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Old 28th September 2009, 07:54 PM   #1
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Default Threshold CAS 1

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?
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Old 28th September 2009, 09:01 PM   #2
gl is offline gl  United States
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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
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Old 29th September 2009, 12:22 AM   #3
jam is offline jam  United States
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Default 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; 29th September 2009 at 12:26 AM.
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Old 29th September 2009, 03:09 PM   #4
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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...
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Old 29th September 2009, 05:24 PM   #5
gl is offline gl  United States
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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
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Old 29th September 2009, 06:03 PM   #6
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How many shall I put you down for?

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Old 29th September 2009, 06:53 PM   #7
gl is offline gl  United States
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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
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Old 29th September 2009, 09:13 PM   #8
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Maybe you would settle for a ride to BAF.

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Old 29th September 2009, 09:43 PM   #9
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CAS1 schematics from the old barn!
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Old 29th September 2009, 09:45 PM   #10
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Barn must have been empty.... Or me to trigger happy.
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