Happy Victor is back. Victory over health. (I'm just out of the ward too where I went with a broken heart).
The case looks good . .
My question is: does anyone already have experience with the LL3720 in Single End? I want to use it for a 10Y (which is said to be in the 45/50 family and maybe has a plate resistance of below 1.000Ω) and . . . I also have an older 25W/30W version of the 10Y.
Per Lundahl informed me yesterday they have that available. Looks great. No snake oil. Just great engineering. E.g. Look at the way the windings are spaced.
Are you sure?
The datasheet shows 5000R plate resistance even at 425V ... at 250V it's 6k.
Below 10k plate load it's "mission impossible" (high distortion).
Yes, I agree. The specs are strange. Because maybe there are various versions (I have the long plate one; as well as the standard short plate version). yes, old designs went for 16KΩ load, to the expense of HF (I had that); but I did get 5Watt out of the tube with ease.
But I should test the tubes some way (I do have a tube tester but it is not calibrated so it is just for a Go/No Go and for matching).
A project almost by itself. Also the delta-Iplate/delta-Vg should be measured by hand (=S). See where it gets me.
Only then select the transformer.
But I should test the tubes some way (I do have a tube tester but it is not calibrated so it is just for a Go/No Go and for matching).
A project almost by itself. Also the delta-Iplate/delta-Vg should be measured by hand (=S). See where it gets me.Only then select the transformer.
"I have the long plate one"
It's VT25A, which is different tube, than 10, 10Y/VT25 series: designed for larger plate dissipation (19W versus 8/12W), hasn't thoriated tungsten filament (barium-oxid coated filament), and some version -may- required different filament voltage (6.3V, 7V).
See these comments: http://www.jacmusic.com/techcorner/ARTICLES/English/Portraits/VT25A/Index-VT25.htm
It's VT25A, which is different tube, than 10, 10Y/VT25 series: designed for larger plate dissipation (19W versus 8/12W), hasn't thoriated tungsten filament (barium-oxid coated filament), and some version -may- required different filament voltage (6.3V, 7V).
See these comments: http://www.jacmusic.com/techcorner/ARTICLES/English/Portraits/VT25A/Index-VT25.htm
Thanks Euro.
Yes the higher plate wattage was clear to me as I got a high almost 5W outcome. I had a 5K transformer on the 4 ohm winding, and used a 20 mA trickle. Highs were not abundant but had a softness to them.
How I got the VT25A tubes? At a local military dump shop. They had bought a pack of airplane recievers, where a pair of V25A (7.5V) and Vt52 (5V) were used - in series. That means - their filaments could be used with on a 12V (=13volts) lead battery.
Then the question - as I remember it was stated - is the 10 (10Y/VT25/VT25A) like the 45 or 50? Now the feedback here was: NO. The Ri is mucho higher . . . So can't be used in this designg with a mere 5K transformer.
Yes the higher plate wattage was clear to me as I got a high almost 5W outcome. I had a 5K transformer on the 4 ohm winding, and used a 20 mA trickle. Highs were not abundant but had a softness to them.
How I got the VT25A tubes? At a local military dump shop. They had bought a pack of airplane recievers, where a pair of V25A (7.5V) and Vt52 (5V) were used - in series. That means - their filaments could be used with on a 12V (=13volts) lead battery.
Then the question - as I remember it was stated - is the 10 (10Y/VT25/VT25A) like the 45 or 50? Now the feedback here was: NO. The Ri is mucho higher . . . So can't be used in this designg with a mere 5K transformer.
