Many amps from Mr. Nelson are SE inspite +/_ supply and two output devices. One device is typically current source. Symmetrical supply is to avoid big cap on output.
I have not been following this discussion very closely lately, I see mentions about a darlington upper device that makes me curious. Is there a schematic, or even better, a sim of that mod somewhere in the thread?
It's getting quite long (and the amp deserves the interest), and I was not able to find anything when quickly going through the posts.
It's getting quite long (and the amp deserves the interest), and I was not able to find anything when quickly going through the posts.
Sam,
I will email you tomorrow.....
2SD2560 is a drop in.
Hugh
I will email you tomorrow.....
2SD2560 is a drop in.
Hugh
@AKSA
Please include me as well or just post here with any changes to the output stage so we can all benefit from the Sanken Darlington BJT substitution 2SD2560 of the current NMOS. I have a feeling just a small change in value of the gate resistor is required. Then we can update the 1st post on the 1st page of this thread for people to get a direct link.
Best,
Anand.
Please include me as well or just post here with any changes to the output stage so we can all benefit from the Sanken Darlington BJT substitution 2SD2560 of the current NMOS. I have a feeling just a small change in value of the gate resistor is required. Then we can update the 1st post on the 1st page of this thread for people to get a direct link.
Best,
Anand.
Sam, Anand:
1. Drop in of Sanken 2SD2560 but check pinouts SOURCE to EMITTER, DRAIN to COLLECTOR and GATE to BASE.
2. Do not increase the rail voltages beyond 24V; this will threaten the SOAR limitations of the Darlington.
3. Use a 43R base resistor for the Darlington.
4. Do not increase any other amp components. The bootstrap resistors and Source/Emitter resistors may remain unchanged.
5. Take extra care to cool the darlington, as bipolar are highly susceptible to local hotspots if the cooling is not uniform.
Benefit? A little slam and impact, more like a SS rather than a tube.
HD
1. Drop in of Sanken 2SD2560 but check pinouts SOURCE to EMITTER, DRAIN to COLLECTOR and GATE to BASE.
2. Do not increase the rail voltages beyond 24V; this will threaten the SOAR limitations of the Darlington.
3. Use a 43R base resistor for the Darlington.
4. Do not increase any other amp components. The bootstrap resistors and Source/Emitter resistors may remain unchanged.
5. Take extra care to cool the darlington, as bipolar are highly susceptible to local hotspots if the cooling is not uniform.
Benefit? A little slam and impact, more like a SS rather than a tube.
HD
Hugh ... surely that suggests the Darlington option is only suitable for the AN4R - given its DC rails are +/-21v ... whereas the AN8R has +/-27v?
Hi Andy,
Actually the darlington is fine for 8R, and in fact you raise a good point here, we can increase the rail voltage to 30V with 8R because the load current is halved.
This darlington will withstand 3A at Vce of 60V for 10mS , and available at Digikey right now.
HD
Actually the darlington is fine for 8R, and in fact you raise a good point here, we can increase the rail voltage to 30V with 8R because the load current is halved.
This darlington will withstand 3A at Vce of 60V for 10mS , and available at Digikey right now.
HD
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Have not heard of "Littlediodes"; sure GBP3.50ea might be a good price ... but are you sure they're genuine? 😵
At least buying from the majors - like RS, Digikey or Element14 - you can be sure that their supply lines are kosher.
Hi Francois,
It is a difference of sound presentation; just another version.
Slam and impact is a big issue with orchestral music and rock concerts, and an advantage with many instruments and voices all playing at the same time. The laid back, rounded and organic sounds of tube sound are preferred by many, but in my personal view best suited to simpler music, and particularly jazz vocalist music. To me nothing beats a good 300B SET with a jazz quartet.
BUT audio is a bit like clothes, or food. Lots of variations, different strokes for different folks........
Good to see you in the thread!
HD
It is a difference of sound presentation; just another version.
Slam and impact is a big issue with orchestral music and rock concerts, and an advantage with many instruments and voices all playing at the same time. The laid back, rounded and organic sounds of tube sound are preferred by many, but in my personal view best suited to simpler music, and particularly jazz vocalist music. To me nothing beats a good 300B SET with a jazz quartet.
BUT audio is a bit like clothes, or food. Lots of variations, different strokes for different folks........
Good to see you in the thread!
HD
Thank you all for the help and advice. I decided to build the 4R version. Pics attached and THD graph showing 1 khz into 4 ohms at 1 watt. I gotta say, the variety of components makes this pretty fun to build, and I totally dig the outboard output MOSFET arrangement.
Congratulations rdb64 on your successful build.
Let us know your impressions once you have some playing time with your loudspeakers.
Let us know your impressions once you have some playing time with your loudspeakers.
Yeah, this sucker runs hot. Each amp goes in a Modushop monoblock chassis, so that's a pair of 4U x 200mm heatsinks (so each output MOSFET is on its own 4U x 200mm heatsink). I have a thermal camera (FLIR TG267) which is reading about 55 degrees (celsius) on the heatsink and 63 degrees on top of the MOSFET helper PCBs. With the thermocouple reaching behind and directly on the MOSFET, it reads 74 degrees. So hot!
As for bias, I measure 334 mV across the 0.12 ohm resistor (R141), so that's 2.8 A. On the LTP, I measure 11.1 V across the 5 kohm resistor (R112), so that's 2.2 mA.
They'll go into the chassis and playing music later today (I hope).
--- Bobby
As for bias, I measure 334 mV across the 0.12 ohm resistor (R141), so that's 2.8 A. On the LTP, I measure 11.1 V across the 5 kohm resistor (R112), so that's 2.2 mA.
They'll go into the chassis and playing music later today (I hope).
--- Bobby
The measurements I posted were with a bench power supply at +/-20V. My built PSU (Antek AS-3218s driving @xrk971's SLB rectifiers/filters) is supplying closer to +/-21V under the load.