| hienrich |
:rolleyes: CONFUSED
I'M PLANNING TO ASSEMBLE AN AMP WITH 2SC5200/2SC1943
AND A PLUS/MINUS 78VDC AT THE RAILS. IS IT SAFE FOR THESE DEVICES WITH THAT SUPPLY RAILS?:bigeyes:
AM I KILLING THEM? BUT IF POSSIBLE HOW MANY OF THESE DEVICES WILL I USE BETWEEN THE RAILS?
:whazzat:
HIENRICH |
|
|
| Duo |
You'll be absolutely fine with this power supply voltage of +-78VDC. These transistors can handle up to 230V, you're total power supply voltage is only 156 so there's no problem as far as too much voltage being on the transistors.
As far as how many to put in parallel for your speaker, lets see.
If you're doing 8 ohm load, then you'll probably get about 300W at that voltage. This means that at worst, the transistors dissipate about 200W(half swing). They'll have to also deal with 10A if you deliver a square wave at full clip into a resistive load. Turn this load into a speaker and that could become a lot more. Let's say about 18A to be safe. Being that these devices are good for 15A, it is simply a must to at least use two pairs in a channel.
Being that these devices are 150W each and 15A, I would say that four pairs are needed to be relatively safe.
On a 4 ohm load, you'll need a lot more. |
|
|
| hienrich |
:)
CONFUSED?
NOT ANY MORE. THANKS . THIS TIME IM GOING THRUOGH THE PLAN.
HIENRICH;) |
|
|
| Duo |
| Hehe, I'm glad I could help you out. |
|
|
| Workhorse |
| quote: | Originally posted by hienrich
:rolleyes: CONFUSED
I'M PLANNING TO ASSEMBLE AN AMP WITH 2SC5200/2SC1943
AND A PLUS/MINUS 78VDC AT THE RAILS. IS IT SAFE FOR THESE DEVICES WITH THAT SUPPLY RAILS?:bigeyes:
AM I KILLING THEM? BUT IF POSSIBLE HOW MANY OF THESE DEVICES WILL I USE BETWEEN THE RAILS?
:whazzat:
HIENRICH |
Hi Hienrich,
happy new year!
You can use 2SC1943/2SA5200 even at +-140VDC rails without any type of destruction.
QSC exculsively use these trannies at +-150VDC
Regards,
Kanwar |
|
|
| uli |
| quote: | Originally posted by Workhorse
You can use 2SC1943/2SA5200 even at +-140VDC rails without any type of destruction. |
N E V E R ! ! !
They will blow in the first second of driving beyond their voltage capacity!
| quote: | QSC exculsively use these trannies at +-150VDC
|
QSC uses them in class H configuration!
Class H (and Class G) is not comparable to Class B concerning supply rails.
Uli
:nod: :nod: :nod: |
|
|
| Duo |
haha, uli, I think he might mean 140V P-P, thus, +-70V rails.
+-140V would be 280P-P, and yes, that would destroy the transistor instantly as the swing approached 230.
Also, +-140 would yield about 1080Wrms into 8ohms. Might need just a few of these transistors in that situation even if they did that voltage. lol.
I do think, though, that people should be very specific whether they mean +-140 or +-70 being 140V rails.
I hope I clarified helpfully;)
EDIT: And if workhorse did mean actualy +-140V rails. hahaha.... ouch for those transistors. |
|
|
| Eva |
QSC uses these transistors in such an arrangement that they are never exposed to more than 60V Vce when conducting [altough the 230V blocking capability is still required when not conducting]
For standard sagging +-78V rails use two pairs as an absolute minimum for 8 ohms loads and three pairs as an absolute minimum for 4 ohms loads
Feel free to add additional pairs, but be careful since there is a big fake market of 2SC5200/2SA1943 and the fake units have very poor dissipation capabilities [you would probably need 10 or more fake pairs for reliable operation at 4 ohms...] |
|
|
| Duo |
yes eva knows the business.
Those absolute minimums are definitley minimums of course. Wouldn't want to accidentaly put 4ohms on an amp with just two pairs lol. |
|
|
| AndrewT |
Hi,
No one has mentioned SOA curves for these devices YET.
5200/1943 are not particularly good above 60volts.
SOA shows absolute maximum DC current of 650mA @ 80volts.
This will apply to the transistor with the highest current draw in a parallel output. I would suggest that for short circuit condition you allow a maximum current per output transistor of between 50% and 70% of maximum say 400mA. 4 pairs will only carry 1.6amps. Again I suggest this is far too low for a 300w amp.
Next design consideration is maximum power. Current peak (Ipk) is about 78volts divided by 8 ohms giving 9.75 amps.
I recommend you design for Ipk at half supply volts to allow for inductive or capacitive loading into real 8 ohm speakers. This results in your ouput transistors carrying 9.75A @ 39v. 4 pairs give only a 25% margin at this voltage.
But the problem gets worse; you should consider designing the output stage and drivers for about half the intended load impedance which will double all the currents considered so far, and finally would you ever want to drive 4 ohm speakers or 2 *8ohms in parallel? then you have to quadruple all the currents.
We are not finished yet, you will be running quiescent current in the output stage? Then it follows that the transistors are at elevated temperatures. All the SOA data is based on a case temperature (Tc) of 25deg C. you now have to apply a reduction factor on all your design data at a fair guestimate of your running temp at the hottest time of the year and with maximum voltage coming from your electricity supplier.
I DO NOT recommend 1943/5200 at these rail volts!
Please do not suggest rails above 100volts without thinking (designing) of the consequences for the originator of this thread.
regards Andrew T. |
|
|
| uli |
| quote: | Originally posted by Duo
EDIT: And if workhorse did mean actualy +-140V rails. hahaha.... ouch for those transistors. |
Hi Duo,
imagine rails at +-65V constant is 130V pp. add another +-85V
which are activated in class G or H then you reach +150V, -65V
or +65V, -150V. this is 215pp then it works (see Crest, QSC etc).
Uli
:nod: :nod: :nod:
PS: in pro audio there are awful lots of outputpairs used! |
|
|
| Duo |
Yes, I understand that in class G or H you can have a swing not allowable in a normal full swing amplifier. Thus allowing the use of 230V transistors in a system with a theoretical swing of 300V.
I see valid points AndrewT, but one idea: As the voltage across the transistor increases, the current decreases until the crossing point. We start at 78V with just Q current, and would have to move down by 12.8V to achieve the maximum 80V current of 1.6A for four transistors on 8 ohms. Obviously, this 1.6A (400mA) is now at 65.2V across the transistor (in a world with no power supply droop. Add in supply drooping/sagging, and you get even less voltage across the transistor. I imagine in this situation that the SOA would rarely be exceeded...
Of course, as far as reactive loads and heat are concerned, there is definitely area to be careful. |
|
|
| uli |
imagine driving this amp with 2/pi of the maximum voltage,
this is about 50 volts. assuming a resistive loade this is
6.25 A into 8 R.
the 2SC5200 is only capable of delivering 5 A at 30V (~80-50).
this means that you have to use at least 2 pairs, better 3 pairs.
IMHO there exist better hi power transistors than the 2SC5200.
I prefer the 2SC3264/2SA1295 combo. It is fast and reliable
A N D there are no fakes known of those Sanken devices!
Uli
:nod: :nod: :nod: |
|
|
| Duo |
Well, obviously there are better transistors around than this for the job. We are just trying to help with a case involving just the original transistors stated.
If I had my way, I'd use some MJ21193/21194 or similar onsemis in my amp;) |
|
|
| uli |
| quote: | Originally posted by Duo
If I had my way, I'd use some MJ21193/21194 or similar onsemis in my amp;) |
You are right, but in the first post there is stated a "planned"
amp so I think good advice is to start with another transistor
couple.
Uli
:nod: :nod: :nod:
PS: those motorolas are like diesel engines :D
powerful but SLOW:devilr: :devilr: :devilr: |
|
|
| Duo |
Of course. If one might be able to scrape the slate for new specification in transistors, I'd definitley not mess around with the 1943/5200 pair.
As far as 21193/21194, yes, not the fastest, but bloody indestructable compared to most transistors.
For faster ones though, onsemi has some really fast transistors that'll take as much beating. ;)
EDIT: Yes, the MJL4281/4302 pair are very nice. Wicked SOA and fast like an oiled pig. |
|
|
| uli |
| quote: | Originally posted by Duo
Yes, the MJL4281/4302 pair are very nice. Wicked SOA and fast like an oiled pig. |
good choice!
Uli
:nod: :nod: :nod: |
|
|
| hienrich |
:) :)
ok, ok, I change my mind. Upon going with the thread, and lists of
expert advice and mathemathics from you guys. I change my mind.
I'd rather go for MJL's, so I will never have problems unlocking our old
expired fire extinguisher.
with MJL's, maybe I could go more farther than +/- 78vdc or even go as far as +/- 96vdc. Sankens are too expensive.
Actually by this time, I'm still in the process with my new project.
Hey hobbyists, audio freaks check this out.
http://www.eserviceinfo.com/downloa...tel_rb1090.html
:) :) :)
HIENRICH |
|
|
| Workhorse |
Hi ULI & DUO
Class-H is similar to Class-AB Except there are 2 or more power Supply TIER's are present. In this situation If the output swing is less than the Reference voltage then the lower rail is used and when it exceeds the reference point the high voltage rail is switched on by switching Mosfets in rails. This Class-H simply increases the efficiency a little bit.This simply ellaborates that the trannies are very well exposed to high voltage.
QSC uses +140 & -140 rails for high voltage swings.
Regards
Kanwar |
|
|
| Duo |
| workhorse: Thanks for re-iterating what we've already said.;) |
|
|
| Duo |
| That's really interesting reverse engineering how that output stage on the QSC works. Certainly not a typical style of output stage. |
|
|
| uli |
| quote: | Originally posted by Workhorse
Hi ULI & DUO
Class-H is similar to Class-AB Except there are 2 or more power Supply TIER's are present. |
1) Class H is in no way similar to class AB as AB is something
to avoid at all costs. It is a pure class B design at the constant
supply level.
| quote: | This Class-H simply increases the efficiency a little bit.
|
2) Class H (or sonically better Class G according to D. Self)
increases efficiency not only a little bit but dramatically.
| quote: | | This simply ellaborates that the trannies are very well exposed to high voltage. QSC uses +140 & -140 rails for high voltage swings. |
3) As I described already the transistor is NEVER exposed to
+-140V pp but to +140, -47 or vice versa -> 187V.
4) It is better to think before giving bad counsel to beginners
just to show what you know.
Uli
:nod: :nod: :nod: |
|
|
| Duo |
Well, I hate to be so sharp cut, but they are situations like this that remind me to be wary of information taken for granted and to test everything carefully against standards. :)
The good comes even in this though, it has given me interest in designing a class H amplifier for personal use. ;) |
|
|
| Workhorse |
| quote: | Originally posted by uli
1) Class H is in no way similar to class AB as AB is something
to avoid at all costs. It is a pure class B design at the constant
supply level.
2) Class H (or sonically better Class G according to D. Self)
increases efficiency not only a little bit but dramatically.
3) As I described already the transistor is NEVER exposed to
+-140V pp but to +140, -47 or vice versa -> 187V.
4) It is better to think before giving bad counsel to beginners
just to show what you know.
Uli
:nod: :nod: :nod: |
hi ULI HAPPY NEW YEAR !
If a Class-H amplifier during its high voltage rail in operation and the output swing is just near the clip point, so can we say Still its efficiency is greater than Class-B of same voltage rail .
Regards,
Kanwar |
|
|
| Duo |
| Workhorse: Two posts ago, Uli just stated that point... |
|
|
| uli |
| quote: | Originally posted by Duo
The good comes even in this though, it has given me interest in designing a class H amplifier for personal use. ;) |
Hi Duo,
this particular QSC design is something special in 2 ways:
1) As it seems to be design philosophy of QSC the output nodes
are reversed. This means that you have a floating high current
psu and the output of the active stage is connected to gnd.
The output itself is formed by the centertap of the mains XFMR.
This leads to a simpler drive circuit for the switching fets in the
power rails as the input stage is in turn referenced to gnd and
thus the more the output is driven the lower is the difference
between gnd and the powerrails.
2) All powerdevices are driven to, or rather beyond their limits.
I would not clone this design as the Toshibas are driven out of
spec!
This design should be good for 2000W RMS into 2 Ohms.
So you got 6 NPN devices to deliver e.g. 30A peak with a Vce of
about 35 Volts. This means 35V/5A per device. This is IMHO
hard on the limit of the SOA of those devices.
I would prefer Class G for my personal use, I believe they sound
better.
Uli
:nod: :nod: :nod: |
|
|
| Eva |
Remember that in class AB circuits each half of output devices only conducts half of the time and that music signals are not continuous peak-to-peak sinewaves
In practice this allows to expose output devices to instantaneous dissipations substantially higher than their DC SOA without failures, since that only happens during a small fraction of the time
As an example, I have a single pair of ancient TIP35C/TIP36C with +-41.5V regulated rails driving a Rdc=3.4 ohms bass driver [part of an active 3-way system] mounted in a hybrid horn/reflex loaded enclosure [quite reactive load], and I haven't been still able to blow them altough I like to play just at clipping threshold most of the time and the heatsink easily exceeds 50șC :D |
|
|
| uli |
| quote: | Originally posted by Eva
Remember that in class AB circuits each half of output devices only conducts half of the time and that music signals are not continuous peak-to-peak sinewaves
In practice this allows to expose output devices to instantaneous dissipations substantially higher than their DC SOA without failures, since that only happens during a small fraction of the time
|
Hi Eva,
in Class AB one half conducts more than half of the time.
What you mean is Class B where each half conducts exactly
180° or 50% of the time!
Its a common mistake to believe that class B needs no bias.
This is class C.
The SOA area in this case (QSC) has nothing to do with the
waveform of music and the device does not care either.
Driving a BJT beyond its specs leads to desaster, music or
sine wave.
When you drive this amp to the 3rd rail with about 35V below
the rail leads to a Vce of 35V, music or not!
Even Assuming that this highes rail drops to say 110V leads
to 75V at the output. This in turn leads to 37.5 A current.
37.5 divided by 6 is 6.25 A per device peak current.
Not even the 2SC3264 is able to deliver that safely!(218.75W)
It is astonishing how fast a BJT dies if driven beyond SOA.
This worst case scenario happens sometimes.
When I was in the PA business some years ago, QSC was not
among the most reliable amps.
Uli
:nod: :nod: :nod: : |
|
|
| Eva |
But DC SOA only makes sense for DC operation. You should look at pulsed SOA
Another example are switching transistors, these are exposed to dissipations as high as 2KW for a single TO-220 device during 200nS at turn-off, and this is perfectly within SOA
Remember that the percentage of time the third floor supply is active in QSC amps is very small, and even smaller when plaing music
Also I'm not aware of such QSC reliability problems. As a reference I had a friend that owned a local music group with 4 QSC EX4000 and 4 QSC EX1600. The EX4000 were driving 4 ohms on both channels and the EX1600 were driving 4 in one and 8 in another. He bough all the amplifiers and loudspeakers second-hand and after 4 years he sold all them when he left the live-audio business. There were no failures in the amplifiers at all, altough he destroyed several LF, MF and HF drivers due to massive overpowering
The EX1600 uses +-54V and +-108V supply rails and mounts three pairs of 2SA1302 and 2SC3281. The EX4000 uses +-46V, +-94V and +-142V supply rails and mounts six pairs of 2SA1302 and 2SC3281
These amplifiers are probably still playing in some live-audio performance somewhere this night with no failures yet, altough they are probably 7 or 8 years old and QSC has discontinued EX series long ago
Also, note that the heatsinks of these amplifiers were only warm when playing at clipping threshold and driving 4 ohms reactive loads [4 EX4000 were driving a total of 16 horn-loaded bass-bins]
How class-H affects amplifier efficiency when playing music signals [and not sine waves] is not allways well understood, in practice the lower supply rails are active more than 90% of the time |
|
|
| uli |
Hi Eva,
yes I know that all, there is a reason why choosing the -10dB
point as the first switching point. But when I worked for the
biggest Austrian ( ;) ) PA company we threw all QSCs out after
blowing some. Now they own Crown Macrotech and are happy
with them.
My point is, with that huge price tag and size why dont they
put 8 pairs in?
Uli
:nod: :nod: :nod: |
|
|
| EWorkshop1708 |
| quote: | Originally posted by Duo
For faster ones though, onsemi has some really fast transistors that'll take as much beating. ;)
EDIT: Yes, the MJL4281/4302 pair are very nice. Wicked SOA and fast like an oiled pig. |
I just got 25 each of the 4281 and 4302. I figured since they are 350V, 15A, I could use them in just about any amplifier I build.
I'm thinking of even using a pair of them to make a variable split power supply for testing amps, or whatever, and want to make it +/- 40V, 1 or 2A. Just not sure how many pairs would be good for that. |
|
|
| Workhorse |
| quote: | Originally posted by uli
Hi Eva,
yes I know that all, there is a reason why choosing the -10dB
point as the first switching point. But when I worked for the
biggest Austrian ( ;) ) PA company we threw all QSCs out after
blowing some. Now they own Crown Macrotech and are happy
with them.
My point is, with that huge price tag and size why dont they
put 8 pairs in?
Uli
|
hi ULI,
The fact is that QSC simply wants to maximize its profit in every aspect, whether it is a simple question of paralleling devices or not.
In our case we use 16 IRFP250N devices per channel to get 1000 WRMS . This is ofcourse an overmargin but it simply makes the product more reliable in harsh conditions.
regards,
kanwar |
|
|
| K-amps |
| quote: | Originally posted by hienrich
:) :)
ok, ok, I change my mind. Upon going with the thread, and lists of
expert advice and mathemathics from you guys. I change my mind.
I'd rather go for MJL's, so I will never have problems unlocking our old
expired fire extinguisher.
with MJL's, maybe I could go more farther than +/- 78vdc or even go as far as +/- 96vdc. Sankens are too expensive.
Actually by this time, I'm still in the process with my new project.
Hey hobbyists, audio freaks check this out.
http://www.eserviceinfo.com/downloa...tel_rb1090.html
:) :) :)
HIENRICH |
If you are one of those with "Golden" ears, also know that devices have sonic characters.... To many, the 1943/5200 sound sweet, the MJL's sound big robust and hard...... if you don't hear the difference, then you are among the lucky ones...
:D |
|
|
| hienrich |
:D
K-amps: ya, actually not so lucky with me here in my place,
why? becuase fake 5200's/1943's are really very ramphant here
:whazzat:
but very lucky! enough to acquire some Onsemi power outputs
as free of charge about two years ago. but still on the crave of having
some 5200's/1943's (originalls).
as for my experience, I have a friend which owns a PA system
they are using these devices (I mean with the originals)
and they sound great.
regards,
hienrich
:D |
|
|
| K-amps |
Heinrich,
Actually you can get genuine 2sc5200/a1943 from www.digikey.com and also from www.avnet.com.
Other places have a mix of fake and real...... but the above have genuine parts as they buy directly from Toshiba. Digikey has stock on both NPN and PNP while AVNET has only PNP (but at better price). Perhaps if you buy enough, it will make up for shipping from the US. ;) |
|
|
| hienrich |
:D
maybe I can get those genuine devices later, since
financial distortions are still present for the moment.
I have bought two pairs before.
and used them as drivers, driving Onsemi's Mjl21196(quasi complementary output stage)
I wonder why MJL21196's are not popular,
actually these devices are the highest in SOA if im not wrong in
Onsemi's list
It's really hard to kill these devices, since I've tried (through
forgetfulness) my amp playing without thermal tracking and fans,
driving 4 ohm loads full power
playing with in an hour or more perhaps
its heatsinks are very very hot, you can almost light up a
cigarette,
but still after putting it off for a while they're alive and
kicking.
regards,
hienrich |
|
|
| GEirin |
Hi all.
I have decided to repair and to improve an old Kenwood KA 59. It had completely lost two channels. I think to substitute power transistors, one pair 2SB 1163 - 2SD 1718 (180V 15A 150W 20Mhz) by one pair 2SC 5200 - 2SA 1943 (230V 15A 150W 30Mhz).
The power supply voltage is:
+- 66,5 V DC for 8 ohm load
or +- 46,5 V DC for 4 ohm load.
A question:
I can to use one pair transistors or two pair transistors.
Thanks.
Guillermo. |
|
|
| hienrich |
:D
hi ,
GEirin: for best results and safer operating conditions as what
have been said in the thread multiple outputs are better than a pair
specially for higher rail voltages.
good luck.
hienrich |
|
|
| K-amps |
| quote: | Originally posted by GEirin
Hi all.
I have decided to repair and to improve an old Kenwood KA 59. It had completely lost two channels. I think to substitute power transistors, one pair 2SB 1163 - 2SD 1718 (180V 15A 150W 20Mhz) by one pair 2SC 5200 - 2SA 1943 (230V 15A 150W 30Mhz).
The power supply voltage is:
+- 66,5 V DC for 8 ohm load
or +- 46,5 V DC for 4 ohm load.
A question:
I can to use one pair transistors or two pair transistors.
Thanks.
Guillermo. |
One pair is clearly enough. The Kenwood rails drop as much as 30%-35% giving you more virtual SOA than worst case. The 5200 will surely work better than the originals especially under load. |
|
|
| GEirin |
Hello.
Thanks for the replies.
I' m thinking yours recommendations.
Regards,
Guillermo. |
|
|
|
