I've put a B.O.M together for a stereo version of the BA-2. I've attached the file. If anyone sees an error please let me know so I can fix it. I've got finish filling it in with prices, who get my parts from etc. I.E. Blues for 2SJ74's.
This is my first build in several years, so I'm little rusty. I'm not sure if the resistors that don't have the wattage next to them on the schematic should be 1/4 or 1/2 watt.
All the caps on boards and post transformer should probably be 40vdc or better.
Chad
P.S. Nelson thank you for donating your time and designs to help us DIYers. Now I'm gonna have build a converter after I finish this amp.
This is my first build in several years, so I'm little rusty. I'm not sure if the resistors that don't have the wattage next to them on the schematic should be 1/4 or 1/2 watt.
All the caps on boards and post transformer should probably be 40vdc or better.
Chad
P.S. Nelson thank you for donating your time and designs to help us DIYers. Now I'm gonna have build a converter after I finish this amp.
Serbian Nickel Alloy Heatsinks.
you can always use Serbian nickel perfect alloy
Great move Zen Mod. I never thought about making my own washers out of spare change before. Any idea of the c/w of those chunky Serb numbers?
English 2p's could be good, although I was told once that destroying currency could land you a stint in the Tower of London from the Queen. Never mind I won't tell her if you don,t. I am definitely going to use 2p's on the trannys in my new amp build. Cool tip Zen Mod.
Cheers Holmes
How you doing audiok?
The simple and reliable way to get DC volts from AC for this type of PSU is:
ACvolts X 1.41 = DCvolts
18volts X 1.41 = 25.38volts
20volts X 1.41 = 28.20volts
25volts X 1.41 = 35.25volts
I shall be using transformers with 18volt secondarys giving 25.38volts.
Nelson reckons 7watts of heat/PSUvolt.
So the amp output stage will dissipate 177.66watts of heat/channel.
The amp will have 12 MOSFET's/channel.
The transformer will also produce significant heat, some thing often overlooked. Check my post on transformer cooling in BA-1 forum.
All the best to you Simon
How you doing audiok? I like your avatar. This is how I always do my PSU's
The simple and reliable way to get DC volts from AC for this type of PSU is:
ACvolts X 1.41 = DCvolts
18volts X 1.41 = 25.38volts
20volts X 1.41 = 28.20volts
25volts X 1.41 = 35.25volts
I shall be using transformers with 18volt secondarys giving 25.38volts.
Nelson reckons 7watts of heat/PSUvolt.
So the amp output stage will dissipate 177.66watts of heat/channel.
The amp will have 12 MOSFET's/channel.
The transformer will also produce significant heat, some thing often overlooked. Check my post on transformer cooling in BA-1 forum.
All the best to you Simon
How you doing audiok? I like your avatar. This is how I always do my PSU's
The simple and reliable way to get DC volts from AC for this type of PSU is:
ACvolts X 1.41 = DCvolts
18volts X 1.41 = 25.38volts
20volts X 1.41 = 28.20volts
25volts X 1.41 = 35.25volts
I shall be using transformers with 18volt secondarys giving 25.38volts.
Nelson reckons 7watts of heat/PSUvolt.
So the amp output stage will dissipate 177.66watts of heat/channel.
The amp will have 12 MOSFET's/channel.
The transformer will also produce significant heat, some thing often overlooked. Check my post on transformer cooling in BA-1 forum.
All the best to you Simon
Dear Simon,
Thanks your advise.
Now I using transformer 600VA with 20VAC secondary. It produces around 23.6VDC. Bias current at 3A per channel.
I am a little bit in trouble....
in BA-1 we have only one cap that influences the sound between front end and output stage C203 10uF going to the upper IRF240 bank. (lower bank only CCS)
But in BA-2 we have two caps that influence the sound C203 and C101, like in F4!?
So it is useless to invest in C203 much money when C1o1 is of low quality? Should both be of the same quality? Could I also take 2 x 220uF like in F4?
Any answer before I invest to much money in C203 welcome!!
THX
in BA-1 we have only one cap that influences the sound between front end and output stage C203 10uF going to the upper IRF240 bank. (lower bank only CCS)
But in BA-2 we have two caps that influence the sound C203 and C101, like in F4!?
So it is useless to invest in C203 much money when C1o1 is of low quality?
Should both be of the same quality? Could I also take 2 x 220uF like in F4?Any answer before I invest to much money in C203 welcome!!
THX
Sorry, but it doesn't work that simple in real life - there are loses: voltage drop on diodes in rectifier, ESR of the filter capacitor, transformer's voltage sag under heavier load - not to mention electrical network instabilities...
That's why you'll never see 25.38 V DC coming from 18V AC - as soon as you load it it will be about 23V DC at most.
Audiok, you filter caps might have a bit higher ESR or your transformer sags a bit more, but generally, the values you mention are acceptable with 3A load.
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I heard BA-2 in comparison to BA-1. It sounds very similar to F4 when driven without frontstage directly by pumpkin, very dynamic, but not so fine colors like BA-1.
With pumpkin and the frontstage the sound of BA-2 was a little worse in my ears.
With my 4 Ohm speakers and only 87 db I prefer mostly F4 and BA-2!
Only BA-1 tuned with Semisouth and a very high current had so good colors that I can nearly forgot some time the lack of dynamics.
To tell the truth I am switching from one to the other solution not yet decided..... I have time!
With pumpkin and the frontstage the sound of BA-2 was a little worse in my ears.
With my 4 Ohm speakers and only 87 db I prefer mostly F4 and BA-2!
Only BA-1 tuned with Semisouth and a very high current had so good colors that I can nearly forgot some time the lack of dynamics.
To tell the truth I am switching from one to the other solution not yet decided..... I have time!
I heard BA-2 in comparison to BA-1. It sounds very similar to F4 when driven without frontstage directly by pumpkin, very dynamic, but not so fine colors like BA-1.
With pumpkin and the frontstage the sound of BA-2 was a little worse in my ears.
With my 4 Ohm speakers and only 87 db I prefer mostly F4 and BA-2!
Only BA-1 tuned with Semisouth and a very high current had so good colors that I can nearly forgot some time the lack of dynamics.
I love BA-2 too. It's simple and easy to install, but Hi-Fi.
Now I'm going to build little bit high power (60W) with cascade input.
Hello again audiok
I have been gathering PSU and case parts, but can't decide on BA-1 or BA-2, Have also been looking at Son of Zen-X v6 and also Aleph-X.
What made you decide to make a BA-2, how does it sound in your setup & do you have any advice.
Have you made any other Pass amps ?
Simon
Hi Simon,
I have been built 2 Aleph-X, 1 UGS preamp and 1 BA-1 (Now is BA-2)
I love BA-2. It was because I don’t have big enough heat-sink for BA-1.
BA-1 can reproduce little bit musical sound than BA-2. But you have to bias it into high current.
If you can found enough big heat-sink for your project, please try BA-1.
Thanks for the recommendation audiok, I am pleased you think I should try the BA-1.
You converted your BA-1 to a BA-2 in the same chassis, do you have any photos ?
I am thinking of building the amps without the front-ends, have you listened to the BA's with other front-ends ? Like:-
- CD - Passive Preamp - BA or
- TT - Phono stage - BA
& what are your speakers 2/4/8/16 Ohms ? Mine are 8 Ohms.
I saw in one of your posts an idea for a B1-Transformer attenuator-B1 type front-end, did you make this ? and if you did, have you listened to BA's with it ?
I am interested to make a transformer attenuator and having a B1 before and after it is a great idea. I have been looking at the SOWTER transformers. I have AUDIO SYTHESIS PAS-02 at the moment.
As you say BA's are all about cooling and PSU, I think I will have to use fans as I don't want amps big and heavy.
Cheers Simon
Well I got my 25 IRFP240's and 25 IRFP9240's today from Allied elec. So this weekend will consist of doing some matching. Each set is from the same date code so I'm hoping they are all pretty close. Allied has great pricing on these, they blow Digikey and Mouser out of the water. If enough of the 240's match I might have to build a BA-1 to hear a class A single ended amp, after I finish the BA-2. Unless some can recommend a better Pass design. I'm thinking of building the power supply in it's own enclosure so that I can switch between the amps, plus lots of Nelson's designs use the +&-24 volt rails since the transformer and psu caps are the largest cost I could easily switch between units.
Can anybody recommend a good way to match the 2sj74's?
Also I found 8 240's in my electronics drawer yesterday, these are original International Rectifier pieces. Is ther any difference between these and the newer Visays. Six of these are matched, they must be left over from my last build that was an Aussie amps N-channel back in 2001/2.
Chad
Can anybody recommend a good way to match the 2sj74's?
Also I found 8 240's in my electronics drawer yesterday, these are original International Rectifier pieces. Is ther any difference between these and the newer Visays. Six of these are matched, they must be left over from my last build that was an Aussie amps N-channel back in 2001/2.
Chad
for N channel JFETs Nelson writes in his B1 Buffer pdf .....
" ...The Idss is simply the current that flows through the JFET when the Gate and Source are grounded and +10 volts or so is applied to the Drain. "
You have p-channel types (2sj74), at the moment I cannot say if you have to put the drain to the ground for your parts, like done by Vgs matching.
" ...The Idss is simply the current that flows through the JFET when the Gate and Source are grounded and +10 volts or so is applied to the Drain. "
You have p-channel types (2sj74), at the moment I cannot say if you have to put the drain to the ground for your parts, like done by Vgs matching.