most of BF245A ( at least those available in my neck o' wood) are in 2~3mA Idss range ;
that's solution for ones lazy as ZM
non-lazy ones will use BF245C degenerated to 2mA , with mucho ohms going from gate to gnd, too .
better and cheaper CCS than with 2SK
edit: important thing with BF245A is that you can still squeeze it where low DS voltage is must , and still have stable CCS
that's solution for ones lazy as ZM
non-lazy ones will use BF245C degenerated to 2mA , with mucho ohms going from gate to gnd, too .
better and cheaper CCS than with 2SK
edit: important thing with BF245A is that you can still squeeze it where low DS voltage is must , and still have stable CCS
Many thanks Salas!
I will try it tomorrow, this evening I make a quick try to get rid of the hum probably produced by the resistor serpent......
Hello Gerd,
And the supply is +48V. Are the Lowthers 16 Ohms or 12? What Id and Vds?
If you let me know, I'll run a test for you. (for a six of Hauff Pils
the six-pack Hauff Pils is ready.......!
off course
and while we are having fun - with BF , you can stack several of them in Papa Borbely's high pinch cascode manner , with LED on top , and have multiple pleasure
edit : just for fun - rofl CCS
He had full cascode for the small and the big semis, but he wants to listen to something else less parts also. Only to insulate the TO-220 mounting screw too is a reminder if the sink touches something that it shouldn't. The other one had TO-247s which aren't a pain to insulate.
He had a BF245C there topping for a fast ''tail'' CCS in the previous test. The Toshiba will push the PSRR hard in the lows with its large gm and let it loose progressively due to high Ciss, maybe its the ''different'' sound he seeks or not. He can try 2SK170 BL with that resistor, or a low IDSS BF245A and decide, provided he likes the plain CCS in general of course.
Thank Salas and Zen Mod for the technical discussion you unfolded for me!
Quick check of the hum, first results
Half of the hum was gone after putting the case to signal ground.
( I hadn't to do it with the MU and the CCS solutions)
The other half must be due to the resistor solution and my insufficient PSU.....
So resistor solutions do not have the same PSRR...... That is new to me....first time I have this resistor solution....
That is a bit disappointing..... I have a 500W xformer and the normal +- 24V FW CRC PSU but instead of the 8 x 15.000uF I have already 8x 22000uF and of course the four 0,47 Ohm resistors. Can I take them out?
But I suppose I still get more hum.... So I have to take the decision to make a completely new PSU.
Now I know why there are this monster caps in the picture of Tonys builds BTW showed us.
Tomorrow the Salas Solution with one IRF.....
Quick check of the hum, first results
Half of the hum was gone after putting the case to signal ground.
( I hadn't to do it with the MU and the CCS solutions)
The other half must be due to the resistor solution and my insufficient PSU.....
So resistor solutions do not have the same PSRR...... That is new to me....first time I have this resistor solution....
That is a bit disappointing..... I have a 500W xformer and the normal +- 24V FW CRC PSU but instead of the 8 x 15.000uF I have already 8x 22000uF and of course the four 0,47 Ohm resistors. Can I take them out?
But I suppose I still get more hum.... So I have to take the decision to make a completely new PSU.
Now I know why there are this monster caps in the picture of Tonys builds BTW showed us.
Tomorrow the Salas Solution with one IRF.....
hi Mike ,Here is already sleeping 23.11 PM, so only a small answer.....
I make the test with cynch plugging in and out tomorrow....
I drive at the moment only the SIT with the PSU..
The colors are unfortunately mixed from black over red and blue....
No wonder hum is coming.....
And the worst message at the end....
I never drank beer, I never played football.......
Should I change the forum now......
How close is the PSU to signal circuitry? Papa says that you must turn the transformer to get lowest noise. Also, you are using almost all the VA of the transformer (this project needs 400VA per channel). Therefore, transformer will tend to hum more.
If you have some inductors lying around (>1mh), you can try them after the PSU... they could reduce hum. Certainly looks like you have enough capacitance.
If you have some inductors lying around (>1mh), you can try them after the PSU... they could reduce hum. Certainly looks like you have enough capacitance.
Re: ......Hauff Pils brings back good memories.
Prost!
That's odd...... Hauff Pils caused me to LOSE a lot of memories....
@Tea Bag
Mike,
Here are some quick tests I did for a 16 Ohm speaker load:
16 Ohm Speaker (2 Bulbs)
50V 2.4A 19.6V
45V 2.2A 19.1V (Both approx. 8dB with 1W THD approx. .07%)
That's pushing it on the dissipation so, for an alternative flavor, you can unscrew a bulb and try these:
16 Ohm Speaker (1 Bulb)
50V 1.2A 21.0V
45V 1.1A 19.3V (Both approx. 9dB with 1W THD approx. .2%, 5W @ 2%)
Makes me wish I had some 16 Ohms speakers to try.
These are just starting points, of course you can twist the knob in small increments until you're happy.
Hope that helps,
Mike
Mike,
Here are some quick tests I did for a 16 Ohm speaker load:
16 Ohm Speaker (2 Bulbs)
50V 2.4A 19.6V
45V 2.2A 19.1V (Both approx. 8dB with 1W THD approx. .07%)
That's pushing it on the dissipation so, for an alternative flavor, you can unscrew a bulb and try these:
16 Ohm Speaker (1 Bulb)
50V 1.2A 21.0V
45V 1.1A 19.3V (Both approx. 9dB with 1W THD approx. .2%, 5W @ 2%)
Makes me wish I had some 16 Ohms speakers to try.
These are just starting points, of course you can twist the knob in small increments until you're happy.
Hope that helps,
Mike