Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Diverted on May 28, 2021, 03:13:25 pm

Title: Component layout, SE reverb
Post by: Diverted on May 28, 2021, 03:13:25 pm

I've built a few small single ended reverb amps. First one was really clean and hum-free; the most recent has some reverb hum which I haven't been able to eliminate yet. I didn't use a choke in either.
I'm going to build another one and see how a choke works.
It's a pretty tight 15" vibroverb chassis. Only change from schematic is I'm using diodes to rectify the AC. How does this look?

Thanks,

Ted

Title: Re: Component layout, SE reverb
Post by: sluckey on May 28, 2021, 08:29:54 pm

Lot of familiar stuff. Should work.

Title: Re: Component layout, SE reverb
Post by: Latole on May 29, 2021, 03:37:02 am

Hum !
May not come from what you build but how you built it .
Picture of your wiring may help.

Title: Re: Component layout, SE reverb
Post by: Diverted on May 29, 2021, 07:11:46 am

Thanks Latole.
Here's the only shot I have of the hummy version, but I can get more once I open it up. It's got the standard low hum that increases as reverb is turned up; it's quiet with no reverb.
The other version of this amp that has no hum has the same chassis, same schematic and same layout. Very odd. After this pic was taken I tried a few things to tame it: using more shielded wiring in the reverb path and isolating the reverb jacks and running their grounds to the main preamp ground buss. Neither had any affect either way.

Three things not shown in the schematic but in the amp pictured are (1) preamp cathode cap switch, (2) mid boost switch and (3) negative feedback switch.

Title: Re: Component layout, SE reverb
Post by: Diverted on May 29, 2021, 07:16:45 am

Quote from: sluckey on May 28, 2021, 08:29:54 pm

Lot of familiar stuff. Should work.

Thanks. Just wanted to confirm that the transformers' and chokes' orientation looked good. Thanks!