prose:
The calibration procedure is particularly useful for people who have no ASY-transistor, for example because they have not bought a whole kit, but only one board. The Jensamp works equally well with a BC560 transistor-transistor instead of ASY.
But the people with the HDW-transistor can be used instead of R6 and RV6 Jensamp times calibrate their "right". The fixed resistor R6 is actually a white lie to the people who just want to paint-by-numbers, not the balance to be expected.
So, go for it ....
When the transistor and the trimmer (on the center position) are used to set a gain level 1, a low impedance signal fed into the DI input and measures the level before the output transformer with no load on the output. Please override the amplifier is not, otherwise the measurement is meaningless.
The gain between the input and the output should be for - whether or ASY BC - are 4.5 dB. This is the only gain from the electronics without the transformers, or other factors.
That's it.
Germanium transistors have a high variance during production, so I would recommend the measurement actually already.
As an example ...
By the time we play for Jensamp Volkers. As I re-measure the values can not, I charge some times ...
You received the first gain stage 14 dB gain and 18.7 dB (depending on impedance) when the mob version with Lundahl there were 16.7 dB and 21.4 dB have been.
When we need to subtract 3.51 dB crowd, because that adds to the 2:3 output transformer. In Lundahl, we subtract 6 dB, because the output transformer is connected 1:2.
If without the output transformer has a gain of 10.5 dB (for 2040Ohm) and 15.19 dB (for 591Ohm) at Haufe and 10.7 dB (for 2020Ohm) and 15.4 dB (for 586Ohm) at Lundahl.
From each of the first number (10.5 dB and 10.7 dB) for the measurement, we must deduct 2400Ohm 7.932 dB, because there was a 1:2.5 transformer in the game here, making its 2.568 dB and 2.768 - each for crowd and Haufe.
Each of the second number (15.19 dB and 15.4 dB) for the measurement 600Ohm we draw from 13.932 dB, because here was a 1:5 transformer in the game, making its 1.258 and 1.468 dB - also for each mob and Lundahl.
Now we are not there yet, by the 144Ohm source and the 2.4 kohm and 600 Ohm inputs, which act as voltage dividers are a few dB before amplifier has been lost, we must add up to.
In the 2040Ohm-heap-entrance it is 0.59 dB, that is 2.567 dB + 0.59 dB = 3.157 dB
In the 2020Ohm-Lundahl input are 0.596 dB, 2.768 dB + 0.596 dB so = 3.364 dB
In the crowd-591Ohm input are 1.888 dB, 1.258 dB + 1.888 dB so = 3.146 dB
In the 586Ohm-Lundahl input are 1.902 dB, 1.468 dB + 1.902 So = 3.37 dB
So if you eliminated all outside influences, one can say your electronics amplified at a gain stage between 3.15 dB and 3.35 dB - depending on the measurement. You notice this small rounding errors and inaccuracies, in particular, because I have back Gege reefs on numbers from your table, which originated with 1% THD at your measurement. You should carry out the measurements and the calculations again with a non-controlled Jensamp and no load on the output, then it would fit. We assume, however, simply assume the numbers in your measurement would not be the limit.
3.15 dB or 3.35 dB below the 4.5 dB, which should be to see the original schematic, as it stands, ie if you had used a trimmer instead of the 470ohm resistor, you would have to rotate as long (resistance make them smaller), the gain would have increased by approximately 2.3 dB, ie electronics alone make the 4.5 dB gain at the lowest level would gain.
The difference that you have with the targeted 4.5 dB can, on a production spread of transistors - are situated in your specific case to the figures from the measurement, because it was conducted as described above at 1% THD - in particular the ASYS . I am assuming that you actually lie very close to the 4.5 dB.
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