Flubby Bass

[suede]

Hi everyone I've read around the forum for quite some time but I've never posted. So here goes. I have a Marshall 50 watt plexi clone that's I've tinkered with up one side and down the other. I cannot get my head around the bass. I've done everthing and the bass is still too flubby especially at high volume. Well it's more noticable I guess. This might be unattainable in this life but I love the way the amp feels with lower filtering but that kills the bass. Is there a way to keep the looseness and have the bass tighten up.

Thanks, Suede...

[Structo]

Well yes B+ filtering is the first thing that comes to mind.

What are your bypass and coupling caps at value wise?

[suede]

Bypass caps are 0.022 uf and coupling caps are 0.022 uf. Mains filtering is 64uf (32x32 in series), Screens and PI filtering is 32 uf each and pre amp is 33x33 uf. Removed the v2a cathode cap. B+ is 433 vdc at idle. El34's biased at -35ma @ 60%. Power resistor in series between bridge rectifier and mains filter cap 10 watt 120 ohm. A little less clean head room. Tone stack is 47k/300pf. That's off the top of my head.

Thanks, Suede....

[mlp-mx6]

Are you sure that's 32/32 in series? If so, that is only 16uF. Double check that, please.

[suede]

My bad that's parallel

[dobbhill]

V1 cathode bypass cap value??
D

[KT66]

Changing the PS caps ( cap cans I assume ) to 50/50s will help . I built one once with 2 220U in series in the first spot ala Fender and it was pretty tight also. There is a reason though why some call the normal channel the "mud" channel.

[j-po]

I think taking 3 stages off one B node gives a loose feel even without a big bass.

[suede]

V1 cap is 0.68uf. How does one go about doing this. ("I think taking 3 stages off one B node gives a loose feel even without a big bass.") I've done the 50x50 uf thing and it does tighten up the bass but it also takes away that loose feeling. It's why I went to 64uf on the mains.

[suede]

Does anyone have any other ideas. I know there has to be a way I've heard amps that have that loose feel with the bass thing taken care of. It's just getting someone willing to cough up the mod.

[John_P_WI]

OK, what is the rating of the power transformer?
Did you use a choke?
SS or tube rectifier (assuming SS as you said 50 watt)?
What type of output tubes? EL34's with weak vacuum can sound soft.
What is the neg feedback resistor, what tap on the OP transformer?
What is the PI filtering? PI voltage?
What is the PI input cap?
Preamp voltages?

What are the tone stack values?

What type of speakers? What type of cab?
There is no real magic trick without knowing what you have. You can make 50 watters so stiff drop D is no problem...

I would try to stiffen up the power amp and bring things back a little with some resistance between the caps and center tap of the OT, larger screen resistors etc, or playing with the feedback loop. Give a little more info, there is a lot of experienced guys here....

John