Tube reverb/monitor amp
« on: January 07, 2019, 07:01:08 PM »
So I've re evaluated things and made a few purchases off ebay ,

a dual channel 6AU6/6L6 SE pcb           12 euros
two 6x4/diode bridge hybrid ht boards     20euros
two12ax7/12au7 stereo pre amp board    20euros
two mains tx                                              50
C core op/tx pair                                        85
two oil filled chokes                                    75

I decided against the simple  EL84 scheme I had been thinking about before  , instead I'll go 6L6 with proper driver stage ,it better suits my 3.5k primary C core , and takes full advantage both the valve and transformer  in wattage terms.

So just a general purpose SE hifi amp 7 watts per channel ,separate psu , four reverb  tanks ,each with its own  attenuator off the speaker line outputs ,also lightbulb limiters switchable per tank ,for non linear drive  ;)
 12ax7/12au7 board for recovery/line output of wet signal .

Possibly two more small chokes for screen grid control on the 6L6s , some screening cans for the transformers , and I at least have the iron for this project together ,its gotten out of hand quick .

Im finally repurposing the case from a Darcy/Belhman Invertron I hauled out of Army surplus years and years ago , that should account for the signal stages and tanks and controls ,dual Tx and choked  psu will be housed seperately to try and get hum below the noise floor in the signal stages ,
I though about remoting the tanks ,which is a good idea normally ,but with screened and magnetically shielded signal transformers Im hoping for two boxes not three ,theres a couple of metal partitions in the rackmount case as well ,so I can have several layers of steel between inductive components to keep these things very quiet magnetically .

Hopefully with a little work something more than a one trick pony spring reverb will result , parralel/series and out of phase connection of the multiple  tank transducers can also make it sound signifigantly different , the sound becomes much less choppy when you blend the outputs of two springs .

 Mostly in guitar combo  amps the bass is very much rolled off from reverb tanks to prevent feedback on low notes , in a seperate stand alone unit its not such an issue , so a lot more lows can be dialed in if desired ,guitar amps also typically dont have tone control over the tank outputs ,which very much limits their flexibillity .I'm experimenting with a transducer in the middle of the long tank made from a pole piece from a guitar pickup wound with a high z coil and a tiny magnet epoxied directly to the spring  , bass output is astonishing ,loads and loads of low end if you want it ,might be able to blend that back with the regular transducer outputs somehow ,maybe a big mono low end dial so you can add in just as much 'weight' as you like  with the regular accutronics transducers panned L/R .





alexc

Re: Tube reverb/monitor amp
« Reply #1 on: January 08, 2019, 12:18:59 AM »
That's very interesting stuff ... Tubetec. I applaud the commitment to getting the most out of some tubes, traffos and spring reverbs  ...  in the plural!

Good luck with it all.
I ping therefore I am


 

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