constant current source

tubem · 26th August 2011, 03:40 PM

I want to build the Pass Delite amp with an 80v supply,using a constant current source instead of light bulbs. I was wondering which of the already made designs in the Pass diy site suit this best?

Nelson Pass · 26th August 2011, 03:50 PM

That would work fine, although ZV9 is not a constant current source.
If you have an 80 volt supply you may find that the current source and/or
gain devices run very hot. Most of the 80 volts is intended to be dropped
across the light bulb. With a current source you probably want to get down
to 40 to 50 volts.

tubem · 26th August 2011, 10:22 PM

Thanks Nelson, I will take another look at the many power supplies on your diy site and choose one in the 40-50v range.

tubem · 26th August 2011, 11:45 PM

Looking back at the ZV9 there are 10 pages of discussion, with different variations of power supplies,one is a cascode type and another called an ALEPH current source with 50v supply down to 23v on the drain the amplified fet.Would the ALEPH current source be a good choice for an alternative to the light bulbs in the delite amp,I'm using the IXTH6N50D2.

Nelson Pass · 27th August 2011, 12:36 AM

Yes, it would be a good alternative. Some AC gain on that source as presented
will help the Ixys part out a bit in the distortion department.

buzzforb · 01:46 AM

When using a depletion mode device with CCS instead of a load resistor, what determines the drain potential of the amp? If the CCS is stiff enough, does the load detemine drain potential while the CCS gets ignored?

tubem · 27th August 2011, 04:11 AM

There will be a 100 ohm resistor across the output which will be the load reference,additional negative feedback can help reduce it more, but I will listen to it without first,I usually listen to tube amplifiers anyway so I'm not worried about finite levels of distortion.

Nelson Pass · 27th August 2011, 05:58 PM

Quote:

Originally Posted by buzzforb

When using a depletion mode device with CCS instead of a load resistor, what determines the drain potential of the amp? If the CCS is stiff enough, does the load detemine drain potential while the CCS gets ignored?

This has been addressed in another thread, "R085 Zen"

tubem · 27th August 2011, 06:47 PM

OK now I'm confused, does the depletion fet need a resistive load at the drain,like the simple lightbulb circuit or is the ALEPH CCS going to work fine anyway, in the circuit I saw there was a resistor across the output?

buzzforb · 27th August 2011, 07:44 PM

No, but you have to be able to set the drain potential of the Jfet.

26th August 2011, 03:40 PM	#1
tubem diyAudio Member Join Date: Jun 2010 Blog Entries: 1	constant current source I want to build the Pass Delite amp with an 80v supply,using a constant current source instead of light bulbs. I was wondering which of the already made designs in the Pass diy site suit this best?

27th August 2011, 01:33 AM	#6
buzzforb diyAudio Member Join Date: Oct 2010 Location: Burlington, NC	When using a depletion mode device with CCS instead of a load resistor, what determines the drain potential of the amp? If the CCS is stiff enough, does the load detemine drain potential while the CCS gets ignored? Last edited by buzzforb; 27th August 2011 at 01:46 AM.

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26th August 2011, 03:50 PM	#2
Nelson Pass The one and only Join Date: Mar 2001	That would work fine, although ZV9 is not a constant current source. If you have an 80 volt supply you may find that the current source and/or gain devices run very hot. Most of the 80 volts is intended to be dropped across the light bulb. With a current source you probably want to get down to 40 to 50 volts.

26th August 2011, 10:22 PM	#3
tubem diyAudio Member Join Date: Jun 2010 Blog Entries: 1	Thanks Nelson, I will take another look at the many power supplies on your diy site and choose one in the 40-50v range.

26th August 2011, 11:45 PM	#4
tubem diyAudio Member Join Date: Jun 2010 Blog Entries: 1	Looking back at the ZV9 there are 10 pages of discussion, with different variations of power supplies,one is a cascode type and another called an ALEPH current source with 50v supply down to 23v on the drain the amplified fet.Would the ALEPH current source be a good choice for an alternative to the light bulbs in the delite amp,I'm using the IXTH6N50D2.

27th August 2011, 12:36 AM	#5
Nelson Pass The one and only Join Date: Mar 2001	Yes, it would be a good alternative. Some AC gain on that source as presented will help the Ixys part out a bit in the distortion department.

27th August 2011, 04:11 AM	#7
tubem diyAudio Member Join Date: Jun 2010 Blog Entries: 1	There will be a 100 ohm resistor across the output which will be the load reference,additional negative feedback can help reduce it more, but I will listen to it without first,I usually listen to tube amplifiers anyway so I'm not worried about finite levels of distortion.

27th August 2011, 06:47 PM	#9
tubem diyAudio Member Join Date: Jun 2010 Blog Entries: 1	OK now I'm confused, does the depletion fet need a resistive load at the drain,like the simple lightbulb circuit or is the ALEPH CCS going to work fine anyway, in the circuit I saw there was a resistor across the output?

27th August 2011, 07:44 PM	#10
buzzforb diyAudio Member Join Date: Oct 2010 Location: Burlington, NC	No, but you have to be able to set the drain potential of the Jfet.

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