Transformer questions

[frankeg]

Maximum power transfer theorm does not apply with tube amp outputs, although it's confusingly similar wording.

The thing is that the maximum power transfer theorm applies to a power source with an internal impedance and an external load. That is not what is happening in a tube amp because transformer does not match the speaker load to the plate impedance of the tubes. Pentodes and power beam tubes have a plate impedance that's much, much higher than the transformed speaker load. The "matching" speaker loads idea was noticed when back in the Tube Golden Age, the savants noticed that by varying the plate load on tube outputs, the power had a broad, sloppy maximum at some value. The value was not the tube plate impedance, but was determined by power supply, tube current capability, and other esoterica.

So tubes do have a power maximum, but it's not the simple one predicted by the maximum power transfer theorm.

Please bear with me RG, I'm trying to wrap my head around this... In addition to my previous question about encompassing the broad max pwr band, would it also or more correctly alter the frequency response? In other words, certain frequencies within the spectrum are enhansed (or unaltered) while others are attenuated based upon the transformers properties? I noticed a real chage in the sound of my PR build using the Deluxe style OT. The lower freqs come through much stronger than the original which suggests to me that my overall frequency responce has changed.

[tubeswell]

Yep it sure is a cool little amp. I got another sig12S and stuck it in an extn cab, and the amp is quite a bit louder. I've used it at 3 gigs with the extn cab now - it punches through the mix a lot more.

[frankeg]

Yep it sure is a cool little amp. I got another sig12S and stuck it in an extn cab, and the amp is quite a bit louder. I've used it at 3 gigs with the extn cab now - it punches through the mix a lot more.

So are you running two 16 ohm speakers that way or do you have a choice of taps on your ot? I only have 1 tap (8 ohm). I've always mic'd my amp...

[tubeswell]

Nah they are both 8R speakers (and they are in parallel) so the OT load is halved, but the tubes I'm running are JJ6V6S so they can handle it.

Here's a soundbyte with the Weber (amp without the extn cab) I did 'properly' this evening (i.e.: through my little mixing desk and into garbage band on my mac. The amp's vol was on about '2' (because I didn't want to annoy Mrs tubeswell) and the treb on '7' bass on '2', 'verb on '2' for WDR and on '3' for FBI - speed on '6' depth on '2'ish IIRC

If you take the vol up to about 7 it sounds really good (but that might have to wait until she is out of the house for the afternoon)

The 'bass cut' button on the mixer channel was pushed in and I was running an SM57 about 6" away from the speaker

[frankeg]

Wow, Where's my surfboard... That sounds really cool Tubeswell! I'm pretty much sold on "your sound" with the 12s. Thanks for posting the sound bites.