Quick Question - Audio Note M1 or AR SP-6?

[john65b]

I have these preamps "on the line" - Which would you prefer?

Rest of system...Krell KSA-50 Clone, Magnepan MGIIIa...

Leaning toward the SP-6. Both are within $100...and 50 miles from home...

[HollowState]

Hi John,
I'm not familiar with the Audio Note M1, but I know something about the AR SP-6. Basically it's a close copy of the old Marantz 7 circuit using all 12AX7's (cascade + cathode follower phono into cascade + CF line out) and more modern (70's) parts. It's old enough that it will probably need some sprucing up if it hasn't been modified already. I've never owned an SP-6 but I've heard them. I have owned and listened through a 7 for many years. (still have two, not in use) They're not bad sounding but they don't have the airy fine inner detail of today's modern preamps.

I do know that the M-1 uses 12AU7's and that the phono stage is optional. So if you need that, be sure it's included. Since I have a little retro in me, I'd probably go for the AR too. I also think it looks better then the M-1 which is just a plain black box. And it appears to be more flexible with inputs and switching. I can't find a circuit of the M-1, but here's a link to the SP-6.

http://www.arcdb.ws/SP6/SP6.html

Actually the Maggies you have deserve better then either if these.

Victor

[john65b]

Hmmm, I have an Audio Note M7 clone, but looks nothing like the real one with 6072 tubes. Is is basically a 5687 tube in parallel modded with LED Bias. It does sound nice, but I have a bug up my **** to try a "real" pre.

Also have a Aikido that is not yet built....and I had a Foreplay III that I really liked too...regret selling it...

I appreciate your opinion...in your view, what would best these two in the sub $600 range?

[limono]

There were a few AN M7 circuits ,the linestage was based on 5687 , full preamp on 6072. Some were "silver" some used copper PIO's.
I did have M1(phono) unit with failed power transformer and I built tube based PSU with choke . It's a really good sounding unit. Audio Research always leaves me cold ,along with Magnepan and I have and access (friendly dealer) to top of the line of both. So yes, AR seems like a better choice for Maggies.

[john65b]

Well I bought the AR SP-6C. So far I am quite happy. With one isues...

The gain is a bit high-ish (and yes, I have reduced the gain switch on the back of the unit)...

I know the linestage tubes are 12AX7/12AX7/6922.

I am thinking of swapping the 12AX7s for 12AT7 to reduce gain...also have a number of 12AU7's too, but that may be too much of a leap from the 12AX7...

Also have a 6N1P that I could swap the 6922...

Thoughts??

[SY]

Not only will the 12AT7 be very suboptimal at those operating points, the gain will hardly change- it's set by the feedback loop. Even in open loop situations, the difference would be about 3dB, not exactly night and day. More feedback will drop the gain but will be a bit tricky to keep stable. Still, it could be worth a shot if you've got a scope and square wave generator to adjust the compensation.

[kevinkr]

IMO Just build the Aikido board, put it in a really nice box with all the features you need and leave the SP-6 to the collectors. It will never equal any of the newer designs in transparency and you will only be able to reduce the gain very slightly by tinkering with the feedback network before you start to encounter linearity issues with the CF at the output of the line stage.

Enjoy it the way it is, use an external resistive pad at the power amplifier input to fix the excessive gain issue temporarily while you build the Aikido..

A confession: Around 20yrs ago I would have killed for an SP-6, (or even an SP-3A, the SP-10, 11 and 12 being completely out of reach) and decided to clone the thing. Ultimately I built a copy of that line stage, and was incredibly disappointed in the overall performance although it measured nearly flawlessly. (I guess over 40dB of feedback will do that for you.) I thought it sounded dreadful, my answer to that started my odyssey in audio design and ultimately an audio business which kept me very busy for the better part of a decade until the crash in 2000 killed my prospects.

[john65b]

Well I have a fully populated Aikido, power supply board with rectifier tube, and both transformers. Also the pair of 6N1P and 5687 too.

I also have a very nice condition Adcom GTP-740 preamp that has issues (keeps re-booting, thought I fixed it but problem keeps returning).

I was looking at the Adcom the other day and realized I could rip out the preamp guts and keep the power supply and remote control volume pot. Drop in the Aikido with its power supply board and tranformers...maybe drop in a nice DAC too...I may be able to take a 6 volt DC from the Adcom power supply to feed the 6NP1 and 5687 heaters....

Hmmm, I have been putting off the Aikido for over a year now...maybe a good time to pick it back up...

[kevinkr]

Originally posted by john65b
Well I have a fully populated Aikido, power supply board with rectifier tube, and both transformers. Also the pair of 6N1P and 5687 too.

I also have a very nice condition Adcom GTP-740 preamp that has issues (keeps re-booting, thought I fixed it but problem keeps returning).

I was looking at the Adcom the other day and realized I could rip out the preamp guts and keep the power supply and remote control volume pot. Drop in the Aikido with its power supply board and tranformers...maybe drop in a nice DAC too...I may be able to take a 6 volt DC from the Adcom power supply to feed the 6NP1 and 5687 heaters....

Hmmm, I have been putting off the Aikido for over a year now...maybe a good time to pick it back up...

Sounds like a good plan.. I would recommend though that you include a filament and high voltage supply in the Adcom pre-amp box, that way if someday you want to use it with another power amplifier (hopefully a tube one.. ) it will simply be a matter of moving a few audio cables. Power supply capacity and potential ground loops are other issues you might encounter stealing power from the amp..