Power amplifier designs

[fossilshark]

Hi, I recently finished a JCM800 2204 clone head for my rythm guitarist and I play through an LA50BL clone ("clone" is a loose term).

When we jam the 800 quakes the place before hitting 1, as I recall another amplifier I based off the same amp a few years ago did so too so this is expected. Unfortunately the LA50BL requires about 3x the volume turning effort to close to mix level and it's really hard to get them equal output and not one louder than the other. I know the 800 is supposed to have weapons grade treble (we have installed a "plexifier" switch that almost helps) and from what I read so should the LA, while it doesn't sound muddy and I have always THOUGHT I sounded exactly like grainy live tapes of Iommi, the low end seems to be what it pushes out the most when compared.

My guesses: Classic tone jcm800 output transformer, and on the LA50BL I stole the output transformer off a Dynaco ST-70 (I now very much regret) so should I just swap it out for the same transformer as on his? I crammed a p2p 2204 into an 18W marshall chassis because the website said 2204 kit and lied, so thats NOT getting swapped.

My 3 year old power tubes? I never remember this amp being a serious earth shaker but I know I should do it anyways and I do plan to. I figured they were matched though due to the abuse his power tubes received during some failures to engineer properly.

And what I really hope it is: Should I just rewire one of the power amps into the same output design? I followed them pretty much exact (idk about plate voltages though honestly) and I was wondering if I could get some insight on the differences in the two topologies? Or is there none.

all advice is appreciated!

[d95err]

By being very loud at "1", do you mean the master volume? If so, what's the setting of the Preamp volume? You can't really compare knob settings between the amps, as one has a master volume and the other does not. They may also have different taper pots, etc. Many factors that could affect how the range of the knob settings affect volume.

What speakers are you playing through? Is the loudness difference still there if you swap speakers between the amps?

What are the anode voltages of each amp? Does the Laney run the 590V shown on the schematic? What about the 2204?

From what I could Google, Dynaco the ST-70 OT should be designed for 35W each, so that may limit the actual output of the Laney a bit. However, the difference between 35W and 50W is so small it should not account for any obvious volume difference.

[fossilshark]

yes I am referring to 1 on the master volume and I should've clarified, its preamp gain dimed on both amps with similar distortion pedals. Further inspection concludes about 500v off the rectifier on the 800 and 440v off the rectifier of the LA.

[sluckey]

JCM-800 2204... Plug into the LO input and set the MV to max. Now compare the two amps.

[d95err]

Does the Laney have a master volume? If so, what type? Are you comparing mater volume settings on the amps?

Also again, what speakers for each amp?

[fossilshark]

we use the 800 on the low gain channel and the laney has a 1M master vol right off the tone stack just like the 800 (forgot thats not in original specs). for speakers we have a 2x12 loaded with celestion G12T-75s with little low end, a Traynor 1970s PA 2x12 with the expected full range response we tend to plug the 800 into, A Peavy 1x15 full range cab (from some SS combo its built like a brick), and my 4x12 loaded with random eminences I managed to have lying around with no low end at all. weve tried all concievable combinations and found the 4x12 and the Traynor 2x12 with the laney and 800 respectively get it kind of close but we also change things around based on what we feel like moving.

What has also helped a bit is we both use a Rangemaster boost design (with darlington pair) and his is tweaked to be a full range while mine is the standard treble booster.

[d95err]

Did you accidentally use a linear taper pot for the master volume on the 800?