I like the idea of winding a custom choke onto a better core. I would probably target an inductance of 70 mH with a DC resistance of about 0.50 to 0.60 Ohm.
I think it would be easier to ship used 120V MOTs from the states or china to Europe
but where to find a supplier?
but where to find a supplier?
The DCR of 240vac MOTs is in the 2-3ohms and wire is skinny. It would require 4 in parallel - now the cost advantage is lost. Plus 24lbs of chokes per channel is heavy.
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X, Daanve, others,
Throwing this out there, how about this:
https://www.lundahltransformers.com/wp-content/uploads/datasheets/2773.pdf
With both coils in series configuration and 3.5A rating?
Best,
Anand.
Throwing this out there, how about this:
https://www.lundahltransformers.com/wp-content/uploads/datasheets/2773.pdf
With both coils in series configuration and 3.5A rating?
Best,
Anand.
I think I'll go for 195T5 or custom FIAT inductors. And a modified Marantz7 for the big voltage gain...
A dumb (Or maybe not)question, would it be possible to use a tube for the the voltage gain. maybe 6C45 or 6SL7 or maybe a 2step with 6SN7?
Maybe simple two stages 6sl7 with cathode follower on output would be ok.
Wow, X, they're very nice!!! Waiting for GB or Etsy selling 🙂
Wow, X, they're very nice!!! Waiting for GB or Etsy selling 🙂
Does anyone know if the Marantz 7 tube pre can drive 50Vpp out?
A quick search turned up some clones pre-built:
Finished Marantz 7 m7 Tube Pre-amplifier 6z5p+12ax7b Tubes Amp | eBay
We need to verify that it works first and correct any errors before they are released. Thanks for your patience.
A quick search turned up some clones pre-built:
Finished Marantz 7 m7 Tube Pre-amplifier 6z5p+12ax7b Tubes Amp | eBay
We need to verify that it works first and correct any errors before they are released. Thanks for your patience.
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Marantz 7 should be able to drive 50Vpp, but it is not the best option IMO and E to drive the gate of a power fet.
12AX7 tubes run on low current, despite the fact that it has a CF output; I saw a schematic with two 12AX7 in series with feedback to get the voltage amplification down to workable values, followed by 12AX7 cathode follower...arghhh...my tube heart hurts...
A much better option will be an Aikido preamp/driver stage.
A 6N1P as input tube and a potent tube as cathode follower (5687; 6H6P; ECC99) would give a stage with a bit over 1 VRMS sensitivity to drive a LuFo.
Broskie has high quality PCB's and multiple options as well for power supply.
A Broskie CCDA might work equally well, however, as LuFo is a quiet amp an Aikido might be a better fit.
12AX7 tubes run on low current, despite the fact that it has a CF output; I saw a schematic with two 12AX7 in series with feedback to get the voltage amplification down to workable values, followed by 12AX7 cathode follower...arghhh...my tube heart hurts...
A much better option will be an Aikido preamp/driver stage.
A 6N1P as input tube and a potent tube as cathode follower (5687; 6H6P; ECC99) would give a stage with a bit over 1 VRMS sensitivity to drive a LuFo.
Broskie has high quality PCB's and multiple options as well for power supply.
A Broskie CCDA might work equally well, however, as LuFo is a quiet amp an Aikido might be a better fit.
Just thinking out loud.But is a 6C45 able to do this (by it self),it has a mu of 52 and can drive some current.
Edit: And use a CCS.
Edit: And use a CCS.
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Here is a Broskie Aikido Noval:
New topic - LuFo as headphone amp:
I ran some simulations with 24v supply and a 20mH 0.5ohm inductor. The results were very promising as a headphone amp driving a 32ohm load. I might have to give this a try - will need to order these iron core speaker inductors.
ERSE Super Q 20mH 16 AWG 500W Inductor Crossover Coil
I was getting nothing but second harmonic distortion at 500mW into 32ohms (a little under 12vpp) and 0.0007% THD.
New topic - LuFo as headphone amp:
I ran some simulations with 24v supply and a 20mH 0.5ohm inductor. The results were very promising as a headphone amp driving a 32ohm load. I might have to give this a try - will need to order these iron core speaker inductors.
ERSE Super Q 20mH 16 AWG 500W Inductor Crossover Coil
I was getting nothing but second harmonic distortion at 500mW into 32ohms (a little under 12vpp) and 0.0007% THD.
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With mere simulation don't you take possible core saturation out of the equation?
I'd like to see some real measurements with MOT's running in a 3A DC bias LuFo driving an 8 ohm load at 20 Hz full power.
That would give real info on the requirements for these chokes.
In the meantime I also had a prototype choke wound on a 300 watt c-core.
It has some 0.4 ohm DCR and 50 mH induction; this induction is measured with a (professional) induction meter at 100 Hz and 250 mV sinus.
It has quite an airgap, but behaviour must be checked in a working amp; I would not be surprised if a 600 watt core is required in the end.
I'd like to see some real measurements with MOT's running in a 3A DC bias LuFo driving an 8 ohm load at 20 Hz full power.
That would give real info on the requirements for these chokes.
In the meantime I also had a prototype choke wound on a 300 watt c-core.
It has some 0.4 ohm DCR and 50 mH induction; this induction is measured with a (professional) induction meter at 100 Hz and 250 mV sinus.
It has quite an airgap, but behaviour must be checked in a working amp; I would not be surprised if a 600 watt core is required in the end.
