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Aikido 24V headamp - Page 3

post #31 of 570
Originally Posted by fierce_freak View Post
-edit- Could the same be said for C11? It seems the same logic would roughly apply.
Yes, the same logic applies. It goes something like this: wherever a capacitor is needed, one is used. Sometimes such a large value is necessary that there is no other practical way than using electrolytic capacitor. These are, by design, usually polarized. In such a case one has to be careful about orientation, which is then indicated on a schematic. However, this indication does not mean that polarized capacitor was needed at the beginning, it just helps a builder not to mess it up.
post #32 of 570
I think non-polar is fine, just that the typical non-electrolytic cap is hard to get at the kinds of capacitance JB recommends. You're going to bypass with a non-polar anyway.


PS: on that tread heatsink, my smaller one does get pretty hot so I think I'm going to stick a bigger one on it when I have the case open again. I'd say its at maybe 70deg C - won't burn you but hot enough for to be uncomfortable to keep your finger on for say >20secs.
post #33 of 570
Listening impressions with HD650:

Again same setup as for my earlier comments with the k701, source is:

PC>>monica 2>> either aikido or millet max mosfet>>HD650 rewired with SPC in teflon.
The millet has a DACT type stepped attenuator, aikido has the optivol.

Short version: more or less the same effects as with the k701.

Longer version:

I based my listening around a few tracks of different types of music. I use Pierre Bensusan - Altiplanos as a bass test. Track 3 on this has some really low bass in the background. I use a Buddy Holly track "True Love Ways" which has the most amazing soundstage ever (you should hear on my quads!). Donald Fagen - Kamakiriad track 5 "Tomorrows Girls" for PRAT and sharp transients. Little Pink Anderson - Carolina Bluesman has a great version of St. James Infirmary. Simple arrangement where you can hear the singer leaning from side to side as he sings. Likewise Muddy Waters - Folk Singer - almost any track. I find some of the stuff from DSOTM very good for detail - if you can clearly hear some of the dialogue in the background you have good resolution. Kings of Leon Aha Shake Heartbreak for some good rock and Bob Dylan - Oh Mercy for a heavy dense Daniel Lanois production that challenges.

So what do I think;

To be honest I think the aikido has more dynamic range, better presentation and a fuller more well rounded sound than the max. The max sounds a bit more spacey - which initially I thought might mean that it would soundstage a bit better than the aikido, but in reality what it really means is that it sounds more recessed while the aikido is more lively. It clearly has more resolution too - things like the background stuff in DSOTM is easier to decipher. You know those quieter spoken bits - everyone will hear the "short sharp shock" bit, but the other stuff in there that's quieter. I'm pretty useless at putting into words what I'm hearing, but the aikido also sounds more intimate. Again this goes back to the soundstage bit mentioned above. If a singer is close miked, it sounds really close to your ears. Initially this appears like the soundstage is small, but then you hear something that genuinely has been recorded with a big soundstage and you can hear that clearly. Drums come alive more too, the ring of drums is more dynamic and the thump of a kick drum is very real and alive.

So that reads like I think the max is a POS. However that ain't the case. The max is a great amp and I think is one of the best offerings out there (and I own one and also a revMH millet too). But the aikido does better them. The aikido circuit is very clever, probably one of the best sounding ones out there. What I'm amazed at is the use of the LM317 in the output stage. I was pretty skeptical of this as JB had earlier talked about using a BUF634, but since they are unobtainium at the moment i thought the LM317 was just a stopgap. But no, they sound great.

So heres the thing: Say you are on the lookout for an amp to build. If you go tube, you can go for a standard high voltage amp, you can go millet max or you can go aikido. The aikido I think will cost about the same to build as a max, but while JB is very helpful and will answer your emails, there is not the same level of support available to you as with the max. That thread is pretty extraordinary in the DIY world. So if you have say one or 2 builds under your belt, then the aikido is well worth a shot. The other thing is that you get a full preamp in the deal. I have mine set as I said above with 6 inputs. You could easily wire in a tape loop too if you wanted. It is a fairly big board so it does need a fairly big case. Think full width (430mm) and at least 75mm high, 100mm would make life easier for you. I make my own casework so its not that much of an issue for me, but compared to the standard hammond case for the max, it might be an issue for some. The other detail that needs to be fully sorted out is the startup DC offset. Certainly a e12 delay would sort that out and is most likely what I'll end up doing. You need to factor that in to the build cost when your at it.

I hope that helps or gives some impression of how it sounds. I am looking forward to hearing what you think fierce freak. I am going to email JB with a link to this thread and see if any other who have bought the board and built it would be interested in posting some build info here.

post #34 of 570
Fantastic write-up, Fran. I also appreciate the detail you've gone into regarding support for build in case a newer builder is considering it.

I've been wanting to put together some form of Aikido as headphone amp for a good while, especially after hearing looser101's awesome high voltage build last November (which I felt on par with a single-ended B22, perhaps beating it out slightly). I also want to get a pre-amp out of the deal, so this looks like a winner to me.

The max certainly is a great amp (better than most commercial offerings I've heard). I'm glad to hear your impressions about the Aikido as they are though, as they seem to point to exactly to what I'd like improved/changed about the max's sound to bring it up to the next level.

It's funny that you should mention it as a large amp. I suppose it is, but one of the reasons I'm excited about it is that it will be a down-size for me, in terms of size I'm still looking at casing options, but that's something I'm going to leave open until after I've actually put the amp together. The three sizes I'm hovering between at the moment are 12x8x2 (tubes sticking out the top), 12x8x3 (if I decide to fit a hammond 159zc choke (60mH, 2a, 0.7dcr choke) in there), or 12x12x4 if I feel cramped (I don't want to go that large though, which is why I'm using a TREAD).

Also, thanks Fran for pointing me to SKA. I might pick up a GB150S amp and supply in a few months as reviews look good compared to price.
post #35 of 570
My case runs to about 430mm wide x 250mm deep x 150mm high. Basically it looks "tall". That's primarily though because I was using a recycled transformer which was way oversized and is the tallest thing in the box. On my other aikido I have the tubes sticking out of the top, but because of the heatsinks on this one they are enclosed.

I too looked at the SKA mps too - but they work into large enough dough when you factor in the power supply and so on.

have you seen the build thread on diyaudio for the naim clones on ebay at the moment? If I was to build a SS amp, I think thats where I'd go right now.

post #36 of 570
Yeah, with that transformer you'd definitely need to have a case of that size, though it would probably match well with the size of most commercial CD players.

It is a decent amount of dough for the SKA amps, but it's still less than what I'd planned to do (B24 when amb has it ready for production), and you can get one (GB150S) in a pretty compact form if you're careful with layout. I'm not in a hurry to do it, but it's certainly something I'm looking forward to.

I haven't been following anything over at diyaudio lately, except for the sabre dac which I'm looking forward to. I'll have to take a look, though.

As far as my own setup, I'm at a bit of a crossroads. I finished up my balanced b22 today (also setup as pre). It's a fantastic amp, no question, and I don't really expect tubes running at such low voltage to necessarily quite match up (even with the clever aikido topology). There is a large part of me that would like to simplify my rig, though, and downsize, both in terms of space and in terms of cash output. Sure, when I say my BOM comes out to around $450, that might seem like a lot, but when the amp I finished today cost at least three times that, perspective changes. I'm strongly considering selling the just-completed amp...I don't think there's an amp better than it out there (maybe different, not better), but being on that leading edge makes me want to only stay there in every aspect of my system, and that takes cash to do, cash I'm not sure is worth it (for me). I think pulling back just a hair from that edge would put me where I want to be in regards to a system to live with.
post #37 of 570
Whats the rest of your system fierce_freak? What speakers etc are you using? Can't that B22 be used as a power amp or am I dreaming that?

post #38 of 570
I have a nice twisted pear audio Opus DAC to the B22. I don't actually have a speaker setup, though I do have some Silver Iris drivers that I haven't made 'enclosures' for yet. The B22 can be used as a power amp if you build it with the proper heatsinking (this build actually started on proper heatsinks but changed into it's current form when I decided I'd like to try balanced again).
post #39 of 570
Just a little side note:

Originally Posted by fran View Post
The other thing is that you get a full preamp in the deal [Aikido]
Virtually every headphone amp can be used as a preamp. MAX too. After all, the title of the original Pete Millett's article was "Build a Low-Voltage Tube Hybrid Headphone/Line Amp".
post #40 of 570
Yeah, this is true. I think the thing I like best about it is that there are seperate outputs for both built into the board. Sure, it's a small thing, but it's something I appreciate.
post #41 of 570
I placed the order today for all the parts except tubes and case. I hope to order both next week.
post #42 of 570
Thought I'd post a pic or 2 to let you see how it turned out. I ended up putting in a e12 delay for safety sake. Panasonic FM caps for c4 bypassed with 2.2uF and then further bypassed with the KY42 russian 0.22uF caps.

Other than that its fairly standard stuff:

post #43 of 570
That's a beautiful case. I ordered the tubes last night, too, so all I have left to order is the case. Do you feel any differently about the amp now that you've had the chance to listen to it a bit more?

-edit- What did you replace the TREAD with? I see it has rounded corners on the PCB, and I've only seen that from JB's stuff.
post #44 of 570
What sharp eyes you have there!!

Yes, JB was kind enough to send me a new PS PCB that he is trialling. I built it up and had to install it just to keep it all aikido!

Beautiful PCB from him as always. It builds up very easy - the heatsink is a better one than on the tread, but it still is pretty hot. I don't know how good that gonna be long term. Its bigger than the tread too BTW.

No, feel just the same about the amp. Excellent.

Oh yeah, I put in the panasonic FMs. No real difference - I didn't try bypassing it with other caps, just kept the ones I had in so it would seem like the bypass caps are all important here (C3).

post #45 of 570
That's awesome. It's a very nice looking board (like all of the stuff JB does). I imagine he'll blog about it when he gets around to it. Thanks again for the info
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