The "Octal" Derby Amplifier
The "Octal" Derby is a brown Derby with the first channel modified to utilize a 6SC7 tube, which is a large 8 pin otcal preamp tube like might be found in an early Fender "Pro" amp from the 1940's.
The Octal Derby uses all the same construction methods and components as the stock Derby amp. If you haven't read the details of that amp yet just follow the link to the Derby Amp in the navibar.
In addition, I use the 6sc7 tube and preamp circuitry from the Pro amp on the normal channel. Both inputs have a different value cap it is coupled to. This allows some variation of tone so you have more than one choice. It's a somewhat subtle difference but can really come in handy if you use a variety guitar types.
This preamp circuit is wired in true PTP (point to point) from the input jack, to the tube socket, out from the tube to the volume and tone control. From there it does take a wire path to the phase inverter but the benefit of the PTP wiring is seen mostly from input to tube. Using this PTP method and careful testing and screening of tube stock keeps microphonics to a minimum.
I am using an NOS Tung Sol 6sc7 that the Government was kind enough to keep safe for decades. They were meant for fire control systems aboard ships in WWII! Talk about swords to plowshares.
The sound of these octal tubes is just awesome. Very much a blues and harp kind tone, but also it has some great cleans too. I hate to use such words but these tubes are rounder, warmer, more "tubey", with a smoother and richer harmonic content then the venerable 12ax7.
They have much to offer but in most cases the only time they are heard is when they are worn from decades of use and misuse, and almost always in an amp that suffers a handful of problems. New old stock tubes, inside a new amp is something every guitarist should hear in their lifetime.
Because of using this tube I have freed up a triode of a 12ax7. So I put a switch on the rear panel that will switch this spare triode in parallel with the stock derby channels triode. This will thicken up the tone and add harmonic richness and well as net about a 25% boost in gain, not much but a little goose none the less. It's kinda like doubling tracks in a studio. Gives things a nice harmonic girth.
Also because the difference between the stock normal and bright channels is so small I added a switch to the front panel (optionally under the chassis) that will allow you use stock Derby channel as either a bright or normal voiced channel. So with the Octal Derby you have not only your choice of normal or bright channel voicing, but you also have the option of running a second triode in parallel. Any of which can deliver great tone.
Optionally sold with an unloaded 15" Cabinet. These Octal tubes really sound nice with 15" Speaks.
Now if only Tone Tubby will come out with that 15" for guitar they are working on so I can offer these loaded!
Two channels each with it's own distinct and distinguished tone it's really is like having two great amps in one.
These Octal Derbys are only available in head with cab versions. Brown or Cream color scheme. I have changed to a deeper color faceplate since these pics were taken.
Prices:
Octal Derby Amp Head Only $1700
Octal Derby Head with Unloaded 15" Quinn cab $1900
Octal Derby Head and Small 1x12" Quinn Cab loaded w/ 12" Tone Tubby Alnico $2050
Octal Derby Head and Large 1x12" Quinn Cab loaded w/ 12" Tone Tubby Alnico $2075
Octal Derby Head and 2x10" Quinn Cab loaded w/Tone Tubby Alnico's $2325
All prices include shipping in the continental US.
The "Octal" Derby is a brown Derby with the first channel modified to utilize a 6SC7 tube, which is a large 8 pin otcal preamp tube like might be found in an early Fender "Pro" amp from the 1940's.
The Octal Derby uses all the same construction methods and components as the stock Derby amp. If you haven't read the details of that amp yet just follow the link to the Derby Amp in the navibar.
In addition, I use the 6sc7 tube and preamp circuitry from the Pro amp on the normal channel. Both inputs have a different value cap it is coupled to. This allows some variation of tone so you have more than one choice. It's a somewhat subtle difference but can really come in handy if you use a variety guitar types.
This preamp circuit is wired in true PTP (point to point) from the input jack, to the tube socket, out from the tube to the volume and tone control. From there it does take a wire path to the phase inverter but the benefit of the PTP wiring is seen mostly from input to tube. Using this PTP method and careful testing and screening of tube stock keeps microphonics to a minimum.
I am using an NOS Tung Sol 6sc7 that the Government was kind enough to keep safe for decades. They were meant for fire control systems aboard ships in WWII! Talk about swords to plowshares.
The sound of these octal tubes is just awesome. Very much a blues and harp kind tone, but also it has some great cleans too. I hate to use such words but these tubes are rounder, warmer, more "tubey", with a smoother and richer harmonic content then the venerable 12ax7.
They have much to offer but in most cases the only time they are heard is when they are worn from decades of use and misuse, and almost always in an amp that suffers a handful of problems. New old stock tubes, inside a new amp is something every guitarist should hear in their lifetime.
Because of using this tube I have freed up a triode of a 12ax7. So I put a switch on the rear panel that will switch this spare triode in parallel with the stock derby channels triode. This will thicken up the tone and add harmonic richness and well as net about a 25% boost in gain, not much but a little goose none the less. It's kinda like doubling tracks in a studio. Gives things a nice harmonic girth.
Also because the difference between the stock normal and bright channels is so small I added a switch to the front panel (optionally under the chassis) that will allow you use stock Derby channel as either a bright or normal voiced channel. So with the Octal Derby you have not only your choice of normal or bright channel voicing, but you also have the option of running a second triode in parallel. Any of which can deliver great tone.
Optionally sold with an unloaded 15" Cabinet. These Octal tubes really sound nice with 15" Speaks.
Now if only Tone Tubby will come out with that 15" for guitar they are working on so I can offer these loaded!
Two channels each with it's own distinct and distinguished tone it's really is like having two great amps in one.
These Octal Derbys are only available in head with cab versions. Brown or Cream color scheme. I have changed to a deeper color faceplate since these pics were taken.
Prices:
Octal Derby Amp Head Only $1700
Octal Derby Head with Unloaded 15" Quinn cab $1900
Octal Derby Head and Small 1x12" Quinn Cab loaded w/ 12" Tone Tubby Alnico $2050
Octal Derby Head and Large 1x12" Quinn Cab loaded w/ 12" Tone Tubby Alnico $2075
Octal Derby Head and 2x10" Quinn Cab loaded w/Tone Tubby Alnico's $2325
All prices include shipping in the continental US.
