Bash_Man
Well-known member
Let me know what I can do for you.
Taming the Bass in My Splawn Comp
- Thread starter Junk Yard Dog
- Start date
PDC
Well-known member
As far as glass is concerned, the EL34-II adds a touch of low end and the E34L adds even more. A ‘regular’ EL34 offering will pull a bit of low end out. In the pre section, I have found that Electro-Harmonix EH12AX7 tightens up the low mids and adds a bit of sizzle to the tone. I also endorse trying various speakers as certain speakers and enclosures are definitely darker sounding. Finally, I wholly agree with the previous post stating that rolling the mids and treble up while rolling the bass down will definitely create the impression of taking more of the bottom end out. Boosting the mids / treble / presence while rolling the bass back will make the amp sound and feel louder without all the low end.
harddriver
Well-known member
I haven't done it to my Splawn but I have installed a standard depth and NFB feedback control on another high gain SLO/2203 build I did both the depth and NFB pot made the amp super flexible from high gain plexi to tight metal. If you don't want to install an NFB feedback control then the standard depth mod would give you total control over how much/ and what bass/lowmid frequencies you want in your tone.
Spider is 100% correct about the .22uf cap feeding the tonestack, they are also in the PI. If you like the muscle of the Splawn then maybe leave the .22uf caps on the tonestack and PI but eliminate the .22uf cap after the NFB resistor and replace the cap with insulated wire step 1. If you don't want to install a 1 MEG depth pot you can also experiment with say three different values caps on a three way switch with the stock .22uf and two other different values giving less bass as you might have to drill a hole in the chassis for the 1meg pot and you may not want to do that.
If you still want the Depth mod pot method then have the Tech install a standard Depth mod and use differenet capacitor options to let you fine tune the low end frequencies that you want to emphasize, standard is .0047uf but you can use other values to change from big lows to more low mids which shouldmake the amp more tight. IF tow different cap values work for you then have him install a 1 meg push pull for the other maybe .0022uf(less bass) then parallel another .0022uf which would equal .0044uf (more bass) or he can even install a 3 way switch with 3 different cap values giving you three selections of freqeuncies for the depth mod to boost.
Maybe Spider can double check my capacitor UF selections for the depth mod standard pot, I know the .0047uf cap has the most bass. It's been awhile since I messed around with depth mod pot values.
Do topic search Psychodave had threads discussing different depth mod pot cap values and what frequencies where enhanced. I'm not sure what year this quickrod is but it should be somewhat close. Whatever way you chose to go it should be a relatively easy prject for a decent tech.
I just had a quick look at this Quickrod pic and it looks like above the 220K NFB resistor there is no .22uf cap in place like in an old Splawn mod board (which is what I have) from what I can see, I only see a piece of buss wire. If your has the buss wire there then all your bass is coming from up stream in the circuit like the tonestack capacitor and PI caps.
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harddriver
Well-known member
Here's are good threads that will give you some ideas and what to expect from different cap values and maybe help you decide what methods you want to try.
https://www.rig-talk.com/forum/threads/negative-feedback-question.231911/page-2#post-2608247
Here's the Psychodave thread on the depth mod....more good info for you to select values and decide if you want the fixed depth mod like Friedman or the depth mod pot method.
https://www.rig-talk.com/forum/thre...fferent-range-feel.312315/page-3#post-4013781
https://www.rig-talk.com/forum/threads/negative-feedback-question.231911/page-2#post-2608247
Here's the Psychodave thread on the depth mod....more good info for you to select values and decide if you want the fixed depth mod like Friedman or the depth mod pot method.
https://www.rig-talk.com/forum/thre...fferent-range-feel.312315/page-3#post-4013781
Junk Yard Dog
Well-known member
This is great, thank you! I would love to add a Depth & NFB knob to my mini comp. So my question is, is there anyone on this forum that is willing to do the work? I could ask my amp tech here in DFW, but he doesn’t really do any mods.
headlessdeadguy
Well-known member
Have you tried the treble on zero and presence dimed ? Looks crazy but worked wonders on my Nitro. A Gup Tech Quebec in the loop was the finisher.
harddriver
Well-known member
As long as you don't mind drilling a couple of holes and you have room, you can use mini pots if you need more room. Maybe talk to your tech and replace the .22uf capacitors with maybe .1uf caps which will still be beefier but less bassy emphasis but still more than a stock Marshall and then add the depth mod with at least two different caps on a switch for tweaking and you could remove the 220K fixed NFB resistor and replace it with a 250K pot I don't remember if I used an audio pot or linear ask your tech which would be best for this.
You would almost have to be present to make sure that when he made the changes from .22uf to .1uf you liked it, before adding the depth mod pot and NFB pot. I think going .1uf there would still keep it beefy but reduce the excess bass that you don't care for, then the depth mod would add bass in the amounts depending on how much you turn the depth mod pot up to your liking instead of being fixed.
I'll try to confirm what I used and let you know what i used.
On my high gain build I originally used Splawn values in the tonestack and PI and the amp was thick as hell like the QR but I ended up going back stock Marshall values in the TS and PI and used .047uf PI coupling caps instead .022uf and then added the Depth mod and NFB mod that way it was completely flexible to dial in what you wanted.
Here's a layout for reference of a Stock Marshall regarding the tonestack caps and Phase Inverter caps values so you can see the difference.
Pm me and I'll send you something else for reference. These should be relatively straightforward and simple mods for him to do.
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reignman454
Active member
I know a few things have been thrown around... We literally fixed some of that on my amp in one cap being clipped....Took it from "Farty" (it wasn't but man it was in comparison after clipping it)
What cap?
reignman454
Active member
A good tech will know. I'm NOT a tech. It was on the pots, not anywhere on the board. I believe Scott did them to make it fuller sounding. Me personally, I like my tone to bite... Cut etc. Bot be "rounded" FWIW, I think it's a pretty common thing someone can answer as we did it to my Splawn modded 800 as well.
morgansbluff
Member
It's inside yeah. Once I got it where I wanted it I never touched it again. It doesn't effect gear 1 or 3. Just gear 2. I've never heard a noticeable difference between tube brands. The only reason the mullards made a huge difference is because I am certain the original PS vanes were damaged. Since I posted that my amp tech has had brand new PS vanes flash but still bench test ok. The new tubes did not take away the bass but brought back the treble.
Something crazy I found - turn your bass and treble to 10. The bass almost disappears. I found as long as the treble is above 6 the bass can come way up.
This is a bright amp so I embrace it. My jcm800 is also very bright. Sounds great in a mix.
I run gear 2 old switch. Eq relatively noon. Speakers are Greenback/A-type mix.