My P-version is playing on the workbench... I am happy! Got a scare however when I tried to set the proper voltage with p1. I measured the full supply voltage on the case of the mosfet and turning the p1 did not do anything with that value. After pulling the powerplug in panic I reread the article of Nelson, again...
That measuring point was for the N-version, with the P-version the case of the mosfet has the full supply voltage. For P-version the 20 volt is indicated on another place.... Now I measured at the correct spot between Z1 and R2 , and voltage could be adjusted as ordered. Pfff and a big relief.
Now wait for larger heatsinks from Modushop as my 20 by 12 cm heatsink is a bit too warm with both channels on it...
And thanks again Nelson and the people at diystore for helping with this great hobby
That measuring point was for the N-version, with the P-version the case of the mosfet has the full supply voltage. For P-version the 20 volt is indicated on another place.... Now I measured at the correct spot between Z1 and R2 , and voltage could be adjusted as ordered. Pfff and a big relief.
Now wait for larger heatsinks from Modushop as my 20 by 12 cm heatsink is a bit too warm with both channels on it...
And thanks again Nelson and the people at diystore for helping with this great hobby
I have one of the new VFETs for K60. I am thinking of designing a PCB that uses the front end circuit design by Mr. Pass for the VFET kits from 2021. His design uses Edcor PC600/15K and I wonder about using Cinemag CMOQ-4LPC instead. The Edcor is a fine transformer but I have several of the Cinemags already. I know the Edcor is 1:5 turns ratio and the Cinemag could be wired as 1:2, so substantially less gain. Would that be anywhere near enough gain or am I just whistling dixie?
Cinemag - isn't that autoforming as 1+3, which is 4?
I mean, it is , that was a trick question ..
4V/V = 12db
Edcor 600:15K is practically having pri to sec voltage ratio of sq. root of (15K/600) = 5
wired as autoformer , it is getting gain of 1+5, which is 6V/V = 15.56db
difference is there, between 4V/V and 6V/V , but it is not night and day ...... if you move it to preamp level, just 3.5db of gain difference
I mean, it is , that was a trick question ..
4V/V = 12db
Edcor 600:15K is practically having pri to sec voltage ratio of sq. root of (15K/600) = 5
wired as autoformer , it is getting gain of 1+5, which is 6V/V = 15.56db
difference is there, between 4V/V and 6V/V , but it is not night and day ...... if you move it to preamp level, just 3.5db of gain difference
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Could be, but I don't understand how to use as autoformer. The datasheet shows it as 1:1 with dual primary and dual secondary. As per usual, the problem is likely my limited knowledge. A quick sketch of how to wire it for the FE would be helpful, if you are so inclined to humor my lack of know-how. The datasheet is attached although I know you might already know it since it's used in several of your designs (which is why I have several)...
it is shown in every damn autoformer amp I concocted of lately
in exact same way as used in Papa's DEFiSIT and it's commercial offspring - SIT-3
I mean - it is (Cinemag) shown how-to on these schematics and it's pretty much simplest way how I can describe how it is wired
now, if you need some simple nudge to grasp it, I believe it is this:
in exact same way as used in Papa's DEFiSIT and it's commercial offspring - SIT-3
I mean - it is (Cinemag) shown how-to on these schematics and it's pretty much simplest way how I can describe how it is wired
now, if you need some simple nudge to grasp it, I believe it is this:
Hi hirscwi,
in the Frontend Nelson designed, the transformer is not wired as an autoformer. The secondary is wired ground-free - in that way, it is easy to reverse phase out of the frontend by just swapping D+ and D-.
I have actually modified one of Mark's Bulwark frontends for a Cinemag CMOQ-4PC by creating a daughterboard on which the transformers sit. In that way, I can also try different transformers.
(Still need to post my experiences in building this modification).
I have wired the Cinemag with the two primary halves in parallel and the secondaries in series. In this way, I get a gain of 1:2. The Bulwark has no problem driving the parallel Cinemag primaries, and I expect Nelson's frontend would not have problems either, as in the F6 a similar frontend drives paralleled primaries of a Jensen transformer that has similar parameters to the Cinemag.
You don't need the overshoot dampening network of C4 and R6 (as per the schematic in Nelson's article "DIY SONY VFET pt1") with the Cinemag, and I simply left them unstuffed.
I love the sound of the Cinemag in the frontend, and for me the frontend gain of 1:2 works very well. But you would have to make an estimation of how much gain you need in your system.
As a few data points, I have gain to spare with Wayne's BA2018 - Sony DIY VFET w/ Cinemags - Jericho Horns (100 db/W). I did also have enough gain with an F4 as power amp and the BA2018 as pre. I was running out of gain on my phono stage frontend with a buffer (no gain), and F4, and the Jerichos. For normal listening levels from a DAC, the F4 with buffer usually could go loud enough.
I hope this helps,
all the best,
Claas
in the Frontend Nelson designed, the transformer is not wired as an autoformer. The secondary is wired ground-free - in that way, it is easy to reverse phase out of the frontend by just swapping D+ and D-.
I have actually modified one of Mark's Bulwark frontends for a Cinemag CMOQ-4PC by creating a daughterboard on which the transformers sit. In that way, I can also try different transformers.
(Still need to post my experiences in building this modification).
I have wired the Cinemag with the two primary halves in parallel and the secondaries in series. In this way, I get a gain of 1:2. The Bulwark has no problem driving the parallel Cinemag primaries, and I expect Nelson's frontend would not have problems either, as in the F6 a similar frontend drives paralleled primaries of a Jensen transformer that has similar parameters to the Cinemag.
You don't need the overshoot dampening network of C4 and R6 (as per the schematic in Nelson's article "DIY SONY VFET pt1") with the Cinemag, and I simply left them unstuffed.
I love the sound of the Cinemag in the frontend, and for me the frontend gain of 1:2 works very well. But you would have to make an estimation of how much gain you need in your system.
As a few data points, I have gain to spare with Wayne's BA2018 - Sony DIY VFET w/ Cinemags - Jericho Horns (100 db/W). I did also have enough gain with an F4 as power amp and the BA2018 as pre. I was running out of gain on my phono stage frontend with a buffer (no gain), and F4, and the Jerichos. For normal listening levels from a DAC, the F4 with buffer usually could go loud enough.
I hope this helps,
all the best,
Claas
Questo è il DCR e l'induttanza di ciascun induttore?
https://www.diyaudio.com/community/...no-defisit-of-papas-koans.314822/post-5244029
https://www.diyaudio.com/community/...no-defisit-of-papas-koans.314822/post-5244029
I think that is "not quite" ...
The Cinemags have four separate coils - the 9-10 and 3-4 connections are not automatically made in the transformer, you would have to make it externally.
My best guess how to wire it:
- start with your schematic, and then change:
- no connection between 3 and 4
- no connection between D- and Gnd
- wire 3 to D-
I'm not sure if the 2-3 coil is in phase or inverted to the two "secondary" coils when you wire it like I wrote above ... if you don't get a 3:1 voltage gain, reversing 2 and 3 should fix that.
All the best,
Claas
simple difference
xformer mode;
ref to picture I posted there, regarding pin numbers:
Input hot to pin 3 (dot)
input GND pin 5
rest of coils connected in series ( take care of dots) , GND ut to one end without dot, output hot other end with dot
xformer mode;
- wired as 1+1:1+1, which is equal to 2:2, which is effectively ratio 1:1
- wired as 1:1+1+1, which is equal to 1:3, so effective ratio 1:3
ref to picture I posted there, regarding pin numbers:
Input hot to pin 3 (dot)
input GND pin 5
rest of coils connected in series ( take care of dots) , GND ut to one end without dot, output hot other end with dot