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Akai M-8 R2R SE pentode amplifiers

Yeah, my main reason for wondering about using the Sansui's preamp, is to be able to use several different sources, mostly a tuner & TT. I'm assuming the voltage is correct then, and I'd just need to leave the volume on the Roberts pretty far up, then use mostly the volume on the Sansui, right? :scratch2: Sorry if I sound like an idjit, but I'd rather do that than screw something up. :yes: As a bonus, both my Sansuis & the Roberts have black faceplates with silver knobs, so they'll look great together. :smoke:
 
OK, I got mine out of the case finally. :smoke: The only thing I'm kinda concerned about, is the wires I had to cut coming from the R2R itself. I suspect most if not all of them are mentioned but not fully explained, in the "remove unnecessary wires" statement. Does anyone have the service manual, or wiring diagram, so we can make sure what we're doing? That would also be really useful, if anyone else is thinking about mounting things on a different chassis, at some point in the future. :naughty:
 
I really need to get to work on the Akai/Roberts amps I have. I have a pair at Jay's, two here and a line on two more pair. Need to get a cap list made and an order any.

Anyone already have a cap list for these amps?
 
OK, here's a list of the caps, but don't shoot me if I missed any. ;) The large one by the tranny is the only multi-cap, 350V 20+20MFD. Then the following list is for one amp, so double it for a pair. 2x 315V 22uF, 3x 400V .02uF, 1x 350V 3.3uF, 3x 400wv .01uF, & 3x marked a little different, 25wv 30sv 25uF. There's also one 100V .05M that goes to the DIN connector, but I'm going to figure out how to just eliminate that, if possible. Now there are several components labeled Fox of various values, gray in color, and I "think" those are resistors, right? :scratch2: I'd think if we want to check those, that would be done after recapping. Feel free to correct me, & help me figure this stuff out. :yes:
 
spaceman said:
OK, I got mine out of the case finally. :smoke: The only thing I'm kinda concerned about, is the wires I had to cut coming from the R2R itself. I suspect most if not all of them are mentioned but not fully explained, in the "remove unnecessary wires" statement. Does anyone have the service manual, or wiring diagram, so we can make sure what we're doing? That would also be really useful, if anyone else is thinking about mounting things on a different chassis, at some point in the future. :naughty:
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I have an M-8 and will be interested in your results.

My Edit: I snipped misinformation out of my post related to mic preamps. Thanks Rex. I was thinking of the more detailed explaination that the original author of had documented the modifications needed to tweek the preamp for mic performance.
 
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spaceman said:
OK, here's a list of the caps, but don't shoot me if I missed any. ;) The large one by the tranny is the only multi-cap, 350V 20+20MFD. Then the following list is for one amp, so double it for a pair. 2x 315V 22uF, 3x 400V .02uF, 1x 350V 3.3uF, 3x 400wv .01uF, & 3x marked a little different, 25wv 30sv 25uF. There's also one 100V .05M that goes to the DIN connector, but I'm going to figure out how to just eliminate that, if possible. Now there are several components labeled Fox of various values, gray in color, and I "think" those are resistors, right? :scratch2: I'd think if we want to check those, that would be done after recapping. Feel free to correct me, & help me figure this stuff out. :yes:
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Thanks Spaceman. Time to get an order started. I guess A.E.S. may be the best spot to order these?
 
That's where I get my stuff. You may find cheaper (by a hair), but AES is hassle free and has what you need everytime.
 
Unfortunately I missed the ones close by. Guy had never seen them powered and was not sure if they powered up and was firm on his price.

I'll keep my eye out for more so you can have a set Jay. I need to catch a train or plane or summin over your way and we could each build one amp or one set of amps and check them out.
 
Welp, I got my trannies rewired, & so at least found the main hot wire to the tape deck & removed it. :thmbsp: The rest are most likely various line in/line outs, for the deck, plus the DIN connectors, that still need cleaned up. I rigged up an old interconnect to use for the speakers, from the front external jacks, & ran in a Sansui tuner through a Marantz 1060, & fired them up. It sounded OK, but the first time, I was using the old 4" drivers (expendable), so not really great. Then I decided I might as well test those 12"s I pulled from an organ recently, & that made a huge difference, obviously. :yes: I still need to recap & clean up those extra wires, but so far I'm REALLY liking what I hear, even with the stock tubes (mine are all original NEC). :smoke: BTW, watching the bouncy meters, I couldn't help thinking they'd look even better with some color, kinda McIntosh-ey. ;)
 
spaceman said:
Welp, I got my trannies rewired, & so at least found the main hot wire to the tape deck & removed it. :thmbsp: The rest are most likely various line in/line outs, for the deck, plus the DIN connectors, that still need cleaned up. I rigged up an old interconnect to use for the speakers, from the front external jacks, & ran in a Sansui tuner through a Marantz 1060, & fired them up. It sounded OK, but the first time, I was using the old 4" drivers (expendable), so not really great. Then I decided I might as well test those 12"s I pulled from an organ recently, & that made a huge difference, obviously. :yes: I still need to recap & clean up those extra wires, but so far I'm REALLY liking what I hear, even with the stock tubes (mine are all original NEC). :smoke: BTW, watching the bouncy meters, I couldn't help thinking they'd look even better with some color, kinda McIntosh-ey. ;)
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Hey don't forget to document with pics along the way. Might come in handy should you need to reverse a step or two and of course us voyeurs need a fix every now and then.
 
Well, like I say, they still need recapped, which includes the cap for the tone pot, but otherwise, yes, I used his instructions. I removed all the slide-switch linkage, & replaced the one odd-shaped screw with a normal-headed one, so the slide switch itself is mounted securely. I can't wait to get them recapped, to see what's missing from the top-end. One thing's for sure, the bass is not missing, sounds real nice. :smoke:
 
OK, time again to admit I'm a dummy. :D Those DIN connectors just unplug from the amps, as clearly shown in the manual. That's the blue covered largish wire bundle, that also has a receptacle mounted to the case. You can save yourself a lot of time & trouble by unplugging them before pulling the amps. Mine were pretty stiff, & needed to be rocked out, kinda like a tube, is how I missed it. ;) I listened to them for quite awhile today, off & on, & noticed the very high frequencies missing, so that cap on the tone pot is pretty important. But all that's noticeable is parts of cymbals, higher keyboards, & such, so it still sounds pretty darn good. :yes: They played Pink Floyd's "Saucerful of Secrets" on Think Pink tonight, & the drums & organ sounded really good, with excellent bass & mids. :music:
 
Swapped my speakers to the Stephens Trusonics with horns, & that brought back a lot of the highs. Then I went ahead & rolled in a couple Mullards, and that really helped. :thmbsp: I still want to try it with Telefunkens & Baldwins (I think they're Sylvania), but it's gonna be tough to improve on the Mullards. :music:
 
I posted a thread about the Akai M8 alooonnng time ago on diyaudio.com . Here's the thread:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=33734

There might be some useful info there.

I now have the M8 and it's cousin the Roberts 770. I have sold another M8 (STUPID, STUPID) before I realized what they were capable of (oh well, live and learn). tracker-x's info on this thread are great!!!!
I have been collecting a bunch of audio gears for a few years now and I can honestly say that these little guys are very well built and deserve the TLC you give them. I would say that they sounded very good to my ears. I'm not biased to tube gear. I just think it's very cool that glowing tubes that can produce beautiful music. Besides, tube schematic is easier to understand than solid-state. I just think that if the music sounds good, it sounds good regardless of if it's flea SET, P-P, Class-A, B, Triode, Tetrode, Pent, blah, blah, or for that matter chip and Class-D. They each sounds good in their own way.

Happy listening! :music:
 
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