hi Guys,
could you please help me with calculating the:
-gain
-possible anomalies in freq response
-output impedance
of the transformer coupled/loaded line stage based on 46 type tube?
So we speak about single tube gain stage.
B+ around 250VDC
around 10mA current
-10V on the grid
bias using 2.2k resistor and 200uf cap
Transformer spec: 8000ohm : 600 ohm (3.5:1 ratio)
Three load scenarios: 3kohm, 30kohm, 100kohm
My questions are:
- will there be any gain?
- do you see any issue with frequence response?
- what will be the estimated output impedance?
will there be
could you please help me with calculating the:
-gain
-possible anomalies in freq response
-output impedance
of the transformer coupled/loaded line stage based on 46 type tube?
So we speak about single tube gain stage.
B+ around 250VDC
around 10mA current
-10V on the grid
bias using 2.2k resistor and 200uf cap
Transformer spec: 8000ohm : 600 ohm (3.5:1 ratio)
Three load scenarios: 3kohm, 30kohm, 100kohm
My questions are:
- will there be any gain?
- do you see any issue with frequence response?
- what will be the estimated output impedance?
will there be
Attachments
Ok, i found some calculator to check the gain without considering the transformer step down ratio.
so the voltage gain on the tube will be more than 5, around 5.3 while loss on the transformer around 3.5, so if I am not mistaken overal gain should be 3db.
What about the output impedance? how to calculate it?
so the voltage gain on the tube will be more than 5, around 5.3 while loss on the transformer around 3.5, so if I am not mistaken overal gain should be 3db.
What about the output impedance? how to calculate it?
Attachments
Last edited:
Internal resistance of the tube divided by the impedance ratio 13.3.
Depends entirely on the quality of the output transformer.
46 tube with transformer load will need a bias closer to -35V, not -10V??
Last edited:
Thank you @MerlinB
well, yes, you are right about the operating point, however lets skip this for a moment please. this I should be able to handle, however I have some issues still with understanding output impedance.
This device will be used as simple line stage connected directly to power amplifier with 30kohm input impedance.
30kohm load on the secondary winding will give 400k in the primary side, right?
30k / 600R = 50
50 * 8000k = 400k
400k in parallel with 2.7k is close to ~2.7k
Transformer ratio: 3.5 : 1
3.5*3.5 = 13.3
2.7 / 13.3 = 200ohm roughly
Is that calculation OK?
Is there any potential risk if load will be higher than 30kohm?
well, yes, you are right about the operating point, however lets skip this for a moment please. this I should be able to handle, however I have some issues still with understanding output impedance.
This device will be used as simple line stage connected directly to power amplifier with 30kohm input impedance.
30kohm load on the secondary winding will give 400k in the primary side, right?
30k / 600R = 50
50 * 8000k = 400k
400k in parallel with 2.7k is close to ~2.7k
Transformer ratio: 3.5 : 1
3.5*3.5 = 13.3
2.7 / 13.3 = 200ohm roughly
Is that calculation OK?
Is there any potential risk if load will be higher than 30kohm?
my issue is - shouldnt all there calculations be done with consideration of the load on the secondary side?
I am a tube newbie, sorry for easy questions.
I am a tube newbie, sorry for easy questions.
Sorry, I made a mistake and misled you. Input impedance has no effect on the output impedance calculation.
Output impedance = 2700 / 13.3 = 200 ohms
That will affect frequency response and distortion, but it will not change the small-signal output impedance.