More Bass/Less Mid mod for a Sovtek Mig 50h

[Stringbassfellow@]

Hello all,

Looking to mod my Sovtek amp to work better with my pbass. Anyone suggest a mod if I can dig up a schematic?

Thanks!

-Chris

[Jazz P Bass]

Sovtek Mig50 Schematic.

Here is the schemo.
(courtesy of Bruce Collins @ Mission Amps)

Realizing that it is only a 50 watt amp may curtail your endeavors.

I would assume that you have a decent 15" speaker.

[Stringbassfellow@]

Yes, just curious if I can get some of the mids out and lows more present.

I am using an Eminence 15" and 12" cabs. Bot cabs sound great with my b-15n.

Just want to see it is possible to get more from this amp.

[Jazz P Bass]

Download the Duncan ToneStackCalculator.
TSC

There appears to be a mid control on the amp.

Use the TSC, plug in the cap & resistor values for the amp & see if you can change the stack to your liking.

[Chuck H]

If it's just a matter of it's EQ and not the amps power I would say increase the value of all the caps in the tone stack. Maybe 390p treble and .047u bass and mid.

[soundguruman]

In these amps you almost always need to change the control pots.
I put PEC pots in...or You can use alpha, Bournes, etc...
otherwise you will have problems with the pots dropping out.

Bass pot: change to .1 uF
Mid change to .047
Treble change to 500 pf
Change interstage coupling to .047 instead of .02
Change phase inverter coupling to .1 instead of .02
Change bypass of first preamp cathode to 25 uF

I mean it's just a copy of Marshall, Bassman, so use the Marshall / Fender bass amp schematics.

The transformers are nice and beefy, should have good bottom end.

But 50 watts is kind of small for a bass amp.
Will never have a lot of headroom for bass.
OK for low volume clubs, if that's what you are looking for.

Mig is actually a pretty stoutly built chassis, except for the pots.
They gotta go.
And I would use cliff jacks for sure.

[Stringbassfellow@]

Thanks everyone for the input.

This is great info!

[soundmasterg]

Do you have a Mig 50H Midget amp, or a MIG 50, or the Bass version of the Mig 50?

I'm not sure that the schematic posted previously is the correct one. If it is the first amp (50H), then that circuit is similar to a JCM800 Marshall design and isn't really a bass amp. See the schematic I posted.

They did make a bass amp version of the Midget head, and these are a different circuit from the 50H that they called the Bassov in their literature. I've played one before with a bass and it was ok and had enough bass for most people. The guitar version would certainly not have enough bass for a bass player and would be way too distorted too. The Midget amps had decent quality pots and were the best made and most reliable of the Sovtek amps....this would include the 50H guitar and bass versions. The other Sovtek amps like the regular Mig 50, the Mig 60, and the Mig 100 had lousy quality pots and jacks and should be replaced as noted above. You can find most of the Sovtek schematics at the following site: http://el34world.com/charts/Schematics2.php

Greg

sovtek_mig50h_midget.pdf

[The Dude]

In these amps you almost always need to change the control pots......Mig is actually a pretty stoutly built chassis, except for the pots. They gotta go.

Agreed. The pots in these things are shi+. Changing them all would be the best thing you could do for this amp. I've done many. I usually use CTS pots and just run wires to the board. Time consuming, but well worth it.

[Stringbassfellow@]

Just got the caps replaced with the larger values and this is one beefy little tank.

Thanks for all the suggestions!