Any diy curve tracer for tubes?

Well, actually you can. Edcor USA has an OK selection of tube aimed PT and a good selection of OT for tube like projects. More
Specifically for your case they will custom wind anything you want. It is a little slow as they do everything by hand and it isn't China-cheap as they manufacture here in the US, but their quality is excellent and the results are strong.
 
Well, actually you can. Edcor USA has an OK selection of tube aimed PT and a good selection of OT for tube like projects. More
Specifically for your case they will custom wind anything you want. It is a little slow as they do everything by hand and it isn't China-cheap as they manufacture here in the US, but their quality is excellent and the results are strong.
Custom winding cost a lot of money though. Actually I have been playing with the load line and if that work out, I can use 2.5K primary which is standard.

Do you have experience comparing Edcor to the more expensive Lundahl or Sowter?

I incline to go to 2 pairs of 6L6GC so I can use lower primary impedance. Lower primary impedance means the winding technique is not as important, which means the advantage of going to the exotic transformer is lesser.
 
Do you have experience comparing Edcor to the more expensive Lundahl or Sowter?

My experience with Edcor is limited to X Class power transfromers and off-the-shelf output transformers. I built Bruce Heran's tube-based Groovewatt phono preamp and tube-based Headwatt headphone amp. Then I used Edcor's PT and OT for a scratchbuilt reproduction of a tweed era '59 Fender 52A-F Princeton guitar amp and a micro-sized version of the Fender Princeton amp based on the 6112 and 5902 subminiature tubes.
 
The OPT of guitar amp is different from hifi amps. Too bad.

I use Classic Tone Bandmaster OPT for my last two amp I designed. I really don't think the brand make much difference. I experiment replacing with the Weber Marshall Plexi 50W clone, it did not make a dent of a difference in the sound. Weber supposed to be very good transformer for guitar amps.
 
I really don't think the brand make much difference.

I'm not sure I'd agree with you, for somewhat odd reasons.

When I was doing the research for "which tweed era Fender amp should I build" there were plenty of designs to choose from and the parts were seemingly simple. I picked an Edcor power transformer because it was close to the specs of the one used in this particular Fender amp.

I got the transformer, it was great-looking and certainly performed well. During the build process, however, I had to do more research on which caps and why this or that wasn't working as expected... and discovered my Edcor transformer was probably TOO GOOD for the design I'd chosen.

Lots of anecdotes about early Fenders mention Leo choosing the cheapest parts he could find and sometimes pushing things a bit too far... and a good number of "why does this amp distort so nicely" that include power transformer sag.

While not the only reason these vintage amps sound a particular way, at least some of the performance (pleasant distortion) comes from the power transformer not being able to keep up with the settings and demand from the load / rest of the circuit.

Then I stare at the Edcor, reread its specs, read all the testimonials about how edcor is excellent quality and always underrate their transformers... and realize this brand and/or their manufacturing is probably limiting how much (if any) of that characteristic power transformer sag based distortion that the amp is supposed to generate. Doh!

The amp ended up sounding GREAT, exactly what the owner wanted. But I bet that if all other components were the same, we'd find the high-quality Edcor performed differently, at least under certain conditions, than the orginal, different-manufacturer power transformer.
 
There are a lot of ways to work around things. For example, I read enough about rectifier tube sagging, and all those. All I have to do is to put a series resistor on the +B line, so when the amp draws more current at high signal level, more voltage drops across the resistor and sag!!!! There's no difference from sag by the tube, by the transformer or a resistor!!!! They sag!!!

From experience of designing a few guitar amps, you change the value of one resistor in the tone circuit, or one cap, you change the characteristics of the amp. There are so many critical components that change the sound, the transformer is not one of them from my experience.

Tone control.jpg

This is a typical tone control used in Fender, Marshall and many other amps. People are just copying from each other. BUT by changing R1 from say 100K to 50K, you make the amp graw, changing C3 change the sound again. I put the value of Fender, I believe Marshall use 0.022 for C2 and C3. Fender has a more refined sound, more bass because C2 is 0.1. Marshall has a more brawy sound with less bass because C3 is 0.022. I have a switch in my amp to parallel another resistor to R1 to lower the value so it's better for rock music, or leave the 100K to have a more refine sound for other music.

If you use 50K for VR3, it will make the amp very mid heavy.

These are where one work on the sound. Use the resistor to create sag. I use power scaling to turn the power down so I can get to the sweet spot of the amp and any power output level.

The made of particular component is the last thing I worry about. I buy the cheapest of the cheap Shinghan tubes on ebay, I use all ceramic caps even in the tone circuit. I use all metal film resistors. I intentionally went against all the conventional things people said. I try to make a statement about this. I hope you can listen to my amps.

I tried changing the OPT from classic tone Bandmaster to Weber Plexi 50W, no difference I can aware of.

Go experiment the tone circuit yourself.

I have one amp using 6V6GT, another one use EL34......I think!!!! There's no difference. I use two different type of speakers, that change the sound of the amp completely. I like the Warehouse speakers.
 
I'm not sure I'd agree with you, for somewhat odd reasons.

It's not so much the brand as it is the design spec.

As long as the transformer is built to the same specs using same/similar materials then it should perform same/similar, regardless who built it.
 
It's all about the design. Guitar amps are so different from hifi amp. Gruitar amp glorifies distortion......the right distortion. It is all subjective, no rhyme or reason. When I design guitar amps, I have a basic configuration I want, build the basic circuit, use scope and test equipment to bring it up and make sure the voltages are reasonable, then PUT ALL THE TEST EQUIPMENT AWAY. From that point on, it's purely design by ears.

After experiment enough, I get a feel what component do what and adjust accordingly. You really don't need to know a lot about tubes to design guitar amps. That's the reason every Joe Blow start with a Fender and modify the amp and call it their own. I seriously question the knowledge of their electronics. That's why you look at schematic of a lot of amps, they look the same except some value of the components are changed. Look at the front end of Mesa, they are Fender stacking up more stages, put caps to ground to drown out the highs to avoid feedback and oscillation and called their own. Carlos Santanna used Mesa and made them famous.

Even I have a lot of experience in tube guitar amp, but it's pretty much useless when coming over here. I literally have to relearn everything to design hifi tube amps. Sure, I have the common sense knowledge of tubes, but when come to design, it's all new, studying RDH4 and other books and articles.
 
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