Bassman Homebrew

[xtian]

I recon you spotted the issue!

[BillyBob]

Hello,
Thanks for the message and help.
My plans are to play this thing and see how it performs in the coming days or weeks.

Hopefully its finished now.! (you know how that goes..)

Bill

[BillyBob]

Hello,
Bassman Homebrew sounds great! And is fun to play!

Id like to reduce the Bass response somewhat though.

The amp sounds great, but I run it with the Basss knob on zero....Mid on 50% and Treble on 75-90%

Any ideas on how to reduce some Bass.? Just so the knob doesnt sit at or near zero?

Bill

[sliberty]

Hello,
Bassman Homebrew sounds great! And is fun to play!

Id like to reduce the Bass response somewhat though.

The amp sounds great, but I run it with the Basss knob on zero....Mid on 50% and Treble on 75-90%

Any ideas on how to reduce some Bass.? Just so the knob doesnt sit at or near zero?

Bill

In my 864 clone, I have repurposed the deep switch so as to change the first cathode cap between Fender and Marshall values (22uF vs .68uF). The Marshall value is much tighter and offers a great variety option.

But in an earlier post, it was mentioned that your cathodes are unbypassed. Not sure how adding in these switchable caps will work out for you.

[BillyBob]

Hello,
Thanks for the message.

In doing my (amature) circuit mods, I removed the bypass caps as a gain reduction method. At some point after I had cascaded the stages I had too much gain going on.

Now the gain is just about right. Usually I rock out with my Marshalls or my recently finished Express but this amp rocks! No foot pedals required here. From mild break-up to classic crunch, to metal chuga-chug stuff its 99% awesome.

Ill try experimenting with those caps again to see the effect it has on tone and on the range on the Bass knob.

I thought of changing the Bass pot value but dont know if thats worthwhile.


NOTE: for the record I own two other unmoletsted Fender Bassmans; 864 and AB165, and I love the original Fender tones too.!

Bill

[BillyBob]

Yes!
Thank you sliberty..
I tried as you suggested, with great results. I ended up leaving in the .68 The effect was impressive.
Just what I was looking for.
And I learned something..
Thank you.

Bill

[pdf64]

In addition to setting the bias for EL34, you also have to consider the speaker load. EL34s expect about half the load (3K-ish) than 6L6s (6K-ish)...I THINK I got that right. someone please check my brain.

I think that Fender have tended to use an OT ~4k per 6L6 pair, at least from the 5Fx era onwards; so a bit lower than the 5k6 value would would seem to be the best fit from the info sheet http://www.mif.pg.gda.pl/homepages/fran ... /6L6GC.pdf
A standard EL34 OT impedance in AB1 fixed bias is ~3k5.
So they're close enough for rock'n'roll.
EL34 will draw more screen grid current, so screen grid resistors need upping in value and rating above the standard 470 ohm 1 watt 6L6 spec.

[BillyBob]

Hello,
Thanks for the input PD64.
For those power tube screen grid resistors Im at 1k at 2w.
Should be kosher.?


Bill