Where to go from here? upping the tube ante

Budrew, I use the same Mullard 12AX7's (CV4004) and the 12AT7's from Upscale in my Mac and they are leagues better than the original tubes. That said, this vintage (80's) Mullard isn't supposed to be the best available.

I plan to try to find something better.

Now.. for the real deal. GEC KT88's will make your amp much more natural sounding. I was blown away when I discovered that having a pair of GEC KT88's in there along side the rest of the Svetlana KT88's made a monumental improvement in tonality and listenability. I since purchaed 6 more GEC's but discovered that the amp sounds best with Two Svetlana's and six GEC's. Running with all eight GEC's was too much of a good thing... Having a single Svetlana on each channel opened up the midrange without losing the splendor of the GEC. Nice.

I'd suggest you give the GEC's a try. The MC2102 is softer sounding than the MC2000 and as a result, may require less GEC's to get the same result.

Recently a friend of mine took this advice and inserted two GEC KT88's in his Conrad Johnson P8 amps - (which hold 16 KT88's). The improvement made by having only two GEC's in his amp was even more substantial than what I had in the Mac.

Bwhite, I thought you had a Berning ZH 270?

Did you buy one and not like it? It has always been on my audition list.

Bwhite, Thanks for the info. Are there any concerns about matching different tube brands in the amp at the same time? I found a review of several KT88s and they found the Electro-Harmonix to be the clear winner, though they did not include any GEC tubes, of which I've heard there are many variations.

Hi Fiddler, I've never owned a Berning.

Budrew... Just buy two GEC's and plug them in - you'll notice a new sense of emotion to your music. The improvement is rather significant.

Prior to trying this in my amp, I emailed McIntosh to find out if putting KT88's and 6550's in the same amp at the same time was okay. They replied saying - No problem, the tubes are electronically the same.

Look for GEC's with the 3 getters and the Z date codes. That's about all you need to know. Let your ears tell you the rest.

RE: Electro-Harmonix, I believe they are not exactly a tube company - they buy tubes from "real" manufacturers and then brand them Electro-Harmonix. If you read a review which said the EH are good, odds are they were the Svetlana KT88's which have received good press. Just so happens the McIntosh branded tubes in your amp are also Svetlana. Two GEC's and 6 Svetlana's in that amp will be a HUGE eye opener.

No joke.