An OPT is a big investment. Question is how it would work from 350Hz and up for my horns, with an MOFO buffer for my favourite 6B4G?
This topology will output 4W at ca 1,6V input(clipping at 6W 5%), while the 4P1L has 0,7Vrms sensitivity.
It seems quite simple using a depletion mode MOSFET and a low budget Hammond choke, when we don´t have to deal with the lowest octaves.
Off course this is just brainstorming from a cheapskate, will anyway try it with an amp for 6.5kHz and up with stuff from the parts bin.
This topology will output 4W at ca 1,6V input(clipping at 6W 5%), while the 4P1L has 0,7Vrms sensitivity.
It seems quite simple using a depletion mode MOSFET and a low budget Hammond choke, when we don´t have to deal with the lowest octaves.
Off course this is just brainstorming from a cheapskate, will anyway try it with an amp for 6.5kHz and up with stuff from the parts bin.
I thought about the same thing with the 4P1L. If the goal is to do away with iron I say why the chokes and not full SS output?
You can make a CCS cheaper than a choke, but better to do a class-A PP in that power range for a very few bucks. Personally, I don't love tubes enough to bother with them in the IPS either. Have a look at what Papa is doing with JFETs (etc.).
Agree, the concept is interesting, but question is if you keep the sonic quality of the driver tube. You get better effiency with iron and it makes design easier. The choke is at least five times cheaper than an OPT and you will not have to invest in as big heatsinks. I have nothing against iron per se.
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I believe that the big output cap will literally kill the magic of the DHT and dictate the sound more than anything else. For me the first priority would be to get rid of that.
Don´t think so. The output cap would anyway be present in a passive loudspeaker crossover. It should actually be 57uF to cut 6db/octave at 350Hz. This is how it would appromaximately look with a 12dB Bessel.
Zout without filter is in the ballpark of 0.8ohm/1kHz.
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I use Martin Seddon iixo. This is the x over in my horns system:
https://www.azurahorn.com/azurahorn_system_files/iixoMamps.png
No phase shift to speak of, insane clarity, it's the final frontier for tube/horn systems at home IMO.
It was pretty cheap when I ordered mine.
https://www.azurahorn.com/azurahorn_system_files/iixoMamps.png
No phase shift to speak of, insane clarity, it's the final frontier for tube/horn systems at home IMO.
It was pretty cheap when I ordered mine.
There are no such things as miniscule OPTs, if you want an extended high frequency response, without spending serious money. If you have the answer please specify!
Is an 2.5-3.5k OPT really the answer, as it makes the 6B4G work unlinear?
Is an 2.5-3.5k OPT really the answer, as it makes the 6B4G work unlinear?
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Thought of that too, but to much expensive iron involved, which contradicts my aim.
Another problem that you maybe could help me with, is to prohibit the sand to blow from the pulse when the DHT heats up. Maybe a delay relay or something else?
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Is 60 Euro too much for a nice looking (black endbells) 5/8k:4/8/16R transformer that goes to ~30kHz and has a 70mA airgap?
I would suggest looking into laterals for the source follower mosfet . 3A5 can be microphonic , 2P29L are low microphony , ymmv with 4P1L . My go-to choke load for middbass up is the £14 Triad C-56U . 35mH 2A 0.75 ohms DCR , can also be used in the power supply . It may be a good idea to have a diode protecting the mosfet gate if using a depletion mosfet
316a
316a
Thanks 316a, you nailed it! At less than half the price of the Hammonds, this will take you down to below 20Hz, with low phase shift at 60Hz. Working on the protection issues with the help of Fuling. Why lateral, lower capacitances?
Yep, budget is tight and I am so curious about finding out about MOSFET buffers+DHT.
For what kind of frequency extension are you after?
Smaller transformers require less interleaving to achieve similar values of leakage inductance, compared to bigger ones.
As for the load, remember there is a tradeoff between distortion and power output.
Interesting things happen when you AC load on the 6B4G more. Nicer harmonic structure with gate resistor R16 2.5kohm, even though THD gets higher!
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Laterals are rock stable , unlike IRF series etc . I use Exicons in a circlotron and have a Magnatec BUZ900 based mofo type amp . Good devices for class A . As long as there is a protection diode , practically industructable . Also sound good .
Did a sim and it looks better than a randomly choosen IRF. About the 35mH Triad the inductance corresponds to 10H for an OPT.
