Thanks Juma, I didn't realize that is a way of raising the gain. Learning all the time here...
+1. I hadn't realised that either.
Yes, just lower the MOSFETs' source resistors to 10R and provide adequate heatsinking.
That lowers the degeneration too, but the total effect depends on gm of devices used.
Also, my experience shows that it's worth sourcing the Toshiba's k2013/j313 - the k1058/j162 worked great too.
That lowers the degeneration too, but the total effect depends on gm of devices used.
Also, my experience shows that it's worth sourcing the Toshiba's k2013/j313 - the k1058/j162 worked great too.
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I used a 50VA... but only because I had it laying around looking for a good home.
Anything from about 7.5VA/winding on up will be fine.
This transformer is the smallest shielded one that Antek makes, if you need to order something for the project, this is a fine choice - AS-0520 - 50VA 20V Transformer - AnTek Products Corp
Anything from about 7.5VA/winding on up will be fine.
This transformer is the smallest shielded one that Antek makes, if you need to order something for the project, this is a fine choice - AS-0520 - 50VA 20V Transformer - AnTek Products Corp
Resistor questions
I want to use a quality resistor(s) for the project. At the beginning of this guide, the photos appear to show Vishay Dale resistors installed on the BA-3 board. So for instance, looking at the BOM, a 1K, 1/4 watt resistor, would the Mouser part number 71-RN60D-F-1.0K be a quality choice for audio purposes?
I want to use a quality resistor(s) for the project. At the beginning of this guide, the photos appear to show Vishay Dale resistors installed on the BA-3 board. So for instance, looking at the BOM, a 1K, 1/4 watt resistor, would the Mouser part number 71-RN60D-F-1.0K be a quality choice for audio purposes?
The RN60's may fit on the board. They're quite large.
I used RN55's for all the ones I've built.
Hi ammel and thanks, but the RN55 appear to be only 1/8 watt. The BOM specifies 1/4 watt.
I had to download the RN55 datasheet, because i doubted the 1/8th W rating.
These are Mil spec and to meet that spec they are rated as 1/8th W when Ta = 70°C
But go to the Thermal resistance graphs.
1/8W into RN55 gives a temp rise (deltaT) of <20C degrees
1/2W into RN55 gives a deltaT of ~62C degrees.
Add that to Ta=25°C and you get a temperature of ~87°C
This will be well below the temperature of other 500mW and 600mW resistors.
I would suggest that the MiL spec is not a fair comparison.
These are Mil spec and to meet that spec they are rated as 1/8th W when Ta = 70°C
But go to the Thermal resistance graphs.
1/8W into RN55 gives a temp rise (deltaT) of <20C degrees
1/2W into RN55 gives a deltaT of ~62C degrees.
Add that to Ta=25°C and you get a temperature of ~87°C
This will be well below the temperature of other 500mW and 600mW resistors.
I would suggest that the MiL spec is not a fair comparison.
I'm fairly sure I ordered the 1/4 watt Dale/Vishay and they fit fine. I always order way more than called for so I have extras stuck away. also, I understand these resistors are conservatively rated as well.
Russellc
The RN55 is a Mil-spec resistor, and has a 100% thermal de-rate. It's a 1/4W resistor, but the specs say it's to be used for 1/8W.
The CMF55 (same resistor, different spec sheet) differs only in the "max" watt rating and that the CMF can be built with steel or copper leads, where the RN must be copper.
SO... Use the RN55 if you have them. I do.
The CMF55 (same resistor, different spec sheet) differs only in the "max" watt rating and that the CMF can be built with steel or copper leads, where the RN must be copper.
SO... Use the RN55 if you have them. I do.
I have 1/2w PRP in mine. I am pretty sure 1/4 RN60's would fit.
RN60's are good. Really, brand or series is not going to make that much difference as long as the temp co is low and the tolerance is low as well. I prefer to use PRPs (fancy red colored) or Dales but sometimes I can't get the values I need to I use ego or whatever.
RN60's are good. Really, brand or series is not going to make that much difference as long as the temp co is low and the tolerance is low as well. I prefer to use PRPs (fancy red colored) or Dales but sometimes I can't get the values I need to I use ego or whatever.
Jpaul, the Vishay/Dale wattage ratings have been discussed before and if I remember correctly it has to do with temperature.
NONE of the RN55's I've used for the BA-3 preamp have gone up in smoke or even got remotely warm. R13 is the only resistor that should have a higher wattage rating.
If you're afraid the RN55's won't work, by all means go with the RN60's.