Vox AC30 OT vs. Marshall MP50 OT

[hans-jörg]

Hello,

I want build an other Rocket clone and want use a 50 Watt Marshall replacement OT instead of an Vox AC30 replacement. The reason: I have it at home but have to buy the Vox one new.
What kind of different sound I have to expect and/or is it a No Go?

Please delight me

Best

Hans-Jörg

[pdf64]

The Marshall probably has a primary impedance around 3k4, whereas the Rocket should be rather more, from the Trainwreck files it's 5k2.
You could double the intended secondary load on the 3k4 OT, to get a 6k8 primary.
It would be best to get a transformer of the correct spec.
Pete

[randalp3000]

Dumb question, can the Marshall OP handle the 180+mA current this circuit needs?

[hans-jörg]

Hi Pete,

to double you mean to use 4 Ohm at the 8 Ohm Imp. Right?

I agree with " use correct specs"!
But how does it sound? Brighter, darker. I play with the option to put it in now and replace it when I have the money for. But What I have to expect?

Best

Hans-Jörg

[hans-jörg]

Dumb question, can the Marshall OP handle the 180+mA current this circuit needs?

As lon I know the Marshall has there above 400VDC handling and I think current wise higher too.
Or do I misunderstand. Marshall: 2xEL34, Vox/Rocket 4xEL84.
Are there +180mA required?

Hans-Jörg

[pdf64]

You could double the intended secondary load on the 3k4 OT, to get a 6k8 primary

eg put an 8 ohm load on the 4 ohm OT tap.

As to how that sounds, it's most instructive to try it for yourself - give it a go!

My experience is that switching, say, a 16 ohm cab between the 16 and 8 ohm taps (with no global negative feedback), the tone seems to have more low order harmonics, similar to switching between pickups on les paul but much less extreme.

Marshall: 2xEL34, Vox/Rocket 4xEL84

The EL34 in a Marshall tend to have 40, maybe 50mA static current each.
Similarly for EL84 in AC30 type amps, so that's twice the static current.

Pete

[hans-jörg]

Marshall: 2xEL34, Vox/Rocket 4xEL84

The EL34 in a Marshall tend to have 40, maybe 50mA static current each.
Similarly for EL84 in AC30 type amps, so that's twice the static current.

Pete[/quote]

That means, as long I understand, that my 4 EL84 will draw around 80mA more Current from my 50W Marshall OT. And the question if it stands that.

But this resumes also in a tonal difference. More stiff?

Best

Hans-Jörg

[pdf64]

But this resumes also in a tonal difference. More stiff?

The concern is that the transformer winding may overheat, as the static (=continuous) current is twice that of the original application.
It would be a good idea to check your transformer supplier (eg can it cope with a continuous 100mA per primary leg?).
Pete

[hans-jörg]

But this resumes also in a tonal difference. More stiff?

The concern is that the transformer winding may overheat, as the static (=continuous) current is twice that of the original application.
It would be a good idea to check your transformer supplier (eg can it cope with a continuous 100mA per primary leg?).
Pete

Ok,
i finaly got it: its not for use!

Thank you for your time.

Best
Hans-Jörg

[pdf64]

It may be ok with that current, but it would be a good idea to check.

[Structo]

Some of the best sounding amps have been happy accidents, meaning although you should choose the proper current ratings, some OT's just sound better than others.

That was rather ubiquitous isn't it?