Domestic vs. Export Power Transformer?

[David Root]

I'll shortly be starting on an ODS #004 first generation build. I have a '64 Bassman OT but am wondering about the PT.

Mag. Components have a BF Bassman PT in both domestic and export windings. The export is $25 more than the 120V, I guess because it has two primary windings with a bunch of taps on each.

My question is, (having seen some references that the export PT has more headroom and gives better performance that you can actually hear. Headroom, if you will), is that true in your experience and if so, is it even appropriate to use an export PT on a #004 build when the original probably used a domestic voltage PT?

ie is there any downside to using the export PT in this build? Or should I stop worrying about it??!

[67plexi]

David, I don't know about more head room on a export PT.
One thing on the Magnetic components transformers are low on the secondary voltage.
My guess is the low quality new power tubes may be the reason for the low B+ voltage.
If you want head room up the secondary voltage to 350v-0-350v VDC 495-500 volts.
I just tested a SF Bassman export PT 500 AC volts no load.
The Marstran JTM 45 1202-55 is a fine export Power transformer and you can use the 100v tap for the
bias run a 15k off of the 100v lug and a 6k on the bias board with a 27k tail resistor.
I have a Magnetic components twin PT that only reads 400 VAC under load I'm going to float test
it in the harbor. For the ODS 100 watt 465 volts is what I want. For your BF Bassman I would want 440
B+ VAC under load minimum.

Steve.

[PaisleyTube]

some things to look at:

the more you use of a wiring (16 ohms vs. 4 ohms or 240 Volts vs. 110 Volts) the better the performance of the transformer

a PT designed for 50 Hz in stead of 60 Hz should have a fatter stack

[David Root]

Steve, thanx, the 004 schematic specs 445V on the plates at idle.

I just cranked up my #102 y'day with a Mag. Cpts. BF Twin 120V PT and it gives 447V plates at idle and with a cathode draw of 31 mA. Need 460-465V so I see your point. I need a new PT fpr my 102.

So in this particular case 004 I should be OK with the M-C Bassman PT.

Paisley, thanx for the heads up. Even so I recall some comments here that the export PT on 120V 60Hz duty has more beef than a 120V only wind. If so, there must be some advantage to the parallel double wound primary, or is it just the extra laminations for 50Hz operation?

[talbany]

Dave
Export gets my vote

T

[PaisleyTube]

Paisley, thanx for the heads up. Even so I recall some comments here that the export PT on 120V 60Hz duty has more beef than a 120V only wind. If so, there must be some advantage to the parallel double wound primary, or is it just the extra laminations for 50Hz operation?

Two diffferent things;
- stack-size (most of the time more "beef" if fatter)
- double wound primary: more efficient use of the windings; in all cases (100/110/220/240/etc) you'll using at least 80-90% of the windings and that's "better" than (let's say) 50%.

[dreric]

Dave

I have a ton of NOS Fender export PT's from the mid 70's 2-6L6 amps.

On the left in the picture.

PM if you're interested.

Eric

[hitchcaster]

Dave
Export gets my vote

T

don't u mean in regards to MM transformers? are sure this "trick" applies across all brands? I've heard the differences between brands but I haven't listened to the export ones yet

[martin manning]

Dave
Export gets my vote

T

don't u mean in regards to MM transformers? are sure this "trick" applies across all brands? I've heard the differences between brands but I haven't listened to the export ones yet

You only have to look at the spec sheet to answer that question.

[talbany]

Dave
Export gets my vote

T

don't u mean in regards to MM transformers? are sure this "trick" applies across all brands? I've heard the differences between brands but I haven't listened to the export ones yet

In 10+ years @ VVT we use (or have used) Mag Comp,Mercury Mag,Schumacher (Fender) Heybour, (Off the Shelf Fender Marshall equiv),Marvel, Peavey, Hammond, Weber (China),Edcor..And a few more I can't think off the top of my head..Exports for me always seem to have a kind of increase in dynamic energy about them.
I prefer an export power wired FWB..(like 102)

Tony

[rp]

Non Technical but: I built a couple amps over the years all 120V, and why not I'm in the USA, right? Then I moved to Italy and had to buy 4 new PTs!!! If you build with world taps your amps can go anywhere with anybody. Just something to keep in mind, life is full of surprises.