Looks like the heatsink demands of the F6 will be slightly less than that of the F5? The R100 disipates 114W versus the F5 Mosfets 150W.
Regards,
Dan
That absolute max output and not continuous for parts.
Best guess is 1.5-1.8a at 23v for each jfet
some news from the F6 builders front....
When I tried to build in in one channel an ISKRA xformer and stayed with the Jensen on the other side, I had an heavy oscillation on the ISKRA side. So I thought with hint from Zen Mod that one of the polarities of the ISKRA might be wrong. Zen Mod was so friendly to look at his ISKRA and the oscilloscope to determine the polarities.
New wiring with the corrected polarities, again oscillation....
not the ISKRA was the culprit, but
- either using two different xformers on the same PSU
- or at the same time one channel had one Semisouth guilty to make a changing offset from 15mV to 0,6V in seconds. After changing the two SS and the using two ISKRAS in the left and right channel all problems were gone.
So I do not really know, but most plausible explanation, one channel was a bit unstable, and this was augmented my using two different xformers.
Of course the reason was that I wanted to compare the sound of Jensen and ISKRA in mono mode.
So if you are doing this too, be careful the chance to get oscillation seems to be greater.
The more amusing part....
From the xformers I like most the ISKRA, the dryness is gone and it seems to be the most charming sound in comparison of the three, Jensen, Edcor and ISKRA.
So I suppose Zen Mod knew already about the merits of his ISKRA....
When I tried to build in in one channel an ISKRA xformer and stayed with the Jensen on the other side, I had an heavy oscillation on the ISKRA side. So I thought with hint from Zen Mod that one of the polarities of the ISKRA might be wrong. Zen Mod was so friendly to look at his ISKRA and the oscilloscope to determine the polarities.
New wiring with the corrected polarities, again oscillation....
not the ISKRA was the culprit, but
- either using two different xformers on the same PSU
- or at the same time one channel had one Semisouth guilty to make a changing offset from 15mV to 0,6V in seconds. After changing the two SS and the using two ISKRAS in the left and right channel all problems were gone.
So I do not really know, but most plausible explanation, one channel was a bit unstable, and this was augmented my using two different xformers.
Of course the reason was that I wanted to compare the sound of Jensen and ISKRA in mono mode.
So if you are doing this too, be careful the chance to get oscillation seems to be greater.
The more amusing part....
From the xformers I like most the ISKRA, the dryness is gone and it seems to be the most charming sound in comparison of the three, Jensen, Edcor and ISKRA.
So I suppose Zen Mod knew already about the merits of his ISKRA....
blame the Gremlins , but no two different xformers on channels , in same time
condition for that to be the case is/are both crappy (common) power supply and active part of amp (schematic) , in same time ......... and that's not likely the case
so - Gremlins ........ or not enough Tai Chi this week
condition for that to be the case is/are both crappy (common) power supply and active part of amp (schematic) , in same time ......... and that's not likely the case
so - Gremlins ........ or not enough Tai Chi this week
What was the frequency of the oscillation? In my early Teaser-6 build using a Jensen transformer, I could get it into a sub 1Hz oscillation. This turned out to be sensitive to the time constant of the bias circuit, which in Nelson's newly released F6 schematic is RC = 10k * 1000uF = 10sec. I now am running with RC = 10k * 100uF = 1sec. Spice simulations show a poor phase margin with very high values of RC.
some news from the F6 builders front....
When I tried to build in in one channel an ISKRA xformer and stayed with the Jensen on the other side, I had an heavy oscillation on the ISKRA side. So I thought with hint from Zen Mod that one of the polarities of the ISKRA might be wrong. Zen Mod was so friendly to look at his ISKRA and the oscilloscope to determine the polarities.
New wiring with the corrected polarities, again oscillation....
not the ISKRA was the culprit, but
- either using two different xformers on the same PSU
- or at the same time one channel had one Semisouth guilty to make a changing offset from 15mV to 0,6V in seconds. After changing the two SS and the using two ISKRAS in the left and right channel all problems were gone.
So I do not really know, but most plausible explanation, one channel was a bit unstable, and this was augmented my using two different xformers.
Of course the reason was that I wanted to compare the sound of Jensen and ISKRA in mono mode.
So if you are doing this too, be careful the chance to get oscillation seems to be greater.
The more amusing part....
From the xformers I like most the ISKRA, the dryness is gone and it seems to be the most charming sound in comparison of the three, Jensen, Edcor and ISKRA.
So I suppose Zen Mod knew already about the merits of his ISKRA....
with the ISKRAS I have more hum at the moment, I have to care for a better position and possible grounding....
At the moment I find the sound with the ISKRAS the loveliest, but this is only a first impression and for sure a matter of taste.
The Jensens excel in the medium range, ISKRA cares more for the highs....
it is too early to say more and maybe useless...
At the moment I find the sound with the ISKRAS the loveliest, but this is only a first impression and for sure a matter of taste.
The Jensens excel in the medium range, ISKRA cares more for the highs....
it is too early to say more and maybe useless...
Apropos of that, I think you'll find that its the time constant of the upper
bias circuit relative to ground. I haven't checked that on the F6, but I
recall seeing similar in another output stage using a similar bias.
