Best transistor substitutes for Heathkit ar-15

ar15guy · 27th March 2008, 03:28 PM

Hello,
Anyone have good substitutes for these heathkit ar-15 transistors?

RCA 40408
RCA 40409
RCA 40410
RCA 40411

Thank you

djk · 28th March 2008, 12:26 PM

RCA 40408 700mA 90V 1W 100Mhz ~2N5681
RCA 40409 700mA 90V 3W 100Mhz ~2N5681+heatsink
RCA 40410 -700mA -90V 3W 100Mhz ~2N5679+heatsink
RCA 40411 30A 90V 150W 800Khz ~MJ15003

Newark has them in stock.

Real 40409/40410 are still available for obscene prices (for McIntosh lovers).

ar15guy · 1st April 2008, 03:11 PM

Is there going to be a difference in the sound quality when replacing the original Qs?
Thank you.

Mooly · 1st April 2008, 05:26 PM

Hi, Will sound exactly the same, transistor properties are determined by the material used, silicon in this case, and provided you choose similarly specified components you won't have any problems. As well as obvious ratings like power, voltage and physical properties, try to pick devices of similar speed (ft) as this can effect stability of some designs. i.e. don't fit output transistors of 20mhz ft if the originals were closer to 1mhz, the design may rely on this fact to help with stability margins.
Regards Karl

ar15guy · 8th April 2008, 02:21 PM

Ok, thanks for the help.

27th March 2008, 03:28 PM	#1
ar15guy diyAudio Member Join Date: Mar 2008	Best transistor substitutes for Heathkit ar-15 Hello, Anyone have good substitutes for these heathkit ar-15 transistors? RCA 40408 RCA 40409 RCA 40410 RCA 40411 Thank you

28th March 2008, 12:26 PM	#2
djk diyAudio Member Join Date: Feb 2001 Location: USA	RCA 40408 700mA 90V 1W 100Mhz ~2N5681 RCA 40409 700mA 90V 3W 100Mhz ~2N5681+heatsink RCA 40410 -700mA -90V 3W 100Mhz ~2N5679+heatsink RCA 40411 30A 90V 150W 800Khz ~MJ15003 Newark has them in stock. Real 40409/40410 are still available for obscene prices (for McIntosh lovers). __________________ Candidates for the Darwin Award should not read this author.

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1st April 2008, 03:11 PM	#3
ar15guy diyAudio Member Join Date: Mar 2008	Is there going to be a difference in the sound quality when replacing the original Qs? Thank you.

1st April 2008, 05:26 PM	#4
Mooly diyAudio Member Join Date: Sep 2007	Hi, Will sound exactly the same, transistor properties are determined by the material used, silicon in this case, and provided you choose similarly specified components you won't have any problems. As well as obvious ratings like power, voltage and physical properties, try to pick devices of similar speed (ft) as this can effect stability of some designs. i.e. don't fit output transistors of 20mhz ft if the originals were closer to 1mhz, the design may rely on this fact to help with stability margins. Regards Karl

8th April 2008, 02:21 PM	#5
ar15guy diyAudio Member Join Date: Mar 2008	Ok, thanks for the help.

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