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Tube Amp Questions
Tube Amp Questions
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Old 2nd October 2002, 03:25 PM   #1
Tom D is offline Tom D
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Default Tube Amp Questions

I own the Musical Fidelity X-Can v2 headphone amp. My question is about the AC Power Transformer that is needed to power it up.

It is supplied with a 12 VAC-500ma wall transformer. Now, a lot of other owners of this amp claim that a transformer with a much higher amperage rating is better to use. So, here's what I tried:

First, I tried a 12 VAC- 1A transformer. It worked fine, but the amp got much warmer. Sound-wise, I couldn't hear any significant difference.

Then, I rigged up a bigger power transformer rated at 2 Amps; and Yes, it did sound way better. The only problem is that the amp was getting much hotter. So, I'm concened about using this transformer because I don't want to shorten the life of the amp, and/or Tubes.

So, I guess my main question is: Is it safe to run the amp hotter for the better sound? or safer to go back to the original transformer? Thanks for any advice.
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Old 2nd October 2002, 04:13 PM   #2
fdegrove is offline fdegrove  Europe
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From what I could find:

Total powerconsumption of the circuit is 490mA/12V when idle.

Running this from a 500mA/12V AC adaptor may give you trouble in the long run and starve the circuit for current.

IMO running it from a higher rated transformer will not hurt neither the tubes nor the transformer itself and I would certainly recommend it.
You even build your own PSU unit and include mains filtering.

Best regards,
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Old 2nd October 2002, 04:34 PM   #3
tiroth is offline tiroth  United States
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One explanation for the behavior is regulation. A 12V @ 500mA xfo is probably putting out pretty close to 12V at 490mA, but a 2A one might be putting out 13-14V+. Depending on what is inside your black box it could be getting a lot warmer than the 17% additional voltage would seem to indicate. Try measuring this?

Additional amperage alone shouldn't have any effect on the temp.
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Old 2nd October 2002, 04:41 PM   #4
fdegrove is offline fdegrove  Europe
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I measured 11.4 VAC at the trafo lead.
Why it puts out the extra heat I can only guess but I've seen this happenig on quite a few of their products.
Be that tube or solid state.

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