Having an ultra high-end headphone amplifier is pretty pointless, is it not? What will you use it with? Provided their are enough vain manufactures claiming the prefix Ultra High End you are not left with many choices of products to pair it with. I guess if it does not perform as you claim, you could blame anything lesser than ultra equipment in the chain.
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Surely, even if you were unable to discern Tom's meaning from his products and engineering philosophy, this explanation should make it clear.
I suppose, I do now. Anybody can name anything they make what they want. I suppose Ultra High End is just a naming convention which have been adopted by some audio folk to advertise their flair for designing exclusive stuff.
Good luck Tom, I trust that you sell a bunch of these - why not, everyone deserves a break in life and a chance to become a champion at something he/she loves.
Good luck Tom, I trust that you sell a bunch of these - why not, everyone deserves a break in life and a chance to become a champion at something he/she loves.
As I've said before, there is about $250 worth of parts in the HP-1, not including the PCB, chassis, RCA connectors, or volume knob. The ICs alone approach $100 of that... $250 or even $100 is hardly "nothing". If it is to you, you're certainly much better off than I am. Good for you.
The chassis isn't cheap either. Low volume production, custom built. Not cheap.
And, yes, I charge for labour. I don't work for free. I don't know anybody who does. Even then, I charge less than your average auto mechanic. Not to diss or discredit auto mechanics - I do appreciate the guys who work on my car - I'm just stating a reference point.
Tom
Fantastic data and documentation for this amp, as xrk971 said i also would like to hear what a zero distortion plus non signature amp sounds like 
in its said it can work without using parallel LME49600 buffer would like to hear it with single buffer and simple solid core wires to headphones instead of the often used Litz wire.
tomchr,
Saving up for unpopulated circuit board with RCA connectors and volume knob included plus other components in first place and run it without chassis for some time frame to save on costs, will that naked tech setup perform as good as boxed ?
in its said it can work without using parallel LME49600 buffer would like to hear it with single buffer and simple solid core wires to headphones instead of the often used Litz wire.tomchr,
Saving up for unpopulated circuit board with RCA connectors and volume knob included plus other components in first place and run it without chassis for some time frame to save on costs, will that naked tech setup perform as good as boxed ?
Very true! NwAvGuy's take on it, from way back when:
NwAvGuy: Objective Desktop Amp (ODA) & DAC
search through that for "balanced" to get (regarding the never-released ODA and the ODAC):
No Balanced Outputs – Balanced audio is great for pro use with long cables and electrically hostile environments. But it’s generally more of a liability than an asset in home audio gear. All else being equal, balanced stages usually have higher overall noise and distortion than their unbalanced counterparts. Headphone drivers don’t magically somehow work better when driven by a balanced source. Most of the stuff you hear and read about balanced audio for home headphone gear is myth, hype and even snake oil.
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Having listened myself with simultaneous setups ( same headphone, OB-1 in single and modified for balanced), I have to disagree with you guys and nwNavGuy. Having twice the slew rate, 12dB more dynamic range, and double the peak power makes a difference. Especially on material with attacks and percussion or drums. Increased noise was not an issue at all.
Have you guys tried balanced setups?
Have you guys tried balanced setups?
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The HP-1 performs well even without the chassis. Just be careful with the high voltage around the mains inlet.
I did notice a measurable improvement in mains hum in the boxed amp. I forget the exact numbers but I seem to recall the 60 Hz component of the mains hum creeping up a few dB from its current level of -142 dBV. Needless to say, not audible.
Tom
Did you measure any of those parameters?
The SNR, thus the dynamic range, should be the same (2x signal but also 2x noise for the balanced drive, assuming the noise is perfectly correlated between the two amp halves - 3 dB if provement if it's completely uncorrelated). With twice the voltage drive, you'll get 4x the output power - assuming that the circuit can provide the required output current. You do get 2x the slew-rate, but unless the circuit is slew-rate limited (poor design) that shouldn't make any difference.
The theories of Norton and Thevenin should convince you pretty easily that there is no electrical difference between an ideal single-ended drive and an ideal differential drive. Hence my claim a few pages back: There's no difference between single-ended and differential drive as long as the ground impedance is low.
In theory the differential drive should cancel some of the harmonic distortion. This requires the THD of the two amp halves to be completely correlated to work well. It also only cancels the even order harmonics - the ones that are generally associated with a pleasant sound quality - leaving the odd order harmonics (associated with harshness) behind.
In my experience with cancellation circuits of various kinds, I have generally found that it is generally much better to design the circuit to not exhibit the undesirable behaviour than it is to try to cancel the undesirable behaviour. Most cancellation circuits actually make the performance worse rather than better, even though they should work perfectly in theory.
The THD of the HP-1 is -135ish dB. I don't see a problem here, so I won't fix it.
Marketing is an interesting field. One way to differentiate your product is to add features. "Our product is better because..." Pepsi was able to gain quite a bit of market share from Coca-Cola by adding an expiration date on the bottle and marketing their cola as "fresh". The product didn't change but the consumer's perception of it did. And more importantly it created a negative perception of a competitor's product. Humans are funny critters.
Tom
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Note that I said, "4x power if the output driver can provide the current". You need twice the output current for a BTL driver to reach the 4x power. If your driver circuit is current limited, you'll get no advantage at all, you just get twice the build cost...
You can easily verify this by measurement.
Tom
You can easily verify this by measurement.
Tom
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Note that I said, "4x power if the output driver can provide the current". You need twice the output current for a BTL driver to reach the 4x power. If your driver circuit is current limited, you'll get no advantage at all, you just get twice the build cost...
You can easily verify this by measurement.
Tom
P = V x V / R.
P = Power, V = voltage, R = impedance.
V max. in BTL = 2 x V.
P (BTL) = 2 x V x 2 x V / R = 4 x (V x V / R).
If you need more power but do not want BTL, just increase the power supply voltage and modify it to get the quality same or better
... when we consider hi-Z phones, it makes sense. (peak ratio in music up to 10:1, --> peak voltages needed)
With big rails, peaks are never crippled
You're just throwing out stuff without actually understanding it. Tom is objectively correct. Any explanation of balanced drive leading to sound quality improvement is dubious, especially with just "eyeballed" level matching.
The only practical use I can see of a balanced (bridged) headphone setup is to get higher output voltages when you're limited by an IC's supply voltage.
I'll get measurements shortly - it's quite obvious that the increased max SPL achievable went up significantly by ear. The volume knob used to be able to go up to max on the DAC and now it's about at half way before it's uncomfortably loud. My amp is a single ended Class A with a MOSFET source follower. The ZVN4306GTA MOSFET is tied to two 9v Li-ions batteries which I am quite sure, are capable of flowing more than the 55mA bias current. The ZVN4306 itself, is capable of several amps current, and. in non-balanced drive, max signal is limited by clipping due to single rail being at 16v or so with max output at 10v peak to peak and bias around 55mA. Although this is getting a bit extended OT discussion in Tom's thread. So I will have to wife up a load resistor in between the two amps and use a scope to measure max voltage before clipping in parallel drive vs non.
This particular amp uses only two transistors. The input stage is a BF862 JFET with a 20v limited part. There's limited room for raising supply voltage without changing to another part or adding cascoded input topology. It's a few volts shy of max voltage at present.
This particular amp uses only two transistors. The input stage is a BF862 JFET with a 20v limited part. There's limited room for raising supply voltage without changing to another part or adding cascoded input topology. It's a few volts shy of max voltage at present.
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