How to drive 8 pairs of MJL21193/94? - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 16th March 2009, 12:27 PM   #1
sajti is online now sajti  Hungary
diyAudio Member
 
Join Date: Apr 2003
Location: Vác, Hungary
Default How to drive 8 pairs of MJL21193/94?

I want to build 900W/2ohms bridged amplifier, which will use 8 pairs of MJL21193/94, in each amplifier module, with +/-37V PSU.
My only problem, how to drive this amount of output devices? There are 3 options:
1, Drive with same type of transistor. One more pair MJLs with 150-200mA bias, or
2, Parallel connected MJE15032/33, with 70-80mA bias in each pair. Two or three parallel, with base stopper, and small series emitter resistors, or
3, Separate the output devices to 4-4pairs, and drive them with separated driver (MJEs)


I don't know which would be better.

sajti
  Reply With Quote
Old 17th March 2009, 05:00 AM   #2
diyAudio Member
 
Jan Dupont's Avatar
 
Join Date: Apr 2003
Location: Copenhagen, Denmark
Send a message via MSN to Jan Dupont
Hello sajti,

First you won't get 900W/2ohms with +/-37VDC rail Voltages.

Have said that, then I tell you that I have several times with succes used the MJL21193/94 as drivers in large output stages.
Use the MJE15032/33 as predrivers and either BD139/140 or MJE340/350 as pre predrivers.
__________________
Free Schematic and Service Manual downloads www.audio-circuit.dk, Company: www.dupont-audio.com, Joint venture: www.DupontMantra.com
  Reply With Quote
Old 17th March 2009, 05:40 AM   #3
diyAudio Member
 
ostripper's Avatar
 
Join Date: May 2008
Location: Albany , NY (smallbany)
Quote:
pre predrivers.
pre predrivers= quad EF?
OS
  Reply With Quote
Old 17th March 2009, 06:42 AM   #4
fotios is offline fotios  Greece
diyAudio Member
 
fotios's Avatar
 
Join Date: Feb 2007
Location: Δραμα - North Greece
Yes, he (sajti) can do this... i mean to get 900Wrms/2 with +/-37Vdc supply rails per channel, connected to load IN BRIDGE MODE as he reffers.
In bridge mode, the peak-peak voltage in output will be:
[ +37 - ( -37) ] X 2 = 74 X 2 = 148Vpp
The peak voltage will be: 74Vp
And the rms voltage will be: 74 / 1,414 = 52,33Vrms.
So, in 2 load the theoretical power will be:
( 52,33 X 52,33 ) / 2 = 1369Wrms.
It is obvious that sajti has made right calculations... proof for this it is the reffered requirement of 8 pairs of output transistors per channel.
As for the output scheme, of course the better is the tripple darlington arrangement for so high power. There is also the option of using: As predrivers the MJE15030-31 and as main drivers the MJL3281/1302 (both have very good bandwidth).

Regs
Fotios
  Reply With Quote
Old 17th March 2009, 07:28 AM   #5
AndrewT is online now AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Quote:
Originally posted by fotios
As for the output scheme, of course the better is the triple darlington arrangement for so high power. There is also the option of using: As predrivers the MJE15030-31 and as main drivers the MJL3281/1302
I like this suggestion, don't know if it will work, never having done anything like this.

900W into 2r0 bridged is the same as 450W into 1r0 and that is equivalent to 30Vpk and 30Apk.
But, check hFE of the outputs when Ic=10.7Apk/device.
__________________
regards Andrew T.
  Reply With Quote
Old 17th March 2009, 07:50 AM   #6
sajti is online now sajti  Hungary
diyAudio Member
 
Join Date: Apr 2003
Location: Vác, Hungary
Quote:
It is obvious that sajti has made right calculations... proof for this it is the reffered requirement of 8 pairs of output transistors per channel.
As for the output scheme, of course the better is the tripple darlington arrangement for so high power. There is also the option of using: As predrivers the MJE15030-31 and as main drivers the MJL3281/1302 (both have very good bandwidth).

Regs
Fotios [/B]
Not 8 pairs per channel! 8 pairs per amplifier module. It means 16pairs for one channel (2 modules bridged). I'm not 100% sure about the MJL2119X, because I get tons of FJL4X15.

I have lot of NJW0281/0302 (about 70pairs). They would be OK as driver. I think to use 200mA bias, or higher.

Sajti
  Reply With Quote
Old 17th March 2009, 07:52 AM   #7
sajti is online now sajti  Hungary
diyAudio Member
 
Join Date: Apr 2003
Location: Vác, Hungary
Quote:
Originally posted by AndrewT
I like this suggestion, don't know if it will work, never having done anything like this.

900W into 2r0 bridged is the same as 450W into 1r0 and that is equivalent to 30Vpk and 30Apk.
But, check hFE of the outputs when Ic=10.7Apk/device.
30Apk output means only 3.75Apk for the output devices. So hFE must be over 50, and this means 0.6Apk for the driver.

Sajti
  Reply With Quote
Old 17th March 2009, 08:31 AM   #8
fotios is offline fotios  Greece
diyAudio Member
 
fotios's Avatar
 
Join Date: Feb 2007
Location: Δραμα - North Greece
In bridge mode, as we know, the one channel amplifies the initial signal of source in phase and the other channel the same signal inverted. If the output of source it is single ended, then the invertion is done within the amplifier. If the source gives a balanced output, then we can use directly the hot (+) and cold (-) signals to drive directly the two channels of amplifier. From the one channel that amplifies the hot (in phase) signal we get the plus (+) output to load, and from the other channel that amplifies the cold (inverted) signal we get the minus (-) output to load.
This scheme is used in the named "Fully Differential" Hi-End amplifiers. Technicaly this output scheme, it is called "Horizontal Push-Pull".
I had always in my mind to build a monoblock amplifier, but with the usual way of using two heatsinks as sides of amplifier case. I had not idea how could this be done, untill a very known designer-member he told me the way for this, which is the above described. When i asked him, how can do this with single ended signal in input, he replied: simply you have to use an inverter of signal inside the amplifier to drive the second channel, like this used for bridge mode operation.
This method, offers some signifficant beneffits of which the main, it is the lower voltage of supply rails needed. With a power supply of +/-30Vdc we can get an output of about 200Wrms/8. Another one, it is the non-use of power supply ground as return path for the load, avoiding thus a gnd loop.
And of course far better noise immunity.

Fotios
  Reply With Quote
Old 17th March 2009, 08:49 AM   #9
sajti is online now sajti  Hungary
diyAudio Member
 
Join Date: Apr 2003
Location: Vác, Hungary
I will put the schematic today!

Sajti
  Reply With Quote
Old 17th March 2009, 08:52 AM   #10
AndrewT is online now AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Quote:
Originally posted by sajti


30Apk output means only 3.75Apk for the output devices. So hFE must be over 50, and this means 0.6Apk for the driver.

Sajti
30Apk into 1r0.
30/0.35 Apk into a 1ohm speaker when driven by a fast starting or fast stopping transient.

There is evidence that the 0.35 factor be reduced to 0.25 and maybe 0.2 for severe reactance speakers.
__________________
regards Andrew T.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
mjl21193/94 indestructable?? mikefromaus Solid State 2 16th January 2008 02:34 PM
FS: MJL21193 and MJL21194 - new zener_diode Swap Meet 9 27th December 2007 03:36 AM
MJL21193/21194s N-Channel Swap Meet 1 18th September 2005 03:04 AM
MJL21193 and MJL21194 HuntTheShunt Parts 1 5th December 2004 12:11 PM


New To Site? Need Help?

All times are GMT. The time now is 10:07 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2