What shall we build?

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Got into work this morning, the sun is shining, birds are singing, slight breeze through the shop with the doors open, about to start another day building guitar amplifiers. No memos, no faxes, no 'compliance' meetings, no synergy workshops, no faff, no BS.

Basically, I'm in a glorious mood and I don't care who knows it (Hello, sailor).


Sooooooo...

I have this old output transformer sitting on my shelf, pulled from a late 70s JMP 2144, it's a Drake 783-257 also found in the Canadian-spec JCM800 2204.

The basic specs are:

Ra-a 3.4k

0-4-8ohm secondary taps (no 16!).

50w OT, designed for 2xEL34s


So, let's build an amp based around this transformer. I'd like to open up suggestions to the forum as to what spec it should be, and I'll pick the ones I like.

My only stipulations are:

- Head
- 50w EL34 fixed bias

The rest is up to you.


Once the amplifier is completed, I'd like to offer it up for a raffle on here with donations to TFB as entry fee, if that's OK with @TTony?

Suggestions below!





Rift Amplification
Handwired Guitar Amplifiers
Brackley, Northamptonshire
www.riftamps.co.uk
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  • FelineGuitarsFelineGuitars Frets: 5434
    A great sounding 50 JMP/JCM  crossover - like a 2204 . master volume but with blendable normal channel and treble channels and a switchable selector for the coupling capaitors so you can select a slightly fatter sound if you are a single coil player or slightly less low end if going in with humbuckers (to reduce the woofiness)
    A great FX loop and a reverb (digital is fine)
    So you are kind of bringing together a Marshall 1987 and a Marshall 2204 but with reverb and an updated FX loop

    Many guitars have a re-sale value. Some you'll never want to sell.
    Stockist of Earvana nuts, BKP, Oil City And Monty's pickups. Sperzel, Tonepros, Gotoh and Graphtech too!
    Expert guitar repairs and upgrades - fretwork our speciality! www.felineguitars.com.  Facebook too!

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  • SporkySporky Frets: 13742
    It should have blue sparkly tolex, white piping, and black grillecloth (if you put such onto heads). All fittings should be chrome. The control plate should be black with white text, and it should have white chickenhead knobs.
    Be your own evil twin. 
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  • paulnb57paulnb57 Frets: 1173
    Single channel, master volume with reverb and post FX loop....


    Oh and the raffle idea is both generous and a fab idea....thanks!
    Stranger from another planet welcome to our hole - Just strap on your guitar and we'll play some rock 'n' roll

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  • hywelghywelg Frets: 1529
    Was that to fit the mismatched 6.6k OT like Aynsley's 2144?
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  • RiftAmpsRiftAmps Frets: 1276
    hywelg said:
    Was that to fit the mismatched 6.6k OT like Aynsley's 2144?
    Yes, but it’s not 6k6 ;)
    Rift Amplification
    Handwired Guitar Amplifiers
    Brackley, Northamptonshire
    www.riftamps.co.uk
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  • DrBobDrBob Frets: 1707
    A great sounding 50 JMP/JCM  crossover - like a 2204 . master volume but with blendable normal channel and treble channels and a switchable selector for the coupling capaitors so you can select a slightly fatter sound if you are a single coil player or slightly less low end if going in with humbuckers (to reduce the woofiness)
    A great FX loop and a reverb (digital is fine)
    So you are kind of bringing together a Marshall 1987 and a Marshall 2204 but with reverb and an updated FX loop
    What my learned friend suggested above sounds quite frankly marvellous !

    Great gesture re the raffle, I'm in
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  • WezVWezV Frets: 9078
    very interested in this raffle idea... I don't mind what the amp is too much, but if we can arrange it so I will the raffle that will be great!  ;)
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  • normula1normula1 Frets: 260
    Rather than the obvious Marshall influenced design, how about something more clean with just a touch of drive and configure the output stage to cathode bias with perhaps reduced voltages too so that you don't have to blast the room out to get it to that slightly driven sound.
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  • impmannimpmann Frets: 7375
    normula1 said:
    Rather than the obvious Marshall influenced design, how about something more clean with just a touch of drive and configure the output stage to cathode bias with perhaps reduced voltages too so that you don't have to blast the room out to get it to that slightly driven sound.
    Howabout a HiWatt influenced design?
    Never Ever Bloody Anything Ever.

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  • MtBMtB Frets: 417
    A Sound City 50 Plus-alike with great loud cleans but no flaimin' hiss. Great pedal platform and the SC power reduction switch - one that really does cut the volume down to bedroom friendly levels.
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  • ThorpyFXThorpyFX Frets: 4218
    An ac50 with more gain from the preamp
    Adrian Thorpe MBE | Owner of ThorpyFx Ltd | Email: thorpy@thorpyfx.com | Twitter: @ThorpyFx | Facebook: ThorpyFx Ltd | Website: www.thorpyfx.com
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  • RiftAmpsRiftAmps Frets: 1276
    impmann said:
    normula1 said:
    Rather than the obvious Marshall influenced design, how about something more clean with just a touch of drive and configure the output stage to cathode bias with perhaps reduced voltages too so that you don't have to blast the room out to get it to that slightly driven sound.
    Howabout a HiWatt influenced design?
    I'm listening...
    Rift Amplification
    Handwired Guitar Amplifiers
    Brackley, Northamptonshire
    www.riftamps.co.uk
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  • impmannimpmann Frets: 7375
    RiftAmps said:
    impmann said:
    normula1 said:
    Rather than the obvious Marshall influenced design, how about something more clean with just a touch of drive and configure the output stage to cathode bias with perhaps reduced voltages too so that you don't have to blast the room out to get it to that slightly driven sound.
    Howabout a HiWatt influenced design?
    I'm listening...
    Just that... a HiWatt based circuit. Same tone stack, same gain structure... perhaps an effects loop.

    I know absolutely nowt about how a HiWatt differs from a Marshall electronically except that one is vile and from Bletchley, the other sounds like Angels (or Angels on crack if the gain is dimed).

    :-)
    Never Ever Bloody Anything Ever.

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  • meltedbuzzboxmeltedbuzzbox Frets: 7651
    A dual channel DR103 that has all the awesome cleans of the DR103 with an additional overdrive channel?

    Maybe on a 2x12 format in a chassis that doesnt weigh more than the moon?
    The Bigsby was the first successful design of what is now called a whammy bar or tremolo arm, although vibrato is the technically correct term for the musical effect it produces. In standard usage, tremolo is a rapid fluctuation of the volume of a note, while vibrato is a fluctuation in pitch. The origin of this nonstandard usage of the term by electric guitarists is attributed to Leo Fender, who also used the term “vibrato” to refer to what is really a tremolo effect.
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  • vasselmeyervasselmeyer Frets: 2335
    Something Voxy with a gain control, a master volume and three-band EQ. No reverb but a post EQ FX loop with a mix control.
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  • andy1839andy1839 Frets: 550
    Something along the lines of a Matchless Clubman but more useable for people who play at home.

    Treble, middle, bass, presence, gain, reverb, fx loop, master volume and a variable footswitchable solo boost.

    And a half power switch.

     :) 
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  • andy_kandy_k Frets: 10
    i'll be in the raffle, all i can offer
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  • RiftAmpsRiftAmps Frets: 1276
    Ok guys, thanks for all of your suggestions so far.

    I'm really enthused by the non-Marshall ideas, especially the HiWatt and Vox stuff. I mean, is another modded-Plexi type really needed when we have the opportunity to do something different?!

    I think that's the route we'll go down, it's certainly got me really excited about this project.

    So, preliminary specs are:

    • Single channel Hot-rodded Vox-inspired preamp section with Gain, Treble, Mid, Bass, Master, and Presence(or Cut?) controls
    • Hiwatt style 50w OP section, with switchable GZ34/SS rectification
    • Series FX Loop with level control
    • Some form of outrageous boost to melt faces
    I'm going to start the circuit design shortly :)

    Rift Amplification
    Handwired Guitar Amplifiers
    Brackley, Northamptonshire
    www.riftamps.co.uk
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  • interstellarinterstellar Frets: 484
    valave driven acoustic amp
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  • vasselmeyervasselmeyer Frets: 2335
    Damn @RiftAmps that's left me drooling. How about a build thread?
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  • paulnb57paulnb57 Frets: 1173
    Sounds good to me!
    Stranger from another planet welcome to our hole - Just strap on your guitar and we'll play some rock 'n' roll

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  • normula1normula1 Frets: 260
    And to me.
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  • sweepysweepy Frets: 1862
    I’d go very minimal, imagine a 50w Fender Champ 
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  • mr-macmr-mac Frets: 196
    How about a selmer trebble n bass 50 but with some tweaks to make it more useable at lower volumes and maybe a 2nd channel with some more gain.
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  • mr-macmr-mac Frets: 196
    edited June 19
    RiftAmps said:
    Ok guys, thanks for all of your suggestions so far.

    I'm really enthused by the non-Marshall ideas, especially the HiWatt and Vox stuff. I mean, is another modded-Plexi type really needed when we have the opportunity to do something different?!

    I think that's the route we'll go down, it's certainly got me really excited about this project.

    So, preliminary specs are:

    • Single channel Hot-rodded Vox-inspired preamp section with Gain, Treble, Mid, Bass, Master, and Presence(or Cut?) controls
    • Hiwatt style 50w OP section, with switchable GZ34/SS rectification
    • Series FX Loop with level control
    • Some form of outrageous boost to melt faces
    I'm going to start the circuit design shortly

    How about a midrange control on a lead boost... To allow cut or boost mids for solo to either give it a scooped or fatter sound???  
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  • paulnb57paulnb57 Frets: 1173
    Would it be possible to make it variable power output?
    Stranger from another planet welcome to our hole - Just strap on your guitar and we'll play some rock 'n' roll

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  • RiftAmpsRiftAmps Frets: 1276
    paulnb57 said:
    Would it be possible to make it variable power output?

    We could I suppose, but each option also has drawbacks.

    For example, a half-power switch (pentode/triode) results in only a 30% volume drop, which is never enough and nearly always results in a degradation in tone, something which is a no-no in my book.

    Powerscaling never works as well as you hope for, it always adds fizz, and suppresses those lovely top-end harmonics that you spend so long dialling in. Seems counter productive to me.

    The most effective form of power reduction is a simple MV control, which we have :)
    Rift Amplification
    Handwired Guitar Amplifiers
    Brackley, Northamptonshire
    www.riftamps.co.uk
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  • sweepysweepy Frets: 1862
    Agree 100% on Power Scaling, I’ve never found one that works convincingly 
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  • PhilKingPhilKing Frets: 255
    I'd add another vote for something around the original Selmer Treble & Bass.  They have a really lovely sound when you drive them a bit, so upping the preamp gain on one channel would give a really useful sound and having the channels switchable would give you the nice clean sound (which could be an EF86 (or 6BR7) valve, to give that Voxy tone.  Though if you were really going for an interesting second channel, something around the 6SN7 would be really cool too.
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  • RiftAmpsRiftAmps Frets: 1276
    OK, managed to find some spare time to make progress on the build.

    I started off by drawing a few simple lifesize board layouts on paper, this one is the final 'clean' version that I'm happy with



    I find 'perf' board really easy to work with for custom-builds/prototypes, here's a sexy little blue number supplied by our good friends at @Modulus_Amps. The holes are 2.5mm in diameter so will need enlarging to 3.2mm to accept the eyelet terminals




    I use masking tape to cover the topside, then punch through with a pencil to mark which holes need enlarging




    Then it's over to the drill press to drill them out





    Once that's done, I remove the masking tape and press the terminals into the board using an eyelet tool in the chuck of my drill press. The piece of Bubinga underneath provides enough back pressure to allow the eyelet to seat properly without being squashed



    Completed board



    Then it's over to the solder station to populate the board with components.



    Board is done! Next stop is marking out, drilling, and punching the chassis.
    Rift Amplification
    Handwired Guitar Amplifiers
    Brackley, Northamptonshire
    www.riftamps.co.uk
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