Tweaking Blues Deville Bass Response

[slapbackdaddy]

Thanks again for recently helping with my deville's voltage questions. I've fitted a bias trim and have taken the amp out on a serious road test...all is great, purring like a kitten. I do however have a question about the bass response of the amp and wondered if there's a way to mod the circuit to actually reduce the bass a little. I always run the bass control at zero but as i'm mostly playing hollow or semi hollow archtops i sometimes wish the bass control went to minus 10! It's great sounding amp and i realise that the response is coming mostly from the size of the amp and the 4 10" speakers.

What do you think? Any suggestions?

[MWJB]

First off try a 12AT7/ECC81 in V3 and/or a GE5751 in V1. This will reduce gain a little and the amp may be less stodgy. If this is not enough try reducing the values of C1 & C8, you might try 1uf to 4.7uf & decide by ear?

If your amp has the Eminence 102 speakers, these can be a little attenuated in the high end and "thick" sounding for guitar, a Jensen P10R style speaker will be chimey-er, more scoped in the mids - perhaps start off just by replacing the top 2 and see where that gets you?

[pdf64]

Hi SBD, from what you've said I would reduce the value of the phase splitter input cap. The schematic on the fender site indicates that this (c23) is 0.022uF. The value used in a lot of the BF types was 0.001uf, 20 times smaller. Try that and see if you like it, it should get rid of the excessive woofiness and make the bass control useable again. If it cuts a bit too much low end out, try 0.0022uF, then 0.0047uF, till you find what suits your application. Some Orange amps had a multi position rotary switch labelled FAC to make this type of tuning user adjustable.
Hope that helps - Peter

[slapbackdaddy]

Thanks MWJB

I have some some 12at7's knocking around, i'll try one in the PI and let you know how i get on. After biasing the amp and replacing the filter caps etc it's actually twice as loud so reducing the gain a little might be good. I just backed the bias voltages on the output tubes to nearer 29/30ma....had them at 33, sounded great but was a bit of a handfull.
Thanks again for your instant help! I love this forum.

[isaac]

Yea that's my advice too. Make the input coupling cap a .002 or .001 You might change the tonestack to match a blackface twin, look at the schematics, and change it, that might help, im not sure of the response difference, but I ALWAYS like a BF twin tonestack in my amps. If it were me, and I were rebuilding the WHOLE AMP, I would remove all the SS stuff and make basically like an older designed thing, and get rid of the drive channel, or build a nicer marshall or similar drive, all tube too. But those are MAJOR and your problem is with bass not the whole amp...