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Review of my 5 DIY amplifiers. 2012/03/21: Bottlehead Smack and new analyses

post #1 of 68
Thread Starter 


2012/03/21: Added new analyses

2012/03/20: Added Bottlehead Smack

2011/02/12: Added Speedball Crack with 5998A tube in audio analyses, modified the headphone analyses to add the new measures.

2011/02/11: EHHA vs Castanet with the Grado HF-2, audio analysis for the k601 and DT-770/600, and pdf by amp.

2011/02/10: Added audio analyses done with Rightmark audio analyzer.

2011/02/04: Modified Castanet vs Crack, Crack tube rolling and moved the conclusions to the end.

2011/02/03: Added EHHA vs Speedball Crack and modified conclusion.

2011/02/02: Added EHHA Revision A and headphone protection.


Let me start with the usual warnings: these are my opinions. They should not be taken as absolutes, they are the results of my listening tests, with my ears, on my headphones and with amps that I built. Your results will vary.


Now that I have taken this out of the way, a small introduction. When I discovered the Audez'e LCD-2, I knew I had to upgrade my rig before being able to fully use them. Thus, some head-fi'ers recommended that I build myself a desktop amp. After some research, I purchased a MiniMax kit, and I caught the DIY bug. Fast forward to this summer and, with the help of some disposable income, I purchased a Crack kit, its Speedball upgrade kit and the components for a Castanet.


And now I don't have the cash for the LCD-2... Sorry for my wallet indeed.


And now, unto the show.


Headphone protection

I now have two headphones with popped channel because of voltage rush at amp start-up. If your amplifier does not have a muting circuit (like in the MiniMax) or output transformers (like in the Castanet) play it safe and CHECK if your headphones are still plugged in before switching your amplifier on. I personally unplug them before turning my amplifiers off, and so they are never plugged in on start up.



AMB Gamma2 DAC (built myself) plugged in my HP HDX9494NR with a standard USB cable.

Millett Hybrid MiniMax headphone amplifier (with Black Gate caps upgrade at C7). 12FM6 tubes.

Bottlehead Crack headphone amplifier with Speedball upgrade. NOS 5963 (12AU7 equivalent) and NOS RCA JAN 6AS7G tubes.

Hagerman Technology Castanet headphone amplifier. Sovtek 6H30PI tube.

Alessandro MS-1i headphone. (I call it a Grado)

Audio Art IC-1 interconnects.


Cost (including taxes and brokerage fee , thank you UPS))

MiniMax: kit from Beezar 302.89$CAD

Speedball Crack: kit from Bottlehead 428.41$CAD

Castanet: half-kit from Hagerman and pieces from several sources ~800$CAD (includes $20 shipping and $30 brokerage fee from UPS on a 77$ package, **** UPS)


The lesson here is that kits are generally cheaper for Canadian, since they often escape taxes, brokerage fees and multiple shipping fees. And that the Castanet costs more than the other two combined, especially with all the iron.


Ease of Build


+ Case work already done.

+ Manual is relatively good for new comers, but it is split up in several pages, and some information can be hard to find (the jumps at RB8 and RB9 for example).

+ Low voltage is less dangerous (but it still is).

+ PCB populating with minimal wiring.

+ You can easily get help for it on Head-Fi.


Speedball Crack

++ The manual is a thing of beauty, with plenty of full colour pictures for all steps.

+ No casework (except gluing four pieces of wood together, which you even get a manual for!)

- Point-to-point is longer to do and harder, but the manual really helps here.



+ PCB populating with minimal wiring.

- The manual, while complete, is not user friendly and assumes you already have basic tube amp knowledge. For example, it doesn't tell you where to read the voltage during testing (and isn't the plate voltage and B+ the same thing? Might just be my limited knowledge)

- The PCB is missing several component identifications, especially the chokes. You have to refer to the pictures.


My recommendations: don't start with the Castanet. It is still a relatively easily build, but you won't have all the information you need for a first project. Bottlehead's manual is very new user friendly, while the MiniMax is less dangerous.


The Glow (and other aesthetic considerations)



MiniMax: As you can plainly see, I've cheated: the glow comes from LED (one of the recommended modifications). The central LED changes colours, so it is quite a looker. The case itself looks really nice, is very small and quite light. It could be used as an office amp.


Speedball Crack

Speedball Crack: Big tube! The glowing cathode can be seen from most angles, glows nicely and the 6AS7G coke bottle form is quite nice. The 12AU7 however barely glows. Putting a 12BH7 in its place looks nicer, but changes the sound (more on that later). The case itself is made of wood, and that's always good, however the cables will be sticking upward.



Castanet: The 6H30 looks nice, especially when viewed from an upward angle, and runs very hot, but it's half hidden by the enclosure. The amp is much bigger than I expected, is quite heavy and looks like laboratory equipment in stock form. It's very beige.


Music used for comparative listening

Rush – Tom Sawyer

Hawkwind – Orgone Accumulator

Manilla Road – Necropolis

Mekong Delta – Dances Of Death

Charles Mingus – Better Git It in Your Soul

Ornette Coleman – Lonely Woman

Harmonium – Depuis l'automne

Solstice – The Sleeping Tyrant


All of these are 256 VBR AAC vinyl rips I have made myself from original LP issues or, at the very least, vinyl from the analogue era. The most recent is Solstice – New Dark Age, but that's because it's the most recent album (1998).


Amp vs. Amp

MiniMax and Speedball Crack

Both of these sound similar at first. I'm listening through Grados, so the soundstage is pretty limited on both. The MiniMax sounds pretty neutral, nothing seems to be in front, while the Crack has an emphasis on the high frequencies, probably due to the impedance imbalance. The details on both are pretty good, but the Crack does better in the highs, and the MiniMax in the bass. The MiniMax sounds bloomy at times, on the vocals on Tom Sawyer and the brass on Lonely Woman, while the Crack doesn't loose control on its highs. On the other side, the Crack sounds somewhat dry on the bass in Necropolis, with the MiniMax giving a better reproduction.


There is one major weakness on the MiniMax: I find it boring. It's more neutral, yes, but it comes with several prices. For one, you can only hear the impacts on the drums or cymbals, you can't feel them (I believe they're called transients but I may be mistaken). The instrument separation is also weak: you know there are only two channels, and you can't pick an instrument in the band. The Crack is more exciting, but they're also a few trade-offs. The cymbals often get over the rest of the music, and when they're used to keep a beat, you can't ignore them. The amp also sounds quite bright, but as I said, it's probably linked to the high output impedance.


If I had to pick a winner, I would say the Speedball Crack. It's more exciting to listen to and there's better separation, but the brightness can get fatiguing, especially the cymbals.


MiniMax and Castanet

...Where do I start? Frankly, everything the MiniMax does, the Castanet does as well, except better. First impression is that it is bassier, but you actually have better details and extension with it! I was barely able to get the bass from The Sleeping Tyrant from the MiniMax, while the Castanet does gives you the very low rumble. Harmonium's Depuis l'automne sounds so good on the Castanet it's not even funny. The guitar plucks sounds so realistic, and the decay is so very extended.


The Castanet is also very dynamic, you can hear the subtle variations in the volume of the notes, which you can miss with the MiniMax. The instrument separation is fantastic on all but Dances of Death, where it is still good (though it's probably due to the recording). It's even giving me a good soundstage on a Grado! It's musical, has great details and separation, great extension, good soundstage and can reproduce the most complex music. The MiniMax is simply out of its class (remember it's my opinion).


Speedball Crack and Castanet

Since I finally have some broken-in, high impedance headphones, I'll give my new impressions here.


The Speedball Crack is not meant to drive orthos, so I haven't tested them.


The AKG 601, which I always found too tilted towards the highs and too sterile, doesn't match well with the Speedball Crack. This combo gives an edge to the sound that I find unpleasant. With the Castanet, the sound is more relaxed and much more agreeable. The bass is noticeably more present, without being boomy. Of all my amps, the Castanet does the best job with this headphone, though it still isn't enough for me to like the AKG.


Moving on, the Sennheiser HD 600 is, from the start, a more laid-back headphone than the AKG. The Castanet gives a very relaxed, well-balanced sound that never gets harsh... the trouble is that I'm listening to METAL! The Castanet with the Sennheiser HD 600 is far too laid-back for my genres. In the other corner, the Speedball Crack gives a good cunch to the guitars and a good ring for the treble, and the bass is still well represented. This round goes to the Speedball Crack.


For the Beyer DT 770/600 (ported version with strong bass), both amps give a good show. The bass is a bit boomy and can overpower the rest of the spectrum a bit with the Speedball Crack, but only in songs where bass is already strong. The Castanet maintains a good control on its bass.


There are some observations that I made on all these headphones. The Castanet maintains a good balance to the sound, no matter the impedance, while the Speedball Crack's bass quantity seems to increase with impedance (though that could also be a factor of the headphones I bought). The treble rings better with the Speedball Crack, but that can be a problem with certain headphones. The Castanet has better instrument separation, a more precise, but also more restrained soundstage, and an excellent dynamic range (the changes in volume on the recordings are very apparent). For vocals and bass I prefer the Castanet, for guitars and jazz brass, the Speedball Crack. The drums can go either way.


Tube Rolling

MiniMax: Using the 12AE6 instead of the 12FM6 gives better impacts from the drum, but at the cost of the treble. All of it. I found that it sounded very heavy, very closed, with absolutely no air. The impacts can also sound overpowering. Let's just say I changed back fast and never looked back.


Speedball Crack: Tube rolling done with Sennheiser HD 600 and NOS RCA 6AS7G.

  • NOS 5963: The treble is too hot.
  • NOS GE Canada 5814A Triple Mica: The treble is too cold.
  • Gold Lion Reissue 12AU7: The treble is just right... Joking aside, I don't particularly like the 5963, while the 5814A and 12AU7 are quite close in sound and I would be happy with either. Unfortunately, the 12AU7 has become noisy, which is very noticeable with the HD 600 when there's nothing playing (not so with the AKG, which needs more volume).
  • Electro-Harmonix 12BH7: Good balance, but a bit less warm than the 12AU7. Also a good choice.
  • JJ ECC99: It's not a recommended tube, so try at your own risks. A good balance, but the bass sounds hollow.


For the second tube, done with Sennheiser HD 600 and Gold Lion reissue 12AU7.

  • NOS RCA 6AS7G: Needs more volume, a good warm sound.
  • NOS GE 5998A: Needs less volume, the sound is a bit drier than the 6AS7G. Probably better extension, but I prefer the 6AS7G's warmer sound (and its coke bottle). Also, the GL 12AU7 is now unlistenable due to the noise.


Castanet: The choices are rather limited for the 6H30, it's either Sovtek, Electro-Harmonix or a $160 NOS tube. Not happening.


Headphone synergy

Will update this when I get the time, with the Shure SRH-840. And with the LCD-2 when I get around to buying one.



Is the Speedball upgrade worth it?

I have not had much time with the original Crack, since I upgraded it two days after assembling it, and it's hard to do A/B tests with an upgrade, but my impressions are that it was worth it. The bass has more presence than before, and I believe it has reined in the brightness a bit.


Cavalli Audio Embedded Hybrid Headphone Amplifier Revision A (EHHA Rev.A)



EHHA Revision A with 6GM8 tubes

Gamma 2 DAC

Audio Art IC-1 cable



Around 550 $CAD. I've also bought a front panel for $100 or so.


Ease of build

+ PCB construction.

+ Good instructions, particularly for testing.

+ Relatively low voltage.

- A lot of wiring to do

- Not all needed parts are listed in the BOM. You have to make certain decisions.

- No casework (no default enclosure for that matter).


I do not recommend this for a beginner. It is not particularily hard to build, but you will have to choose certain parts for youself, and won't have instructions on how to wire them. There is also quite a bit of wiring to do, though the instructions on that part are quite good.


The Glow (and other aesthetic considerations)

Small tubes on top of a LED. Since the case isn't standardised, it will vary widely from one build to the other. I have used a Par-Metal 20 series 12" X 12" X 3" amplifier enclosure (with the vents). Photos will come when my front panel arrives.


Headphone compatibility

As an hybrid design, it has no troubles with low or high impedance headphones, or with orthodynamic headphones. I never had to push the volume over half the potentiometer's limit (an Alps RK27 100K Ohms). That said, don't leave high sensitivity headphones plugged in on start-up!


Amp vs Amp


vs the Hagerman Castanet

With the HifiMan HE-5LE, the EHHA shines with a very detailed presentation. The instrument separation is probably as good as my 256kbps VBR AAC can manage and the soundstage is quite good. The cymbals are crystal clear and the guitars sound quite nice and crunchy. I could wish for a bit more bass, but that's probably linked to the "no grill cloth" mod. Switching to the Castanet, the sound is coming a bit blurred. It's not quite as detailed,the instruments blend a bit together and it sounds a bit slower; it's possibly linked to how far I have to push the volume to get a good level. On the other hand, the soundstage is fantastic and I can easily pinpoint the provenance of the sound, though the EHHA is no slouch in that area. The vocals also sound sweeter on the Castanet, a result of the "SET magic". All in all, the EHHA does a better job here.


With the AKG 601, the EHHA sounds very airy and the treble is scintillating. The overal effect makes for a strong "out of the head" experience. The Castanet sounds noticeably darker, with somewhat stronger bass, which gives a closer, more intimate presentation. Since I find the AKG 601's sound too thin and metallic, I find that the Castanet's presentation is precisely what the doctor ordered: more body to the music. Of course, I listen to Metal and Rock mostly, so classical fans might have a different opinion.


For the Beyer DT 770/600, the differences are much reduced. I attribute this to their closed nature: the resonance giving a closer sound and reducing the audible differences between the amps. Overall, I'd say the EHHA gives better extension, while the Castanet has sligthly stronger bass, but I might be splitting hairs.


With the Grado HF-2, it depends on the genres. The greater speed and instrument separation of the EHHA absolutely beats the Castanet when it comes to fast and complex music, such as Thrash Metal. The Castanet however, brings the music closer and gives it some warmth and emotion, which is fantastic for Jazz. Between those two extremes, I feel like the Castanet more emotional presentation gives it an edge to the more detailed, and somewhat colder, EHHA. The differences are, however, much smaller than the similarities between these amps, and I am quite happy jumping from one to the other.


vs the Bottlehead Speedball Crack

The Speedball Crack is driven by a Gold Lion Reissue 12AU7 followed by a NOS RCA 6AS7G.


It's completely unfair to even try the HifiMan HE-5LE, but for the Speedball Crack's defense, it does a fair job: it just isn't able to produce much bass and the sound is rather veiled.


For the AKG 601 and the Senneheiser HD 600, the choice is between accuracy and fun. The EHHA's details and instrument separation are excellent, especially on complex passages where the Crack can become congested, and its bass extends deeper. However, the Speedball Crack does a nice job for guitars and vocals, adding some sweetness and crunch. The EHHA sounds very neutral with nothing being emphasized over the others, unless the recording calls for it. For the AKG 601, which is already very neutral, it just makes it too sterile for my ears. For the HD 600, I'd say it's a toss-up: I love the added sweetness, but I miss the precision of the EHHA.


For my Beyer DT-770/600, which is the "strong bass" version with ports, the results are different. With strong bass in a song, say Black Sabbath - Wasp/Behind the Wall of Sleep, the Speedball Crack sounds boomy, with the Bass overpowering the rest, which I did not notice in my other headphones. On the EHHA, the bass is better controlled and the song does sound better. Where there is less bass, what I have said about my other dynamic headphones still applies.



Audio Analyses


These were made with Rightmark Audio Analyzer, into a Presonus Inspire 1394 at 24/96, into the amps, then an headphone splitter, with one branch to the headphone and the other back to the Inspire 1394. If I understand correctly, that's the method to do it, but I may be mistaken.


First, the test equipment:


Now by headphones:


Finally by amplifier:


New analyses done on 2012/03/21

Since I switched to a E-MU 0404 USB, the previous test are no longer comparable to the new tests. My new audio interface appear to have a sharp drop-off at 20 khz, which you will now see in all the following analyses, which I have redone:  




And here's a picture of my testing set-up:

My test set-up



Bottlehead Smack (2012/03/20)




Bottlehead Smack SET
Hagerman Castanet SET
Cavalli Audio EHHA rev.A Hybrid
Bottlehead Speedball Crack OTL

Audez'e LCD-2
Grado HF-2
Sennheiser HD-600

256 kbps VBR AAC recordings of original vinyl records, from my laptop using a AMB Labs Gamma 2 DAC

RUSH - Tom Sawyer
MEKONG DELTA - Dances of Death
HARMONIUM - Depuis l'automne
CHARLES MINGUS - Better Git It in Your Soul 




I bought it during the pre-order offer of $475 USD (I was actually the first). With shipping and taxes, about $550 CAD.


Ease of build

++ The fabled Bottlehead manual.

++ All drilling already done.

- Half point-to-point. Get a good wire stripper.

- Really cramped at the end if you need to troubleshoot it.


There are better choices for beginners (namely something that is on a PCB), but it is doable if you follow the steps carefully.


The Glow (and other aesthetic considerations)

Two small tubes completely exposed and they give strong glow. Otherwise it's a metal plate on a wooden base, and it feels slightly empty.




Bottlehead Smack

Headphone compatibility

Any dynamic headphones and just powerful enough to handle the Audez'e LCD-2 to an acceptable level. That said, I don't recommend using orthodynamic headphones with it.

Compared to Hagerman Castanet

Grado HF-2
The first thing that strikes me is how silent the Smack is: the Grado are so sensitive that I can clearly hear the power supply of the Castanet when no music is playing. With Rush, both amplifiers are close, with the Castanet having more weight and the Smack having more air. Both have good soundstage (for a Grado) and the instruments come clear, with a slight edge to the Smack. Harmonium was always great on the Castanet, very emotional and the reproduction of the darkness between the sounds. It still holds on to that last part, thanks to its warmer sound, but the added air of the Smack really gives an added brilliance to the single pinched cords and greater power to the crescendo. On Charles Mingus, the Castanet gives more presence to the bass, but sacrifices instrument separation. Since Mingus was a bassist, I would have preferred more weight from the Smack, but the better reproduction wins in the end.

The Castanet always loses it on Mekong Delta (which is one of the reasons I always pick that track), and today was no exception. The Smack, however, gave a much superior instrument separation and was able to follow the complex passages, which I found remarkable for a SET (though I must say I only ever had the Castanet as a SET). 

Audez'e LCD-2
It always makes me sad to use the LCD-2 with my Castanet, since it reminds me why I stopped using it. On all tracks this combination sounds slow, muffled and lifeless. The impulses (when the drums are hit) are especially dull. The Smack does a much better job here, though not as good as it did with the Grado. Comparing it with the EHHA will be a much better indication of how it plays with orthodynamic headphones.

Sennheiser HD-600
For the rock tracks, it's petty similar to the Grado HF-2: better air, better separation and better dynamism (drum impacts) from the Smack. The Smack also does a good job on the Mekong Delta track: the guitars are crunchy, the drums are dynamic and the instruments are well separated. In comparison, the Castanet makes the whole too smooth and loses the energy of the track.

Then I got to Charles Mingus. Wow! All instruments are well separated, it's easy to pinpoint the directions of the instruments in the soundstage and the cymbals and brass instruments sound alive! The added air really brings out this jazz track. The Castanet sounds dark and the separation is not as good, though the soundstage is still wide enough. As I type this, I am listening to Blues and Roots, and I must say I am impressed at how life-like it sounds.

No matter how much I like my Castanet, it's not contest: the Smack is the better amplifier. With dynamic headphones, the Smack has great air, dynamism, instrument separation and soundstage. It does a fantastic job at jazz, which was the strongest point of the Castanet in my previous amp shootouts. It is also fast enough to handle Thrash metal, which the Castanet can't. I think we clearly see the advantage here of custom iron against off-the-shelves Hammonds. 

Compared to Cavalli Audio EHHA rev.A

Grado HF-2
It's really an age-old debate: transistors vs tubes, technical perfection vs subjective enjoyment. The EHHA comes out with better instrument separation and better extension on both sides, but the Smack does better on a few other points: soundstage and volume changes in the music are more apparent. The Smack really plays Harmonium well, and keeps the emotion, while the EHHA is too cold and analytical for it. Mekong Delta is better reproduced on the EHHA, but the volume changes in it are brought up by the Smack, giving it a more life-like presentation. I've always preferred my Grados on SET, because of that increased soundstage, and the Smack is no exception. This is, of course, highly subjective.

Audez'e LCD-2
This was closer than I thought it would be, but it seems the EHHA survives the challenger. On Charles Mingus and especially Harmonium, the warmth of the Smack and the better representation of volume differences give a more emotional representation of the music, which is very pleasant. On the other hand, on Rush and Mekong Delta, the Smack starts to lose it on fast and complex passages, and the drums and guitars lose their edges. To be fair to the Smack, it is still a very respectable performance: I was writing the same thing last year, when comparing the Castanet against the EHHA, but it was with the Grado, not with an orthodynamic headphone! 

Sennheiser HD-600
Now that's a tough one. The EHHA is clearer, faster and has better extension, but the difference is slight. The Smack does have better soundstage (but the Sennheiser is not starved for it like the Grado) and more warm. I feel it is better on Mingus and Harmonium, while the EHHA is better on Rush and Mekong Delta. I must also say that the Smack manages to do a very good job on Mekong Delta, a fast and complex track, which is no small feat for an all-tube amplifier.

The Smack gives a very good fight against the EHHA, and I am quite happy with the both of them. For dynamic headphones, it's all about what you prefer: clarity vs soundstage, extension vs warmth, transistors vs tubes (yeah, I know the EHHA has tubes, but it's still a very SS-like sound). If you have an orthodynamic, I still prefer an hybrid or SS amplifier for the higher current, but the Smack still manages a decent performance here, and the EHHA is no slouch.

Compared to Bottlehead Speedball Crack

Sennheiser HD-600
Once again, I have to give it to the Smack. There's better extension, especially in the bass, better separation of the instruments and it is slightly more capable of handling complex music. The Smack was more capable when handling Mekong Delta, which surprised me, and really did a fantastic job with Charles Mingus. Frankly, as was the case with the Castanet, I believe it's an improvement on all the line.





Millet Hybrid MiniMax: It's a great first time project, that will look good and won't take much place. It's also much better than the headphone port of your computer, but it doesn't hold well to my other amps. It may be the compromises forced by the size, or by the low voltage, but I found it sounded quite dull compared to the others, with no soundstage to speak of. On the plus side, it is quite neutral, and it was a great learning experience.


Bottlehead Speedball Crack: A good match for high impedance headphones, especially Sennheiser. It adds a good crunch to guitars, a nice ring to the treble and a bit of warmth to the vocals. Great for laid-back headphones and rock/metal. Fantastic if you want to roll tubes (a costly hobby). Not for low impedance headphones or orthos, but can still manage to do a fair job with both. It's not the most transparent amplifier, nor the most neutral: i's a fun amp. Just don't leave headphones plugged in at the start-up!


Hagerman Castanet: is my favourite (2013/03/20: the Bottlehead Smack has supplanted it). The main negative point is that, stock, it is not the best looking, especially when compared to Bottlehead amps. Apart from that, the tube actually glows well, even if it's half hidden. It's compatible with most headphones short of electrostatics, though you have to push it pretty far for high impendace or low sensitivity headphones. The sound is well-balanced, detailed and it has a precise soundstage. Love it with Grados, but a bit too laid-back with Sennheisers for rock and metal. For orthos, the EHHA has supplented it, but it is still competitive for dynamic headphones. Don't expect to do much tube rolling. The output transformers protect the headphones at start-up, and I have no qualm about leaving them plugged in.


It was my most costly project, and unfortunately it is no longer available (though you can try asking Hagerman nicely, he has/had a few boards left).


EHHA Rev. A: The Embedded Hybrid Headphone Amplifier revision A is a very capable amp. It can easily drive any headphone short of the electrostatic (and maybe the K1000, which I have never seen in person), with excellent details, instrument separation and a good soundstage. Frankly, it does everything well to excellently and the negatives I have found during comparaisons can be linked to the age-old solid state vs hollow state debate: tubes add a coloration that can be pleasant to the ears. (Yes, I know it's an hybrid, but they tend to sound more like solid state amps than tube amps IMHO) The only headphone that I really couldn't stand with the EHHA was the AKG 601 which, try as I might, I have never liked anyway.


For dynamic headphones, I will generally choose the tube warmth of my Castanet or Speedball Crack over the EHHA's precision, but that is a personal choice. For an orthodynamic, it's EHHA all the way: it's the first of my amps that can really push my HE-5LE.


It was the most complicated of my projects to date, and I would not recommend for a first project. You'll need to chose a few parts, including the enclosure, make the case yourself, with no standardized design, and there is quite a bit of wiring to do. The instructions are good and should get you a working amplifier without major problems, but they don't hold your hand. Hey! At least there's no SMD.


Bottlehead Smack: The Bottlehead Smack is a clear winner from the Doc. This amplifier has the SET magic, soundstage and warmth, yet still manages to have great resolution, speed and extension. It is quite capable of handling varied musical genres, with very different headphones (you can't get much further apart then Grado and Sennheiser!) and is even capable of doing a decent job on current-starved orthodynamic headphones. If you use mainly dynamic headphones and want some of that tube musicality, the Smack is a great choice.




Finally, let me reiterate again: don't leave your headphones plugged in when starting it!


Thanks for reading.

Edited by WyldRage - 3/21/12 at 4:18pm
post #2 of 68
Thread Starter 

Second post reserved just in case.

post #3 of 68


Castanet circuit topology is parafeed with plate choke load. One lead of the choke is connected to the power supply - that's your B+, the other lead is connected to the plate. You'll be dropping 10-15V across the plate load choke.


Originally Posted by WyldRage View Post

...... (and isn't the plate voltage and B+ the same thing? Might just be my limited knowledge)

post #4 of 68

That's a nice write-up WyldRage. I've heard variants of each of those, and (IMHO) I wholeheartedly agree that the Hagerman Castanet is the winner. I know it costs more, but you get more. I've read some forum posts from Jim Hagerman elsewhere, and he seems to really know his subject.

Edited by JB197 - 7/23/10 at 3:07am
post #5 of 68
Thread Starter 
Originally Posted by Parafeed View Post


Castanet circuit topology is parafeed with plate choke load. One lead of the choke is connected to the power supply - that's your B+, the other lead is connected to the plate. You'll be dropping 10-15V across the plate load choke.


I see, guess I should have looked more closely at the schematic, the +100V is written there, leading into the choke.

post #6 of 68

Nice review.  I might have to build a Casanet (or a variant).


With your low impedance headphones, I suggest you try 12FK6 tubes in your miniMAX and try again. Far more current to drive bass and more open highs, especially with the right tube construction. In the long run, the miniMAX is really best suited with high impedance phones. For low-impedance, you really need to consider a MOSFET-MAX


Good stuff all around though! I am really interested in the "single tube" implementation of the casanet. Whose transformers did you us? 

post #7 of 68
Thread Starter 
Originally Posted by jdkJake View Post

Good stuff all around though! I am really interested in the "single tube" implementation of the casanet. Whose transformers did you us? 

It's built with all the components listed on in the manual's parts list, so the transformers and the chokes are Hammond.


I'll try the 12FK6 when I get back, since they are quite cheap. I've never seen the MiniMax output impedance: I didn't know they worked better with high impedance headphones. It's unfortunate I don't own high impedance headphones, but there's simply no model I've ever wanted to buy.

post #8 of 68

My Minimax is anything but boring, It's very lively and upfront and the dynamics are excellent. what it lacks in resolution it makes up in charater.  

post #9 of 68
Thread Starter 

I once found it quite exciting as well: it's certainly much better than no amp at all! It's once I compared it to the other two that I found it boring (though that may have been a bad choice of word). The Crack, being bright in my system, will make the other amps sound boring (even the Castanet), but it is fatiguing. The Castanet, on the other hand, had more details, better separation and extension, and was more dynamic: I simply couldn't go back to the MiniMax after listening to it.


Does this mean that it is a bad amp? No, it simply means that, to my ears, in my system, it is not as good as another amp that costs three times as much

post #10 of 68

The 12FK6 have the lowest gain of all the millett tubes. This allows the maximum current drive to be delivered. Most important for low impedance phones. The 12AE6 are the opposite. They represent the highest gain.


Get a decent matched pair of 12FK6 and give them a go. I am a realist. I know the millett is not the end-all-be-all, but, it represents a dramatic step up from no amp at all. One could die happy with a millett miniMAX or MOSFET-MAX. Then again, this is a journey and not a destination. There is always another option to consider....

post #11 of 68

Just to clarify, the Crack is not intended for use with low impedance headphones like the Grados used here. We make that pretty clear in the product description. The result would indeed be a lack of bass. We also make a headphone amp designed for low impedance headphones that might have made for a more useful comparison.

post #12 of 68
Thread Starter 

I realise this, and I believe I have noted it at least twice in this comparaison. What I was going for here was that I wanted to try out different designs: one hybrid, one OTL and one transformer-coupled amp. I've chosen your OTL because I wanted to try my hand at point-to-point, I wanted an easy to build box or enclosure, and I believe it was one of the best deals on the DIY market.


Unfortunately, it is true that I have only low impedance cans and that the MS-1i is not the best headphone to test it, but it is the one I am most familiar with. I believe the Speedball Crack still sound very good with it, and I find it very exciting for fast music.


When I get back home (late August), I will have two new medium and high impedance headphones to try them out with: a Beyerdynamic DT770/600 (bought on sale at B&H) and an AKG K601 (120 ohm, bought on sale at TTVJ). They should be better suited to the Crack, and I will add to the review accordingly.

post #13 of 68

Great info. I've built two of these amps, the MiniMax and the Bottlehead, and agree that Tomb and Doc both did an amazing job with the instructions. I've been very curious about the Hagerman, there don't seem to be many people that have it on these forums. I did read on the asylum that the Hagerman can be bettered with ElectraPrint iron, but I'm glad now to have some reference as to where the amp stands to begin with.


If you don't like the beige exterior, why not drop it off at the powdercoater and get something a little more exciting?


The Bottlehead can be a bit bright for me with certain tubes (I'm very sensitive to brightness, so I'm sure it would be fine for most users), I was able to settle it down with some older Sylvanias, now it's puuuurfect :)

post #14 of 68

OP:  How do you like the K601 with the Crack?  I have been been in musical bliss with my K400 which is 120 ohms but still takes alot of current to get a proper handle on.

post #15 of 68
Thread Starter 



I have both [Crack and k 601] and I just tried it with 3 different tubes. With the NOS 5963 in the kit, I find that the sound is bright, with a subdued bass that lacks definition. With a Electro-Harmonix 12BH7, the sound is more neutral, but lacks extension on both sides, especially the bass. With a EH 12AU7, the amp sounds better: it's still bright, but the bass is present and well-defined, if a bit lacking for my tastes.


In any case, the Crack has no problem driving them.


What I posted in the Crack thread. I love the comfort of the k 601, but I don't like the "distance" of the sound. The sound coming out of the Crack is, to my opinion, slightly bright, with a subdued or bloated bass, depending on the tube, and that seems to be true for all my headphones. Remember however that my point of comparaison is an amplifier that costs at least twice as much as the Crack: for the price, it sounds very lively.

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Head-Fi.org › Forums › Equipment Forums › Headphone Amps (full-size) › Review of my 5 DIY amplifiers. 2012/03/21: Bottlehead Smack and new analyses