Something really cool

[arthurs]

A friend of mine lent me these to check out as a possible acquisition. They are Western Electric 6L6 amps (11 really strong watts) made in 1958 for Western Electric by...McIntosh Labs! Unity Coupled Transformers and all, updated and brought back to original spec by a really talented tech. These cosmetically are pretty damn good for their age but could use some help. I just hooked them up to the Vosne Romanee and the Westminsters and holy cow these are something else! I'll report more as they settle in but these are some smooth, articulate beasts, really an incredible statement to US production from that era and to what McIntosh was doing back then....wow, just wow. Like 225 or 240 on steroids....

Happy 4th weekend to all, you know where I'll be!

 

[mep]

Are those amps running in Class A? A pair of 6L6 tubes can give you 25 watts in Class A/B.

 

[arthurs]

Here are specs, I'm guessing this is in Class A but will find out.

ELECTRICAL: 10w. Response 20-20kHz (+0.5 -0.5dB). Distortion 0.5%. Noise & hum -55dBm. Output impedance 2, 8, 16, 600 ohms matched and 600 ohms unmatched. 70.7V may be obtained from the 600 ohm unmatched output. Damping factor 10. Input impedance: 150 or 600 ohms balanced or unbalanced. 10k ohms bridging. Gain 63dB for 150 0r 600 ohm inputs. Uses McIntosh transformers M-174, 195 and 196. 6L6's are wired to function as tetrodes.
MECHANICAL: Bell system gray panel, hammertone gray chassis. Output terminals for all output impedances located beneath front panel. Input attenuators: 10 steps in 5dB/step and 0.5dB/step.
TUBES: 2-6L6 output, 12AX7, 12AU7, 12BH7, 5U4 rectifier.

 

[BlueFox]

Do the horizontal tubes have any type of restraint to keep them securely in the socket? Otherwise, I suspect over time gravity will loosen them, which might result in a gradual signal quality loss. Other than that, I like the design of hiding the tubes and transformer. Too bad it didn't catch on.

 

[arthurs]

No restraint I can see but they are in there really firmly. I do agree though, that would be something to keep an eye on over time.

 

[mep]

Do the horizontal tubes have any type of restraint to keep them securely in the socket? Otherwise, I suspect over time gravity will loosen them, which might result in a gradual signal quality loss. Other than that, I like the design of hiding the tubes and transformer. Too bad it didn't catch on.

ARC has mounted tubes horizontally for years in some of their amps one of which I owned. The tubes will not loosen with gravity. The tubes simply don't weigh enough to work against the strength of the pins making contact with the tube socket around its circumference. Having said that, if you are one of those people who pulls their tubes out daily to clean the tube pins and you have managed to ruin the tension of the tube socket, you might have an issue.

 

[arthurs]

ARC has mounted tubes horizontally for years in some of their amps one of which I owned. The tubes will not loosen with gravity. The tubes simply don't weigh enough to work against the strength of the pins making contact with the tube socket around its circumference. Having said that, if you are one of those people who pulls their tubes out daily to clean the tube pins and you have managed to ruin the tension of the tube socket, you might have an issue.

Thanks for that insight. If I keep these I would likely not pull the tubes very often. Getting a good chassis fabricated for them would be an important step. Listening again this morning, they are just so unbelievably rich and tonal with really solid control on the Westies...just beautiful.

 

[mep]

Since the description of the amps say the amps are wired for tetrode, I would assume you could run KT-66 tubes also. If so, if you bought two matched pairs of real NOS Genelex KT-66 tubes, you might be so blown away we would have to send a search party out to find you.

 

[Ki Choi]

In my early days of tube amp education, I realized how good the ~20W Heathkit W5Ms were driving a pair of Klipshorns. Most of the W5Ms came with replaced 6L6s but some of them came with original gray glass Genalex/GEC KT-66s. Magic!