Vintage Asylum

RE: Well, that's pretty cool....

71.194.241.37

In Reply to: RE: Well, that's pretty cool.... posted by doodlebug on May 11, 2008 at 08:52:50

Thanks for the heads up Julien!
Just a bit of info to add to the review...
1. That was a very early Cit II - the large meter in the back is what tells you it was early. The later units had some small changes, but nothing that would change the reviewer's impressions I'm sure.
2. The ability to handle difficult speakers is greatly dependent on the power supply and the peak power the amp can generate. One of the goals of my kits for the amp (as an example) is to lower the power supply impedance across the entire frequency range and increase the reserve/peak power the amp can deliver. With careful parts selection and some judicious revisions to the power supply circuitry this can be accomplished. The results are the amp can handle much more than the 60 watt RMS power rating would lead you to believe. Peaks of over 150 watts are within the realm of the updated amp. My AR-9s (87 db sensitive) and the updated Cit II are magical!
As well, there are significant gains to be had with some revisions to the grounding scheme.
3. While the Genalex reissue KT-88 remains my tube of choice for the Cit II (with the demise of good Ei KT-90s), the performance of the KT-88 EH is excellent. It's is a bit lighter in the deep bass, but the mid and upper bass regions are superb (as the reviewer noted). It has a bit more top end than other KT-88s which means it can be used to tune a system that may be a bit bass heavy. If you bi amp and use the Cit II on the top then use the KT-88 EHs. They're perfect for that application, and less expensive.
4. Shuttle astronaut, Audio Express author, and Nelson Pass' audio designer associate Dr. Norm Thagard and I determined a few years ago that the Cit II responds well to use of high Gm tubes in the V1/V4 voltage amp positions. We find RCA and Sylvania tubes to have higher Gm than GE generally. The more rare brands such as Hytron, Tung-Sol, etc. are good in the voltage amp sockets too.
For the phase inverters GEs are fine, but to get the last bit of performance out of the amp use a high Gm tube (even a GE if you have high Gm examples on hand) in the voltage amp sockets. You'll get a tiny bit more power and lower THD.
5. As has been mentioned, the amp MUST be updated before you can expect much out of it. The amp in the review was built in 1961 or 1962 which makes it 46 or 47 years old. Even if an amp still amp still works after all that time it's working at a fraction of its capability. Plus it WILL fail, and soon.
All new power supply stuff, new coupling caps (save your money - "boutique" caps are not needed), MANY new resistors, new RCAs and speaker terminals, new AC balance pots, new octal sockets, some new wire and input shielded cables, and of course good tubes are ALL needed on virtually every unrestored Cit II. The iron is usually fine, although a few power trafos have failed. If it's just the bias winding that has failed there's an easy fix, drop me a note if you need help. But sadly a VERY few do fail and must be rewound. Doc Hoyer at Audio Transformers can do them, and possibly Heyboer as well (I can't confirm Heyboer as capable yet, but they are a good outfit!).
Sorry to be so long-winded, but I thought this info might help flesh out the review.

Edits: 05/13/08

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