Answered Using 220v hybrid amp in the UK

[andyrlb]

I’m reading mixed comments about the above so I thought I’d ask for clarification.
The hybrid amp has been used now in the UK for many years but I wondered if it could be having a detrimental effect on the amp or the tubes .
The manufacturer does/did make a 240v version.

 

[mac72]

Definitely not ideal but difficult to answer your question without knowing the circuit.
Small signal tubes should be fine and should work at different working point ,possibly would distort bit earlier than designed.
Output stage , I guess some sort of mosfet AB class should be fine at normal listening volumes .
Biggest problem would be PSU if smoothing caps weren’t over specd also small tubes heaters would age quicker at higher voltage and tubes would have shorter lifespan
All above is just a guess work at best am afraid , circuit diagram would help if you have one

 

[Beobloke]

Where was it made?

 

[Jazid]

A bucking transformer wouldn't cost much and would resolve any issue and worry. Clearly the manufacturer thought a different trafo was required.

I have a 220V Chinese amp that runs the smoothing caps hard on their specified voltage. The chap I got it off had used it for a couple of years off the mains without issues, but I just saw an accident waiting to happen. Even at 220 V the caps remain marginal: one duff output tube and the voltage would become excessive.

 

[andyrlb]

Where was it made?

Italy

 

[Beobloke]

Italy

Italian electrics? In that case, yes, get a proper step-down for it as a matter of urgency!

In all seriousness, if it has been properly tested to CE regulations then it should be fine, however running the valves at the correct, lower voltage should make them last longer.

 

[andyrlb]

Italian electrics? In that case, yes, get a proper step-down for it as a matter of urgency!

In all seriousness, if it has been properly tested to CE regulations then it should be fine, however running the valves at the correct, lower voltage should make them last longer.

Thanks Adam

 

[awkwardbydesign]

I have made several bucking transformers for different 220V amps. Simple and effective. http://sound-au.com/articles/buck-xfmr.htm

 

[audio_PHIL_e]

FWIW I had a chinese-built guitar practice amp which lunched its EL84 within months. Mr FixElectronics sorted it, and told me he'd moved the mains i/p from the 230V tap on the transformer to the 240V tap. This reduced the anode voltage on the EL84 to within spec, and prevents the cathode material from being splatted all over the anode. That was 14 years ago, and the same o/p valve has lasted me ever since

EDITS

1. The product was a Harley-Benton GA5. It is an Epiphone Valve Junior knockoff, with a "tone control" in a -ve feedback loop.
2. The valve complement is 1x ECC83 and 1x EL84

 

[andyrlb]

I have made several bucking transformers for different 220V amps. Simple and effective. http://sound-au.com/articles/buck-xfmr.htm

Thanks mate

 

[andyrlb]

FWIW I had a chinese-built guitar practice amp which lunched its EL84 within months. Mr FixElectronics sorted it, and told me he'd moved the mains i/p from the 230V tap on the transformer to the 240V tap. This reduced the anode voltage on the EL84 to within spec, and prevents the cathode material from being splatted all over the anode. That was 14 years ago, and the same o/p valve has lasted me ever since

EDITS

1. The product was a Harley-Benton GA5. It is an Epiphone Valve Junior knockoff, with a "tone control" in a -ve feedback loop.
2. The valve complement is 1x ECC83 and 1x EL84

I will check if the amps transformer has a 240v tap which I would imagine it would being as the amps are sold worldwide ( Pathos )

 

[bencat]

As an alternative and that could used with other things would not a Variac be okay for this ?

 

[awkwardbydesign]

As an alternative and that could used with other things would not a Variac be okay for this ?

Yes, but bigger and more expensive than a bucking transformer. I have 3 of them (2x2A, and 1x15A) and prefer the bucking transformers.

 

[audio_PHIL_e]

As an alternative and that could used with other things would not a Variac be okay for this ?

As @awkwardbydesign said, it would work, but

• it has to be able to deliver the current
• variacs usually have a continuously variable control over the o/p voltage. You'd have to mark the scale so you could set it to exactly what you set it to last time.

 

[andyrlb]

I reckon a bucking transformer is the best option IF the amp doesn’t have 240v taps on its huge transformers .

 

[awkwardbydesign]

As @awkwardbydesign said, it would work, but

• it has to be able to deliver the current
• variacs usually have a continuously variable control over the o/p voltage. You'd have to mark the scale so you could set it to exactly what you set it to last time.

I have added cheap digital voltmeters to mine.
An added advantage of bucking transformers is that they only have to be current rated for the voltage dropped. So if you drop 20V, for a 300VA amp transformer, that is only about 25VA. I generally double it, so if I have a 50VA one I will use that.
But make sure (test it!) that it is wired the right way round, or you will buck the voltage up by 20V!

 

[andyrlb]

I should perhaps mention that it’s a class A hybrid too , 240watts consumption at rest !