Gain/voice mods for silver EL34 Shiva

[matt505]

Hi folks,
I'm looking for help with possible gain/voice mods for a silver chassis EL34 Shiva.
Like some folks, I think the Shiva is awesome, but if I could just get 'a bit more'
I've been googling and searching forums and have gotten bits and pieces, but could use some help with details on how to apply them to the silver Shiva.
I'm working off this schematic snippet I found, seems a bit odd, but maybe good enough for reference
http://spinoo.free.fr/sloclone/Shiva preamp.png

I've come across mods to preamp tube bias resistor/bypass cap - what I believe are called the Cantrell or Cameron mods?? - but they're for the Ecstasy
https://web.archive.org/web/2009042...0 ... dt967.html
I don't know which gain stage and what values work for the Shiva.

I also saw jumping R21, the 470k resistor between V2 and V3 to send a ~2x hotter signal into V3.

Looks like BrentSP has done similar, hoping to touch bases. (I can't PM yet)

Any help would be greatly appreciated!
Thanks!
Matt

 

[garey77]

Do you already boost in front of the amp? A Maxon OD808 or something like that might make the difference for you w/o having to mod.

 

[matt505]

Hi Garey,
Sure that's always an option, but I like mods.
Some of the vids I've seen/heard seem to have more good stuff going on than typically what a boost can achieve, IMO...
viewtopic.php?f=59&t=183833

-Matt

 

[ericsabbath]

I recently had to sell my 2002 silverback shiva
it was the best amp I ever played
although I love extensive modding, I wouldn't change a thing about that amp
my bandmate is well known tech in my city and he had lots of shivas in his bench, and this was the best
we even made a comparison side by side with a newer shiva combo and a 20th anniversary el34 shiva and the 2002 was the punchiest and most open sounding
and my amp came without a small mod to tame the power tube voltage supply a bit, cause most tubes can't handle that much (over 500v), which means it wasn't even running at its full potential

when I wanted more gain without adding an overdrive and without changing the core tone of the amp, I used a tc classic sustain to add a little compression and boost the center mids
it worked really really well

I wouldn't mess with the circuit to make it sound oversaturated like a Friedman or something
are you really looking for extra gain or just a different voicing? (more upper mids or attack)

 

[ericsabbath]

I wouldn't fully jump R1, but you could use a lower 220k, maybe 100k resistor
if you really want a more bitey marshally tone, you could replace c3 and c9 with 680nf (0.68uf) and add a 470pf bright cap bypassing the pot
this will deliver more upper mids and a little more grit on the gain

 

[matt505]

Thanks for the info Eric!
I really dig the Cantrell/Cameron mod 3 way switch heard/seen in the video from the link above.
From what I was able to glean, it's different combos of R/C cathode bypass - I'm trying to find out what values and which gain stages work for the Shiva...

 

[ericsabbath]

you could also mess with the tonestack a bit, by replacing R26 with 39k and swap the 470pf with 680pf (or just add 220pf in parallel) to shift the mids a bit towards the upper range
messing with the negative feeback resistance makes a huge difference too
using lower resistor values makes the amp tighter and more controlled

but the cathode capacitors I mentioned alone should do the job
I wouldn't bother installing a switch, though
switching cathode components demands some small tricks to avoid popping and will require drilling or removing stuff from existing holes

 

[4406cuda]

You probably want to BrentSP

He is on Rig-Talk and has the those mods on his Shiva