Preamp CCS
- pre65
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#1 Preamp CCS
I was reading a forum post (not on here) about using an Ixys 10m45s CCS chip on a preamp.
It seemed to suggest that if the 10M45s was the anode load you could ground the cathode, as the chip set the current.
Or could I have misunderstood ?
Also, I've read of cascoded 10M45s being better than a single one, can anyone point me to information on that ?
It seemed to suggest that if the 10M45s was the anode load you could ground the cathode, as the chip set the current.
Or could I have misunderstood ?
Also, I've read of cascoded 10M45s being better than a single one, can anyone point me to information on that ?
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
#2
Must be true, it s on the net.
Grounding the cathode will force it into grid leak bias. it will work for some values of work.
Cascoding CCS's will create a composite CCS with higher impedance and better power handling, so yes, it is "better", but you need to know if it was good enough before, or if the weak point is somewhere else.
Grounding the cathode will force it into grid leak bias. it will work for some values of work.
Cascoding CCS's will create a composite CCS with higher impedance and better power handling, so yes, it is "better", but you need to know if it was good enough before, or if the weak point is somewhere else.
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
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#3 Re: Preamp CCS
I imagine the anode Voltage will fall to the point where it stabilises at that current, which could be quite low, depending what valve it is, not sure I like that idea. I'd still want to bias the valve 'properly'.pre65 wrote:It seemed to suggest that if the 10M45s was the anode load you could ground the cathode, as the chip set the current.
Also grid will behave like a diode to ground for input signals.
"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
- pre65
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#4 Re: Preamp CCS
Talking of diodes, if one wanted to use diodes instead of a resistor at the cathode, is it a case of adding up the forward volts till one gets to the desired voltage ? And then no bypass cap is needed ?Mike H wrote:I imagine the anode Voltage will fall to the point where it stabilises at that current, which could be quite low, depending what valve it is, not sure I like that idea. I'd still want to bias the valve 'properly'.pre65 wrote:It seemed to suggest that if the 10M45s was the anode load you could ground the cathode, as the chip set the current.
Also grid will behave like a diode to ground for input signals.
I could be suffering from information overload.
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
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#5
There are still a few oases of sanity in a sea of dross, but I've noticed the increasing weight of the latter is reinforcing the impression that the former is dwindling. Though it probably isn't, just seems like itNick wrote:Must be true, it s on the net.
"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
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#6 Re: Preamp CCS
This is like using LED's isn't it?pre65 wrote:Talking of diodes, if one wanted to use diodes instead of a resistor at the cathode, is it a case of adding up the forward volts till one gets to the desired voltage ? And then no bypass cap is needed ?
Not tried it but I'd worry that the diode(s) impedance is non-linear vs changing current, and probably also frequency. Although I've seen it done in transistor circuits, but then the base-emitter of the transistor is also non-linear and anyway global NFB would be applied to compensate.
"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
- pre65
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#7 Re: Preamp CCS
Some bod tried it with Shottky diodes and reckoned it was ace.Mike H wrote:This is like using LED's isn't it?pre65 wrote:Talking of diodes, if one wanted to use diodes instead of a resistor at the cathode, is it a case of adding up the forward volts till one gets to the desired voltage ? And then no bypass cap is needed ?
Not tried it but I'd worry that the diode(s) impedance is non-linear vs changing current, and probably also frequency. Although I've seen it done in transistor circuits, but then the base-emitter of the transistor is also non-linear and anyway global NFB would be applied to compensate.
As we know, must be true.
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
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#8
I used to have enough aggro making things work from magazine articles, now with the Internet it's 1,000 times worse
"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
- pre65
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#9
I have enough aggro (or I used to have) making things work when following a known working design.Mike H wrote:I used to have enough aggro making things work from magazine articles, now with the Internet it's 1,000 times worse
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
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- Old Hand
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#10 Re: Preamp CCS
See my Snail PreAmp thread. I used a pair of cascoded 10m45s on both ECC82 gain stage and CF, in that instance both running at 5mA without any heatsink. Went straight to the cascode because the cost of an extra chip and resistor seemed a cheapish thing to do.pre65 wrote:I was reading a forum post (not on here) about using an Ixys 10m45s CCS chip on a preamp.............. Also, I've read of cascoded 10M45s being better than a single one, can anyone point me to information on that ?
TD-125/RB250/MC25FL & 'Snail' phono, NAS/SBT with CS4398 DAC, 41MP pre & MoFo Power, still messing with OBs.
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- Old Hand
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#12
Knew I had a photo. Set resistor was 520R for 5.0mA.
TD-125/RB250/MC25FL & 'Snail' phono, NAS/SBT with CS4398 DAC, 41MP pre & MoFo Power, still messing with OBs.