BPA-200 w/ six chips working w/ pics! - Page 3

Mattyo5 · 22nd August 2004, 02:46 PM

Ok, now i've got some idea of whats up

Kinda dissappointing actually. Basically I need a bigger PS. But first the real story. Ok, so we hooked it up, the only clip leads still attached were input gnd and from the output of the input buffer to the chip inputs. We hooked the whole thing up to the scope, and noise/occillations like crazy. Yikes. So we tested the output of the input buffer, and that looked pretty. Then we tested each parallel side of the amp individually. The - side, then the + side. Both of those looked good. When we hooked them together (bridged), oscillations like crazy. So, what I need to do now, is rip out the clip leads, and solder in real wires, and see if that helps. Ok, now as for the power. Looks like i'm getting (before bridging) about 30 watts out of each parallel side RMS into 8 ohms and close to 50 watts into 4ohms (dang it...could have done this w/ one chip!). Maybe a touch less. The ps voltage just isn't high enough, and it sags 3-4v per rail when the amp is just beginning to clip. So, first I'll solder the input wires, if the oscillations are really robbing of lots of power, then maybe i'll keep the current PS and use it and deal w/it. If I can get rid of the oscillations and the power output is still not adequate, time to get a big toroidal and slap it into my tiny chassis and see what happens

more updates to come. later!

-Matthew K. Olson

Mattyo5 · 22nd August 2004, 07:35 PM

Ok, soldering in real wires instead of clip leads. There used to be a buzz coming from the tweeters, no more buzz. There is still a hum, but it is minimal

I may just build up the other monoblock amp as is, because i really don't want to throw any more money at this project...and because there is no room for a nice toroidal in this chassis. Oh well. I already have the other monoblock chassis drilled, so I guess I might as well just use it. Now I know the design works, and if I want to do it right, i'll get pcb's made and make things eaiser on myself. ptp for a gainclone is easy, for 3 parallel chips...what a pain. Its sure is cool looking though ...i'll post listening impressions when i get the 2nd amp done. Later

-Mathtew K. Olson

carlosfm · 25th August 2004, 10:52 PM

You need one trafo per channel at around 400VA (National says 380VA), or, better, 500VA.
I would use 2x22 or 2x24V trafos.

And...

those MUR860 diodes are good for two chips, you have 8.

Please, use those 35A metal-case bridges there.

If you want to fiddle with serious power, don't think it's cheap.
You need a decent PSU, heatsinks, etc.
The amp will not be small.
Otherwise, use just one chip per channel.
Your trafos and rectification are just perfect for that.

Mattyo5 · 25th August 2004, 11:01 PM

Oh yeah, i know

Next amps will be more powerful. This PS just happened to fit in this case, and so did 6 chips. Way more complicated than it had to be. Oh well. Btw, those diodes don't get as hot as you might think. They were tested. Anyway, thanks for the advice though, although i'm well aware of the need for almost obscene ps's

i'm usually a fan of excess

-Matthew K. Olson

li_gangyi · 25th August 2004, 11:38 PM

it didn't get hot because the trafo couldn't put out the required current I guess...

Mattyo5 · 26th August 2004, 12:21 AM

That sounds valid. Trafo's are probably not uh, sufficient. Oh well. I'll get em next time

-Matthew K. Olson

Menno Keizer · 29th August 2004, 10:58 PM

why not just put 3 lm3886 in paralel insted of 2x3bridge/paralel
I personaly tested both and canot say that I prefer one of them.

My experiece with the mur860`s are not that good(one 3875 pc)
they sounded a little harch and not as open as two MB252 bridges.

Does anyone have simular experience on that?

This is the way the bridges are connected......
http://www.geocities.com/rjm003.geo/...s/diy_gc2a.gif

Mattyo5 · 30th August 2004, 12:49 AM

Well, the 3 in parallel work just fine, you are right about that. The only thing is, the configuration i have my chassis in, it wouldn't be ... convenient. So, i'm finishing the 2nd chassis bpa-200 as we speak.

-Matthew K. Olson

Mattyo5 · 30th August 2004, 02:17 AM

Ok, both bpa-200's w/ 6 chips are working... monoblock style

I know that the ps's are a little small, but the amps are dang small as well. 2 rack spaces each

They sound quite nice. Pics to come soon.

-Matthew K. Olson

cdoggy81 · 31st August 2004, 11:55 PM

Hey Matt, lets see those pics

25th August 2004, 11:38 PM	#25
li_gangyi diyAudio Member Join Date: Jun 2003 Location: Woodlands Circle	it didn't get hot because the trafo couldn't put out the required current I guess... __________________ Kids in the back seat cause accidents...Accidents in the back seat cause kids...

31st August 2004, 11:55 PM	#30
cdoggy81 diyAudio Member Join Date: Feb 2004 Location: Gainesville, FL	Hey Matt, lets see those pics __________________ It's better to have loved & lost than to never have had a good pair of speakers at all.......

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22nd August 2004, 02:46 PM	#21
Mattyo5 diyAudio Member Join Date: Aug 2002 Location: Farmington, CT	Ok, now i've got some idea of whats up Kinda dissappointing actually. Basically I need a bigger PS. But first the real story. Ok, so we hooked it up, the only clip leads still attached were input gnd and from the output of the input buffer to the chip inputs. We hooked the whole thing up to the scope, and noise/occillations like crazy. Yikes. So we tested the output of the input buffer, and that looked pretty. Then we tested each parallel side of the amp individually. The - side, then the + side. Both of those looked good. When we hooked them together (bridged), oscillations like crazy. So, what I need to do now, is rip out the clip leads, and solder in real wires, and see if that helps. Ok, now as for the power. Looks like i'm getting (before bridging) about 30 watts out of each parallel side RMS into 8 ohms and close to 50 watts into 4ohms (dang it...could have done this w/ one chip!). Maybe a touch less. The ps voltage just isn't high enough, and it sags 3-4v per rail when the amp is just beginning to clip. So, first I'll solder the input wires, if the oscillations are really robbing of lots of power, then maybe i'll keep the current PS and use it and deal w/it. If I can get rid of the oscillations and the power output is still not adequate, time to get a big toroidal and slap it into my tiny chassis and see what happens more updates to come. later! -Matthew K. Olson

22nd August 2004, 07:35 PM	#22
Mattyo5 diyAudio Member Join Date: Aug 2002 Location: Farmington, CT	Ok, soldering in real wires instead of clip leads. There used to be a buzz coming from the tweeters, no more buzz. There is still a hum, but it is minimal I may just build up the other monoblock amp as is, because i really don't want to throw any more money at this project...and because there is no room for a nice toroidal in this chassis. Oh well. I already have the other monoblock chassis drilled, so I guess I might as well just use it. Now I know the design works, and if I want to do it right, i'll get pcb's made and make things eaiser on myself. ptp for a gainclone is easy, for 3 parallel chips...what a pain. Its sure is cool looking though ...i'll post listening impressions when i get the 2nd amp done. Later -Mathtew K. Olson

25th August 2004, 10:52 PM	#23
carlosfm Banned Join Date: Mar 2003 Location: Lisbon, Portugal	You need one trafo per channel at around 400VA (National says 380VA), or, better, 500VA. I would use 2x22 or 2x24V trafos. And... those MUR860 diodes are good for two chips, you have 8. Please, use those 35A metal-case bridges there. If you want to fiddle with serious power, don't think it's cheap. You need a decent PSU, heatsinks, etc. The amp will not be small. Otherwise, use just one chip per channel. Your trafos and rectification are just perfect for that.

25th August 2004, 11:01 PM	#24
Mattyo5 diyAudio Member Join Date: Aug 2002 Location: Farmington, CT	Oh yeah, i know Next amps will be more powerful. This PS just happened to fit in this case, and so did 6 chips. Way more complicated than it had to be. Oh well. Btw, those diodes don't get as hot as you might think. They were tested. Anyway, thanks for the advice though, although i'm well aware of the need for almost obscene ps's i'm usually a fan of excess -Matthew K. Olson

26th August 2004, 12:21 AM	#26
Mattyo5 diyAudio Member Join Date: Aug 2002 Location: Farmington, CT	That sounds valid. Trafo's are probably not uh, sufficient. Oh well. I'll get em next time -Matthew K. Olson

29th August 2004, 10:58 PM	#27
Menno Keizer diyAudio Member Join Date: Dec 2003 Location: The Netherlands	why not just put 3 lm3886 in paralel insted of 2x3bridge/paralel I personaly tested both and canot say that I prefer one of them. My experiece with the mur860`s are not that good(one 3875 pc) they sounded a little harch and not as open as two MB252 bridges. Does anyone have simular experience on that? This is the way the bridges are connected...... http://www.geocities.com/rjm003.geo/...s/diy_gc2a.gif

30th August 2004, 12:49 AM	#28
Mattyo5 diyAudio Member Join Date: Aug 2002 Location: Farmington, CT	Well, the 3 in parallel work just fine, you are right about that. The only thing is, the configuration i have my chassis in, it wouldn't be ... convenient. So, i'm finishing the 2nd chassis bpa-200 as we speak. -Matthew K. Olson

30th August 2004, 02:17 AM	#29
Mattyo5 diyAudio Member Join Date: Aug 2002 Location: Farmington, CT	Ok, both bpa-200's w/ 6 chips are working... monoblock style I know that the ps's are a little small, but the amps are dang small as well. 2 rack spaces each They sound quite nice. Pics to come soon. -Matthew K. Olson

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