Bottlehead Forum
Bottlehead Kits => Crack => Topic started by: albertoduarte on December 02, 2011, 10:36:56 AM
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Hello,
I'm interested on a Crack Headphone amp and I will like to know if can be configured to allow balanced outputs.
Best regards
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Nope. But the Smack kit has balanced outputs.
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Thanks Doc.
Since still I don't decide wich headphone I will use, Senn HD650 or AKG K702, I am checking options.
The first ones, as far as I know works very well with the Crack because its high impedance, but not the AKG's (62 OHMS). The later works well with both? The Smack has 16,32,64 and 128 OHMS loads, but the senns has 300, more than the double.
The AKG are a little less expensive than the Senn's, so I can expend the extra money on a little more expensive but better match amp.
I know that most people say that the way that sound an equipment is a subjective matter, but I believe it is not. I believe that one of those combinations sounds closer to the natural thing.
Regards,
Alberto
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Yes, the Smack amp is designed to work with any dynamic headphone that doesn't require an unusual amount of power (i.e. K1000s). The 128 ohm tap is great for headphones with impedance anywhere above 120 ohms. Smack was designed to address the needs of users who have several different headphones of different impedances.
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Thanks so much again Doc.
OK, so in sum if I get the HD650 I can use both headphone amps. In your opini
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Again I may be repeating myself, but though I am obviously proud of all of them my favorite amp of our product line is the Smack. My taste is to really good extension of both frequency extremes, nice even tonal balance and a very quick and articulate sound. When I listen to music I am very familiar with, like things my friends have recorded, I get the best sense of being in the control room listening to the original capture on the Smack. The Crack can give the sense of more bass bloom on some headphones (which might be advantageous if you have cans that tend to be lean on the bottom), it has higher sensitivity to deal with low output sources and can put out a bit more power into high impedance cans. The output transformer circuit in the Smack seems more suited to my taste than the cathode follower of the OTL amp in the upper mids and top end.
One must take these kinds of things on a case by case basis rather than letting generalizations influence our final decisions. Having headphones that can be run balanced on the Smack can, in my opinion, create another jump up in realism. But if you have high impedance cans and desire a more "tube-like" experience (what a lot of people think tubes have to sound like, something that might sweeten up less than optimal digital sources) I think the Crack or S.E.X. might be more suitable.
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OK.
I do hear a lot of analog music. I do prefer, when I can get it, an original LP record or an "all analog" reissue using the original analog masters. I have a 300B SET amp that really sing with well recorded music. I have tried some tubes and keep the ones that offer me the detail and the sweetness, but not excesive sweetness. I also hear a lot of live orchestal concerts and band concerts, so that's my reference, a live concert; the real experience. Thats why I believe that is an objective matter.....but I'm not a musician and I did not have absolute ear. Digital music tends to sound diferent to reality, analog is more lifelike. Excesive sweetness is not lifelike neither.
Since I can't hear this amps or headphones before I buy it, in your opinion, based on your live music auditions, wich formula have all the ingredients to emulate the real thing: 1)AKG K702 + Smack, 2)Senn HD650 + Crack or 3)Senn HD650 + Smack.
The best for you,
Alberto
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"Monty, I'll take door number three - with a balanced cable, please."
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Instead of opening a new thread let me ask something related:
Is it possible to set 2 Cracks on balanced?
I read somewhere on head-fi that maybe the Smack is not "fully balanced" as it does not have a balanced input. I'd like to try my HD600 in balanced and I'm thinking on getting the HD650 too. The Smack tempts me but since I have 1 Crack building another one is also an option if it's possible.
Also I'm thinking on getting a DAC like the NFB-1 where it's told that the RCA output from this DAC is like the balanced one from this same one on performance. It came to my mind, maybe the Smack would perform nice with a DAC with such RCA output. What would it be?
With an extra Smack I would have 2 stations if I also get the HD650, that would be nice too.
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Let me try to clarify, since "balanced" is a term that seems to be losing its meaning in widespread usage.
"Balanced" refers to a type of interconnect with two signal wires, and the signal is the voltage difference between them - independent of any signal common to both wires. The best performance is achieved when the impedance to ground is the same from either line, and the impedance to ground is small at the source but large at the destination. It has nothing at all to do with how the signal is amplified, and there is no requirement that the signals be equal in amplitude relative to ground; in fact the whole point it to make them independent of ground - it's only the difference between the two wires that matters. There is no such thing as a balanced amplifier; interconnects can be balanced or unbalanced.
"Push-pull" is the term that means there are two equal and opposite signals relative to ground. An amplifier with push-pull inputs and push-pull outputs can accept balanced inputs and produce balanced outputs, but it is easily overloaded by a common-mode signal at the input. However, this can be done without expensive transformers, and many so-called "balanced" inputs and/or outputs are achieved this way. This cost-cutting practice has fed the confusion of terms. There are no push-pull interconnects; amplifiers can be single-ended or push-pull.
The final bit of confusion comes with headphones. Most headphones and headphone jacks have three wires for stereo - two unbalanced signals and one shared ground. In many cases, you can get a sonic benefit by using four wires, so the return signal current is not shared on a single ground wire for both channels. Such a headphone cable is a balanced cable, since there are two wires for each channel and the signal is the voltage difference between them. This is true even if one side of each pair is grounded at the amplifier. The impedance of the amplifier output to ground is of course not equal to the impedance of ground to ground (i.e. zero) so it is not an optimal balanced interconnect application, but the headphone does not much care, it only sees the difference between the two wires and knows nothing of any ground potential. You can achieve a more optimal source by using a transformer with a center tap (like Smack) or a push-pull topology or simply adding a resistor to ground from the second interconnect wire.
There are many more things that can be said on the subject, but this post has become pretty long already. Bottom line, any headphone can be converted to balanced lines. Then you can wire one line of each side to the "shield" connection at the plug and use a normal headphone jack, or you can use a pair of XLR connectors, or some other connector that will accommodate four wires for stereo. In the latter two cases you can use an amplifier that has more-optimal impedance balance between the two wires.
The DAC claim makes no technical sense, so I can't address it. Might have bee written by the marketing department? :^)
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Thank you Paul,
Very useful technical information.
I think what really counts is to enjoy the music, and why not also the pleasure to build your own amp.
I don't have so much experience on DACs nor headphones amps but surely I like how the Crack sounds when compared to almost any solid state I have tried.
From what I have read also from other people that have tried the Smack, it's enough to try it, nor because it's balanced or not, but because the listening impression that can be perceived from the writer.
To be sincere while I try to understand what you write and draw a diagram for the differences in my head, it's impossible for me to really imagine how different could it be heard one setup from another. Yet, I think that anyone pushing so much energy wondering this or spending time listening to the differences, is not doing what it's supposed to be doing: enjoying music and the emotions provoked.
About the DAC line, it sure it's about marketing. But I really don't know what to believe from anything that could be read and not heard. You know, it's hard to make decisions from just reading and not listening, but almost any time we would have to spent the money before trying, that's the hard part and not always easy for many.
Well, enough for my unrelated words. Thank you again Paul!
For anyone: Balanced or unbalanced, just enjoy your music! :)
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It looks like on the NFB-1 that it has regular outputs, and with it's balanced outputs those are most likely where you have four signals: L+, L-, R+, R-, where the negatives are inverted signals of the positives. The RCA outputs mostly likely just give you L+, R+, and a ground.
If you plan on building two Cracks, you'll want to take the XLR outputs from the NFB and run each side into it's own Crack, then you'll have to build another adapter so that your headphone can plug into both Cracks. A bit convoluted, but doable.
For the greatest flexibility, you could run a L+, R+, G into one Crack, and a L-, R-, G into the other one, and finagle the output connectors as appropriate. This would give you the ability to run two normal headphones separately off the two Cracks.
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Hello
I have some peerless 15356 which are 600 ohm to 150/150 ohm. Would this work to make crack output balanced? I would put the crack output across the 600 ohms and the headphone output across the 150/150 with the center taps grounded.
Thanks
Michael
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The 15356 appears to be good for +15dBm, which is 32mW. The Crack can put out about 300mW.
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I guess I better look for something a bit more substantial.
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Hello.
This is my first post in this forum and I'd like to recover this question.
I've recently purchased and built a Crack+Speedball. I'm very happy with that and my Senns HD600. But now I'm thinking in a balanced amplifier to use my 600 in balanced mode. I wonder if it would be possible with adding another Crack and build a simetric balanced amplifier with two Cracks.
Then, the question again is if is possible build a balanced amp with two Cracks.
In balanced mode, output to the phones must be only connect + and - lines each channel and amp, not ground. And I don't know if it is possible with a OTL, and how this affects to the output impedance.
Thanks,
Ignacio
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You can do this with pretty much any stereo amp. The process is to invert the signal going into one half of each of your two amps. Then you configure the output +/- from the signal + output of each channel, the noninverted + output will remain as signal hot (+), the inverted + output will become signal cold (-).
So you will need an inverter ahead of each amp and of course a reconfigured headphone connection with a hot and cold connection for each channel.
Or you could sell the Crack and use the proceeds to finance a Mainline, which is already set up to do this more cleanly and more easily. You could also do this with a S.E.X. amp by installing the impedance switching kit and making an adapter that goes from the speaker binding posts to whatever connector you use for your balanced headphone cable.
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Then, the question again is if is possible build a balanced amp with two Cracks.
Hello Ignacio,
I built this amp some years ago, before the Crack came out:
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fusr.audioasylum.com%2Fimages%2F2%2F27873%2FDSCN2398.JPG&hash=6c6019c93f1c175ed221225a0a8217d729ec1bae)
In all honesty, a single Crack sounds much, much, much better than this amplifier ever did, despite the massive amount of work and experimentation that I undertook in attempting to get this right.
-PB
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Paul, that looks great. I can't even imagine how much time you spent to experiment and build that beast.
Also... are these HD600? Neeeah...they are probably HD600 mutated with HD800, mutated with some Beyerdymanics... etc.
How long ago was that picture taken?
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I built that very early in 2008.
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Hello Ignacio,
I built this amp some years ago, before the Crack came out:
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fusr.audioasylum.com%2Fimages%2F2%2F27873%2FDSCN2398.JPG&hash=6c6019c93f1c175ed221225a0a8217d729ec1bae)
In all honesty, a single Crack sounds much, much, much better than this amplifier ever did, despite the massive amount of work and experimentation that I undertook in attempting to get this right.
-PB
Paul I love the thought and attention to detail of your builds like the way the (Daytons?) capacitors show through the top plate or the offsets on the smaller tubes.
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By doubling the amp and inverting the phase on one side, you create two other effects besides "balanced" outputs. These effects do not occur when you use a transformer to generate the balanced signal, as in the Mainline:
1) You have made a push-pull amplifier, which has quite a different distortion spectrum and does not sound the like a SE amp.
2) You double the output impedance, which is already a limitation of the Crack.
I'm not predicting whether these differences will sound better or worse to any particular listener - we are all different. And it's an exaggeration to compare this to making an automobile by strapping two motorcycles together ... :^)
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How about two motorcycle engines in one car?
http://sundoulos.us/vehicles/sportstar.aspx (http://sundoulos.us/vehicles/sportstar.aspx)
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Thanks a lot for the answers.
You can do this with pretty much any stereo amp. The process is to invert the signal going into one half of each of your two amps. Then you configure the output +/- from the signal + output of each channel, the noninverted + output will remain as signal hot (+), the inverted + output will become signal cold (-).
Thank you, Doc. Yes, I knew that. It's not really necessary in my case because I want to use a balanced source. This is the reason why I thought in build a full symetric balanced amplifier: maintaining the signal fully balanced from the beginning until the end.
Or you could sell the Crack and use the proceeds to finance a Mainline, which is already set up to do this more cleanly and more easily. You could also do this with a S.E.X. amp by installing the impedance switching kit and making an adapter that goes from the speaker binding posts to whatever connector you use for your balanced headphone cable.
:D Doc, don't believe that I didn't thought it!
But, for the same reason, I don't want a SE amplifier and convert to balanced in the output as I think do the Mainline (I don't know deeply the Mainline and I can be wrong). I don't think that it will be a real improvement. In fact, the Mainline's reviews that I've read agree with the opinion that there are only a light improvement using the balanced output with the HD600. In this case, I prefer use the SE Crack that is really marvelous as well.
By doubling the amp and inverting the phase on one side, you create two other effects besides "balanced" outputs. These effects do not occur when you use a transformer to generate the balanced signal, as in the Mainline:
1) You have made a push-pull amplifier, which has quite a different distortion spectrum and does not sound the like a SE amp.
2) You double the output impedance, which is already a limitation of the Crack.
Thank you, Paul. That explains me the things.
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Thank you, Doc. Yes, I knew that. It's not really necessary in my case because I want to use a balanced source. This is the reason why I thought in build a full symetric balanced amplifier: maintaining the signal fully balanced from the beginning until the end.
The real question here is why?
Having built plenty of fully differential circuits (which has somehow morphed into being called "fully balanced"), they are all amps that sit on the shelf and don't get any play time.
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I apologize, I misspoke. I should have clarified going into this that you are asking about a differential, i.e., push pull conversion. That is different than balanced output. Thanks Peej for clarifying.
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Thank you, Doc. Yes, I knew that. It's not really necessary in my case because I want to use a balanced source. This is the reason why I thought in build a full symetric balanced amplifier: maintaining the signal fully balanced from the beginning until the end.
The real question here is why?
Hello Paul. Probably it will be a misconception from mine. If I have a balanced (or differential) source and I want balanced outputs in the amp, I think that is a better way keep the differential signal all the path instead convert to SE in the input and convert again in the output.
Ignacio.
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PB probably summed up the combined firsthand experience we can give you with his opinion of the amp he built. It's certainly possible from a technical standpoint. Beyond that I think you will just have to try it and see if you like it.
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Thank you, Doc.
Yes, I must think it very slowly. Until now I was only wondering if it would be possible (due to the nature of the amplifier OTL).
It isn't a cheap experiment. Not only I need a new Crack+Speedball, I also need paired tubes.
Thanks to all for help!
Ignacio.