Transformer Questions

[rootz]

Oh well, I should read. Your power transformer will work with 6L6 tubes, because that unloaded voltage will drop possibly 20V with loading.

What was your output transformer again?

[johngovan]

You're welcome John. As I see it there are a couple of standard solutions to guitar amps when it comes down to transformers. 20 Watter: Deluxe (reverb) iron, 50 Watter: Bassman iron; 100 Watter: Twin iron. At least for Fender inspired builds. That includes Dumbles. Marshalls are a different kind here, because of EL34's. Reflected plate loads are a bit lower normally, but EL34's would work with a 4 or 4.2k load for a push/pull pair. Standard Marshall practice is 3.4k though. You can find loads of info from e.g. Blencowe about loadlines and plate loads for output stages.

Anyway, for a standard 50W output stage with 2x6L6 in push/pull a 4.2k secondaries output transformer is a good start. An 8k deluxe transformer will work, just very not optimal. Those transformers are too small to deliver 50 Watts and present an unideal load to the power tubes (which can be corrected by equally mismatching the speaker load). In short: you won't gain much (or anything) from 6L6 tubes with a small output transformer.

As a power transformer 320-0-320V @ 200mA will work. That is what is in e.g. a Bassman. Classictone has got what is needed. Or Hammond. Can't recall what you have got already.

Suggestion: let's get back to what you've already got and make that work. My only point of doubt was your choice of output tubes, the 6L6's with the transformers you have.

Great information Rootz. Thank you for the very detailed explanation. What i have here as of now is a 20w 8k:8R Output Transformer. Meant for 2 6v6's. I'll try to find 50w OT online. But the shipping cost is very painful. Or try to find OPT in Facebook marketplace near me. I'll try to make some progress soon.

[johngovan]

Does a 50w OPT measures 4 inches wide and 3 3/4 inches tall?

[wpaulvogel]

That’s a little bit larger than typical but not bad. Usually 3 x 3 3/4. What’s the primary z? 4K to 4.2K?