Thanks @jjs once again @AudioSan has assumed that we haven't done any research or calculations on this.
@AudioSan please know we have looked at the this from dare I say it, every possible angle. Once again I ask you to ask us a question before trying to find a issues with the work the team has done. Through asking questions people are more inclined to work with you and not become defensive. Unless of course you don't need to ask questions because you know everything. If that's the case why are you subscribed to this thread? What are you contributing?
I thought your last post was a few days ago?
Mine is air cooled, uses 70V rails, drives 4ohm loads and has run for well over 8 hours continuously. It gets hot, but that's expected at 150Wrms... Hasn't stopped working yet
Brettn56. You drive it at the edge of clipping for 8 hours straight using 3 pair of 150W output BJT's? if not, your post is useless. As this is the senerio discussed.
Of cource any amp at any voltage (within the parts limit) will survive having a 4ohm load connected. As long as the volume level is within reason.
Of cource any amp at any voltage (within the parts limit) will survive having a 4ohm load connected. As long as the volume level is within reason.
Stuartmp. my last post few days ago? please find that post for me. Maybe you learn that it's either the wrong tread and week/month. Or the wrong person.
On a side note. This is about general rule of tumbs and senerios to take into account. So i ask you. read once more.
But hey, since you don't want anyone that is not on the groupbuy to post anything. After all, no one else can contribute to any spesific here
On a side note. This is about general rule of tumbs and senerios to take into account. So i ask you. read once more.
But hey, since you don't want anyone that is not on the groupbuy to post anything. After all, no one else can contribute to any spesific here
I'm not on this forum to argue, taunt, mislead or be a general nuisance. I'm here to offer advice when necessary, and I'm here to learn.
I'm not going to argue with you here as I can already clearly see where this is going.
I work in electronics installation/design, and have an electronic engineering degree, computer systems degree and many others. I've never used or seen liquid nitrogen used for cooling in consumer grade amplifier or linear regulated power supplies.
I think your comment about requiring liquid nitrogen is the true definition of a useless post.
I you don't want to believe that I and others have built and tested the amp in question that's fine.
Please don't go misleading others on the forum. Please share your results from the Amp that you have built, run it at 76V rails, put a 3ohm resistive/inductive load on it and run it for 12hours at 150WRMS. Post your results here and either prove or disprove all parties involved.
If you aren't willing to do that, then go annoy another forum elsewhere.
+/-76Vdc rails loaded at 3 ohm gives you around 650W average and 1300W peak. With 3 pair of 150W BJT's??? And you gonna push those figures for 8hours straight. Right. A good role of thumb is for power output to stay within 1/5 of the total capacity of the outputstage. 150x6=900/5=180W average. But hey. you could try 650W average and see if the 900W outputstage can handle it.
Incase your wondering D and E are different HFE grades with E being higher. Ideally the pnp and npn pairs should have the same hfe grade. Check the datasheet for details. And just so you know these were not sourced from china. The are original toshiba 2SA1381E and 2SC3503E. They came with certification and were purchased from a reputable company in the USA
Attachments
Let me double check and Ill get back to you. I don't have those output transistors loaded in my SOA spreadsheet. This takes a a little bit of time to read the log graphs. How many output pairs?
Jeremy
Sorry Guys I cut a pasted the rail data for the 300mm to the 400mm deep heatsinks. Here are the corrected values.
3U 0.40°C/W, 40×120×300mm ~50V rails
4U 0.31°C/W, 40x165x300mm ~60V rails
5U 0.18°C/W, 40x210x300mm ~70V rails
3U 0.25°C/W, 40x120x400mm ~60V rails
4U 0.19°C/W, 40x165x400mm ~70V rails
5U 0.14°C/W, 40x210x400mm ~80V rails
Jeremy
0.3°C/W might be a little small for 70V rails but falls in around my 4U 400mm deep example (size wise). It will probably be ok if you're not running for long periods. If you do need to run it for long periods at full output a fan on the sinks will be necessary and will be so loud you won't hear the fan. Really this applies to everyone.
The 2SC5359/2SA1987 are basically the best 2SC5200/2SA1943. The SOA lines are almost on top of each other for 4 pair. Theses will run roughly 5°C cooler because of the 180W dissaption limit versus the 150W limit of the 2SC5200/2SA1943. Your drivers are not an issue, but I'd check/screen their hfe though.
Jeremy
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