My Magnapan Tube experiment

[ehoove]

I have a pair of Tri-amped Hardwood Framed MGIIIa's that I have been running using Acurus A200 Power amps on all 3 drivers. Then I picked up a pair of Quicksilver Mono Blocks and ran the ribbons with them (2 ohms). after that I moved them to the mid range panels (4 ohms) and added a bit of boost. Both applications provided great results with the tubes on the Midrange panels the winner. I recently picked up a pair of Conn 6L6 PP mono blocks and installed them to drive the midrange panels, and I am amazed at the increase in lower midrange bloom I am hearing. Is this a good thing? I am not sure, as I think the Quicksilvers have a lot more speed and control over the panel. The quicksilvers are more refined and articulate, but the Conn mono blocks have more drive, and have that tubey sound. Thoughts?
Regards,
Jim

[ehoove]

I have heard some of these old organ company tube amps sound stellar. Wurlitzer, Conn, Allen etc. I have wanted to tinker and upgrade a pair to see what improvement in a simple pp tube amp can be had. These will be my tube audio project for 2015, and I will post as they near completion.

The main rig is back to previous form with tubes on the midrange and SS on the subs, bass panels, and ribbons and all is good in my main rig world! :^)

Regards,
Jim

[jdandy]

Jim.......Looking forward to following tube amp adventures.

[ehoove]

I plan on starting upon my return from vacation next month, I'll keep you posted.
Regards,
Jim

[cma29]

[ehoove]

Well I tried a few things first. I switched out the computer grade power cords with better ones, and built a new set of lifted shield interconnects using DHLabs Silver Sonic II Cable and WBT RCA's. I also switched out the NOS Sylvania 6L6 tubes for a matched Quad of 6BG6GA Raytheon's using adapters, and used the Audiomagic Excaliber II speaker cables instead of the cables supplied, and the result is night and day! These monoblocks may have some real potential, which I suspected due to the size and weight of the transformers. They have more warmth and drive than the Quicksilvers as Midrange Amps. I am running them from 550Hz to 3850Hz with 12db Butterworth slopes.

Regards,
Jim

[ehoove]

Today I pulled the Conns and inserted a pair of Quicksilver M60 mono Blocks I just picked up. Wow, what a difference. Double the power via 4 EL34's yields control, detail, and liquidity. Now to add the Quicksilver 30 watt Mono Blocks to the ribbons. This will allow me to pull the Conn Mono Blocks out of service to work on them. Aha, the rabbit hole beckons!
Regards,
Jim

[cmalak]

Jim....sounds like fun. Maggies have always mated well with ARC tube amps, and your MGIIIas despite being quite insensitive at 84dB they are only a moderately tough load to the tube amp but present a relatively flat impedance curve so from that perspective are somewhat tube-friendly. My guess is dynamics are going to be limited with the tube amps as compared to the tri-amp Acurus A200 setup but you will gain in the areas of tonality, dimensionality and probably bass depth and texture, although you might lose some articulation and punch in the bass. Just theorizing here, so how would you describe the comparison, understanding full well that the tube amp configuration is a bit of a moving target?

[ehoove]

The tubes added some upper bass warmth to the speakers, but the Acurus A200's are still driving the pair of subs the bass panels, and ribbon tweeters. Overall some of the midrange speed and articulation are missing, but the silky liquid vocals and percussion presentation more than make up for it. Vocals are not as forward in the sound stage, but the imaging is excellent. I will try to move the other Quicksilver mono blocks (30 watts each) to the ribbons tomorrow, but for now the MGIIIa's sound as good as they have to me. I have not noticed a loss of dynamics at high volumes with the tubes, but I don't really crank them past what is comfortable listening levels to me(which is still quite loud). I'm running my subs from 42Hz down, running the bass panels to 32Hz with reversed polarity due to the slope employed.
Regards,
Jim

[cmalak]

Jim...thx for the response. Sounds like a nice improvement. Will be interesting to see how the second Quicksilver amp on the tweeters change things up