Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: fossilshark on February 22, 2017, 08:34:32 pm

Title: Amp sounds horrible
Post by: fossilshark on February 22, 2017, 08:34:32 pm: Ive been working on this build for a few months and i just got sound out of it. Theres absolutely no sound (no noise no ambience) coming out of the speakers until i play a note then it kind of sags and fades out. I thought mabey there wasnt enough signal but my distortion pedal had no effect. The weirdest part, when i turn it off you can heard my hands on the string and the feedback for a split second and it shuts off. Does this sound like the plate voltage is too low? Ill take some readings and post them here.
Title: Re: Amp sounds horrible
Post by: fossilshark on February 22, 2017, 08:44:45 pm: When i measure the voltage it wont stop rising
Title: Re: Amp sounds horrible
Post by: p2pAmps on February 22, 2017, 09:24:03 pm: Detailed pictures would be helpful
Title: Re: Amp sounds horrible
Post by: uki on February 22, 2017, 11:36:20 pm: Also the schematic of the amp can help !
Title: Re: Amp sounds horrible
Post by: hesamadman on February 23, 2017, 09:43:53 am: Does it act as if there is a heavy noise gate? Like if you barely hit the strings there is no sound but if you pluck them good there is a sound but with a very fast decay?
Title: Re: Amp sounds horrible
Post by: pompeiisneaks on February 23, 2017, 09:52:36 am: As others have mentioned, if we don't know what 'kind' of amp and don't have a schematic, it becomes impossible to even guess intelligently. Also, pictures of the amp will help us look for things in the schematic that don't match on the actual amp.
Title: Re: Amp sounds horrible
Post by: MFowler on February 23, 2017, 10:04:27 am: You need to go over your schematic/layout against your amp to see if it is wired correctly and measure every resistor. I usually check resistor values with DMM before I wire them in and when I don't I find that I have mistakenly inserted a 100 ohm for a 100k (example) and no sound or gated sounded happens.

Hello Phil (pompeiisneaks)

Mark
Title: Re: Amp sounds horrible
Post by: pompeiisneaks on February 23, 2017, 11:25:24 am: Quote from: MFowler on February 23, 2017, 10:04:27 am

You need to go over your schematic/layout against your amp to see if it is wired correctly and measure every resistor. I usually check resistor values with DMM before I wire them in and when I don't I find that I have mistakenly inserted a 100 ohm for a 100k (example) and no sound or gated sounded happens.

Hello Phil (pompeiisneaks)

Mark

I see you've come over to the dark side :) or is this the light? I'm not so sure lol
Title: Re: Amp sounds horrible
Post by: fossilshark on February 23, 2017, 11:49:39 am: I made a dummy, plate voltage was too high. I was using the wrong transformer line for tha plate voltage
Title: Re: Amp sounds horrible
Post by: pompeiisneaks on February 23, 2017, 12:45:34 pm: Is this some kind of multi tapped Transformer? usually the highest voltage output is the one for the plates. ?

~Phil
Title: Re: Amp sounds horrible
Post by: fossilshark on February 24, 2017, 12:23:47 am: Yes its really weird theres a 700v line with a few center taps with different voltages like 280v and 390v
Title: Re: Amp sounds horrible
Post by: pompeiisneaks on February 24, 2017, 02:42:19 pm: OH ok, gotcha, possibly an UL transformer, I think they do have two sets of taps for UL mode or some such.