317 CCS Question

pftrvlr · 25th June 2008, 04:54 AM

I read a article in Audio Xpress regarding CCS. It mentions that 317 CCS require minimum 10mA for regulation.

In one of prototype, I use 317 as cathode current sink at 2.5mA. It works. I have no way to run it at 10mA in the input stage, so I have no comparison. Anyone has any experiences of 317 at diffetent output current?

If 317 is not a good candidate for <10mA application, what other simple solutions we have?

Shoog · 25th June 2008, 10:09 AM

If you look at the LM317 datasheet it indicates that the minimum current needed to keep it operating is 3.5mA. I would choose to run it at higher currents of at least 5mA.

A better performin choice in this application would be

CCS for tubes/valves: PCBs

These are increadably easy to build and are configurable to any current by choosing the appropriate transistors.
It is generally very easy to find salvaged transistors to build these for nothing.

Shoog

316a · 25th June 2008, 12:13 PM

LM317 makes a horrible sounding CCS . Look at JFETs or depletion types for a simple CCS (add a resistor) or cascode BJT (there used to be boards available on DIYAudio) .

316a

alexmoose · 25th June 2008, 01:47 PM

why does it sound so bad? its poor Frequency response?

Shoog · 25th June 2008, 02:58 PM

Quote:

LM317 makes a horrible sounding CCS

This very much depends on the application and is at least partly prejudice.

They don't sound bad if fully bypassed (ie in cathode duty), the capacitor resistance is tiny compared to the LM317 and so it totally dominates the response. In an anode role it has a falling impedance at higher frequency which scews the overall circuit response to bass heavy. The same will apply to a lesser extent when used in a LTP unbypassed.

There are considerably better options. The only time I have, and would, use them is in a bypassed output stage.

Shoog

pftrvlr · 25th June 2008, 04:00 PM

How much better is other CCS options? My experience is that the tubes and the overall topology have more impact on the sound than the usage of CCS in my headphone amp.

I am looking for a simple option - minimal components and no PCB. I need to replace the cathode resistors in my point-to-point constructed amps.

zigzagflux · 25th June 2008, 06:21 PM

Apples for apples, using a 10M45S or DN2540 TO-220 device is identical to using an LM317, as far as soldering, mounting, etc.

Measured performance is better. Voltage capability is higher. Price difference of little consequence. That's all I need to steer away from the 317.

For the good stuff, cascode either of those devices. Case closed, IMO.

Shoog · 25th June 2008, 06:40 PM

Quote:

Apples for apples, using a 10M45S or DN2540 TO-220 device is identical to using an LM317, as far as soldering, mounting, etc.

I would agree in all but one respect - the LM317 will produce a more consistent CCS. The others will need selecting from a number. Not a big deal really.

If you have the LM317 go ahead and use them, they will be more than adequate.

Shoog

pftrvlr · 26th June 2008, 12:10 AM

What is 10M45 minimal A-K voltage? In input cathode position, I have only a few volts.

zigzagflux · 26th June 2008, 12:42 AM

You would need a negative rail in order to use the 10M45S (and IMO, the 317 as well).

If you want to avoid this, try the LM334Z, per Morgan Jones. Or possibly an LED ?

25th June 2008, 04:54 AM	#1
pftrvlr diyAudio Member Join Date: Feb 2007 Location: SoCal	317 CCS Question I read a article in Audio Xpress regarding CCS. It mentions that 317 CCS require minimum 10mA for regulation. In one of prototype, I use 317 as cathode current sink at 2.5mA. It works. I have no way to run it at 10mA in the input stage, so I have no comparison. Anyone has any experiences of 317 at diffetent output current? If 317 is not a good candidate for <10mA application, what other simple solutions we have?

25th June 2008, 12:13 PM	#3
316a diyAudio Member Join Date: Dec 2002 Location: West London	Re: 317 CCS Question LM317 makes a horrible sounding CCS . Look at JFETs or depletion types for a simple CCS (add a resistor) or cascode BJT (there used to be boards available on DIYAudio) . 316a

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25th June 2008, 10:09 AM	#2
Shoog diyAudio Member Join Date: Aug 2002 Location: Eire	If you look at the LM317 datasheet it indicates that the minimum current needed to keep it operating is 3.5mA. I would choose to run it at higher currents of at least 5mA. A better performin choice in this application would be CCS for tubes/valves: PCBs These are increadably easy to build and are configurable to any current by choosing the appropriate transistors. It is generally very easy to find salvaged transistors to build these for nothing. Shoog

25th June 2008, 01:47 PM	#4
alexmoose diyAudio Member Join Date: Mar 2006 Location: Michigan	why does it sound so bad? its poor Frequency response?

25th June 2008, 04:00 PM	#6
pftrvlr diyAudio Member Join Date: Feb 2007 Location: SoCal	How much better is other CCS options? My experience is that the tubes and the overall topology have more impact on the sound than the usage of CCS in my headphone amp. I am looking for a simple option - minimal components and no PCB. I need to replace the cathode resistors in my point-to-point constructed amps.

25th June 2008, 06:21 PM	#7
zigzagflux diyAudio Member Join Date: Oct 2006	Apples for apples, using a 10M45S or DN2540 TO-220 device is identical to using an LM317, as far as soldering, mounting, etc. Measured performance is better. Voltage capability is higher. Price difference of little consequence. That's all I need to steer away from the 317. For the good stuff, cascode either of those devices. Case closed, IMO.

26th June 2008, 12:10 AM	#9
pftrvlr diyAudio Member Join Date: Feb 2007 Location: SoCal	What is 10M45 minimal A-K voltage? In input cathode position, I have only a few volts.

26th June 2008, 12:42 AM	#10
zigzagflux diyAudio Member Join Date: Oct 2006	You would need a negative rail in order to use the 10M45S (and IMO, the 317 as well). If you want to avoid this, try the LM334Z, per Morgan Jones. Or possibly an LED ?

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