Tube Amps / Music Electronics
For current discussions, please visit Music Electronics Forum.

ampage archive

Vintage threads from the first ten years

Search for:  Mode:  
previous: Kent Hi,Anybody have success wit... -- 3/10/2002 7:38 PM view thread

Re: Harp Mods

3/11/2002 1:55 AM
Bruce /Mission Amps
Re: Harp Mods
Here's some things I'm playing with... but I'm still in R&D too!!  
First off, use only the normal channel for harp and you don't have to do everyone of these suggestions.  
Increase the 1M resistor on the normal channel's input jack to 2m7. This depends on the mic you are using.  
In the power supply, use a 33K dropping resistor instead of the 22K.  
Try a 180K plate load for the normal channel with a small ceramic .001uF/500v to .0033uF/500v cap across the 180k plate load.  
Split the cathode RCs of V1. Do not share the same cathode parallel cap and resistor anymore.  
Use a 1500 cathode resistor for both bright and normal channel triodes but a 22uF to 68uF cathode bypass cap across the normal channel's cathode resistor and use a 4.7uF across the bright channel cathode resistor.  
On the normal channel, keep the .1uF coupling cap (even a .22uF seems to work OK) to the volume control and try a a .022uF to .047uF to the bright channel's volume pot.  
Use a 1/2 watt 360k to 1M resistor on the wiper of the normal channel's pot right to ground on the pot.  
Let's you turn up a bit more without over doing it in acoustical feedback.  
Lower the single 1m grid load resistor on V2 to 220k.  
Here's a weird one and it seems to work for some and not for others and is for harp only playing....  
try using a 120K grid load resistor on one 6V6 and a 220K on the other.  
This makes one power tube react differently then the other one and harp tone is a little more woody sounding to me.  
Speaker: P12N or slightly dark sounding ceramic of your choice.... the MOJO V12-30 sounds pretty good and isn't too much money.  

Kent Thanks Bruce,On the wierd o... -- 3/11/2002 3:48 PM