Two interesting tables

[Leevi]

I'm testing a new build of 5D3 circuit and made some measurements there.
There is an option for 6L6 usage added.

Interesting finding in the data is the relation between the plate dissipation and measured output power.


https://el34world.com/charts/Schematics/files/Fender/Fender_deluxe_5d3_schem.pdf

6L6 data:

Plate voltage: 346V
Voltage on cathode: 22.2V
Cathode resistor: 200R
Cathode current/tube: 55mA
Plate dissipation/tube: 17W
Measured power total: 18W


6V6 data:

Plate voltage: 357V
Voltage on cathode: 19.2V
Cathode resistor: 250R
Cathode current/tube: 38.4mA
Plate dissipation/tube: 12W
Measured power total: 7W

Leevi

[PRR]

Two 6V6 at 350V should be more than the book-value of 14 Watts out, much more than the 7W you measured.

Suggests a mis-loading (what OT?), or since the 6L6 numbers are not too dubious, a bad 6V6.

[Leevi]

I'm using an OT which is specified for 30W and 8000 Ohm primary.
I have even used in some other projects 5E3 OT.


I don't believe that the question is about bad tubes since they are brand new and I have had similar experiences before.
I have build several 5D3 based amps and the measured power rating has always shown that low values. This has nothing to do with the loudness
of the amp since it sounds very loud. The only common thing with my  builds is that I have always used JJ's 6V6 tubes.


I can increase the measured power by increasing the screen voltage.


Here is the link to the previous thread about this topic I started some time ago.


https://el34world.com/Forum/index.php?topic=22386.msg239442#msg239442


Of course one reason can be my measurement setup. However I'm using an oscilloscope, 8 Ohm power load, and a quality multimeter that should run true RMS.
I have performed my measurements both with 440Hz and 1KHz. And the value is taken with a clean sine wave up to it starts to break.


/Leevi

[shooter]

8 Ohm power load

I don't do much P-P, but with a self biased clean only, your #'s seem about close.  I typically measure full out square also, just so the guitar guys are happy 

I also have a handful of 1-2 ohm DL R's so I can "tweak" impedance for max clean, at 1k, for some reason, 10ish ohms gets me the best rms audio power value.  I think one build was 6-ish, so 8 it is 

[PRR]

> I can increase the measured power by increasing the screen voltage.

Not given in that table.

Yes, high R to G2 matches the measures. For steady-state, Vg2 falls as you approach max output. The 6L6 is a bigger tube and will pass more plate current for similar Vg2.

OTOH, this is not a motor-driver. Not intended for steady sine-wave. It could be interesting to use burst-tones and see if it will deliver a part-second of higher power before Vg2 sags. For pluck-guitar, that's what counts. (Double Muff-Pi in front for sustained total overdrive is different, but came later.)

[Leevi]

Power measured with ~clean sine wave = 7.54V x 7,54 V / 8 Ohm = 7.1W


Power measured with ~square sine wave = 8.79V x 8.79 V / 8 Ohm = 9.7W


/Leevi

[shooter]

 
now you might get a player to like your amp cuz it's 10W
calculate the pk2pk and they get ecstatic 

I just sold a SS 10W amp, the buyers where cork-sniff wanna bez, they wouldn't believe it was just 10W, I had to explain 85db speakers to the +110db one's they were hearing.

my 2nd favorite part of building is doing the specs, playing on 1st power-up....