Hi all.
Just thought I would post this thread, showing a few internal pics of the Gemsound PA-4505 amp (400 watts -8 ohm / channel). - According to their data anyway...!
I haven't had a good chance to put it through its paces yet, but the power supply seems to be a bit better than the old EXA series.. But I do wonder how you can get "400 Watts" at 8 ohms with less than 63v rails (see photos of power supply caps)..
Just thought I would post this thread, showing a few internal pics of the Gemsound PA-4505 amp (400 watts -8 ohm / channel). - According to their data anyway...!
I haven't had a good chance to put it through its paces yet, but the power supply seems to be a bit better than the old EXA series.. But I do wonder how you can get "400 Watts" at 8 ohms with less than 63v rails (see photos of power supply caps)..
Attachments
Hi Eddie,
Its a Class-G amp....2 Transistor pair for upper +-Tier and 3 Transistor for Lower +-Tier..and the Capacitors must be in series Configuration....63+63V assumingly...
regards,
K a n w a r
Its a Class-G amp....2 Transistor pair for upper +-Tier and 3 Transistor for Lower +-Tier..and the Capacitors must be in series Configuration....63+63V assumingly...
regards,
K a n w a r
W is right
Workhose is totaly right.Those 3+3 big tr. is probably BJT, & 2+2 smoller Fet( IRFP 250 ). This is similar construkcion like PHONIC Amps, like PIII 3000/ 2000/1000/600. For example I , have all fabric srvice manual for PHONIC.
Ciao.
Workhose is totaly right.Those 3+3 big tr. is probably BJT, & 2+2 smoller Fet( IRFP 250 ). This is similar construkcion like PHONIC Amps, like PIII 3000/ 2000/1000/600. For example I , have all fabric srvice manual for PHONIC.
Ciao.
I've always thought that series caps in power supplies was a no- no...Maybe a Gemsound innovation (to save money)...
Has any one got any schematic theory links on class 'G' amps.??
Here's a quote on class G from one of my books from G. Randy Slone "Class G is a novel idea.......in light of the requirement to supply quad power supply rails......".
So I think you nailed it Kanwar... The 63v caps would form part of the quad power supply..
Ed.
Has any one got any schematic theory links on class 'G' amps.??
Here's a quote on class G from one of my books from G. Randy Slone "Class G is a novel idea.......in light of the requirement to supply quad power supply rails......".
So I think you nailed it Kanwar... The 63v caps would form part of the quad power supply..
Ed.
Eddie Wolve said:
Hi Eddie,
Here is a link to my Class-H Thread:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=68415
Class-G uses Multiple Supply rails and also uses Series connected Devices to decrease the heat dissipation and boost the efficiency...
regards,
K a n w a r
Well.....here is an update of this amp....To cut a long story short, I bought this amp as a back-up, so I never really used it until recently....The amp is rated in it's specs as bridgable at 4 ohm loads..So I ran 2 Selenium WPU1505's subs and the amp lasted about 20 seconds and the power fuse blew, then kept blowing.. The amp was still under warranty, but would cost me heaps just to get it back for service. Anyway, I pulled it apart and found that 3 of the output transistors had blown. THIS AMP IS NOT A CLASS G. As the photo in my first thread shows, there seams to be upper and lower tier OPT's, but the gaps on the heat sink are just for extra OPT's (probably for the higher spec'd model) The OPT's (which are 5200's and 1943's).
Anyway, I have ordered new 5200's and 1943's (plus extra's for the gaps in the heatsink) to make it more reliable and hopefully handle the lower loads better.
By the way, after pulling the power supply out, the supply caps are infact in SERIES.
There you go..DO NOT OPERATE THIS AMP AT 4 OHM LOADS IN BRIDGE MODE...BETTER STILL DON'T BUY THIS AMP.
Anyway, I have ordered new 5200's and 1943's (plus extra's for the gaps in the heatsink) to make it more reliable and hopefully handle the lower loads better.
By the way, after pulling the power supply out, the supply caps are infact in SERIES.
There you go..DO NOT OPERATE THIS AMP AT 4 OHM LOADS IN BRIDGE MODE...BETTER STILL DON'T BUY THIS AMP.
Yep. Thanks SKYGTR..That looks like the power supply..
You wouldn't have the schematic for the rest of the amp so that I may use it when the amp blows up again....
Cheers.
Ed.
You wouldn't have the schematic for the rest of the amp so that I may use it when the amp blows up again....
Cheers.
Ed.
fakes
watch it my friend i have the exact same amp with simular problems and when i had to repare it i just end up with a full box of fake transistors ......
be very very carefull where you buy them from
sakis
watch it my friend i have the exact same amp with simular problems and when i had to repare it i just end up with a full box of fake transistors ......
be very very carefull where you buy them from
sakis
Thanks Sakis.
I actually wondered if I had genuine transistors in the amp in the first place!!!, which may have been why it blew the first time. I have a reputable supplier in Australia so hopefully I won't get ripped off. I guess I will soon find out. I'll certainly make another post if I have problems..
Cheers.
Ed.
I actually wondered if I had genuine transistors in the amp in the first place!!!, which may have been why it blew the first time. I have a reputable supplier in Australia so hopefully I won't get ripped off. I guess I will soon find out. I'll certainly make another post if I have problems..
Cheers.
Ed.
Hi Eddie
these type of manufactures often lie about they specs .
there is no way this amplifier would handle 2 ohms.
If it wasn't class G or Class H
With +-94 volt rails 3 pairs of output devices would be lucky to
handle 4 Ohms.
I think you are correct in assuming that it is not class G or H.
I have a bunch of 2SC5200 and 2SA1943 Bipolars.
and they are the real deal.
Contact me via my web site if you want a price.
once again you may have damaged drivers as well.
these type of manufactures often lie about they specs .
there is no way this amplifier would handle 2 ohms.
If it wasn't class G or Class H
With +-94 volt rails 3 pairs of output devices would be lucky to
handle 4 Ohms.
I think you are correct in assuming that it is not class G or H.
I have a bunch of 2SC5200 and 2SA1943 Bipolars.
and they are the real deal.
Contact me via my web site if you want a price.
once again you may have damaged drivers as well.
Thanks Anthony.
I have already ordered the opt's through Wes Components ( I have a trade account there..) But you can probably read between the lines...that is, My Amcron finally gave up the ghost and when I went to use my brand new spare Which I have carried arround for the last 7 months (ie the GemSound 4505), that died as well....! Oh well that will learn me.
As it turns out the NoSound err sorry GemSound 4505 has quite beefy driver transisters, they are Toshiba 2SC5198 and 2SA1941, (with a 140v and 10amp rating) and seem to have tested OK in circuit. See how we go.
Ed.
I have already ordered the opt's through Wes Components ( I have a trade account there..) But you can probably read between the lines...that is, My Amcron finally gave up the ghost and when I went to use my brand new spare Which I have carried arround for the last 7 months (ie the GemSound 4505), that died as well....! Oh well that will learn me.
As it turns out the NoSound err sorry GemSound 4505 has quite beefy driver transisters, they are Toshiba 2SC5198 and 2SA1941, (with a 140v and 10amp rating) and seem to have tested OK in circuit. See how we go.
Ed.
more fakes
my amp i thing was also constructed with fakes so thats way they met the creator so fast .....from looks and only the looked cheapy made to me also ......
also in my lab exist a chinese made amp called limit full of these kind of transistors also gone with the wind ...
onother called agusta chinese italian factory with exact same problems
i have been unable to get A1943 and C 5200 that are guarrantied in a resonable prise so i am really tempted to put inside legend 8 boards from bora
will see about that at this point seems that i have made somethings wrong while constructing them so i ma still looking at it
my amp i thing was also constructed with fakes so thats way they met the creator so fast .....from looks and only the looked cheapy made to me also ......
also in my lab exist a chinese made amp called limit full of these kind of transistors also gone with the wind ...
onother called agusta chinese italian factory with exact same problems
i have been unable to get A1943 and C 5200 that are guarrantied in a resonable prise so i am really tempted to put inside legend 8 boards from bora
will see about that at this point seems that i have made somethings wrong while constructing them so i ma still looking at it
Good luck with your search...Sakis. Maybe you could try Anthony, (previous post on this thread) for your 5200's and 1943's....By the way, what price are you paying for these over in Greece...?
a5200 c1943 prize
well a was asked to pay 4.10 euros each and these people claimed that semiconductor was made by HARRIS meaning that its supposed to be a fairly relable and good semiconductor.....and also minimum order 200pcs and delivery after 2 months !!!!!! expensive i think !!!
other provider asked about 3.90 for toshiba but there was a hell of a lot of fake noise arround them .....
funny also story somebody gave me 3.50 euros for the one trs and 5.10 for the other of same brand ...fairchild i think ....and thought how the fu** this can be possible for complementary trs ????
any way greek market can often be strange about things like that ....
still working on boras legend 4 and legend 8 that looks so nice and simple BUT NOT MANAGED TO GET IT RIGHT YET ,......LOL !!!!!
but i am working on it ..... with passion !!!!!
given the opertunity i dlike one more time to thank bora for his very much help so far and this wonderfull community and all this nice people existing here THANKS PEOPLE !!!!!!
well a was asked to pay 4.10 euros each and these people claimed that semiconductor was made by HARRIS meaning that its supposed to be a fairly relable and good semiconductor.....and also minimum order 200pcs and delivery after 2 months !!!!!! expensive i think !!!
other provider asked about 3.90 for toshiba but there was a hell of a lot of fake noise arround them .....
funny also story somebody gave me 3.50 euros for the one trs and 5.10 for the other of same brand ...fairchild i think ....and thought how the fu** this can be possible for complementary trs ????
any way greek market can often be strange about things like that ....
still working on boras legend 4 and legend 8 that looks so nice and simple BUT NOT MANAGED TO GET IT RIGHT YET ,......LOL !!!!!
but i am working on it ..... with passion !!!!!
given the opertunity i dlike one more time to thank bora for his very much help so far and this wonderfull community and all this nice people existing here THANKS PEOPLE !!!!!!
OK....Just an update..
Put in new (and additional) output transistors as the photo shows. And replaced all the mica washers for silicon rubber ones.
As it turned out apart from a diode which also blew that's all that went pop..
Put it on a load test and she seems to be working OK...But haven't (and wont) put her on 2 ohm loads....
It does run very warm however...
Anyway see what happens.
Ed
Put in new (and additional) output transistors as the photo shows. And replaced all the mica washers for silicon rubber ones.
As it turned out apart from a diode which also blew that's all that went pop..
Put it on a load test and she seems to be working OK...But haven't (and wont) put her on 2 ohm loads....
It does run very warm however...
Anyway see what happens.
Ed
