Tweet
Hiya, all. I'm retired from a couple of professions, one of which involved keeping the best audio fidelity possible running from a microphone in one place, through a network of repeater stations, and coming out a speaker in a fire engine, or making things turn on & off remotely.
Granted, lots of this stuff is now solid state (yecchhh, poo!) and microprocessor based, I began learning in third grade when my dad & I were taking a course for Amateur Novice Class licenses. So I learned on hollow state radios, with vibrator and/or dynamotor supplies, snubbing capcitors.......it's not *all* evaporated from my meager gray matter (well, yet.....)
So now that I'm retired, I've got lotsa time to play music, and can no longer afford an old Vox Foundation Bass rig like I used to have, so I've had to settle for a nice professional Hartke stack. At least now the sound guy (when there is one) has lotsa choices about what kinda signal he wants to pull for the mains.
But I diverge. I do that a lot -- I'm old
A recent band addition-hopeful plays harmonica (only OK), guitar (better than most for rhythm) and sings (way too loud). BTW, it's taken awhile for the old symphonic bassist in me to recognize the modern use of the term "harp", so I'll try to comply. Did I mention I'm old? I spent a lot of years where a harp was an even more ungainly instrument than a piano, had about 30 pedals, and would stay in tune for either 20 minutes, or until someone opened a door
So he found out I'm Fender Gold certified for electronics, and Silver certified for acoustic and electric guitars, and asked me to replace his original two-wire death trap power cord (see linked and/included schematic) with a grounded modern version (hooray for attentive youngsters!!!) I showed him a dozen I'd just gotten in for refurbing a stack of Hammarlund receivers and other assorted ham/military radio gear, and he then asked about matching tubes, etc.
The point at which I figured I'd need some help was when he asked if he could modify his amp (switchably, ideally) so it would give him that warm, tube-ish plate voltage sag when he uses it as a harp amp. A corollary to that would be if he could drop this amp's 15 watt output to around 3-5 watts, so he could play crunchy guitar for recording situations with other low powered stuff without being banished to an open cornfield for studio work.
In case I don't yet have enough posts to send in an attachment, here's a link to the schematic: http://silvertoneworld.net/schematic...rtone_1482.pdf
silvertone_1482_amp_schematic.pdf
So I suppose I could come up with a 25-watt sandbox resistor in the B+ supply to the center tap of the output primary and "pre-sag" the B+ to the finals (BTW, these are 6v6 GTA Silvertone-badged finals -- and the rest of the tubes are similarly marked Silvertone, with the exception of one bad 12ax7 that the owner replaced with a GT-rebadged Sovtek.)
For aesthetics, I'm disconnecting the triple-cap filter can on top of the chassis with discrete components under the chassis. Since there's probably no good reason to leave the suicide cord in place, except for looks, I'll give the owner the option of having me pull it out completely and re-drill the hole large enough for the strain relief for the nice big round 3-pin cord, or just disconnect the original power lead underneath, tape it out of the way, and drill a new hold out of sight (like behind the partial back cabinet panel) and run that in correctly -- black to the fuse AND switch, white to the other side of the power tranny primary, and green to a new, solid, shiny chassis ground.
So I'm looking for more conventional ways to drop the output without swapping out tubes, i.e., change a pot out for one with a push-pull switch to change a component's value *someplace* to achieve this.
After so many years of making sure audio was clean & clear, this is quite a "switch" <groan!> for me.
So, any (printable) ideas?
Tnx es 73
Granted, lots of this stuff is now solid state (yecchhh, poo!) and microprocessor based, I began learning in third grade when my dad & I were taking a course for Amateur Novice Class licenses. So I learned on hollow state radios, with vibrator and/or dynamotor supplies, snubbing capcitors.......it's not *all* evaporated from my meager gray matter (well, yet.....)
So now that I'm retired, I've got lotsa time to play music, and can no longer afford an old Vox Foundation Bass rig like I used to have, so I've had to settle for a nice professional Hartke stack. At least now the sound guy (when there is one) has lotsa choices about what kinda signal he wants to pull for the mains.
But I diverge. I do that a lot -- I'm old
A recent band addition-hopeful plays harmonica (only OK), guitar (better than most for rhythm) and sings (way too loud). BTW, it's taken awhile for the old symphonic bassist in me to recognize the modern use of the term "harp", so I'll try to comply. Did I mention I'm old? I spent a lot of years where a harp was an even more ungainly instrument than a piano, had about 30 pedals, and would stay in tune for either 20 minutes, or until someone opened a door
So he found out I'm Fender Gold certified for electronics, and Silver certified for acoustic and electric guitars, and asked me to replace his original two-wire death trap power cord (see linked and/included schematic) with a grounded modern version (hooray for attentive youngsters!!!) I showed him a dozen I'd just gotten in for refurbing a stack of Hammarlund receivers and other assorted ham/military radio gear, and he then asked about matching tubes, etc.
The point at which I figured I'd need some help was when he asked if he could modify his amp (switchably, ideally) so it would give him that warm, tube-ish plate voltage sag when he uses it as a harp amp. A corollary to that would be if he could drop this amp's 15 watt output to around 3-5 watts, so he could play crunchy guitar for recording situations with other low powered stuff without being banished to an open cornfield for studio work.
In case I don't yet have enough posts to send in an attachment, here's a link to the schematic: http://silvertoneworld.net/schematic...rtone_1482.pdf
silvertone_1482_amp_schematic.pdf
So I suppose I could come up with a 25-watt sandbox resistor in the B+ supply to the center tap of the output primary and "pre-sag" the B+ to the finals (BTW, these are 6v6 GTA Silvertone-badged finals -- and the rest of the tubes are similarly marked Silvertone, with the exception of one bad 12ax7 that the owner replaced with a GT-rebadged Sovtek.)
For aesthetics, I'm disconnecting the triple-cap filter can on top of the chassis with discrete components under the chassis. Since there's probably no good reason to leave the suicide cord in place, except for looks, I'll give the owner the option of having me pull it out completely and re-drill the hole large enough for the strain relief for the nice big round 3-pin cord, or just disconnect the original power lead underneath, tape it out of the way, and drill a new hold out of sight (like behind the partial back cabinet panel) and run that in correctly -- black to the fuse AND switch, white to the other side of the power tranny primary, and green to a new, solid, shiny chassis ground.
So I'm looking for more conventional ways to drop the output without swapping out tubes, i.e., change a pot out for one with a push-pull switch to change a component's value *someplace* to achieve this.
After so many years of making sure audio was clean & clear, this is quite a "switch" <groan!> for me.
So, any (printable) ideas?
Tnx es 73
Comment