Jubilee

[alvarezh]

Yes Darin if you want the higher voltage go with the Marstran (or equivalent) 190-0-190.

I believe those Marstans are made for Marshalls so you should be good to go on the current load.

All the best.

[martin manning]

The Mag Comp spec sheet shows 350V at 280mA. You are talking about voltages at idle, where the current draw is only about half of that. As an estimate, suppose the fully-loaded voltage is 90% of the unloaded voltage. Then at half the current draw you will get about half of that voltage drop: 350*95/90*1.414=522, and taking 90% of that for the delivered DC I get 470V.

[dcribbs1412]

The Mag Comp spec sheet shows 350V at 280mA. You are talking about voltages at idle, where the current draw is only about half of that. As an estimate, suppose the fully-loaded voltage is 90% of the unloaded voltage. Then at half the current draw you will get about half of that voltage drop: 350*95/90*1.414=522, and taking 90% of that for the delivered DC I get 470V.

Thanks Martin
I was thinking the Mag Comp would be lower voltage it being 175-0-175
so would the 190-0-190 PT be 567V(380*95/90*1.414)with 90% being 510V on the plates?

Darin

[martin manning]

I don't know if the 190-0-190 is loaded or unloaded, so I can't say. You could try e-mailing Brian Wallace. It may be in effect part-loaded if he is quoting the in-circuit idle voltage.

[dcribbs1412]

Thanks Martin
appreciate the math and theory behind the PT voltages.
I'm feeling better about possibly using the Mag Comp iron.

Darin

[alvarezh]

Martin brought up a good point (as most always). When you are looking at transformer specs, it is a must you know if the published specs are taken at full load or idle.

For example, I bought an HTS9144 from RJ a couple of years ago. In this case, he was recommending subtracting 7% from the published voltages because the specs were "no load".

On my posted recommendation to you, I assumed both manufacturers to have published the specs under identical conditions, which is not necessarily true.

All the best.

[dcribbs1412]

alvarezh
Good info to know.
Makes sense if the 190-0-190 PT is no load
with load(-7%) it would be around 470V to the plates.
You and Martin have given me some good info
appreciate your guys time and knowledge.

Darin

[M Fowler]

Here is the 2550 schematic

[dcribbs1412]

Thanks Mark

Darin

[M Fowler]

I like my build but can't hear much difference when I use the switches?
But I'm hard of hearing so that doesn't help at the volume I play.

Mark

[dcribbs1412]

I like my build but can't hear much difference when I use the switches?
But I'm hard of hearing so that doesn't help at the volume I play.

Mark

Hi Mark
are you saying the Rhythm clip and Channel switches?
Or the Pent/Triode switch?
BTW where did you get the head cab?

Darin

[M Fowler]

Darin, the Rhythm clip and Channel switches.

I had Scott Splawn build one or his cab guy built it.

[dcribbs1412]

I'll make a note of that and see when I get it up and running.
Cool cab...Nik's faceplates leave a few inches on each side.
I might look into some full length plates to use a similar style cab.

Darin

[dcribbs1412]

Some pics of my slow progress...

[alvarezh]

Take your time, looks like it's going to end up a real beauty!

Cheers!