.
You can check out www.dynaco-doctor.com for info on resotration. -
Hi there. There you very much on your help. do you have a favorite? trioed or ultralinear?
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I like the triode sound more. More open, smoother and more delicate top end. But the UL configuration is still very nice. More bass, dynamics and power but lacks the good stuff found in triode.
If you feel you need more dynamics or power, you should try UL.
