Thanks for the schematics! But this is not minimalistic at all! I am looking for one VFET transitor 20W class A....like L amp!
I did it too. But you need a very very big resistor. I used one of 600W and 10ohm. I got almost 20Wrms at 8ohm. And result are spectacular. But it is necessary select very well device and use more or 4A of quiescent point(these are results I got).
Actually I am using one version with 22ohm and low output current because 16 ohm of my speakers.
Actually I am using one version with 22ohm and low output current because 16 ohm of my speakers.
With papa's buffer, you got 25 ohm output.
Jama is the member I mentioned and it's good he speak up right away. Hi Jama, I'LL try that after the bulb.
Hi Albert. My first lamp was with bulbs. Very nice. But with bulbs I got randomly I heard metallic clicks. Because of that I began to search resistor, inductor or ccs options.
Jama,
Did you get hum with bulb version? Did you remember you had CLC, or CRC? I've been comparing my choke version with my 300B with Tango output, and the 2A3 Cunningham. Heeeee 😀
Will report after the coming wine party in my house with all those good ears and some other good amps they bring. I almost can predict there will be lots of dentures on the floor. 🙂
Albert
Hi Albert. Sorry. Hum always will be here. With bulbs or resistors will be a lot. If you use inductor instead resistor you will have less (in my build with 193V almost nothing). At the begining I used CRC. A lot of hum (with 68kuf). Now I am using CLCLC. Hum is there but very little.
Using ccs sure hum will be very little.
Using ccs sure hum will be very little.
I am fine thanks Juan 🙂
Last months i do lot of electronic but was diy music instruments.
Back to V-fet's amps constructions in short time after Part2 pcb's are available in DiyAudio Store yoopi !
One photo with hockey pucks transistors this on left side look similar to 2SK182 ES but is not v-fet
the other on right are probaly most fat & huge transistor made by Toshiba
Greetings
Attachments
A question about Mike's 193V schematics.
The actual voltage at the drain would be 19V instead of 22V in this schematic? I tired to simulate the voltage drop on PSUD2 and LT Spice, and both are suggesting around 19V for 2A load.
http://www.audiohobby.com/pdf/lamp 193V.pdf
The actual voltage at the drain would be 19V instead of 22V in this schematic? I tired to simulate the voltage drop on PSUD2 and LT Spice, and both are suggesting around 19V for 2A load.
http://www.audiohobby.com/pdf/lamp 193V.pdf
Last edited:
I get the same results, also in practice. If i want the indicated voltages, the transformer secondary needs to be higher.
Good to hear that. I was going to get higher voltage transformer, but I was not sure. (Actually I'm planning auto bias, so a lot higher anyway.)
BTW, did you find your best Vds / Bias for your system? Mike and Papa had started to drive 2SK82 with high Vds (23-24V), but many people (including Papa) seem to settle less Vds (19V or so). On LT Spice and Mikes report, higher voltage has better spec, though.
Maybe the "19V or so" are due to the "universal" Papa power supply with 18V transformer secondaries?
Vds in my present set up is 21.7V
As for the power supply if found a way to have the right voltages both for auto bias and fixed bias.
I put the transformer secondaries in series and went for choke input with adjustment of the voltage by adapting the value of the first C.
Currently i am running the fixed bias amp version with 25.5V B+
The selfwound inductors take the voltage down to the 21.7 (@~1.65A)
Also there is a second choke and residual is now 3 to 4mV @3.3A
This supply is for both channels!
Hmm, interesting approach, and it's pretty reasonable to me. As far as I remember, Mike also preferred high Vds inductor version, 23V /2.0A, although on VFET2 schematics, Papa is driving 2SK82 with 19V, but it's probably because of some other practical reasons that I can't understand. I think I'll go buy a bit higher voltage transformer, so that I can reduce voltage later adding extra choke like you do.
If someone in US wants to try motor run cap, this $5 cap would be a good deal for 80uf 400V polypropylene, because it seems like many of motor run cap sold in US are not always guaranteed being polypropylene film.
Icar Capacitor MLR25L4080060138 I MK SH Mlr25l4080060138imksh 80 UF±5 400VAC | eBay
http://www.icar.com/contenuti/pdf/MLR252006.pdf
Icar Capacitor MLR25L4080060138 I MK SH Mlr25l4080060138imksh 80 UF±5 400VAC | eBay
http://www.icar.com/contenuti/pdf/MLR252006.pdf
23V*2A=46W of dissipation
For a 90W die SIT, we need a generous heatsink to maintain a fair chip temperature, but works (at high side of things). Better linearity at higher dissipation but we can found the thermal limit one day 😉😀🙂
I used with 19V/1.7A
The 2SK18x family is supposed supports far higher due to outrageous max pd