Threshold CAS 1

thistlehd · 28th September 2009, 06:54 PM

I have recently acquired a Threshold CAS-1. I have replaced the power supply capacitors, so it plays music again, but I had a couple of questions. It was suggested that I replace the existing tantalum capacitors (green blobs) on the board to a more modern electrolytic type. I also noticed that the output devices are not the same on both channels, one channel has 2n5876 devices and all of the others just say class ab and have a date code. Any thoughts?

gl · 28th September 2009, 08:01 PM

The CAS 1 was/is a great amplifier. The 2N5876 and "CLASS A6" marked transistors are the same part. I would definitely swap out the tantalums for aluminum electrolytic's like the Elna silks.

Graeme

jam · 11:26 PM

The ceramics need to go too. You could also replace the bridge rectifier with a high speed or soft recovery type and how about some 1% metal film resistors for good measure.

Jam

Mark Allen · 29th September 2009, 02:09 PM

I owned one of those baack in the 80s. It was a pretty decent amp and was my first taste of the Mastrer's work...

gl · 29th September 2009, 04:24 PM

I borrowed one from a friend for a couple of days just to see if it would drive the Dayton Wright XG8's. I was told it would and it did.

I consider the CAS 1 and 2 to be noteworthy designs from that period.

I think it would be very cool if FirstWatt were to re-release the CAS 1. The obsolete parts would need to be subbed and perhaps other parts improved but generally the basic circuit could and should be left intact. The FW amp chassis would be perfect.

IMHO.

Graeme

Nelson Pass · 29th September 2009, 05:03 PM

How many shall I put you down for?

gl · 29th September 2009, 05:53 PM

No, no, please, I couldn't possibly accept a gift like that.

I'm just trying to help promote the success of FW in whatever small ways I can. Friends helping friends. Really.

Graeme

Nelson Pass · 29th September 2009, 08:13 PM

Maybe you would settle for a ride to BAF.

R-K Rønningstad · 29th September 2009, 08:43 PM

CAS1 schematics from the old barn!

R-K Rønningstad · 29th September 2009, 08:45 PM

Barn must have been empty.... Or me to trigger happy.

28th September 2009, 11:22 PM	#3
jam diyAudio Member Join Date: May 2001 Location: Charlotte,NC,USA	This brings back some good memories....... The ceramics need to go too. You could also replace the bridge rectifier with a high speed or soft recovery type and how about some 1% metal film resistors for good measure. Jam Last edited by jam; 28th September 2009 at 11:26 PM.

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28th September 2009, 08:01 PM	#2
gl diyAudio Member Join Date: Dec 2003 Location: Sierra Foothills - California	The CAS 1 was/is a great amplifier. The 2N5876 and "CLASS A6" marked transistors are the same part. I would definitely swap out the tantalums for aluminum electrolytic's like the Elna silks. Graeme

29th September 2009, 02:09 PM	#4
Mark Allen diyAudio Member Join Date: Jan 2008 Location: Bountiful, You-Taw	I owned one of those baack in the 80s. It was a pretty decent amp and was my first taste of the Mastrer's work...

29th September 2009, 04:24 PM	#5
gl diyAudio Member Join Date: Dec 2003 Location: Sierra Foothills - California	I borrowed one from a friend for a couple of days just to see if it would drive the Dayton Wright XG8's. I was told it would and it did. I consider the CAS 1 and 2 to be noteworthy designs from that period. I think it would be very cool if FirstWatt were to re-release the CAS 1. The obsolete parts would need to be subbed and perhaps other parts improved but generally the basic circuit could and should be left intact. The FW amp chassis would be perfect. IMHO. Graeme

29th September 2009, 05:03 PM	#6
Nelson Pass The one and only Join Date: Mar 2001	How many shall I put you down for?

29th September 2009, 05:53 PM	#7
gl diyAudio Member Join Date: Dec 2003 Location: Sierra Foothills - California	No, no, please, I couldn't possibly accept a gift like that. I'm just trying to help promote the success of FW in whatever small ways I can. Friends helping friends. Really. Graeme

29th September 2009, 08:13 PM	#8
Nelson Pass The one and only Join Date: Mar 2001	Maybe you would settle for a ride to BAF.

29th September 2009, 08:43 PM	#9
R-K Rønningstad diyAudio Member Join Date: Jan 2006 Location: Oslo	CAS1 schematics from the old barn!

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