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MiniMax Hybrid or Speedball Crack?

post #1 of 21
8/31/10 at 7:43pm
Thread Starter 

As the title suggests...I'm having a bit of a problem deciding which of these projects to undertake and advice from owners would be appreciated.  I've pretty much melted the search feature on this forum trying to find a head to head comparison of these two amps; one reviewer did review both amps, but used 32ohm cans which kind of throws it out the window as the bottlehead is an OTL design and obviously not meant for low impedance(no disrespect there as it was a great review, just doesn't help me out).

 

What draws me to these amps are their accessibility for a person getting started and their apparent bang per buck ratio...and the great communities that help builders.  Yes, this will be my first desktop amp.  I built a couple of cmoys and learned to read color coded resistors because I sourced my own parts, which was all well and good, but behold....these both come in kit form so I can get to building, which I enjoy, and get to listening, which I also enjoy, in a timely fashion. 

 

What I am, thus far, unsure of is the end result.  From what I have gathered pairing 12FK6 tubes with the millet should do pretty well with lower impedance cans and using 12AE6 tubes should work for higher resistance cans.  The bottlehead is pretty much for high resistance cans only.  This seems to make the millet more versatile and I intend to pick up some AKG701s at some point(probably better on the millet), but I have already set out to pick up some Beyer DT990(600ohm) first which will obviously work very well with the bottlehead.  It also may, or may not matter that I don't intend to build a DAC until my amp/headphone needs are met since the general consensus is that phones and amps make the biggest initial difference in new and amazing sounds, ha, ha.

 

Now the questions that I'm really asking are these:  Which of these two gems pair better with the 600ohm Beyers?  If I want to get the amp that doesn't pair as well with the Beyers, later on after I've built the first amp, will it be sonically rewarding to own both a tube amplifier and a hybrid amplifier?

 

I realize that there weren't a lot of DIY questions and I put this in the DIY forum, but as they're both DIY projects I figured this was the right place to post....and I do have this little DIY caveat to throw in here at the end....I've gotten decent at soldering holes in pcb and I want more practice...I want to learn how to do a point to point build...and after all that I want to learn how to do some surface mount soldering(AMB's y2 sounds good for this later on).  In other words, most of my DIY questions will come later after you guys help me decide if I should build one of these amps, or simply build one of these amps first followed by the other and followed yet again(many months later) by a review pitting them against each other.

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post #2 of 21
9/1/10 at 9:05am

FWIW, I've built three Milletts over the years, and thoroughly enjoyed building and listening to them all. I very recently sold my last Millett, and am seriously considering buying and building a Crack with the funds...... not because I think the Crack is any better or worse, but because I want something different, and to ease myself into P2P builds before undertaking my own amp design.

 

The Crack is absolutely less versatile and is not a good option for low impedance phones - I don't think that there is any question about that. But you are right in that the Crack might be better for very high impedance phones like the 600ohm Beyers. Question is, why are you going for the 600ohm version? I think it is silly to specifically buy phones knowing that they are harder to drive with minimal benefit over the easier to drive versions. Though some people do swear black and blue that the 600 is better, so who knows.

 

If I were you, I would build a MiniMax and get the 250ohm Beyers. Then when the itch strikes again, you can buy some K701 without any concern. Then when the itch strikes again, build a Crack.


Edited by Beefy - 9/1/10 at 9:08am
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post #3 of 21
9/1/10 at 11:01am
Thread Starter 

I think I'll take your advice...and since you've owned a minimax and are considering building a crack I can troll around after you finish and read about your impressions.  Honestly I'll probably end up building both anyway as I too want to do a point to point build and from what I understand the people at bottlehead have an excellent set of instructions.

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post #4 of 21
9/1/10 at 1:01pm

Beefy's strategy is sound.  A 600 ohm Beyer is a tough load for any amp, MiniMAX included, unfortunately.  With a strong source and 12AE6's, it may do fine, but 250 ohms will not be an issue, as are all the 300 ohm Senns - the MiniMAX will drive them quite nicely.  Of course, it will have no issue with 32 ohm Grados, too.

 

One thing not mentioned much anymore, but is really one of the primary features of the Millett Hybrid/MAX/MiniMAX/MOSFET-MAX family is that you're only dealing with low voltage.  The closest you get to line voltage is plugging in the walwart and anything higher voltage is non-existent.  That's an important point if you're just starting out in DIY.  Of course, there are many other fine amplifiers that don't involve high-voltage or line voltage, but not with tubes.


Edited by tomb - 9/1/10 at 1:04pm
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post #5 of 21
9/1/10 at 3:03pm
Thread Starter 

Yes, the low level voltage is one of the primary reasons I was initially attracted to the design.  I've done a lot of DIY jobs over the years, but most of it involved building computers and working on cars or motorcycles(if you mess up here you get killed too, just in a different way).  With the exception of the computers, and anyone who has done those knows that it is very difficult to mess up as parts tend to only fit in one spot, I've yet to work on anything that plugs directly into the wall.  Certainly new to DIY home audio.

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post #6 of 21
9/1/10 at 4:01pm

Well, since I have bought a pair of Beyer DT 770/600, I should update my comparaison at some point. Just tried my three amps with these and my impressions are that both the MiniMax and the Speedball Crack have no problem running 600 ohm headphones. The MiniMax does better in bass (slightly stronger and better defined), while the Speedball Crack has better instrument separation and feels more exciting (can't put it into words yet). What I would recommend... either of them is good, with a slight preference for the Crack. Castanet still does better than both however: Harmonium's "Depuis l'automne" just sounds magical on it.

 

Interestingly however, the Castanet has a lot of trouble driving the Beyer DT-770/600. On a scale of 1 to 11 (based on a clock, but upside down), the listening level, for me, on the MiniMax and the Speedball Crack is at 5-6, while it's at 9-10 on the Castanet.

 

Oh well, I'll end my rambling here. Just remember, these are only my opinions.

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post #7 of 21
9/1/10 at 5:34pm

Wyldrage, what tubes are you running in your miniMAX? I am curious how much tube gain you are getting to use that volume setting. 

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post #8 of 21
9/1/10 at 5:38pm
Thread Starter 
Quote:
Originally Posted by WyldRage View Post

Well, since I have bought a pair of Beyer DT 770/600, I should update my comparaison at some point. Just tried my three amps with these and my impressions are that both the MiniMax and the Speedball Crack have no problem running 600 ohm headphones. The MiniMax does better in bass (slightly stronger and better defined), while the Speedball Crack has better instrument separation and feels more exciting (can't put it into words yet). What I would recommend... either of them is good, with a slight preference for the Crack. Castanet still does better than both however: Harmonium's "Depuis l'automne" just sounds magical on it.

 

Interestingly however, the Castanet has a lot of trouble driving the Beyer DT-770/600. On a scale of 1 to 11 (based on a clock, but upside down), the listening level, for me, on the MiniMax and the Speedball Crack is at 5-6, while it's at 9-10 on the Castanet.

 

Oh well, I'll end my rambling here. Just remember, these are only my opinions.

 

More good info.  I've resigned myself to building both, but I am probably going to start with the millet for safety reasons.  The Castanet seems like something one would build after getting your feet a little wetter than my own.
 

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post #9 of 21
9/1/10 at 7:06pm
Quote:
Originally Posted by jdkJake View Post

Wyldrage, what tubes are you running in your miniMAX? I am curious how much tube gain you are getting to use that volume setting. 


12FM6, the middle one. I have tried the 12AE6 with Alessandro MS-1i, and hated them: you get more impacts, but you have to sacrifice the treble. I have recently received a pair of 12FK6, but have yet to plug them in.

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post #10 of 21
9/1/10 at 7:13pm
I agree, the 12AE6 is not as good pairing with grados (or Alessandro I would assume as well). The 12FK6 is a much better match.

I was curious if you tried the 12AE6 with the Beyer 770/600? I think the 12AE6 rules with high impedance cans as long as you bias them for maximum voltage swing (13.5V). They also have the most gain. It would be interesting to see what the relative volume change would be against the 12FM6.
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post #11 of 21
9/1/10 at 7:24pm

I had no trouble driving my 600ohm DT990 with the Millett Minimax (12AE6 tubes at 14.5V) when I owned it.  However, after buying the Audiotailor Jade and upgrading the film caps, it easily bested the Minimax to my ears.  I plan to pickup the Crack and Speedball combo when I get some extra spending money and compare it to my now heavily modified Jade (Blackgate and Nichicon Muse caps and all Kiwame and Takman resistors throughout).


Edited by ecclesand - 9/1/10 at 7:28pm
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post #12 of 21
9/1/10 at 7:50pm

Want to hear a good one? I just tried all the tubes, and they all play at the same volume! What happens is that, after you change tube, you have to adjust the tube bias to the same level, and that's where the gain plays: you'll have to increase bias for the 12FK6, and decrease bias for the 12AE6. At the end, the volume will stay the same, as long as the bias is the same.

 

As for which tube is better, I think the 12FM6 is least coloured, the most balanced, the 12FK6 is slightly brighter, but still keeps a good bass, and that the 12AE6 is absolutely terrible. I'm missing some electric guitars with the 12AE6 where I know they're supposed to be. I might have a bad pair, I don't know, but I will never put them back in again!

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post #13 of 21
9/1/10 at 8:40pm
Quote:
Originally Posted by WyldRage View Post

Want to hear a good one? I just tried all the tubes, and they all play at the same volume! What happens is that, after you change tube, you have to adjust the tube bias to the same level, and that's where the gain plays: you'll have to increase bias for the 12FK6, and decrease bias for the 12AE6. At the end, the volume will stay the same, as long as the bias is the same.


Sorry - I'd have to say something else is going on when you do this.  It could be that you've hit some minimum position on the volume knob where changes in the tubes are not readily apparent.  That's a weird coincidence, though, and not one I've ever experienced.

 

Try adjusting the volume travel from just-audible low to just-tolerable high with each of those tubes and I'm sure you'll see a difference (in the volume knob travel).

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post #14 of 21
9/1/10 at 9:01pm

What can I say? You obviously have more knowledge on the Millett than I do. It's just that I went from the 12FM6, to the 12AE6, and then to the 12FK6, adjusting the bias every time, and I never had to play with the volume. The knob just stayed in the 5 o'clock position, and I did not detect any variation in volume.

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post #15 of 21
9/2/10 at 5:35pm
Quote:
Originally Posted by WyldRage View Post

As for which tube is better, I think the 12FM6 is least coloured, the most balanced, the 12FK6 is slightly brighter, but still keeps a good bass, and that the 12AE6 is absolutely terrible. I'm missing some electric guitars with the 12AE6 where I know they're supposed to be. I might have a bad pair, I don't know, but I will never put them back in again!


That is an interesting observation I had a pair of 12AE6 of GE construction that I just could not abide by. They were brash and even distorted under load even at normal bias. I really did not enjoy them and have avoided GE construction since. Perhaps you have a similar situation. Care to post a picture of them?

 

In any case, I have found there is a variation in tube construction that effects the sound. Perhaps you did get a bad pair.

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