mjl3281a vs mjw3281a

crippledchicken · 16th November 2004, 09:46 PM

hi, has anyone heard the difference of these two transistors, in the same amp for conparison? thanks, crippledchicken

richie00boy · 17th November 2004, 09:11 AM

I think all the MJW devices are just MJL devices but using a case with better thermal properties, i.e. bigger. Therefore the sound will be the same.

crippledchicken · 17th November 2004, 01:59 PM

thanks richieooboy, thanks for the response. i also had an idea of replacing the mjw3281/1302 pairs in it now, with the mjl4281a/02 pairs. the hfe, voltage, wattage, are higher with these and i think, the ft is 35mhz being a little higher than the 3281's by 5 mhz. could these maybe be an upgrade? i also have the drivers that go with the 4281a's but the ones in there now, are 2sd2061's/ 2sb1369's with an ft of 8 mhz otherwise, close parameters every where else. but, i was concerned that the replacement drivers with ft of 35 mhz, might cause occillations and maybe, should just use the original drivers. what do you think? as i'm not to well experienced in this subject. your advice would be appreaciated thanks, crippledchicken

richie00boy · 17th November 2004, 02:22 PM

I got MJL and MJW the wrong way round. MJL is the wider case, MJW is TO247 case.

I'd just leave the transistors be. The differences between the power devices are small and you run the risk of lifting pads trying to remove things. If the originals were TIP devices or something then maybe a small benefit could be had. There's also the possibility (as you pointed out) of upsetting stability.

AndrewT · 17th November 2004, 06:11 PM

Hi,
Crippled chick asks if "ft of 35 mhz, might cause occillations"?
Would the knowledgable out there please confirm if using faster output transistors increases the risk of oscillation or reduces the risk?
I believe that the faster transistor will decrease the phase shift and thereby improve the phase margin. Have I got it right?
regards and waiting to hear
Andrew T.

richie00boy · 17th November 2004, 06:38 PM

As you extend the bandwidth out you run the risk of increased chance of oscillation due to coupling by stray capacitance and inductance.

crippledchicken · 18th November 2004, 12:10 AM

well, i tried the mjl4281a/02 pairs using original drivers because of the ft 8mhz, vs the ft of 35mhz difference. so far i have found no ill effects such as extreme heat or any bad hissing sounds etc. the sound for sure, has better tight sounding and better low bass along with smoother, more detailed full bodied sound. the original outputs when amp was new were 2sc5200/2sa1943 in an onkyo m-282 2 chl. amp rated 105 watts 8 ohm, and 125 watts into 6 ohms per chl. rms. the power supply had 2 10k uf nichicon gold tunes caps and i added another 12k uf gold tune per side along with replacing the 8 amp inline bridge rect. with 30 amp 600v. stealth diodes awhile back. i'll keep a close check for excess heat, or any strange background noises and hope it stays sounding like it does now. just thought i'd share this bit of info about the mjl4281a/02 pairs they do sound good! appreaciate all the valuable info. crippledchicken

16th November 2004, 09:46 PM	#1
crippledchicken diyAudio Member Join Date: Dec 2003 Location: south east mo.	mjl3281a vs mjw3281a hi, has anyone heard the difference of these two transistors, in the same amp for conparison? thanks, crippledchicken

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17th November 2004, 09:11 AM	#2
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	I think all the MJW devices are just MJL devices but using a case with better thermal properties, i.e. bigger. Therefore the sound will be the same.

17th November 2004, 01:59 PM	#3
crippledchicken diyAudio Member Join Date: Dec 2003 Location: south east mo.	thanks richieooboy, thanks for the response. i also had an idea of replacing the mjw3281/1302 pairs in it now, with the mjl4281a/02 pairs. the hfe, voltage, wattage, are higher with these and i think, the ft is 35mhz being a little higher than the 3281's by 5 mhz. could these maybe be an upgrade? i also have the drivers that go with the 4281a's but the ones in there now, are 2sd2061's/ 2sb1369's with an ft of 8 mhz otherwise, close parameters every where else. but, i was concerned that the replacement drivers with ft of 35 mhz, might cause occillations and maybe, should just use the original drivers. what do you think? as i'm not to well experienced in this subject. your advice would be appreaciated thanks, crippledchicken

17th November 2004, 02:22 PM	#4
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	I got MJL and MJW the wrong way round. MJL is the wider case, MJW is TO247 case. I'd just leave the transistors be. The differences between the power devices are small and you run the risk of lifting pads trying to remove things. If the originals were TIP devices or something then maybe a small benefit could be had. There's also the possibility (as you pointed out) of upsetting stability.

17th November 2004, 06:11 PM	#5
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi, Crippled chick asks if "ft of 35 mhz, might cause occillations"? Would the knowledgable out there please confirm if using faster output transistors increases the risk of oscillation or reduces the risk? I believe that the faster transistor will decrease the phase shift and thereby improve the phase margin. Have I got it right? regards and waiting to hear Andrew T.

17th November 2004, 06:38 PM	#6
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	As you extend the bandwidth out you run the risk of increased chance of oscillation due to coupling by stray capacitance and inductance.

18th November 2004, 12:10 AM	#7
crippledchicken diyAudio Member Join Date: Dec 2003 Location: south east mo.	well, i tried the mjl4281a/02 pairs using original drivers because of the ft 8mhz, vs the ft of 35mhz difference. so far i have found no ill effects such as extreme heat or any bad hissing sounds etc. the sound for sure, has better tight sounding and better low bass along with smoother, more detailed full bodied sound. the original outputs when amp was new were 2sc5200/2sa1943 in an onkyo m-282 2 chl. amp rated 105 watts 8 ohm, and 125 watts into 6 ohms per chl. rms. the power supply had 2 10k uf nichicon gold tunes caps and i added another 12k uf gold tune per side along with replacing the 8 amp inline bridge rect. with 30 amp 600v. stealth diodes awhile back. i'll keep a close check for excess heat, or any strange background noises and hope it stays sounding like it does now. just thought i'd share this bit of info about the mjl4281a/02 pairs they do sound good! appreaciate all the valuable info. crippledchicken