Non-mid boost Sentura2 Sunn

[DDusk]

Hi All

I am new here,but i have a question,i am getting a Sentura ii that has no mid boost,so is it possible to add one by using the ground switch (disconnected of course) if so anyone have a diy circuit,or schematic of the mid boost  circuit,i hope i am explaining this so you guys can understand,not a amplifier guru

Thanks
Peace

[Isaac]

I understand, I think. The Sentura II has been modified to have a grounded cord, and the 'death cap' has been disconnected, to the polarity switch has nothing to do. You want to add in the mid boost circuit that is on later models, using the polarity switch. Right?

I see no particular reason it wouldn't work.  There could be an issue with a long wiring run in the vicinity of the power supply section. My Sentura II schematic doesn't have the mid boost circuit, but my Sentura II does. So, if no one else has a schematic, I might be persuaded to open mine up and trace the circuit out. Be warned, though, I'm a lazy old fuck, so it'd likely be a while, if I ever got to it at all!

[loudthud]

I think the mid boost circuit requires three poles and there is no three pole version of the Carling rocker switch. That means you will need a relay and a way to power it. The relay can be located near the Contour pot so the signal leads can be short.

[Isaac]

Could be powered by the heater circuit, maybe.

The Model T has a mid boost circuit that might be adapted for this purpose, and it would need only one pole.

[DDusk]

Hi all
well,i think i will live without the mid switch,but thanks for all the shared info so very much

Peace

[Isaac]

I dunno. Seems like a good idea to me. Last time I played guitar in a band (I usually play bass), I used the mid boost quite a bit. I found that the distortion was rather harsh without it, though useful for some things. Old Rolling Stones stuff, like Jumping Jack Flash, for instance. But with the mid boost engaged, it became much smoother.

[DDusk]

Hi Isaac
just wondering,what if i put a Boss eq pedal in front of the Sentura and upped the mid band on the Boss eq,would this give the amplifier smoother mid.

Thanks

[Isaac]

Could be. Certainly worth a try. My guess is that the center frequency and bandwidth of the Boss might not be exactly the same, but that doesn't mean that it wouldn't be a benefit to the sound. There's also the issue of the boost taking place in a different part of the amplification chain, which makes a difference.

[DDusk]

Hi Isaac
Thanks for the reply

DDusk

[patlaw]

My Sentura II schematic doesn't have the mid boost circuit, but my Sentura II does. So, if no one else has a schematic, I might be persuaded to open mine up and trace the circuit out.

The mid boost circuit is on this schematic. You may be able to find a better copy.

EDIT: See below for schematic.

[DDusk]

Thanks Patlaw
tried to open with the link,did not work??,but thanks

DDusk

[Isaac]

I opened it with the link. It came up, but dimmed, as you say. Washed out. However, I was able open it in another viewer and save it as a jpeg, which helped. Try this: