Included are images of the donor amps PCB and the progress to date.
Wednesday, 8 May 2013
Tuesday, 16 April 2013
Progress to date
Photos attached show the near completed tag board fitted in the amp chassis.
A mounting bracket was required for the smaller valves due to a mismatch in sizing between the sockets to hand and the chassis. Once the amp is tested this bracket will be replaced with a more permanent solution.
A mounting bracket was required for the smaller valves due to a mismatch in sizing between the sockets to hand and the chassis. Once the amp is tested this bracket will be replaced with a more permanent solution.
Monday, 15 April 2013
Design and Implementation Notes
The base schematic is the 'Super-Amp' model number 5F4.
There will also only be a single input channel instead of the 2 separate normal and bright input channels.
The first gain stage above uses a 12AY7 but this is to be substituted with an EF86 pentode. This will result in a modification to the circuit for the first gain stage. The circuit will also take advantage of the ability of a pentode to be run as a triode. This will be controlled by the use of a potentiometer, effectively allowing the player to control the tonal shift of the tube being morphed between either pentode or triode.
The tonestack to be employed will be a simple Fender Bandmaster tonestack. This will consist of a bass and treble potentiometer.
The presence feedback loop is to be omitted from the power amp.
Layout:
The following layout files have been produced as a guide,
The layout files above are rough drafts with the layout split with the first and second stage defined on the first image and the phase inverter and power amp visible on the second image.
The circuit will be implemented on a Tag board.
Changes:
Some early deviations from this schematic are that I will not be employing a rectifier tube or a choke in the power supply. Zener diodes will be used instead. I will also include a resistor placed after the first capacitor with a suitable value to induce sag.
The first gain stage above uses a 12AY7 but this is to be substituted with an EF86 pentode. This will result in a modification to the circuit for the first gain stage. The circuit will also take advantage of the ability of a pentode to be run as a triode. This will be controlled by the use of a potentiometer, effectively allowing the player to control the tonal shift of the tube being morphed between either pentode or triode.
The tonestack to be employed will be a simple Fender Bandmaster tonestack. This will consist of a bass and treble potentiometer.
The presence feedback loop is to be omitted from the power amp.
What stays the same:
The second stage is as is from the schematic. Also aside from the removal of the presence loop, the phase inverter and power amp stay as is.
Layout:
The following layout files have been produced as a guide,
The layout files above are rough drafts with the layout split with the first and second stage defined on the first image and the phase inverter and power amp visible on the second image.
The circuit will be implemented on a Tag board.
Sunday, 14 April 2013
Additional Resources
Web links:
http://www.ax84.com/
A great starting point for amp building and design. Excellent active forum with many discussions covering basic to advanced amp building issues.
http://www.valvewizard.co.uk/
Merlin Blencowe's web site. A great supplementary source of information but his books are much more comprehensive (see books).
http://www.slocloneforums.com/
the focus of the site is on high gain amps (see Slo 100) but resources related to other amps are covered (see Mesa Boogie, Engl, etc).
http://ampgarage.com/forum/
Trainwreck and Dumble amps are the main focus here. There are additional resources for Fender, VOX and Marshalls.
http://www.trainwreck.com/
Books:
I highly recommend 'Designing Tube Preamps for Guitar and Bass' by Merlin Blencowe (ISBN: 0956154506). It's an excellent reference for value preamp theory plus it provides a number of alternative design suggestions not commonly implemented in traditional value amp designs.
http://www.ax84.com/
A great starting point for amp building and design. Excellent active forum with many discussions covering basic to advanced amp building issues.
http://www.valvewizard.co.uk/
Merlin Blencowe's web site. A great supplementary source of information but his books are much more comprehensive (see books).
http://www.slocloneforums.com/
the focus of the site is on high gain amps (see Slo 100) but resources related to other amps are covered (see Mesa Boogie, Engl, etc).
http://ampgarage.com/forum/
Trainwreck and Dumble amps are the main focus here. There are additional resources for Fender, VOX and Marshalls.
http://www.trainwreck.com/
Books:
I highly recommend 'Designing Tube Preamps for Guitar and Bass' by Merlin Blencowe (ISBN: 0956154506). It's an excellent reference for value preamp theory plus it provides a number of alternative design suggestions not commonly implemented in traditional value amp designs.
Saturday, 13 April 2013
The idea...
The Donor Amp
Fender Super 210, current status: not working.
Best attribute:
Great clean tones.
Problems:
Overdrive channel tone is not great.
Prone to issues requiring repair.
The Plan
Perform a complete rebuild of the amplifier. While I want to preserve many aspects of the original, I am keen to explore new ideas which go beyond the stock design. More on these later.
The parts to be preserved for use are the chassis, power transformer, output transformer and switches.
The PCBs from the original 210 are left aside and preserved. If in the future it is required to revert back I should be able to restore the amp to its original condition by substituting these parts.
Why do it?
Why not sell it on as is or get it fixed instead of a rebuild?I have had some previous experience in building both preamps & amplifiers with good results. I also like the idea of exploring new tonal possibilities that a custom build can provide over modifications to an existing design.
A note on using this amp as a donor - while this is a good amp, I would not class it in any way as a collectable, either now or in the future. This being the case I can tolerate introducing changes that are outside the original design for this model.
More to follow.
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