Replaced power/preamp tubes-need help with Channel 3 treble

[ironmaidenfriday]

Hi everyone,

I have owned the Mark V for about a year now, and after reading these forums decided to swap out the 6L6's with EL34s. I put in SED winged C EL34s (bought from Tube Depot - matched quad, 33 bias), and also swapped out the following preamp tubes (previously stock):

V1 - Mesa SPAX7
V3 - Mesa SPAX7
V4 - JJ ECC803 (matched & balanced triodes)
V7 - JJECC803 (matched & balanced triodes)

When I tested the new setup, channel 3 seemed to lose a lot of its gain/bite when using my old settings (across all 3 modes). Typically I used to have the gain set about 2:30-3:00, treble 10-11, mid 12, bass 10, presence 9-10.

Under the new setup, setting the treble anything below 12:00 seemed to choke the gain. In fact, I didn't start getting the high-gain growl until I set the treble to about 3:00. Is this a normal result with EL34's, or could it have something to do with the preamp tube replacements? Any advice/help is greatly appreciated. I love the musical qualities of the EL34s, but was surprised at the impact that the switch had on the tone controls.

 

[JOEY B.]

Preamp tubes, for sure.

 

[eudaimonia02912]

I bet it's your preamp tubes.

 

[Anonymous]

excellent advice here..

i'll place the stock preamp tubes back and from there replace one at the time....... before you try that put the stock V4 back and hear if there any difference (the JJECC803 has less gain than a JJECC83) v4 has an effect on the reverb send and 2nd drive stage for ch 3 so hopefully that's the problem.

good luck

 

[ironmaidenfriday]

Thanks for the advice everyone. I will give it a shot in the next few days and let you know how it turns out

 

[ironmaidenfriday]

Update:
I replaced V4 with the stock Mesa tube, and it turned out much better (left everything else as per my original post). The EL34s feel/sound amazing across all of the channels, so I definitely glad to have made the switch.

However, now Channel 2's volume is markedly louder than Channel 3. I searched the forums, but couldn't find anything about this issue.

Once again, do any of you have any advice?

Thanks

 

[konstantine RK]

first off you should have put your first 3 preamp tubes like this...

V1 - SPAX7
v2 - Chinese 12AX7 (I use a Penta Lab 12 AX7
V3 - SPAX7

and whatever else makes your beenie twirl


try that