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Crack;Bottlehead OTL

Discussion in 'Headphone Amps (full-size)' started by ironbut, Mar 9, 2010.
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  1. i luvmusic 2
    When it comes to Capacitors i like using the SOLEN I have used the Mundorf film caps and compared it to the Solen i did not hear a difference.
    larcenasb likes this.
  2. larcenasb
    Output Capacitor Options:

    I was just now writing this for Paladin79, but this may be useful to others looking to upgrade. Humble Hifi's cap comparisons really are a lot to take in. Here is a sifted list of the common, and some not so common, 100uF caps, many of which other Crack builders have tried. So, based on all my research before starting my own build, this is how I'd break down 100uF output cap options (in bold are my picks within each tier):

    Tier 1 (Sensible):
    - Audyn Q4 400V $24 (Pretty big, mine are only 68uF...)
    - MKP-kondensotor 250V $27 (They seem cheap, but hey they're an option.)
    - Dayton MKP 250V $32
    - Jantzen Crosscap 400V $32

    Seeing as the general consensus is that any MKP cap would be sufficient,--since the effect of film over electrolytics is subtle here--it's hard for me to justify not choosing the German-made, crazy-inexpensive Audyn. But life has so much to offer lol...

    Tier 2 (I wonder how much nicer these are exactly...):
    - Obbligato Film Oil 630V $36 (68uF is the highest capacitance for these, so make sure you won't be using lower-impedance cans...which you shouldn't be anyway. Also, they're big and require a larger wood base, or some creative mounting, to fit. I'm curious how the oil will affect things.)
    - Ansar 100uf 450V $40
    - Solen 400V $41
    - Mundorf MKP 250V $41 (For the pair, you'd be spending $34 more than you would for their German brother Audyns. I'd like to do a double-blind test!)

    Tier 3 (Splurging):
    - ClarityCap PX 250V $51 (Big, requires a larger wood base.)
    - Mundorf EVO 350V $60
    - Mundorf EVO aluminum + oil 350V $68 (If I built an ultimate Crackatwoa, I'd be curious to try the Obbligatos or these just to see what, as Audyn calls it, the "fairy-like oils" are all about hahahaha.)
    - ClarityCap ESA/CSA 250V $90! (Also very big. I have a suspicion that all the previous MKP, non-oils, are indiscernibly similar. But these ones stem from a very rigorous two-year research program "on the audible effects of improved control over mechanical resonance [microphonics] in a metalized film capacitor," and "employs a non-standard polypropylene film." So, I'd like to do another double-blind test with these haha.)

    Tier 4 (The land of irrationality!):
    - Mundorf EVO silver/gold + oil 350V $360 ($720 for a pair lol...)

    To sum up:
    I picked the Audyns because of price and reason. Furthermore, having a matching third as the last PS cap was decided after I read, designer at Bottlehead, Paul Joppa's post on the BH forum:

    "The output audio current flows through the power supply, mostly the last capacitor, as well as through the output coupling cap and the output triode. So the final power supply cap should, in theory, be as important as the output coupling cap with regard to the sound of the amp. This is a characteristic of cathode follower circuits, such as the Crack and the Foreplay."

    "I post this with some frequency: 'I never met a power supply improvement that was not also a sonic improvement.'"

    Continuing on, then bypassing the last Audyn in the PS was a nicety, sure, but the Jantzen Superior-Z is only about $15 ($12 for my 0.68uF version) so I could deal with that as a single upgrade. One day though I hope to get an Audyn True Copper 0.68uF ($45-ish) to replace the Jantzen--only because I've come to really admire Audyn as a company and it would be a nice kingly crown for my much-beloved build. Cheers! :)
    Last edited: Sep 18, 2017
    Paladin79 likes this.
  3. larcenasb
    No problem! I was considering getting an Elekit TU-8100 and some full-range Fostex speakers...until you helped me with the preamp circuit for the Crack! Now I'm looking for a separate amp and speakers to go with my Crack instead. :beerchug:
    Paladin79 likes this.
  4. Paladin79
    I have a good source for caps at a decent price so I may do a few upgrades before I ship the carbon fiber Crack, my Crack has more space as well and I will get a better discount buying the caps ten at a time anyway so I may well do both quickly and have some spares for the next couple Cracks I build. That was not part of my original deal but if i can upgrade the last two for under $100 each I will probably go for it. If I build a TU8600 I have a feeling I will end up owning my own after I hear it, then there are all the nice upgrades lol. $2k can be used up pretty quickly on those amps.
    larcenasb likes this.
  5. Paladin79
    Solen is another brand I can get a decent buy on, they make a 100 ufd 400 v cap that I may have to consider.
  6. mcandmar
    Paladin79 likes this.
  7. Paladin79
    They would most likely cost less as well. One of my amps has double the normal amount of space of a normal cabinet, the other is close behind. I had seen photos of some of the caps that folks tried to position in a normal case and knew going into this that it would be one of three or four major modifications I would make before building the amps. IMG_2166.JPG The next two I build will be more in line with the one on the right so unless I get caps larger than a 12 oz coke can I should be fine lol. I once nearly built a Tesla coil using a bucket capacitor. Consider a capacitor being a five gallon bucket of motor oil and associated parts. My wife was a little worried about the cats getting too close, or the three foot long discharge igniting something in the garage so the idea did not reach fruition. Some women just have no sense of adventure.
  8. Paladin79
    Ok my next Crack build is going to be really radical as far as the internal workings of the amp. I have some parts left over from the first couple Crack builds so I may incorporate some of those. I once heard that if you rebuild enough carburetors eventually you will have enough left over parts to build one from scratch. That is one of the principles I will use in the build. I have been asked to make one major change on the amp that in all honesty, I have not seen done before. The amp is for an electrical engineer so I have been given criteria to meet and there is a wager involved so we will see how it goes. (he is also going to hand me a box of parts I must incorporate in the build.)
    larcenasb likes this.
  9. larcenasb
    Excited to see your build! Maybe it'll inspire me to make another or an ultimate Crackatwoa!
    Paladin79 likes this.
  10. Paladin79
    I can only say it will be one of a kind and may involve toroidal transformers, massive amounts of copper plate. and cold cathode displays (nixie tubes).
    Last edited: Sep 22, 2017
    larcenasb likes this.
  11. Voyst
    Hello guys,

    I really apologize for the following noob question which I imagine has been ask a 1000 times, but I am not willing to read all the 500+ pages...
    I just bought a Crack + Speedball and of what I understood the TS 5998 seems to be the consensus for the output tube. Unfortunately, it is expensive and kind of hard to get (If you have reliable places to buy one <100€, please share). So I was wondering if there is a consensus on budget and easy to get tubes ? The amplifier will be paired with an HD650.

    Thank you very much by advance
  12. Paladin79
    I have had good luck with some older RCA tubes but I will have to check to see what series they are when I get home. I also have some Russian tubes arriving shortly that I wanted to check out and if they pan out well I will give you the sources for both types. I do have Tung Sol 5998's but personally I cannot tell much difference between those and Chatham 6080's and others I have tried but YMMV. Most of my sources come from Ebay and thus far I have been pretty fortunate with the results but I generally buy from folks with only a couple tubes for sale here and there that I take a chance on.

    Good luck with your build by the way. With the current sale going on you are jumping in at a good time. My builds are a little radical but there are many experienced builders here who can walk you through proven modifications if you want to go in that direction.
    Last edited: Oct 5, 2017
  13. attmci
    Try this:

    Paladin79 likes this.
  14. Paladin79
    They are RCA 6AS7G's that I own that I really like the sound of. I found them on Ebay as a one time buy so I cannot say who has any now. You want to look for the ones with the old RCA symbol inside a circle with a lightning bolt under the letters. (I worked for RCA years ago and could have probably owned a huge sign like that if I so desired, I was there when they went to the block capital letters on the building.) The tubes also say Radiotron Electron tube on them.


    This style. They also say RCA in large capital letters but it is not the new RCA logo developed in the 70's I would guess.
    Last edited: Oct 5, 2017
  15. Maxhawk
    My favorites are the Chatham 6080 graphite plate, Sylvania 6080GB, and Cetron 7236. The 5998 is a good tube if you're looking for tighter, better defined bass since it has a lower output impedance compared to the other 6080/6AS7G variants.
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