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Hoffman Amps Forum image Author Topic: Raspy distortion  (Read 3008 times)

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Offline dude

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Raspy distortion
« on: October 16, 2018, 01:05:11 pm »
Where would one look if distortion is raspy?
Marshall amp turned up, 6V6s, distortion has that raspy sound with a power cord and les Paul, coming after the chord is hit hard I hear an unwanted raspy distortion "a fraction of a second after"? Bias is right on, amp sounds great at lower volumes, tubes are good. doesn't do it as much with a strat but it's there if vols are up.
Just where do I start looking?


al
If it ain't broke, don't fix it.

Offline 1blueheron

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Re: Raspy distortion
« Reply #1 on: October 16, 2018, 01:36:28 pm »
Since you are using the term "raspy" I am assuming you are hearing it audibly vs. seeing it on a scope.  Does it sound raspy with other speakers?  A raspy sound and loud volume when you first strike a power chord could be indicative of a speaker distorting, bumping or partially blown. 

Offline dude

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Re: Raspy distortion
« Reply #2 on: October 16, 2018, 01:55:44 pm »
Speakers are good, don't have a scope, raspy with other speakers even a Blue dog. Maybe this is normal when gain is up..? Where can I read about blocking distortion?
If it ain't broke, don't fix it.

Offline sluckey

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Re: Raspy distortion
« Reply #3 on: October 16, 2018, 02:23:53 pm »
Quote
Where can I read about blocking distortion?
Google is the first place I always check.
A schematic, layout, and hi-rez pics are very useful for troubleshooting your amp. Don't wait to be asked. JUST DO IT!

Offline dude

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Re: Raspy distortion
« Reply #4 on: October 16, 2018, 02:39:56 pm »
Read about Blocking Distortion and Crossover Distortion at Aiken's site. All my speakers have that raspy distortion with the same amp, good quality G12H30's, Blue dog and a Red Fang, hopefully their all not blown,  :sad2: . All my other amps have that raspy distortion with a Les Paul too. I think I have the gain up too high and I'm a strat player, my ears aren't use to humbuckers. I need to listen to Hendrix on my CD's and listen if I hear that crunchy, raspy tone, might be normal, ha. I don't usually play with high distortion, just at the edge or a hair beyond. Listen long enough I might hear the cows coming home :laugh: .


This a good site , plain and simple:  https://robrobinette.com/Tube_Guitar_Amp_Overdrive.htm


Don't fix it if it ain't broke!
« Last Edit: October 16, 2018, 02:43:46 pm by dude »
If it ain't broke, don't fix it.

Offline sluckey

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Re: Raspy distortion
« Reply #5 on: October 16, 2018, 02:45:03 pm »
I can't hear raspy for all the string buzzes and other finger farts.   :icon_biggrin:

But raspy is not a sound I would associate with blocking distortion.
A schematic, layout, and hi-rez pics are very useful for troubleshooting your amp. Don't wait to be asked. JUST DO IT!

Offline dude

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Re: Raspy distortion
« Reply #6 on: October 16, 2018, 03:22:49 pm »
Marshall copied the 5F6A Bassman for their JTM45, the bassman used 270K mixing resistors to vols ,the JTM45 uses 470K, what does this difference do to tone?


Also, if I wanted to reduce the brightness on the bright vol (JTM45): what if I take the 500p cap off the 470K mixing R and put a say 100p bright cap on the vol pot, wiper to input, would this give me the 5F6A tones on the vol pots? like the bassman


Also, I have the Neg feedback R 47K (JTM45) to 8 ohm tap, the 16 ohm tap would give more feedback? Thus less or later distortion?
If it ain't broke, don't fix it.

Offline pompeiisneaks

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Re: Raspy distortion
« Reply #7 on: October 16, 2018, 03:32:40 pm »
As I understand mixing resistors, their goal is to reduce channel interaction, providing a worse path backwards for the signal to the other channel, but otherwise they shouldn't impact the tone at all.

~Phil
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Phil Davis
tUber Nerd =|D

 


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