Potato Cakes
Well-known member
Hello, Everyone,
I wanted to share my almost completed custom Vibro Champ build. It's a 10W version that has a tone stack defeat control, negative feedback bypass, half power (with negative feedback bypass), effects loop, and 4, 8, and 16 ohm output transformer selection. The reason it is almost complete is that the vibrato section is not functioning, which should be an easy fix.
When I built the board, I had it oriented as though it was going into a standard Fender type pan, but forgot that it was going into a chassis where the components are facing up. Instead of rebuilding it, I just installed it upside down, which made wiring a bit more interesting.
The amp itself works and sounds fantastic. Going into a 4 ohm load (2x 10" speakers) allows for an increase in SPL that makes turning up this amp a lot of fun. Taking out the negative feedback with the volume past 5 creates a very smooth overdrive effect.
I do still get a bit of heater noise as I have with all of my other builds. Granted, the instant you play anything through it you cannot hear any hum and it is not detectable on a recorded track where the guitar is present. But I still try to get my amps as quiet as the audio gear I build which may be wishful thinking when constructing tube guitar amps. I ran my filament power lines up and over all the other wires to make sure the audio path was not affected. I did an elevated ground with the center tap off of the transformer's 6.3V winding but now that I think about it this method may only work well for push pull amps and not single ended ones. I will mess around with that when I open it back up to fix the vibrato.
The effects send is right before the power tube so as to be able to have the vibrato function from the amp to proceed any effect pedals. I do not currently have an attenuator/make up gain circuit in the amp so this will have to be done externally for now. I also need to do some voltage measurements off of the preamp tube versus the input level to the output tube to see how much gain adjustment I will need at the send and return connections.
I had to drill out the pan chassis as it was blank. I don't particularly enjoy doing metal work but this one wasn't too bad. I would much prefer to find somewhere that can make custom pans or at least have the flats drilled to spec and then bend them with a brake.
I am using a Neutrik True1 power connectors with the output option. Some of the old Fender models have the two prong Edison power plug which I see replaced with a three prong receptacle, but those particular ones that are a direct replacement are a bit too expensive for what they are. The True1 connector allows for power to be locked in place and it has a through that can go to my pedal board which also uses the same connector.
This build has a Soursound power transformer and a custom 15W transformer Bryan wound for me for this particular amp. He said he had always thought about making a single ended 10-15W transformer and this build gave him the excuse to do so. As always his work is exceptional and he is a great guy with whom to do business.
There are still a number of tweaks I would like to do but I was just happy that it powered up and passed audio on the first attempt.
Thanks!
Paul
I wanted to share my almost completed custom Vibro Champ build. It's a 10W version that has a tone stack defeat control, negative feedback bypass, half power (with negative feedback bypass), effects loop, and 4, 8, and 16 ohm output transformer selection. The reason it is almost complete is that the vibrato section is not functioning, which should be an easy fix.
When I built the board, I had it oriented as though it was going into a standard Fender type pan, but forgot that it was going into a chassis where the components are facing up. Instead of rebuilding it, I just installed it upside down, which made wiring a bit more interesting.
The amp itself works and sounds fantastic. Going into a 4 ohm load (2x 10" speakers) allows for an increase in SPL that makes turning up this amp a lot of fun. Taking out the negative feedback with the volume past 5 creates a very smooth overdrive effect.
I do still get a bit of heater noise as I have with all of my other builds. Granted, the instant you play anything through it you cannot hear any hum and it is not detectable on a recorded track where the guitar is present. But I still try to get my amps as quiet as the audio gear I build which may be wishful thinking when constructing tube guitar amps. I ran my filament power lines up and over all the other wires to make sure the audio path was not affected. I did an elevated ground with the center tap off of the transformer's 6.3V winding but now that I think about it this method may only work well for push pull amps and not single ended ones. I will mess around with that when I open it back up to fix the vibrato.
The effects send is right before the power tube so as to be able to have the vibrato function from the amp to proceed any effect pedals. I do not currently have an attenuator/make up gain circuit in the amp so this will have to be done externally for now. I also need to do some voltage measurements off of the preamp tube versus the input level to the output tube to see how much gain adjustment I will need at the send and return connections.
I had to drill out the pan chassis as it was blank. I don't particularly enjoy doing metal work but this one wasn't too bad. I would much prefer to find somewhere that can make custom pans or at least have the flats drilled to spec and then bend them with a brake.
I am using a Neutrik True1 power connectors with the output option. Some of the old Fender models have the two prong Edison power plug which I see replaced with a three prong receptacle, but those particular ones that are a direct replacement are a bit too expensive for what they are. The True1 connector allows for power to be locked in place and it has a through that can go to my pedal board which also uses the same connector.
This build has a Soursound power transformer and a custom 15W transformer Bryan wound for me for this particular amp. He said he had always thought about making a single ended 10-15W transformer and this build gave him the excuse to do so. As always his work is exceptional and he is a great guy with whom to do business.
There are still a number of tweaks I would like to do but I was just happy that it powered up and passed audio on the first attempt.
Thanks!
Paul
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