Cyrus PRE or ACA7

careful with that soldering iron, Eugene
Ianmac
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Cyrus PRE or ACA7

Postby Ianmac » Fri Aug 23, 2019 11:00 am

I have been looking for an old CYRUS PRE to rebuild as pre amp to drive Ncore balanced input amps.
To date nothing has appeared (other than the dreaded ebay where one just sold for 3 times its real value !)
Im broadening my search to include an ACA7.5
I have full info on the old pre and despite what the cyrus paperwork says its not a fully balanced output Its a pseudo balanced output derived from a resistor network. One of my intended mods was to fit an electronic single to balanced convertor.

Does anyone have a circuit diagram or the full service manual for the old ACA7 or ACA7.5

--so I can check whether its output stage is electronically balanced or it follows the "kid on " balanced output on the PRE.

I have built a temporary pre using an old dead 111i. Gutted the power amp out. Fitted smaller mains transformer and two "Jung" regulators and a clean 5v supply for the VC chip. Fitted an electronic single to balanced converter. fitted two XLR's, works fine and will get me by till I sort out a PRE or hopefully an ACA7.5
Sytem 1.
Engineered SA-NMR Renderer (Ianmac PSU) :BelCanto CD-2: Technics 1200 (Ianmac Bearing + Ianmac PSU+Ianmac arm): DACT-Ianmac phono pre >Benchmark DAC2 HGC>2*Ianmac-Hypex NCore monos> ATCSCM40 : Ianmac filters
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Engineered SA-NMR Renderer (Ianmac PSU) :Topping D50 DAC.Sony CDP D11 pro: 2*-Hypex Ncore monos: Kef ref1-2.
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mojo
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Re: Cyrus PRE or ACA7

Postby mojo » Fri Aug 23, 2019 1:04 pm

Sorry, don't have either, nor a circuit diagram, but IIRC the Pre had a motorised volume control, didn't it? The only one that did? If that's correct, I would think that one of the ACA's would be a better choice, because they use the "gain cell" controls, which ~should~ (in theory) be more reliable long-term?

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Re: Cyrus PRE or ACA7

Postby Ianmac » Fri Aug 23, 2019 6:04 pm

Yes your right the PRE uses a motorised volume control, and there are a few comments on the net about reliability issues and availability of spares.
An ACA7 may be a better bet but Im reluctant to line up a relatively heavy set of mods without a circuit. Ill trawl a while to see if I can pick one up.

The canibalized 111i is performing very well, a big performance lift gained by changing the power supply to use Jung regulators. I had a + and - board in the workshop from an earlier phono pre I built. Conversion from single to balanced output uses a £9 board from China again fed from the Jungs.
Ive just fitted a phono board right next to the input connectors and well screened from the outside world so ill see how that goes.
Sytem 1.
Engineered SA-NMR Renderer (Ianmac PSU) :BelCanto CD-2: Technics 1200 (Ianmac Bearing + Ianmac PSU+Ianmac arm): DACT-Ianmac phono pre >Benchmark DAC2 HGC>2*Ianmac-Hypex NCore monos> ATCSCM40 : Ianmac filters
System 2
Engineered SA-NMR Renderer (Ianmac PSU) :Topping D50 DAC.Sony CDP D11 pro: 2*-Hypex Ncore monos: Kef ref1-2.
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Ianmac
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Re: Cyrus PRE or ACA7

Postby Ianmac » Mon Aug 26, 2019 8:01 pm

I have failed to get any response to my request for tech info on the ACA7 from across a few forums
My project is abandoned and I will progress with a DIY pre amp build based on a relay switch, Buffer, Resistor Attenuator, Buffer and conversion to Balanced then a Line Driver. Power supply is already well under way.

Its sad that Cyrus don't give any info on their old product that they no longer support. When it fails I suppose we just have to bin it for Landfill ! --- Do Cyrus claim to be a green company ??

Well someone seems able to get some tech info, I noticed Clones of Cyrus 200 amps are now appearing on Ebay.

https://www.ebay.co.uk/itm/One-pair-DGP ... SwiHpZ90ZG
Sytem 1.
Engineered SA-NMR Renderer (Ianmac PSU) :BelCanto CD-2: Technics 1200 (Ianmac Bearing + Ianmac PSU+Ianmac arm): DACT-Ianmac phono pre >Benchmark DAC2 HGC>2*Ianmac-Hypex NCore monos> ATCSCM40 : Ianmac filters
System 2
Engineered SA-NMR Renderer (Ianmac PSU) :Topping D50 DAC.Sony CDP D11 pro: 2*-Hypex Ncore monos: Kef ref1-2.
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mojo
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Re: Cyrus PRE or ACA7

Postby mojo » Mon Aug 26, 2019 9:15 pm

Ianmac wrote:I noticed Clones of Cyrus 200 amps are now appearing on Ebay.


I've seen these before, but as far as I could see there isn't any similarity at all to any Cyrus amp that I've seen - I think they are just using the name because it's well known.