HILGEN BASSO 2501 Bass Amp Help Needed....

[zozoe]

Good evenin' all~ I obtained this early 60's Hilgen BASS amp. Historically, Hilgen was a NJ company that was tied in with Sano, Giulietti, then what would ultimately be rebranded to Univox. Not that Univox had a model quite like this, but several other Hilgens did; 7591, GZ34, & a host of pre's. This particular amp had a beastly, stiff 15" which I swapped out for a Weber 12", which really steered it more to a guitar amp... But there still remained some slight low end content & was a little shy on gain/OD.... It had 2-7591's, a GZ34 & 2-12AX7's.
It's a 2 channel amp the just 1 tone & 1 volume for each.

Could someone kindly check out these schemes and advise me as to where & what possible cap changes could be done to the tone stack to filter out some lows, as well as what possible resistor or other component changes could give this amp a swift RnR kick in the booty for some more gain/OD....?

Here are the schemes, & thanks in advance or any & all assistance!! Kenny ॐ

Screenshot_2024-04-19_181351.jpg

There seems to be the 2nd 12AX7 missing, to my eye, so here's another scheme from basically the same amp, but it's a BASSO 2502 that seems to have some noted additions to the curcuit, but may be able to be isolated from what I require.....

Screenshot_2024-05-05_003459.jpg

[Raja_Kentut]

first thing I would do is halving the capacitances C1, C2, C3, C5 and check if the sound goes in the right direction.
Then playing around with different combinations.

Could you please share the supply voltages A, B, C, D ?

[TUBEDUDE]

I'd also cut C8 down progressively.
Reduce C9 and C10 to 22nF.
But for what you want I'd redesign it to a single channel to add your gain stages.

[Stevem]

If the 2nd 12 ax7 where missing then the amp would not play.

V2A is the mixer for both channels and V2A is the phase splitter to drive the power tubes.

In terms of any amp with just a tone control all it does is cut back the highs when turned down .

The level of bass produced will only change with how loud you play the amp, that is until circuit changes are made.

[zozoe]

I'd also cut C8 down progressively.
Reduce C9 and C10 to 22nF.
But for what you want I'd redesign it to a single channel to add your gain stages.

Thanks TUBEDUDE!! I'd love to have a great single channel setup instead of 2 just 'okay' channels.
Do you imply that have my tech perform some sort of cascading 12AX7s, or would these added gain stages be of another nature?

No, the amp has NOT had a 'thorough' going thru by my tech. The previous owner did display some amp smarts, but I shouldn't trust any assumptions. It has a 3 prong, it runs cool & sounds 'okay',,,, it just seems, as aptly named, to be a 'bass' amp, but putting in a 15" to 12" rebaffle'r ring certainly changed the amp's attitude, but I'd MUCH rather have one dynamite channel over 2
just 'okay'channels.... Think olde Supro, Gibson'ish....... I'm not an amp tech, but I can follow & identify stuff in a schematic, and pass along any commands or recommendations, to a point, but pickguards are my thing... Low voltage, no danger, & I can make anything imaginable......
thanks again for your 'input' ॐ
Lay it on me!!

[TUBEDUDE]

Yes, with 3 stages feeding your splitter you can get enough gain to satisfy. See if your tech is up for the challenge. Of course after he has verified correct operation as it sits. He could find degraded parts and their replacement might make it sound to your liking.