Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Cups on December 04, 2011, 08:01:27 pm

Title: Would you add grid resistor to Power Tubes
Post by: Cups on December 04, 2011, 08:01:27 pm
Working on a Traynor Custom Reverb. Really cool amp. Trying to make it a little quieter with added filtering and basic cleanup. Reverb needs new wires etc.... anyways:

There are no grid resistors. I was just gonna add the usual 1k5 to pin 5 but thought it might be prudent to ask here first. Thinking about adding 10k grids to all preamp triodes too, and using co-ax cable for input and volume wiring. I know a lot of you are "leave it alone" types but I love reading your wisdom and advice.

Thanks again.
Patrick
Title: Re: Would you add grid resistor to Power Tubes
Post by: HotBluePlates on December 04, 2011, 09:03:24 pm
For a known, working amp, I might leave it alone. If it were a new build, I'd add them without thinking.

If the amp has fairly long grid wires to the output tubes, go ahead and add them. If you expect the output tubes to be in heavy overdrive most of the time (meaning output stage distortion all the time), add them. It will help reduce/prevent blocking distortion.
Title: Re: Would you add grid resistor to Power Tubes
Post by: stratele52 on December 05, 2011, 03:55:44 am
On a second version of Custom Reverb, Traynor use 1.5 K grid resistor; look there , the second schematic.

http://www.el34world.com/charts/Schematics/files/traynor/traynor_customreverb_ysr1.pdf (http://www.el34world.com/charts/Schematics/files/traynor/traynor_customreverb_ysr1.pdf)

Add 10 K to all preamp triode ?  What for  ?
Filer capacitor, not sure it need more.

Some shield wire where single wire are too log to some tube's grid is a very good idea. This will silent the amp. I do that sometimes with success.

Traynor amp are very good amps but sometime they need little work like you said. Go ahead.

Title: Re: Would you add grid resistor to Power Tubes
Post by: Colas LeGrippa on December 09, 2011, 07:57:56 am
I would myself definitely add resistors to any non protected screen grid. To save money , commercial amps manufacturers may not always do what it is not absolutely necessary to do.
They just won't pay for a busted tube so they don't care, to a certain point. Look at any boutique amp, they all have screen resistors.

Colas