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when i first started the amp i had no power at all, very low distorted sound with vol all up. finally found i had left out the output coupling caps. after fixing that the amp seems verry loud. i cant seem to get a good tone at low volumes. the gain is lose and fizzy.

Can you post your voltages and compare them to the layout.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

refering to the s111 plexi layout where voltages are indicated on the board next to the eyelets, from left to right my voltages are 13, 333, 208, 219, 55, 80, 57, 189, 123, 1.24, 100.7, 101.5, .72, .71, measured to ground. voltage across the 150 ohm cathode resistor is 13.17

it looks like im at 14 watts dissipation. do i need to go up to a 180 cathode resistor?

I wouldn't concern myself with the o/p tube bias until you get those preamp voltages in line. That may or maynot change the plate voltages on the o/p tubes and hense the disapation. Is that 2.2K in the center of the board correct?
Stew

No, it's fine. Generally the volatages seem low. The cathodes on V1 should be close to 1V, not .7V

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

just checked that 2.2k and it reads 22k, the colors are red red black red. so 2.2k and 2k2 are 2200 ohms?

Yes, 2.2K = 2K2 .

22K = not correct!

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

does the layout show 22k or is the decimal not visible? if you could change the layout to show 2k2 that would prevent this from happening again. i used the layout to build the entire amp.

Fair enough. It is 2200 ohms, 2W, not 22K

All layouts have been updated, and other notations checked.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

ok heres new voltages, 13, 328, 196, 205, 51.5, 75.5, 53.6, 256, 168, 1.6, 138, 139, .95, .95. looks like 43ma at 13.5 watts. i still think i should increase the cathode resistor to 180 or probably higher. isnt 43ma way to much for el84's?

When doing the dissipation calculation did you remember to subtract tha cathode voltage from the anode voltage? Also did you subtract the screen current from the cathode current?

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Great tones come in small glass jars!

heres what i did,
13/150=.0866/2=.043, 328-13=315x.043=13.5W

this time from the pins
v4 =348 plate pin 7, 335 pin 9
v5=345.5 pin 7, 335 pin 9
voltage across the cathode resistor is 13
voltage across the 100r is .84 wich = .0084, do i divide that in half for two tubes? now
343-13=335, 335x.043-.0042=13

OK, that all looks correct. 13W really is too high. Looks like you may need to use a 180 ohm cathode resistor.

Funny I was talking to some guy on 18watt.com about the exact same subject.

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Great tones come in small glass jars!

no way, really?

Considering you used 150 ohms per spec, why would this be dissipating so much in this case? We have used 120 in the past.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

heres another thought, i got the tubes from lv i think. the box have a sticker that reads 22.5/5.05. are these tubes to hot for this amp?

No idea. Probably LV should be able to advise you.

Another thing, IMO that shared 100 ohm screen resistor (from the classic 18W design) is also too low IMO. I suggest swapping a 1k in its place, and then measuring again.

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Great tones come in small glass jars!

Is it possible the 150 ohm is NOT 150 ohms? Please measure it.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps