Well, I have most of my issues with my build resolved. Thanks for those who advised me on my fuse blowing and grounding questions.
My amp seems to function properly. The only nagging thing left is the hiss. It varies up and down with volume, and seems a little much compared to my professionally built amps. At about 8 it's pretty high. When no guitar is plugged in, it's gone and quiet as a church mouse.
Any things I should look for to tame it?
Hiss on Hoffman Princeton Reverb Build
Moderators: pompeiisneaks, Colossal
-
Stevem
- Posts: 4576
- Joined: Fri Jan 24, 2014 3:01 pm
- Location: 1/3rd the way out one of the arms of the Milkyway.
Re: Hiss on Hoffman Princeton Reverb Build
When you have no cable in a input jack it is shorted and the first gain stage is not functioning from the grid back to the jack.
I would then suspect a bad noisy resistor, either on the input jack or the ground reference which is usual a high value like a 1 meg.
And yes even new resistors can be quite noisy!
I would then suspect a bad noisy resistor, either on the input jack or the ground reference which is usual a high value like a 1 meg.
And yes even new resistors can be quite noisy!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: Hiss on Hoffman Princeton Reverb Build
Thanks Stevem. So just so I understand...Stevem wrote: ↑Fri Feb 23, 2024 11:24 pm When you have no cable in a input jack it is shorted and the first gain stage is not functioning from the grid back to the jack.
I would then suspect a bad noisy resistor, either on the input jack or the ground reference which is usual a high value like a 1 meg.
And yes even new resistors can be quite noisy!
If it's quiet when the cable is unplugged, but hissy when it is, it might be the input jack resistor? I just want to make sure I have the order correct. If it is something to suspect, what would you suggest it be replaced with? It is new as you mention, and it is a 1/2 watt metal film.
I'm spending a little time reading through your responses to a 2020 thread on a similar topic:
https://ampgarage.com/forum/viewtopic.p ... ss#p419393
Thanks for the help!
-
Stevem
- Posts: 4576
- Joined: Fri Jan 24, 2014 3:01 pm
- Location: 1/3rd the way out one of the arms of the Milkyway.
Re: Hiss on Hoffman Princeton Reverb Build
Yes that thread explains what to do.
To test out individual gain stages for hiss you can jump out the plate load resistor and that will kill all the gain.
Also sometimes what people call hiss is 120 hz buzz.
If you have no metal plate covering the open side of the chassis when in the cabinet or when working on it this can be another noise source.
To test out individual gain stages for hiss you can jump out the plate load resistor and that will kill all the gain.
Also sometimes what people call hiss is 120 hz buzz.
If you have no metal plate covering the open side of the chassis when in the cabinet or when working on it this can be another noise source.
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!