what does the weight of an output transformer tell you?

[embotone]

I have been toying with the idea of an Ampeg B25 build using parts I have on my shelf.  I have an output transformer form a Peavyl Vintage amp that ran 4 6l6 tubes at about 480v.  I was planning on using that.  However, I also have an old Hoffman 50 watt OT.  I noticed it is just about the same size.  It has more laminations than the tranny out of the Peavy, and the Hoffman weighs almost 1/2 lb more.  What can I deduce about how  these transformers might perform  based on their weight?

[phsyconoodler]

No,but I bet we could measure how much futher your arm stretches when picking it up.

Based on the quality of Hoffman stuff,Id use it on that merit alone.

[plexi50]

You really cant judge performance by weight.  In the older days of Thor and Zeus transformers were better made using a totally different metalurgy than what is used today. Thats why i love to find and use old output transformers from the early to late 60's in my own personal builds. But thats my belief.  There is a big difference between high grade copper wire and cheap copper wire. Tone factor? I go with the old stuff.

I tried a Peavey 100 watt output from a Peavey (4) 6L6GC Heritage amp and it did the job
That transformer has 2 & 4 ohm impedance taps. Also has ultra linear screen leads. I dont like ultra linear output transformers. There too clean sounding for me and have no mojo

[Willabe]

I dont like ultra linear output transformers. There too clean sounding for me.

If you used a FB loop next time leave the UL taps hooked up but try it with out the FB. You might like it then.


                Brad       

[plexi50]

I didnt use the ultra linear leads and built the amp the old fashioned way. But i did use a NFBL. Without the NFB it would have been a headroom machine and sound very full

[phsyconoodler]

thout the NFB it would have been a headroom machine and sound very full

No,it would be the opposite.No NFB= grindy and nasty.Add NFB and the amp gets mellower.And cleaner.

[jeff]

 The other weight/size thing to consider is the seperate windings. I got a transformer out of an old TV someone was junking. I built a 6V6 out of it. The weight and size of the OT is about the same as a 6L6 transformer and I'm tempted to take out tke 6V6s and use 6L6s. BUT... that TV ran a lot of tubes so I'm not sure if the extra weight/size is due to the fact that the 6.3V can supply much much more mA. Just because it's about the same size I don't know that the 270V can supply enough mA, maybe it's big because of the 6.3V windings not the 270V. Yeah it's extra weight for a 6V6 amp but I don't wanna risk blowing it by using 6L6s if that weight is because the 6.3V not the 270V.

IDK just a thought.

[embotone]

That's a good point to consider when reusing power transformers, but I am talking about output transformers.

[HotBluePlates]

... I have an output transformer form a Peavyl Vintage amp that ran 4 6l6 tubes ...  However, I also have an old Hoffman 50 watt OT.  I noticed it is just about the same size.  It has more laminations than the tranny out of the Peavy, and the Hoffman weighs almost 1/2 lb more.  What can I deduce about how  these transformers might perform  based on their weight?

That the core in the Hoffman OT is bigger, has more material.

*If* the materials of both cores are identical, the heavier core can pass more power, lower.

That doesn't mean the smaller core can't handle the same amount of power as the bigger OT; it will simply saturate at some low frequency that is higher than the bigger OT. So it will not be as wide-range.

It is very reasonable to guess the power handling of an OT by its weight, but you usually need other pieces of info to figure out the proper way to use an unknown transformer.

Your estimates may also be thrown off by exotic cores with a different density than iron, but that's probably not the case with these two OTs.