1614 vs 1614/6L6GC

[cspyon]

As you know, MC30 has both versions of output tubes: 1614 vs 1614/6L6GC
As far as I know, the early models have the lettering 1614 on the chassis, and the later models 1614/6L6GC.
Does anybody know exactly when McIntosh began to produce the later models? Any design difference in both models? Do you recommend buying a pair with close serial numbers or is it okay to buy a pair with one 1614 and the other 1614/6L6GC?
By the way, according to the information available on the website, this unit was Sold from July 1954-June 1962. S/N:10,000~23,655&1E001~10E592(14,246 UNITS)

 

[Refugee]

One major difference is that the 1614 was mostly intended for RF power operation. That makes me think that most of its quality testing during production was done in the MHz ranges. That's not to say it's impossible that they sound great, but 6L6's are made for audio.
The other is that the 1614 has a metal envelope that would not be as aesthetically pleasing as the glass envelope of the 6L6. Sound quality is first but visually pleasing is a close second for me. Maybe it will have a cool retro look but I like all the reflective surfaces on these amps. I'm one of those fools that like to stare at my stereo and actively listen.
I would think you could simply sub these tubes out on an older and a newer unit (**disclaimer: please double check the spechs before you do**).

 

[twiiii]

I remember Davie O'brien of Mcintosh clinic fame saying the 1614's weren't desirable anymore as they tended to be microphonic. You didn't want them near the speakers especially with strong horn loaded systems or speakers that produced loud low pulsing bass.

 

[cspyon]

I remember Davie O'brien of Mcintosh clinic fame saying the 1614's weren't desirable anymore as they tended to be microphonic. You didn't want them near the speakers especially with strong horn loaded systems or speakers that produced loud low pulsing bass.

I have a quad of RCA metal 1614, but hardly use them.