Bottlehead Forum
Bottlehead Kits => Crack => Topic started by: adamct on January 16, 2013, 04:07:49 PM
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My noobie questions continue...I apologize for hogging the boards lately, and I also apologize for starting a new thread each time, but I figure that makes it easier for others to find answers to the same questions later.
So, with that out of the way, I have a couple of questions...a few practical, and one of curiosity. First the practical:
1. I have a two sets of adapters from my Woo Audio WA6. The first adapter lets you run 6SN7 tube in a 6DE7 socket. The second adapter lets you run 6GL7/6EM7 tubes in a 6DE7 socket. Can I use these adapters to run 6SN7s and 6GL7/6EM7s with my Crack+Speedball with the stock 9-pin socket and wiring?
2. I have 6AS7 and 7236 tubes from my WA22, where they are interchangeable with 6080s. Can I use these in my Crack+Speedball with the stock octal socket and wiring?
3. How do I figure out the answer to these kinds of questions on my own in the future, so I don't waste your time?
Now out of curiosity: As you can gather from the above, I have a WA6 and a WA22. I think I prefer the Crack to the WA6, and I consider the Crack to be roughly equal to the WA22. Quite apart from the price difference between the two amps themselves, please note that the WA22 is running tubes that cost $500-600, just by themselves. There are things that favor the WA22, but also elements that favor the Crack+Speedball. Both the WA6 and the WA22 are transformer-coupled. I'm sure the great sound of the Crack isn't just due to the fact that it is OTL (a good design and good parts obviously matter, too). But given that I assume the Crack was designed with a rough price range and a target level of assembly difficulty in mind, I wonder what compromises were made. Has there has ever been any consideration given to creating an even better OTL design/kit (albeit at a higher price)? Would having a greater budget or creating a more difficult to assemble kit permit greater flexibility in design, allow you to use better parts, or...just be a waste of money? Is it possible to SUBSTANTIALY improve upon the performance of the Crack+Speedball by using a different design, or is the design already pretty close to some theoretical ideal when considered in terms of real-world performance? (To clarify what I mean by that, you could have a design that was was radically different, more complex, used more tubes, and was theoretically perfect from an engineering perspective, but which only improved upon the performance by, say, 3-5%. Alternatively, you could have a design that was fairly similar to that of the Crack, but which improved upon the Crack's performance by, say, 20%.). Or would bigger gains be had by using more expensive parts in the Crack, in which case the best idea would be to just keep upgrading the Crack? In short: what would be needed to create a substantially better OTL amp?
Any advice is greatly appreciated!
Best regards,
Adam
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1. I have a two sets of adapters from my Woo Audio WA6. The first adapter lets you run 6SN7 tube in a 6DE7 socket. The second adapter lets you run 6GL7/6EM7 tubes in a 6DE7 socket. Can I use these adapters to run 6SN7s and 6GL7/6EM7s with my Crack+Speedball with the stock 9-pin socket and wiring?
2. I have 6AS7 and 7236 tubes from my WA22, where they are interchangeable with 6080s. Can I use these in my Crack+Speedball with the stock octal socket and wiring?
3. How do I figure out the answer to these kinds of questions on my own in the future, so I don't waste your time?
1. No, that adapter won't work, it will actually not function at all in the Crack socket.
2. Yes, you can use those tubes.
3. Fly out to Washington and take some classes ;) This is what the forum is for, don't sweat it.
Hmm, creating a better OTL amp, yeah, it's possible. One way to drastically increase performance would be to shunt regulate the high voltage supply. This would require two power transformers and two 6080's (or maybe a 6080 and some other tubes to serve as a shunt regulator). This would also require a rather large chassis plate. We could also throw in the attenuator design of the Bee Pre, and use film coupling capacitors, etc. etc.
The cost for a kit of this nature would be well over $1000, it's much more than twice the parts of a stock Crack, and we still haven't addressed lowering the output impedance.
I am currently doing some experiments with some different triodes other than the 6080, mostly to look at the impact of the local feedback in the output stage while attempting to hold all other variables constant.
I also have a chassis that has a differential Crack built onto it (from 2008, when I was originally messing around with the circuit), and this would be a nice test bed for building a shunt regulated Crack at some point.
I guess the take home message from all this is that yes, we can improve the circuit, but at this point there are still a bunch of experiments to do so we know what is worthwhile and what is not. I'm not aware of any other tube headphone amplifier manufacturer that would offer anything nearly this complex.
-PB
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These are great questions that we all wonder about, and I am not qualified to answer, except for some basic observations that have helped guide me in this, at times, insane hobby. First and for-most, we need to focus on what we want to 'improve' on, in the sound that we have now. In other words, fix what is broken, and dont fix it if its not broken.
In terms of circuitry of a given component there will be benefits gained from using 'X' technique, ex. feedback, at the expense of other aspects of sound. I'm not sure that this approach will get you the most bang for your buck in solving your sonic dilemmas. Bob Carver, for example, has been in the business of tube amp design for decades. He is still designing 'new' schematics, or a rehash of old ideas from a different perspective. Will his new amps 'solve' our problems. Probably not. They may help, but just as likely may not.
In summary - Bottleheaders are tweakers by nature, but there comes a point when we need to look at the bigger picture. Sometimes it means a shuffling of the component deck. Some things may need to go, and that may be the best decision on how to move forward.... (Ok Greg - I know what you are thinking - I'm actually fairly lucid, and I am not wedged between the toilet!)
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Paul,
I assume you are saying that neither adapter will work with the Crack, is that right (there are two different kinds)?
And not that it matters, but I'm not interested in lowering output impedence...in my experience, if you are using low impedance cans, solid state is better. I love the Crack with my Sennheiser HD800s, HD600s and Beyer DT990s (600 Ohm) and that is all I would be interested in using with this "improved" amp. So we can keep the price of your (theoretical) kit to only "well over $1,000", no need to jump to "many thousands of dollars", LOL... ;D
Eric,
You make excellent points. My problem, of course, is that I don't know what components have what effect on sound, so I'm flying completely blind. And to be clear, I don't really have any complaints about the Crack sound, other than the noise floor being higher than I would like, even with the Speedball installed. I wouldn't mind if the gain were lower, and I never object to more clarity, but that's about it in terms of wants. I sometimes find treble a little piercing (high drum strikes), but it is tough to point the finger at the Crack for that...could just as easily be my HD800s or the recording.
So at this stage, I'm just casting about for upgrades that are generally considered to be improvements. As I start swapping out components, I figure I will learn what effects they have on the sound. But at some point I need to start somewhere (not that I'm in any rush, since I'm very happy with the Crack as-is, and I haven't even done any tube rolling yet).
Best regards,
Adam
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Yes, both adapters won't work.
Can you describe the nature of the noise you're referring to? We haven't noticed anything in any of our tests.
One possible way to mitigate this might be to remove the black jumper shown on the bottom of page 19 (PT-4 to 22L), and replace it with a pair of 100 ohm 3W resistors from PT-4 to 22L and PT-5 to 22U.
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Eric,
You make excellent points. My problem, of course, is that I don't know what components have what effect on sound, so I'm flying completely blind. And to be clear, I don't really have any complaints about the Crack sound, other than the noise floor being higher than I would like, even with the Speedball installed. I wouldn't mind if the gain were lower, and I never object to more clarity, but that's about it in terms of wants. I sometimes find treble a little piercing (high drum strikes), but it is tough to point the finger at the Crack for that...could just as easily be my HD800s or the recording.
So at this stage, I'm just casting about for upgrades that are generally considered to be improvements. As I start swapping out components, I figure I will learn what effects they have on the sound. But at some point I need to start somewhere (not that I'm in any rush, since I'm very happy with the Crack as-is, and I haven't even done any tube rolling yet).
Best regards,
Adam
Now I get it a little better - I dont know the Crack circuit, but some boutique caps/resistors in the right spots could improve those symptoms. Also volume pot. I'm sure others can chime in on that. From my experience with the Quickie, what you describe as 'noise floor' was improved with high end parts. Not sure how much that would cost for the Crack, but I spent several hundred bucks on the Quickie. Specifically, I noticed a 'maturing' of the sound, opening up between instruments, bigger and better depth. A 'fleshing' out if you will. Tube rolling was also very noticeable. There is much you can do to 'tweak' those problems.
good luck my friend - god speed - piece, love, tubes - Eric
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Try different tubes if there is a perceptible noise floor. HD800s have a reputation for that treble. I don't find it piercing, but it is definitely a bit brighter than HD600s or 650s.
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Which tubes have a greater impact on the sound, the 12AU7s or the 6080/6AS7s? I assume the latter?
Best regards,
Adam
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Hey Adam,
Not sure where you stand on the whole cable thing, but replacing my stock hd-800 cable with a Q-Audio silk headphone cable turned the hd-800s into my absolute, all-time and forever fave cans. :-). Also, the Crack circuit is so simple, that upstream components (dac/phono stage) will show all their warts, especially with the 800s. The good news is that there are now some really incredible dacs for not a lot of money.
HTH,
Jim
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Jim,
Here is a picture of my HD800 cable: http://www.bottlehead.com/smf/index.php?action=post;topic=3702.0;num_replies=8
And here is a picture of my 8-wire HE-6 cable: http://jeaudiodesigns.wix.com/jeaudiodesigns#!HE-6-Blue-and-Purple-8-wire/zoom/c13ay/imageyxg
One of my HD600 cables is pictured here: http://jeaudiodesigns.wix.com/jeaudiodesigns#!Sennheiser-Walnut-and-Oak/zoom/c13ay/imageg9a
All of these cables were made by Justin from JE Audio Designs. I can't recommend him highly enough.
The HD800s are already my favorite headphones... ;D
As for my DAC, I use an Audio-Gd Ref 5.32. I'm very happy with it. I actually think that the irritating drum strikes I mentioned above were just part of the recording I've been listening to lately.
Best regards,
Adam
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Adam,
Well, thanks for the pics, but I'm totally blind so they don't do me much good :-).
Yes, sounds like a really nice setup there and really improvements you may make from here on out are probably going to be incremental, but hey, that's part of the fun too.
-- Jim
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In terms of a "better Crack" for high impedance phones, I think the following are the biggest potential improvements:
1) Speedball!
2) Better output capacitor
3) Shunt regulation
I'd put direct output (not cathode follower) as #4, but it's quite impractical. Something like a 6C33 running 500mA plate current would be needed. You could grill steaks on it!
I'd put a DHT output as #5, but there aren't any that have enough transconductance to compete with the 6080 for output impedance. And we have not been satisfied with paralleled tubes to get more transconductance.
Incidentally, the BeePre has a ~600 ohm output impedance. I don't know whether that is too much for the best sound from 600 ohm phones, but I hope someone tries it and posts... The BeePre has shunt regulation and current source loads, plus a directly-heated cathode and no cathode follower.
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Hey PJ,
We should talk more about a 500mA shunt regulated 6C33 amp!
I have some plate transformers that can deliver the current, and at least 10 6C33 tubes hanging around...
-PB
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Paul,
The BeePre looks like a pretty cool kit! Since I don't need a pre-amp, I wouldn't be willing to lay out >$1,000 only to find out that it doesn't work, but I would definitely be interested in building/modifying one if there was any way to be assured that it would work, or if someone else were able/willing to test it.
Ideally, though, I would want to get the impedance down a bit. While my DT990s are 600 Ohm, my most frequently used cans are 300 Ohm Sennheisers (HD800 and HD600).
Any chance you want to develop a headphone version of the BeePre? You could call it the Marie Antoinette!*
Best regards,
Adam
* Get it? The "BeeHead"! ;D
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Also, I should have mentioned that I've already installed the Speedball... I have to admit, that was kind of fun to assemble. Actually, the whole thing was fun. I found assembling the kit was exceedingly relaxing...
What is a good source of information for learning the very, very basic basics of this stuff? Right now I'm just following instructions (solder 3" black wire to Terminal A), but don't really understand what I'm doing. Imagine a not-very-bright 4th grade student wanted to learn about this, what would you have him/her read? (OK, maybe slightly above that level...)
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Love it - my first electronic project was in the third grade. A headphone beeper; my dad thought I would be eager to learn Morse code. He was wrong, I never did, but it started the soldering bug.
I usually recommend getting a text from a community college electronic technician course. They tend to be much more hands-on and practical. There are some online resources too, I expect others will post some links.
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Hey Jim, thanks for reminding us that you are blind - I sometimes forget about the 'quotes' for folks like you.
Cheers - Eric
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Paul,
I've thought about it some more, and I would actually be interested in pursuing the idea of using a modified BeePre as a headphone amp, but I would need help figuring out what mods would be necessary. Is that something you would be willing to do? Or is this a stupid idea that should be laid to rest?
I think there is a real market for a super high-end headphone amp. People regularly spend over $1,000 for headphones (Sennheiser HD700 and HD800, HiFiMAN HE-6, LCD-2 and LCD-3, Ultrasone Signature Pros, Ultrasone Edition 8 and 10, Stax 007 and 009, etc.), and regularly spend over $1,000 for headphone amps (Beta 22, SPL Phonitor, Burson amps, Woo Audio WA22 and WA5, Eddie Current amps, etc.). Why shouldn't BottleHead get a piece of this pie, especially if it can be had by "merely" tweaking an existing product?
Even if you're not interested in creating this as a regular product, I would still be interested in this as a one-off...
Any interest? Or would the necessary modifications be impractical and too complicated? Is the end result unlikely to be a real improvement?
Best regards,
Adam
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Also, can I use these adapters to run 6SN7s in my Crack?
http://www.tubemalls.com/plated-Gold-pin-tube-socket-adapter-6SN7-to-12AU72PCS-a-lot-52.htm
Note that it says "filament must be 6.3V". Is this a problem?
Best regards,
Adam
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Those adapters will work well.
IMO, the Paramount is highly adaptable to headphone use, so much more so than a BeePre.
-PB
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Paul,
I've thought about it some more, and I would actually be interested in pursuing the idea of using a modified BeePre as a headphone amp, but I would need help figuring out what mods would be necessary. Is that something you would be willing to do? Or is this a stupid idea that should be laid to rest?...
The BeePre can't get below 600 ohms on its own, so damping factor of 1.0 for 600 ohm phones, worse for any others. So I mentioned the possibility but can't say if it will actually work out.
Doc B has several Senns, so does PB I think - let's let them do some critical listening before we get carried away. The only mod I was proposing would be to install a headphone jack.
If it can't be done without a transformer, we have a few different approaches using transformers. I expect there will be a higher end something, eventually.
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Those adapters will work well.
IMO, the Paramount is highly adaptable to headphone use, so much more so than a BeePre.
-PB
There is also a 12V version of those adapters available. Which version is preferable with the Crack?
Would I need 2 Paramounts for use with headphones? If so, I'm afraid that is out of my league...
Best,
Adam
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You'll want the 6.3V version for use with the Crack.
Yes, you'd want a pair of the Paramounts for headphone use. While they are expensive, my AKG K-1000's on 300B Paramounts is a combination that has not been topped by any other headphone systems I have heard.
-PB
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Paul,
I see now that the Paramount price is for a pair. I originally thought it was a per mono block price. That makes the price entirely manageable, although the physical size of two Paramounts would likely be an issue for my intended purpose. I'll have to measure it out...
Best regards,
Adam
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Yeah, they are just a bit on the large side, but man are they fantastic!
To cut down on the size, I believe the bases can be trimmed down a little bit (for height).
You could also build them on one chassis plate to save a bit of footprint.
The Paramount will offer the most step-down of the signal on the plate of the 300B, giving an outstanding damping factor into headphones of any impedance, and offering some serious power!
I'm hoping to cobble together a second set of Paramounts for myself that will become a dedicated headphone rig with balanced outputs.
-PB
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Do you use them with any other cans, or just your K1000s? I have a pair of HE-6s which might be a good match, but would the Paramounts also pair well with my HD800s or, say, high sensitivity, low-impedance cans like my D7000s or Ultrasone Signature Pros? Not a problem if they wouldn't be a good match for the Denons or Ultrasones, but I would like to be able to use them with my HD800s...
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Hi Adam,
I've heard this rig that PB is talking about, but only with the K1000s, and not under the best listening conditions for them (open canjam room at RMAF 2011). I think they'd be wonderful with the HE-6s, and probably finewith all the other cans you mention as well, but you might also want to have a look at the s.e.x. 2.1 which a number of people really liked with the K1000s as well as the LCD2/3s. I heard this amp with my Shure SE-425 IEMs and it was very nice as well -- especially considering that they are the polar opposite in terms of sensitivity from these big guys I mention. I know Doc has also said that it's nice with his HD-800s as well. Don't want to throw a monkey wrench in the works, but it shouldn't be discounted out of hand either. And the s.e.x. can be wired for balanced outputs, as well as have the impedance switching board installed, which will give you a range of impedances and balanced/unbalanced options at the flip of a switch.
You probably can't go wrong with any of these but the paramounts may still be the top of the heap.
-- Jim
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Thanks, Jim. I'm sure the S.E.X. is wonderful, but my goal here was to find the best OTL amp I could. The S.E.X. is transformer coupled, isn't it? (While we're on the subject, are the Paramounts OTL?)
I already have several transformer coupled amps, and I find the Crack to be a miniature revelation...I'd like to pursue that OTL sound. Then again, maybe this is a fool's errand, and I should just be happy with the Crack. I just bought a Tung-Sol 5998, and I will try rolling in 6SN7s. Plus the cap upgrades...we shall see!
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Yes, the SEX and the Paramounts are transformer coupled.
I'll keep you posted on the high end OTL developments.
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Thanks, Paul.