Hello,
I've recently recieved Rod Elliots amplifer board from the 101 project, which is a Lateral MOSFET design. If anyone has experience with building his amplifiers, I have a question about the source resistors R12, R13, R16 and R17. I can't seem to find the ones he recommends in his design. But I have a pretty close match, 0.11 ohms lower to be exact. Also his are rated at 2W and mine are rated at 5W. Could I use these resistors instead?
If you bought any of his boards you will know the actual values, if not you probably can't help me.
Thank you for your help.
I've recently recieved Rod Elliots amplifer board from the 101 project, which is a Lateral MOSFET design. If anyone has experience with building his amplifiers, I have a question about the source resistors R12, R13, R16 and R17. I can't seem to find the ones he recommends in his design. But I have a pretty close match, 0.11 ohms lower to be exact. Also his are rated at 2W and mine are rated at 5W. Could I use these resistors instead?
If you bought any of his boards you will know the actual values, if not you probably can't help me.
Thank you for your help.
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I would think 0.11 is close enough. But you should get same type (metal film).
Can you tell us the spec and exactly what you have? Would allow us to give better responses.
Can you tell us the spec and exactly what you have? Would allow us to give better responses.
zero ohm resistors will work in a lateral FET amp with only one output pair - they are not needed to stabilize the bias point - here they are only for current-sharing between the output devices.
FETs are fast, so inductance in a source resistor is a bad idea - but 0.1 ohms is usually only a few turns (the photo on Rod Elliott's site clearly shows wirewound being used on the prototype, perhaps 4 or 5 turns or so).
I think you'll be OK. Just monitor the supply current on commisioning - any tendancy to oscillate will show up and sudden jumps in the supply current (followed soon by a burning smell!)
FETs are fast, so inductance in a source resistor is a bad idea - but 0.1 ohms is usually only a few turns (the photo on Rod Elliott's site clearly shows wirewound being used on the prototype, perhaps 4 or 5 turns or so).
I think you'll be OK. Just monitor the supply current on commisioning - any tendancy to oscillate will show up and sudden jumps in the supply current (followed soon by a burning smell!)
The ESP website features a newer image of P101 which shows round source resistors but previously, they were square 5W cement type, just like every DIYer has used for 50 years or more. Perhaps the change is because these smaller resistors and other special components weren't widely available here until the internet became the preferred shopping place.
It's worth adding that low inductance, Chinese copies of the common, upright style Japanese KOA cement resistors are available very cheaply. They are a Z-folded alloy ribbon inside, so they have significantly lower inductance than the conventional wirewound coil type. So far, no problems for me but I would not risk over-rating them. This is similar, original KOA product: https://www.koaglobal.com/-/media/F...f?la=en&hash=311D65DF161122CEDF0F58D36E922FD7
It's worth adding that low inductance, Chinese copies of the common, upright style Japanese KOA cement resistors are available very cheaply. They are a Z-folded alloy ribbon inside, so they have significantly lower inductance than the conventional wirewound coil type. So far, no problems for me but I would not risk over-rating them. This is similar, original KOA product: https://www.koaglobal.com/-/media/F...f?la=en&hash=311D65DF161122CEDF0F58D36E922FD7
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Have you tried writing to Rod? If you are a bonafide customer, I've found him to be EXTREMELY helpful.
mpr sr passives - Iskalni niz | Elektronske komponente. Distributer in spletna trgovina – Transfer Multisort Elektronik this are ok for that project.
For hi end apetite i use WSR from vishay.
For hi end apetite i use WSR from vishay.
Niko, the resistors you have are perfectly fine! You will read a lower voltage of course when setting the bias, but this you know. Just build it with those you already have.
Hi Niko, I've got this amp and using 0.22 5W cheramic-cement resistors....even for the soft start circuit....salute,Frank
As Lateral MOSFETs draw less current when they get hot, how about moving the source resistors to the drain, just for current monitoring purpose?
