Mc250 vs mc240

[c_dk]

Digging in a storage closet a few days ago and discovered 7 additional RCA and 1 Sylvania 6L6GCs that DOB pulled out of my MC240s 20 years ago, because they weren't good enough. He had Mike send me the last of his GE6L6 stash because otherwise we needed to go to Grove Tubes from Canada to get decent tubes.

Twii why do you think the sound became inaccurate with higher power, were the mid and high frequency drivers compressing?

 

[tuffstuff1]

Thanks for the interesting posts twiii. This is good stuff.

 

[Pio1980]

When I refurbed a pair of Mac 75s for a friend, I checked them at clipping on a signal generator and o'scope thru a dummy load for power and symmetry to ensure the tubes were good and reasonably balanced/ matched. Randomly swapping tubes would affect how the amps will sound, especially when pushed hard. One must ensure the amp is working properly to make valid judgements on the sonics from making changes.

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[62caddy]

According to Mc, the Unity Coupled Circuit design eliminates the need for critically matched output tubes.

 

[MissionX]

I know this is very long time ago, but I am going to try a MC250 after my experience with my MC225 for 5 years. I have done some tube rolling on it so it is much better than stock (especially the Tesla stuff-which I also put into my MX110). Will see if what they say is true for the MC250 (being very close to the MC275).

It's been awhile........Did you ever compare the two amps?

 

[twiiii]

How about a MC 2505 and 240 comparison? when new a 2505 would clip at 2% around 77 watts a MC 240 at 58 or 59 watts. The SS amp had about a 1/3 distortion at the extremes at rated power. SS unit had about 6 db better signal to noise un weighted. But the early units had a harsher HF sound until and update was added that really reduced IM distortions. I owned both at the same time the 2 240's in mono for the Main speakers and the 2505 to replace the MC 60's for remote speakers. I will say a 275 is more dependable than a 240 and smoother sounding. With my Bozak speakers a 2505/250 is to mushy and warm in the bass so I preferred the 240's running mono and before that with one in stereo. The 240 you can push nearer the envelope with out getting irritating sounds, where a 2505/250 would start making you feel ill at ease. A 2505 reproducing cymbal sounds would go crazy when approaching it limits where a 240 would not, going kind of soft till really over driven. When over driven both sounded horrible but in different ways.

If you have well damped woofers the 2505 has the clear advantage, if you don't having horn loaded or ported or Labyrinth speakers its a real mixed bag. I would choose a 2505 as you don't have near the service issues of the hot running 240. I was always replacing tubes to keep mine with in specs. That was stopped when I upgraded to 275's in 69 and replaced the MC 60's. Now if you really want a warm tube sound then you want a pair of MC 60's or 30's using tube rectifiers. Its a different experience for sure. Loved 60's when driving Altec 604 monitor speakers in large cabinets un-ported.