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Old 30th January 2010, 09:17 PM   #1
brianco is offline brianco  Ireland
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Default THRESHOLD CAS-2 poweramp.

A very simple question! Does anyone know/remember if the mains transformers on these amps can be reconnected to take 230-240vAC mains electricity? If so I shall be delighted to hear - either way - as I have an opportunity to acquire one which appears to be in good condition!

I would also very much welcome a copy of the circuit schematic....please.

[Are you out there Zen MOD????]

Many thanks.

Last edited by brianco; 30th January 2010 at 09:20 PM.
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Old 31st January 2010, 01:06 AM   #2
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Here's what I've got:

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File Type: jpg cas1 sticker.jpg (53.5 KB, 1108 views)
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Old 31st January 2010, 01:12 AM   #3
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally Posted by brianco View Post
....

[Are you out there Zen MOD????]

.......
I am ...... but who needs me , when real McCoy is there , too .......



(even if schm looks as borrowed from this ACME Gentleman )
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Last edited by Zen Mod; 31st January 2010 at 01:17 AM.
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Old 31st January 2010, 01:23 AM   #4
Zen Mod is offline Zen Mod  Serbia
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can't be much different
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File Type: pdf Threshold CAS1.pdf (74.1 KB, 632 views)
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Old 31st January 2010, 12:23 PM   #5
brianco is offline brianco  Ireland
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Many thanks Mr Pass and ZM.

Does anyone know if the PS transformers are limited to US voltages or changeable to UK/Euro voltage? Some of you guys in the Pacific Rim countries may also know the answer?
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Old 31st January 2010, 01:38 PM   #6
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By a CAS-1 exemplar that I had to repair service 2 years ago, it was possible to set both 115V and 220V main voltage (see my own created pdf schematic include power supply transformer).
On the other hand, I cannot rule out, that there are versions (only for the us marked e. g.), where only one primary winding is present for 110VAC mains voltage.
If you have such version, you need an additional isolation transformer from 220-240V VAC to 110 VAC !!! Otherwise, the built-in transformer would be destroyed.
Check the number of windings, and connections on the primary side of transformer in your exemplar - the power supply schematic of CAS-1 could be helpful
I discover a currently ebay auction: Item number: 270510641211
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File Type: jpg Threshold CAS1.JPG (16.0 KB, 927 views)
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File Type: pdf C_tmp_Threshold CAS1_ckt.pdf (21.6 KB, 463 views)

Last edited by tiefbassuebertr; 31st January 2010 at 01:54 PM.
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Old 31st January 2010, 01:40 PM   #7
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I have a prototype CAS-2 I purchased from local store when I lived in Pilot Hill, Ca. Front panel has no markings. Only thing on front panel is power switch and power-on LED. Back panel is complete and marked including stick-on label, but without any SN, date, etc - just blank.

My CAS-2 has only one power supply transformer, one bridge rectifier and eight large capacitors. The primary has three black wires, only two are connected for 115VAC. This transformer is slightly thicker than the ones in my CAS-1's.

From pictures on internet, production CAS-2 had two transformers, two bridges and 2 sets of capacitors. Also had LED meter on front panel.

I also have schematic of CAS-2 I got from Threshold applications engineer in 1990. Schematic is in California, I am in Florida until May.

CAS-2 has three TO-3's as output cascode devices. CAS-1 has two.
CAS-2 has two TO-3's as output devices. CAS-1 has one. Rest of circuit is the same, excepting some resistor values and capacitor values.

Schematic has + and - 57v supply. My CAS-2 measures + and - 50v.

Sorry, but don't think I answered your question.

Last edited by JamesBrennan4; 31st January 2010 at 01:51 PM. Reason: corrected number of capacitors
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Old 31st January 2010, 01:56 PM   #8
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because ebay photos deleted after few months, here three photos from
Item number: 270510641211:
Attached Files
File Type: pdf CAS-2 front.pdf (51.2 KB, 310 views)
File Type: pdf CAS-2 open.pdf (135.9 KB, 305 views)
File Type: pdf CAS-2 open-II.pdf (152.6 KB, 297 views)
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Old 31st January 2010, 02:35 PM   #9
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Thanks for the pictures.

I would think you could rewire the 115v primary of each transformer to be in series, just like the "tiefbassuebertr" power supply schematic shows. The two primary's must be wired in parallel for 115vac operation.

I'm listening to my CAS-2 right now. Have never considered another amplifier.

Contrary to what you read as output power. CAS-2 was rated at 75 watts (8 ohm load) for low distortion and 100 watts for high distortion. Output voltage will start to limit at 90 watts.
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Old 31st January 2010, 03:49 PM   #10
Zen Mod is offline Zen Mod  Serbia
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brianco - seems that you're one lucky bstrd



(NB that I didn't say that you don't deserve that )
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Last edited by Zen Mod; 31st January 2010 at 03:52 PM.
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