Lowering your bias will benefit the bass response; less flubby.

Cranking the presence control and at the same time lowering the treble also has a
good chance to control the flubby bass.

Picking the right speaker is also important; I prefer EVM12L; no flubby bass response at all.

without hearing it.... it could be any number of things..... starting with your guitar pickups, pots , cable, etc

also preamp tubes...... the first one will have most effect on the overall tone of the amp...... and the last one (V3) which is the phase inverter has a larger impact when the amp is turned up. V2 will affect the quality of the overdrive sound. i have no experience with tungsols as i have always used EH and Mullards.......try swapping preamp tubes for different brands and see if there is any difference. Nik has told me that tungsols have given him many headaches as they are not consistent.

but ..... i am just guessing........because i havent heard it.

but i would definitely try trying different preamp tubes

that means you have about 47mA running through the resistor. without further measurement we can assume maybe 5% of that current is grid bias current.... so 95% of 47mA is 45mA. now the plate voltage on the valve is 435 volts.
multiplying them together will give the IDLE dissipation. so 435 x .045=19.75 watts. this is about 66% of the maximum plate dissipation (30w)... a little hot.  60% seems to be the industry standard.

now remember, more power will be put through the tubes when you play, so i would say this is a little on the hot side. most people will bias at approx 60% which gives a good compromise between tone and tube life time.

according to nik, his optimal bias point is 37 mA which is on the cool side. (i remember reading somewhere that dumbles should be biased cool) 40 mA would be a good compromise (which is about 60%) and 43 would be considered "hot"

hope this helps.

according to nik 5mv difference or so is acceptable. 10mV is a bit on the high side (hence my balance pot mod)
did you buy them as a matched pair?

if you look under the chaasis, between to the output tubes you will see a pot with no knob on it. in the first picture you posted you will see two red banana connectors (well the back of them).... and one black one.

to check your bias, you dont need to remove the chassis. you simply use a DVM able to read mV and measure between red and black for each valve. you need to get the voltages as close to identical as practicable. the bia pot will allow you to do this. make sure your tubes have been on for at least 5 to 10 minutes and all master volumes turned to 0.

try to buy matched sets. the reason being is that the bias current is set on the amp, and therefore the bias to balance the valves will be minimal.


hope this helps.