I am revisiting this amplifier of which was my second FW diy project. I say revisiting because I removed the boards years ago to install other boards. I have since found that the j-fets I purchased before the LSK ones became available were fake and I have not heard this amplifier as it should. Another reason is I recently built the F4 and am amazed with the sound it produces which is almost if not the BA-2 amplifier with less output devices. Now I want to rebuild the SE version of the Burning Amp series. I decided to remove the IRFP 240 mosfets I originally installed and buy a tube of 25 and match them better since I like to think I have more experience now building FW amplifiers. I managed to get 15 to .1V tolerance out of the 25. I am using just one set of boards from our store to make a stereo amplifier using 6 output devices instead of 12 but now both boards will have output mosfets that match each other so that if I desire at a later date to build another complete SE BA-1 and have mono's. It would require a massive case to build the BA-1 as described in the article so to me if is more practical to build this project in mono configuration. Right now I am going to build a stereo version using 6 output mosfets per channel.
My personal opinion is that the BA-1 and BA-2 designs are diy projects that may be compared to some of the Passlab designs especially if one builds either with 12 mosfets per channel. At least some of the older Passlab amplifiers.
My personal opinion is that the BA-1 and BA-2 designs are diy projects that may be compared to some of the Passlab designs especially if one builds either with 12 mosfets per channel. At least some of the older Passlab amplifiers.
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I fired up this amplifier yesterday and as Nelson said "it sounds swell." Right now I am using it much like the F4 amplifier in that it only has the output stage, I have not included the front end yet. I have many different tube preamplifiers and horn speakers so the front end is not actually needed but I do have plans to install the BA-3 front end. I did notice that using it as a stand alone output stage I have close to 5V DC on the input. I decided to install couple of 10uh caps on the input to stop the voltages from affecting the preamplifier circuits. Some of my pres have output caps and some do not.
I thought I had all the resistors I needed in stock to build the BA-3 front end without actually checking so I did not order any when I made a purchase of the other components at Mouser but now I find that I do not have any 330 ohm 3 watt resistors. This is the reason I have not installed the BA-3 board yet.
I thought I had all the resistors I needed in stock to build the BA-3 front end without actually checking so I did not order any when I made a purchase of the other components at Mouser but now I find that I do not have any 330 ohm 3 watt resistors. This is the reason I have not installed the BA-3 board yet.
I stuffed these boards years ago when I was less experienced building but I bought the boards from our store and yes I do have those 10uh caps on the board. I was concerned about having DC voltage and wondered if I have a mistake on the board myself. It could possible be that I do not have the input wired correctly. I will double check that separate board and see where I may have gone wrong. From the schematic I should not have any voltage on the input. Thanks Zen.
Zen, looking at the article on page 2 below,
http://www.firstwatt.com/pdf/art_ba_3.pdf
the boards I purchased could be designed around this circuit instead and a cap may be necessary for standalone use. My input wiring seems correct. Opinion appreciated.
http://www.firstwatt.com/pdf/art_ba_3.pdf
the boards I purchased could be designed around this circuit instead and a cap may be necessary for standalone use. My input wiring seems correct. Opinion appreciated.
do not forget to post these pics hereWill do the Monday. I do believe the board is designed around the newer schematic published 2011 vs the original 2009 schematic but then I will need to remove the bias board and look at the traces. Information and comments from you are much appreciated. It does sound swell with the caps I installed but then it played well even before I installed the caps. I was brave and tried it anyways. If anything smoked it would have given me something to do next week.
I have not removed the bias boards yet, it is early central time USA, but I have done some research and I have my doubts on which schematic I used to stuff the bias boards with years ago. For anyone that does not know there are 3 boards to stuff to make the complete B1 SE amplifier.The store schematic uses the BA-1 stuffing for the bias board yet Nelson in 2011 provided a new bias stuffing with the BA-3 article. I am going to remove one of the bias boards this morning and do some checking and provide pictures if I cannot figure it out Zen. I played the amplifier last night with a couple of different pres and the sound is outstanding with the 10uh caps I installed on the input but I want to get to the bottom of which schematic was used on the bias boards provided by our store. With my horns being very efficient any preamplifier will provide more than enough power without having the BA-3 pre board installed inside. I have a BA-3 preamplifier to use when I want to as well. I really like the option of using this amplifier as is being just the output stage like the F4. The designer of the bias boards would know but who and where he is at now is anyone's guess.
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View attachment P-BASB-1V20-schematic.pdf
It appears that the schematic listed on the store is the one used. The R 219 resistor does not have a value listed but an asterik with it so I assumed it is optional. There is no place on the board for C203 that appears on the schematic you showed Zen. I am left to assume that the configuration of the bias is such that it assumes one is going to use the BA-3 front end in conjunction with the BA-1 boards with it's capacitor stopping the DC. From what I see one needs a 10uh cap on the input when the output stage is used as a stand alone amplifier. Your opinion Zen and anyone's else's is appreciated.
It appears that the schematic listed on the store is the one used. The R 219 resistor does not have a value listed but an asterik with it so I assumed it is optional. There is no place on the board for C203 that appears on the schematic you showed Zen. I am left to assume that the configuration of the bias is such that it assumes one is going to use the BA-3 front end in conjunction with the BA-1 boards with it's capacitor stopping the DC. From what I see one needs a 10uh cap on the input when the output stage is used as a stand alone amplifier. Your opinion Zen and anyone's else's is appreciated.
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well , I already gave you my opinion , and that schematic I posted was made many moons ago , for someone having same needs as you have now
fact is that you already have OS biased , so everything is there,except input resistor and 10uF cap
add that , and you're good
post picture of OS pcbs , and we can take a look together for input point , most probably marked as "D" (Papa's for Drive)
fact is that you already have OS biased , so everything is there,except input resistor and 10uF cap
add that , and you're good
post picture of OS pcbs , and we can take a look together for input point , most probably marked as "D" (Papa's for Drive)
Thanks Zen, it would be a PIA to get that board out and take a good picture and since it is working so well and I already have the input cap installed I am just going to install the 220K resistor and smile for right now. I really like this amplifier and the F4 for their big wide soundstage and the fact you can change the sound with different preamplifiers. At least now I know how the board is stuffed correctly. You are correct in that the input is labeled D with (GS) in parentheses to difference it from D+.
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that's (now) only thing important , and I finally got clear confirmation
easiest way for installing input shunt resistor - just solder it on RCA input jack , between hot and gnd
I am going to install a couple of 30uf poly caps I have in the power supply and I have on order 2 Jantzen 10uh polys to replace the silmic 11 input caps. At least maybe replace the silmic's. I have found the silmic 11 to be excellent sounding. This amplifier is living up to it's name as a Burning Amplifier. The temperature without the lid after a couple of hours is approaching 60 C and slightly over 60 C with the lid. I do have it biased somewhat higher because Antek was out of the 18V transformer and I bought a 20V one instead. I measured .61 V and .63V bias on a couple of resistors which not too far from .58V called for by NP. This amp is pushing the limits of the 4U case in my deep south USA home. I may consider a fan but for now I am going to be brave and let it run as long as the temp does not exceed 65C.
Just a follow up. I played this amp for 4 hours straight last night with the temp hovering between 55C and 60C. One heat sink is slightly higher than the other because it is close (10") from the wall. After reading the article again I found that if I want to I can lower the bias installing a 47K resistor for R219. I have scored some extra output boards so that if I choose I can change this amp to mono and build another. I have an F4 and from my understanding the BA-2 is a bigger F4 with more mosfets. I own a number of different pres both SS and tube and what I like about these amplifiers is the ability to change the tone of both by changing preamplifiers. With a tube pre the sound is very much as a SET amplifier and with say my LSK pre more dynamic and quicker. The store is out of both of these boards and I do not know if there is enough interest in them to restock them being they are older offerings but being older does not mean that newer designs sound better.
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I changed out the Silmic's for some $10 Jantzens with a marked improvement. The sound is intoxicating where you do not want to turn it off now and I believe is improving with some hours on it. The heat has settled down some as well. Might be some grease squeezing out with better contact. I am careful to use the grease sparingly but this is just me guessing.