Replacing 2N3055/MJ2955

jazko · 23rd April 2011, 12:42 PM

Good day, I have a NAD 2030 amp with one channel down, I was wondering if I can replace the transistors (MJ2955/2N3055 (all four)) with MJ21195/6 ? What should I look for to know whether transistors are interchangeable?

lineup · 23rd April 2011, 01:49 PM

I think better in this case to take MJ21193/4.
Myself use replacement TIP2955/TIP3055 in my simulator.
It is not much to gain to use faster devices. Try to make it as similar as possible.
This will avoid a mismatch in quality. And work the best.

jaycee · 23rd April 2011, 01:57 PM

If this is the NAD amp where there are no emitter resistors, you will need to add them or it will not be thermally stable. 0.33 ohm 3W resistors will work.

jazko · 23rd April 2011, 02:26 PM

jaycee there are emitter resistors with the values you mentioned.

lineup I can find MJ21195/6 pretty easy, so I suppose I can use them? I know it is a bit of an overkill

jaycee · 23rd April 2011, 03:55 PM

ok, i couldnt remember which NAD amp just used plain old 2955/3055 with none

To be honest yes, the MJ21195/6 should be fine, even MJ15024/5 will be good

One thing NAD often do is use fixed resistors for bias. You may have to change that as the biasing will be different on the newer transistors. If there's a pot, then you're fine

indianajo · 04:28 PM

MJ15015 and 16 datasheet refers to the 3055-2955 spec. They have a higher Vceo and an actual SOA, not as big as 21195. I got my On Semi versions for $1.28 each from farnell (newark in USA). Depending on layout, you might have to put 10-20 pf across the B-E leads to prevent oscillation, especially on the MJ15016 which has ft of 4 mhz. The MJ15015 ft is .8 mhz.

jazko · 23rd April 2011, 04:27 PM

Yes, unfortunately no pots are present, but I think I'll be alright.

Thank you

wg_ski · 23rd April 2011, 05:54 PM

If there is no bias pot, you want something close to the original 3055/2955. MJ21195/6 would *work*, but the bias would need to be adjusted if possible. MJ15015/16 are much closer to the Moto/ON 3055 (only slightly larger die with the same layout and processing) so the bias should be closer to correct without adjustment. The extra 10-20 pF cap trick may be needed regardless of what type is used if they are not the originals.

logawamania · 11th June 2011, 12:01 PM

Hi all, I have same situation with zacko...
I will try to use TIP2955/TIP3055

Btw... I'm sorry for bad english

big jim · 11th June 2011, 03:02 PM

Hi there are no emitter resistors in the 2030 amplifier

23rd April 2011, 12:42 PM	#1
jazko diyAudio Member Join Date: Sep 2009 Location: Manchester	Replacing 2N3055/MJ2955 Good day, I have a NAD 2030 amp with one channel down, I was wondering if I can replace the transistors (MJ2955/2N3055 (all four)) with MJ21195/6 ? What should I look for to know whether transistors are interchangeable?

23rd April 2011, 01:49 PM	#2
lineup diyAudio Member Join Date: Dec 2005 Location: the north	I think better in this case to take MJ21193/4. Myself use replacement TIP2955/TIP3055 in my simulator. It is not much to gain to use faster devices. Try to make it as similar as possible. This will avoid a mismatch in quality. And work the best. __________________ lineup

23rd April 2011, 04:24 PM	#6
indianajo diyAudio Member Join Date: Jan 2010 Location: Jeffersonville, Indiana USA	MJ15015 and 16 datasheet refers to the 3055-2955 spec. They have a higher Vceo and an actual SOA, not as big as 21195. I got my On Semi versions for $1.28 each from farnell (newark in USA). Depending on layout, you might have to put 10-20 pf across the B-E leads to prevent oscillation, especially on the MJ15016 which has ft of 4 mhz. The MJ15015 ft is .8 mhz. __________________ Dynakit ST70, ST120, PAS2,Hammond H182(2 ea),H112,A100,10-82TC,Peavey CS800S,SP2-XT's, T-300 HF Projs, Steinway console, Herald RA88a mixer, Wurlitzer 4500 Last edited by indianajo; 23rd April 2011 at 04:28 PM.

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23rd April 2011, 01:57 PM	#3
jaycee diyAudio Member Join Date: Apr 2004 Location: Norwich, UK	If this is the NAD amp where there are no emitter resistors, you will need to add them or it will not be thermally stable. 0.33 ohm 3W resistors will work.

23rd April 2011, 02:26 PM	#4
jazko diyAudio Member Join Date: Sep 2009 Location: Manchester	jaycee there are emitter resistors with the values you mentioned. lineup I can find MJ21195/6 pretty easy, so I suppose I can use them? I know it is a bit of an overkill

23rd April 2011, 03:55 PM	#5
jaycee diyAudio Member Join Date: Apr 2004 Location: Norwich, UK	ok, i couldnt remember which NAD amp just used plain old 2955/3055 with none To be honest yes, the MJ21195/6 should be fine, even MJ15024/5 will be good One thing NAD often do is use fixed resistors for bias. You may have to change that as the biasing will be different on the newer transistors. If there's a pot, then you're fine

23rd April 2011, 04:27 PM	#7
jazko diyAudio Member Join Date: Sep 2009 Location: Manchester	Yes, unfortunately no pots are present, but I think I'll be alright. Thank you

23rd April 2011, 05:54 PM	#8
wg_ski diyAudio Member Join Date: Oct 2007	If there is no bias pot, you want something close to the original 3055/2955. MJ21195/6 would work, but the bias would need to be adjusted if possible. MJ15015/16 are much closer to the Moto/ON 3055 (only slightly larger die with the same layout and processing) so the bias should be closer to correct without adjustment. The extra 10-20 pF cap trick may be needed regardless of what type is used if they are not the originals.

11th June 2011, 12:01 PM	#9
logawamania diyAudio Member Join Date: May 2011 Location: Logawa City	Hi all, I have same situation with zacko... I will try to use TIP2955/TIP3055 Btw... I'm sorry for bad english

11th June 2011, 03:02 PM	#10
big jim diyAudio Member Join Date: Feb 2006 Location: london	Hi there are no emitter resistors in the 2030 amplifier

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