Tonal balance Kaiju with DC filement add on

[PeterNissen]

I have had the Amplifier for a while,, and now added my MorePlay preamplifier to the setup. It has been a great upgrade, and sound and volumen is better than expected. So far so good - striving to make it perfect ....
However, there is one issue: The tonal balance in the 2 channels are not alike (audible bit not a disastare). One of the channels are missing the treble - and it is easily identified whan listening til the speaker; One side does not give any signal in the tweeter. By moving the 3 "Parts" around I have verified that the diffence only originates from the power amplifier.
Anyone who can provide ideas to why this is the case?
Could it be one of the capacitors that underperform - and what capacitor in the circuit would that be?
What voltage-measurement would be useful to share / what voltage measurents would be relavent to obtain to pinpoint where the error might be and what adjustments is possible (new capacitors to replace existing, bias adjustment, potentiometer adjustment?)
FYI: My speakers dividing frequencies are 700 and 6000 Hz as to compare to the output of the tweeter. Midway speakers seems not to be differenr, as from and audible point of view, based on keeping one ear ciose to the speajer baffle and move the head from tweeter (horn) to woofer passing the midway (horn)

Due to the sequence of buildiing-kit-events I have no data/measurement on the amplifier without the DC filament add-on installed

Best regards Peter

 

[Doc B]

Since you have determined that the Kaiju is where the issue is originating, have you tried swapping the tubes between channels to see if the lack of treble swaps channels with one of the tubes? That would be the next thing to try.

 

[Paul Birkeland]

I have found that the sound of a bad solder joint often present like this, where you get a really dull and lifeless sound, so if swapping tubes doesn't help the issue, reflowing solder joints would be the next thing to try.

(Also don't forget that cables like to act up too, be sure to trade the cables around a bunch to be absolutely positive this isn't the problem)

 

[PeterNissen]

Doc B: Good proposal, but no effect at all on the tweeter output

Paul: I have spend many hours following your advice optimizing the solderingnprocess, so I di not think that where the issue is: The sound comun out is not dull or ligeless, the 6000Hz and above is simply missing. I really can´t understand the cable comment "trade the cables around a bunch" is some kind of slang I may misunderstand. but as explained above the pre amp to power amp cable was also switched around in the attempt to find the error. And the cables are of the more expensive sort
Any comments in the C4S potentiometer adjustment or bias adjustment position and voltages/ measuring points

Best regards Peter

 

[Paul Joppa]

At this point, it would be wise to check the voltages, particularly those around the driver/regulator tube.

If the bias system has too much resistance, that could increase the plate resistance enough to reduce the treble due to the 300B Miller capacitance. Also, if the grid stoppers on pin 3 (driver or 300B) is damaged or badly connected the same possibility arises. Check the level control as well; a partial failure there could interact with the driver Miller capacitance. These possibilities seem unlikely to me, but so far I have not been able to think of any other way to get a rolloff in the treble only.