My Fluke thermocouple says 72,4ºC (close to the mosfet)...I knew my fingertips were fairly accurate 😀
Arne K
Arne K
Henrik said:
Hi Henrik
You are right. Adjusting R101 and R102 affects the quiescent DC values, not bias current.
By the way, if I look into your amp, the so-called X-feedback controls the amp gain as well as lowers distortion and noise. In comparison, if I look into the Pass original design, R15 controls the amp gain as well as distortion and noise. Do you think the lowering distortion and noise with X-feedback is better than, instead, doing the same with R15? My question is with respect to the taste of the sound.
Regards
Henrik,
50°C is a good value when you dissipate around 20-30 watts in the fet. At 1.2 watt you can go a lot higher.
william
50°C is a good value when you dissipate around 20-30 watts in the fet. At 1.2 watt you can go a lot higher.
william
Hi JH6YOU
I haven´t tried to lower the gain by addig more feedback, but since the feedback is relatievly high, i suspect you might get too much, Nelson has stated that too much x-feedback tends to strain the sound.
Hi william!
Thanks for bringing this issue up.
Some years ago i e-mailed Nelson about the heat from my first bosoz, and he replied that i must have done something wrong since i wasn´t able to touch the small heatsinks that he suggests in his article. So since then i just followed "order".
So may be after all, the small heatsinks might be on the safe side.
If i am to take the consequense of the data sheets i gets the following results.
Tj => Junction tempreture in degrees C.
Ts => Sink tempreture in degrees C.
P => Power to dissipate in device.
Rjs => Termal resistance junction to sink.
Thus we have the equations: Tj=Ts+(P*Rjs) and Ts=Tj-(P*Rjs)
IRFP140:
Rjs=1.7
If Ts is 50 degree C and P=25W, then Tj=50+(25*1.7)=92 degree C.
Tj=92 degree C is acceptable as we accept Ts at 50 degree.
Now Irf610:
Rjs=4.0
If Tj=92 degree C and P=1.3W, then Ts=92-(1.3*4)=86.8 degree C.
Heatsink tempreture at 86.8 degree C for an IRF610 dissipating 1.3W is the logical consequence of the acceptance of an heatsinktempreture at 50 degree C for an IRFP140 dissipating 25W.
William, is this also how you see this?
Regards
I haven´t tried to lower the gain by addig more feedback, but since the feedback is relatievly high, i suspect you might get too much, Nelson has stated that too much x-feedback tends to strain the sound.
Hi william!
wuffwaff said:
Thanks for bringing this issue up.
Some years ago i e-mailed Nelson about the heat from my first bosoz, and he replied that i must have done something wrong since i wasn´t able to touch the small heatsinks that he suggests in his article. So since then i just followed "order".
So may be after all, the small heatsinks might be on the safe side.
If i am to take the consequense of the data sheets i gets the following results.
Tj => Junction tempreture in degrees C.
Ts => Sink tempreture in degrees C.
P => Power to dissipate in device.
Rjs => Termal resistance junction to sink.
Thus we have the equations: Tj=Ts+(P*Rjs) and Ts=Tj-(P*Rjs)
IRFP140:
Rjs=1.7
If Ts is 50 degree C and P=25W, then Tj=50+(25*1.7)=92 degree C.
Tj=92 degree C is acceptable as we accept Ts at 50 degree.
Now Irf610:
Rjs=4.0
If Tj=92 degree C and P=1.3W, then Ts=92-(1.3*4)=86.8 degree C.
Heatsink tempreture at 86.8 degree C for an IRF610 dissipating 1.3W is the logical consequence of the acceptance of an heatsinktempreture at 50 degree C for an IRFP140 dissipating 25W.
William, is this also how you see this?
Regards
Thanx, Henrik!
Your last schematics gave me the change I needed, I'm probably too used to my BUF-04 + Dact pre-amp with no gain...😀
Arne K
Your last schematics gave me the change I needed, I'm probably too used to my BUF-04 + Dact pre-amp with no gain...😀
Arne K
Hi Arne
Glad you made it.
And may be your hot regulators are okay, i certainly have to get used to those tempretures.
Regards
Glad you made it.
And may be your hot regulators are okay, i certainly have to get used to those tempretures.
Regards
Hi Arne,
very nice! Can you tell a bit more about your output/input board (wich relais, source etc.).
What volume attenuator is that you use?
I like the front of your amp although I think it would be nice if the knobs were a bit bigger.
William
very nice! Can you tell a bit more about your output/input board (wich relais, source etc.).
What volume attenuator is that you use?
I like the front of your amp although I think it would be nice if the knobs were a bit bigger.
William
Thanx, all, particularly MAD_K, Henrik, Nelson Pass...
All controls are APOX; Front-panel w/remote sense, input boards, and "SHM" 20k volume boards.
http://www.apoxcontrols.com/apox.htm
Yes, I need new knobs, the ones I had did not fit the encoder-shaft.
Arne K
All controls are APOX; Front-panel w/remote sense, input boards, and "SHM" 20k volume boards.
http://www.apoxcontrols.com/apox.htm
Yes, I need new knobs, the ones I had did not fit the encoder-shaft.
Arne K
😀 Some of our scandinavian members may recognize the chassi from LC Audio...😉
(I do not think you get that sound-quality from that box normally...) 😎
It's not a Sidewinder anymore, I call it the "Conquest" !
Arne K
(I do not think you get that sound-quality from that box normally...) 😎
It's not a Sidewinder anymore, I call it the "Conquest" !
Arne K
Hi Arne!
It crossed my mind - it´s a nice case.
What happened to the sidewinder - and what is the difference in sound?
It crossed my mind - it´s a nice case.
What happened to the sidewinder - and what is the difference in sound?
Hi!
The sidewinder was never there! I was lucky getting a "one-off" chassi after they ended sale.
Have heard the sidewinder long ago, and actually wanted to buy/build one myself, but there was not enough inputs!!!
And I do not think/remember the Sidewinder beeing that musical, dynamic, with so much detail as the X -BOSOZ!
Arne K
The sidewinder was never there! I was lucky getting a "one-off" chassi after they ended sale.
Have heard the sidewinder long ago, and actually wanted to buy/build one myself, but there was not enough inputs!!!
And I do not think/remember the Sidewinder beeing that musical, dynamic, with so much detail as the X -BOSOZ!
Arne K
cobra,
I was going to ask you about the transformer so close to the low level signal...no EMI problems? I had lots in my first BOSOZ.
Great job by the way,
I was going to ask you about the transformer so close to the low level signal...no EMI problems? I had lots in my first BOSOZ.
Great job by the way,
ccs'ed, cs'ed
Hi,
I finally managed to build myself a cs-ccs-x-bosoz as a drop in replacement for my "standard" x-bosoz.
The schamatic as along the lines of Metallman's version with a few simplyfications (only one voltage source for the gates of the cascode fets). No zener but blue leds (3 for the voltage source and 2 as a voltage ref. for the current source).
All fets are IRF610 (Harris) and only standard parts are used (an exception are the Black Gate N 47uF at the outputs)
Since it is a drop in replacement for the amp described earlier in this thread it will take +60V and +60V. You can see the 4 470 Ohm resistors forming one 470R/8watt resistor to relief the current source fet.
Instead of fitting the fets to the bottom of the case I have them attached to a piece of aluminium (10mm thick x 40mm high x 160mm wide) with some holes drilled in. This will be connected to the bottom of the case with two M4 screws
I only did some measurements until now and it seems to work fine. Bandwidth is over one MHz (around 1.4MHz) wich also explains the nice square wave at 10kHz😀 This is almost 10x that of my original x-bosoz.
William
Hi,
I finally managed to build myself a cs-ccs-x-bosoz as a drop in replacement for my "standard" x-bosoz.
The schamatic as along the lines of Metallman's version with a few simplyfications (only one voltage source for the gates of the cascode fets). No zener but blue leds (3 for the voltage source and 2 as a voltage ref. for the current source).
All fets are IRF610 (Harris) and only standard parts are used (an exception are the Black Gate N 47uF at the outputs)
Since it is a drop in replacement for the amp described earlier in this thread it will take +60V and +60V. You can see the 4 470 Ohm resistors forming one 470R/8watt resistor to relief the current source fet.
Instead of fitting the fets to the bottom of the case I have them attached to a piece of aluminium (10mm thick x 40mm high x 160mm wide) with some holes drilled in. This will be connected to the bottom of the case with two M4 screws
I only did some measurements until now and it seems to work fine. Bandwidth is over one MHz (around 1.4MHz) wich also explains the nice square wave at 10kHz😀 This is almost 10x that of my original x-bosoz.
William
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