switch transformer relay

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pw8888

Well-known member
Joined
May 13, 2010
Messages
49
Hi everybody, ;D
I have a technical question I hope you can answer :)
I am planning of building 2 different stereo line amp card with both the same type of transformer on it.(input and output)
I would like to avoid buying 8 transformers…but 4 only…
I planned to use a relay system that would “switch” the transformer from one card to another and then switch the “global output” to have the choice between the 2 card (one OR the other) and the transformer will “follow” my choice
I there any “risk” doing that (except a “pop” in the sound I suppose…. Anything else to consider ?
Hope I describe it clearly.

Thanks a LOT for your advice

Phil
 
I would avoid switching the primary mains winding. The secondary should be lower voltage so less dangerous. Can you use a single rectifier and reservoir circuit, switching the unregulated DC?

JR
 
Thanks Jakob :)

yes ... audio signal only

I have 1 transformer per input (audio) and one per output (audio).basically a stereo tube line amp with input output transformer.
usual stuff ... but was just wondering if this is something I could do ... or if I could have problem ...
audio transformer could be a bit expensive , and specially that I will never use both card as the same time .
thanks for your advice !
P
 
Keep DC off the transformers.  Also might be a good idea to have load resistors on the transformers to prove a temporary discharge path when switching.  Other than that should be fine.
 
john12ax7 said:
Keep DC off the transformers.  Also might be a good idea to have load resistors on the transformers to prove a temporary discharge path when switching.  Other than that should be fine.

Do you mean a resisror across the hot and cold on the secondaries? If so, would a zobel network work for this purpose?
 
john12ax7 said:
Keep DC off the transformers.  Also might be a good idea to have load resistors on the transformers to prove a temporary discharge path when switching.  Other than that should be fine.
thanks !!
 
warpie said:
Do you mean a resisror across the hot and cold on the secondaries? If so, would a zobel network work for this purpose?

A resistor across the primary and / or secondary,  depends what is being switched. It could be large to not impact loading,  mostly just to absorb any inductive spike when switching. Or a transformer specific load,  for example 600 ohms,  would also work.

A zobel would be for frequency dependent tuning, it serves a different purpose.
 

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