Mattyo5
In my opinion use the MJE340/350 pair rather than MJE15030/15031.At higher voltage like for example 70 volts DC the MJE 340 can supply a higher current than the MJE15030.Look at the SOA curves for both transistors and you will see what I mean.
MGR
In my opinion use the MJE340/350 pair rather than MJE15030/15031.At higher voltage like for example 70 volts DC the MJE 340 can supply a higher current than the MJE15030.Look at the SOA curves for both transistors and you will see what I mean.
MGR
ok...that makes sense. Should I just sink Q9 and Q8 then? or should I sink others as well? Looks like at least Q9 and 8 should have a heatsink.
www.aussieamplifiers.com/sym-sch.htm
how about Q7 and 6? and the BD139 chip... I have plenty of sinks...just don't want to sink em for nothin! I'll stick w/ the 340s and 350's for now
-Matthew K. Olson
www.aussieamplifiers.com/sym-sch.htm
how about Q7 and 6? and the BD139 chip... I have plenty of sinks...just don't want to sink em for nothin! I'll stick w/ the 340s and 350's for now
-Matthew K. Olson
MGR said:
You're right for DC, but I can't agree with you since I think we shouldn't look only at the DC SOA: the load of the driver transistors is mainly capacitive, so current is not constantly delivered.
The worst case is at higher frequencies, where the gate charge has to be quickly delivered, demanding a high current capability request.
We can note that for 100 uS pulses (corresponding to 10 kHz) MJE15032 ( the substitute I suggested in second instance) can deliver its peak current (20A!), the MJE15030 will be somewhere near 5A and the MJE340 will happily deliver 1A.
IMHO all three BJTs will work fine, but if Mattew needs more outputs the MJE15032 is the best available choice.
Cheers
Andrea
Ok, now we're on to MJE15032 again. Which should I swap...all MJE340's and 50s for the 32's and 33's??? Or just Q6789? And sink all ? or Just Q6789?
-Matthew K. Olson
-Matthew K. Olson
Replacing Q1 also isn't necessary (but it doesn't hurt if you replace it).
I built mine with MJE340s e 350s and feel no need to switch to MJE15032/33 even if I have some... but I use "only" 4 pairs😉 and lower rails.
About drivers heatsinking you'd need to calculate the working point of the MJEs with your power supply and then decide... or just build it and then put your finger on them and let it decide for you.
Cheers
Andrea
I built mine with MJE340s e 350s and feel no need to switch to MJE15032/33 even if I have some... but I use "only" 4 pairs😉 and lower rails.
About drivers heatsinking you'd need to calculate the working point of the MJEs with your power supply and then decide... or just build it and then put your finger on them and let it decide for you.
Cheers
Andrea
I think I'll order those mje15032/3's and use em for Q6789 then...and keep Q1 as is. Won't be too expensive to order all that I hope. 1.22 each at newark. Doesn't matter to me whether its a 50 cent part of 1.22 each. Just want it to work well. I'll sink em too...that'll make things easy. thanks for the help guys
-Matthew K. Olson
-Matthew K. Olson
Hi Mattyo5,
I've built two of those amp's. One with no heatsink on the MJE340/350 and one with heatsinks, both with 4 IRFP's per rail. They do get hot, like 45-50C without heatsink, but with a small heatsink they are just above roomtemp.
I've made room for 5 IRFP's per rail, but I've only populated 4 of them and I'm driving two Peerless XLS 12" that are paralleled without any problem. So I think you should do as said before in this thread, go for a pcb with room for as many IRFP's as you would like, but do only populate 4 per rail as to begin with.
I'll post a picture of my amp's pcb later.
-Pelle
I've built two of those amp's. One with no heatsink on the MJE340/350 and one with heatsinks, both with 4 IRFP's per rail. They do get hot, like 45-50C without heatsink, but with a small heatsink they are just above roomtemp.
I've made room for 5 IRFP's per rail, but I've only populated 4 of them and I'm driving two Peerless XLS 12" that are paralleled without any problem. So I think you should do as said before in this thread, go for a pcb with room for as many IRFP's as you would like, but do only populate 4 per rail as to begin with.
I'll post a picture of my amp's pcb later.
-Pelle
Here comes two picture of the not completed amp. It is now painted and with some real connections for the speaker cable.
-Pelle
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
-Pelle
I have seen that amp before...just beautiful. 🙂 I don't think mine'll look that good. I think I'm going to order the mje15032/3's and use 6 pairs of outputs...slap it together and see what happens! 🙂 🙂 🙂 I'll get pics if I blow stuff up don't worry. 🙂 Thanks for the help guys...and Pelle...again, beautiful amp (any comparison soundwise w/ anything else? p3a? gainclone? etc? Zen's?)
-Matthew K. Olson
-Matthew K. Olson
After my last examinations (next week) I am planning to compare Holton's amp with a P3A and my beloved Aleph30.
One of these will leave me
to become part of a friend's system, probably one of the higher-powered class AB, the others will be used for my next system... waiting for Nelson's electronic x-over 
Cheers
Andrea
One of these will leave me
to become part of a friend's system, probably one of the higher-powered class AB, the others will be used for my next system... waiting for Nelson's electronic x-over Cheers
Andrea
Mattyo5,
I've compared it to a NAD216 THX that I had before to drive my two Peerless XLS, and it outperforms the NAD. Much better control over the elements and the bass is much more 'at the right time' than before. With the NAD it sounded like the bass were delayed by some (read many) miliseconds. 🙂
Highly recommended if you have some experience building amp's.
I'm hoping that Anthony soon will be back answering questions about his amp's.
-Pelle
I've compared it to a NAD216 THX that I had before to drive my two Peerless XLS, and it outperforms the NAD. Much better control over the elements and the bass is much more 'at the right time' than before. With the NAD it sounded like the bass were delayed by some (read many) miliseconds. 🙂
Highly recommended if you have some experience building amp's.
I'm hoping that Anthony soon will be back answering questions about his amp's.
-Pelle
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