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yesterday's harvest

There has been some renewed interest in the DSHA3F (which is our Focal optimized amplifier) of late. In order to keep the manufacturing process as smooth as possible, I am accepting orders for this amplifier for a small batch run for the next 2 weeks or so. I expect these amplifiers to be delivered around late March (with any orders after this batch not being ready until June or so.) Price is $2800, and orders require a 50% nonrefundable down payment.

When I heard these were being released I just had to get a set to see if they matched the supreme crap that the original was. Now after some delays I picked the set up from the postoffice. This first post will focus mostly on the amp, the headphones will be taken apart at a later date. I have been listening to them for a few hours now so some quick impressions are in order though. Same build quality as we've come to expect from Hifiman...i.e. absolute fucking trash. First off, the phones stink badly. These are 1500$ on their own so much like the Shangri-La JR... everything is nasty synthetic crap. Same cable as the Shangri-La and Jr. use which is completely unsuitable for this role. Comfort is ok, I have the headband at max extension and the headpad is a bit uncomfortable due to that. It's odd though as they are feather light. As for the sound, well first thing you'll notice is the utter lack of usable deep bass output. I think there might be a port hiding somewhere in there as they don't squeal as they should. Tonally they are ok though, a bit thin, non offensive and the soundstage is decent. Similar league as the L300 but the bass issue has to be fixed for them to be directly compared. This is off my usual setup (Denafrips Terminator, Carbon CC) and not the included amp. Nothing from China is turned on here without being taken apart... Now for the amp, this is probably the worst chassis design ever and pretty much an utter pain to get into. Now to do so, you have to take off the front and remove the two screws which hold this PCB: Then remove the nut which holds the attenuator (more on that later) and finally remove the screws for the back panel: Undo everything there as well and the power switch and input wires are on connectors. I just cut the IEC off though as the input wires for the switch are nowhere close to safe and so is the earthing in this thing. Just look at how thin that stuff is. Also, why the hell didn't they use push on connectors for the IEC? It would make it much simpler... Once all that stuff is off you can pull out the pcb's and disconnect the transformer: Doing that I saw this gem... the bare wires from the transformer are ziptied to the input lead. Yup...no need to separate that... You can also see the earthing tag there. At this point I'm not sure where the earth is actually connected to the chassis. Two wires connect with a screw to the top PCB at the back, one from the IEC and one from the transformer shield. Granted this goes through some standoffs and to the chassis eventually but that is now how earthing should be done. On the other side of the board there is an earth wire that goes directly to the pot, which is mounted on the chassis but that is also not proper earthing. This is all very China "we don't give a fuck about safety". Now here is the top board as it comes out of the chassis: Clearly the PSU and easy to read the output voltages on the bottom. Fixed regulators for the low voltage stuff (proper JRC parts so that's nice) and simple HV supply. Now anybody familiar with old Stax amps will notice what the amp actually is at this point. Funny to see the mix of crap caps, the input caps for the LV supplies are Lelon (crap) but the output are Nichicon. Same goes for the HV side, input are "JH" (never heard of it) but the output are Nippon Chemicon. Just odd but I'll go more in depth on the PSU when I rip out all the crap caps. Here is the back of the PSU: Now the amplifier, with just three voltage rails, +/-15V and +660V there is just one possible topology here. Resistor current source feeding a single output device. So here we go: Yup this is utter shit and a clone of what Stax did with the SRA-10/12S back in 1972. It gets worse though... Say hello to the mosfet output devices and well...their typical output capacitance of 65pf. That's half the capacitance of the phones and you have two of these per driver. Yup...pure quality here. The 2SC4686A we used in the KGSSHV have a Cob of about 2.4pf and the goal here is to keep it as low as possible otherwise it will mess up the sound signature of the amp. Think Cavalli Liquid Lightning here... Here is the input section and the we need to discuss that a bit. So this amp has a balanced input but it isn't balanced. The volume control is one of those cheapo 21 step steppers you can find on ebay for 15$ and just two decks. There are also just two wires coming from the input board per channel, Rin and ground... Funny too is that the instructions manual specifically states that the volume control is a 21 step relay based attenuator. Yeah...that is a fucking lie. So the amp is resistor loaded mosfet with output capacitance matching the load and isn't actually balanced. The output caps are at least larger what what Stax used back in the day so that is something... Now we need to discuss this board: This is on front panel and for some reason the outputs have relays on them and 1K output resistors. While better than nothing, something in the 5K range would be a better choice. Now comes the point some were waiting for, can this thing be used with Stax sets? At this point I'd say no, there are just 2M ballast resistors on that board for each output (no idea why they used two) so this amp can damage Stax. Ohhh and one funny thing before I go do something productive...they hand matched the output load resistors... Finally just a dump of the extra pics I took if anybody wants to look through them.

Well I was finally fed up with the shit cable so out came the tools... One funny thing, I just read through the manual and it specifically states that these have a gold plated plug...which they don't have in reality. Why state something which ever owner will easily spot as a lie? Similar earpads to the Shangri-La Jr. The protective mesh is just a black PCB and the other side even has some production markings on the silkscreen. First reveal and yup...these are 100% pcb. Just stacked up in the baffle and no glue at all. Now comes a pile of pics: It's an interesting design but from a build quality point of view, this is miles away from what Stax are doing. One other thing, the headphones are wired up backwards, + output is wired to the back stator. The back grills just drop out and are not fastened in any way. Time for a new cable. The wide PC-OCC Stax cable is a tight fit but it does work. All done.

Finally got around to finalize my Megatron, fitted into one chassis with GRHV.

Well I killed my dirt bike this morning so out goes the UTV. Been a lot rain in the mountains on my side of the valley. I'll pull the power washer out after hitting the trails again tomorrow. Was really wishing I spent the few dollars to refill my tear-offs.

Ok, fine. I'm on board. 😁

I swapped to the 009S a few months ago. It’s not better - just different flavour which happens to suit my tastes better. Maybe slightly fuller sound overall and less toppy with my new amp:

I did manage to get the dirt bike going again. The temperature this week has been just ideal for the bike.

My latest track.

Received that Saxonia, and I’m over the moon about it, not only does it look and feel amazing, but the winding is very enjoyable, turning its crown makes a ratchet sound with a reassuring movement, then it kind of springs back slightly when stopping the wind. The only thing I would change which is what I’ll be having done is its strap, I got another strap for my JLC because I was having a problem with its, this other strap I got from Toshi Straps Uk, and I like it much more than the ALS’s, but apart from that I just love this Saxonia. Anyway here are some photos which includes the packaging it came in, because I’m very impressed with it. The 37mm Saxonia probably looks big on me, but that’s because I have thin wrists, 6.25”.

Says the guy that seems to fall down in spectacular fashion several times a year. 😂

I may just step up to the Airpulse 🤔 https://www.edifier.com/us/en/airpulse

Sent from my iPad using Tapatalk

I highly recommend truffles.

Kraftwerk tour de france

Millionaire's Bacon and Eggs -- really more like pork belly and eggs.

making some progress through my Horowitz catalog.. 8&9 this morning.

Coq au Vin, final stages

The answer is always, collusion.

Meet Mittens and Silver. They already follow me around and jump up next to me. A good sign, I think! Mittens is 8 and Silver is about 18 months. They were living happily together at the SPCA, so I couldn’t break them up

New Vampire Weekend. I like it, less mannered, looser. Good.

No pics of the actual meal but made pork chili verde today during winter storm Harper. It was a good batch.

I am back and while the previous debates cleared up differences between class A and AB, I have some further remarks. In order to make these remarks I will use available information through [electronics-tutorials . ws] which I will link to down bellow. If not for anything new, then this entry is in large for myself and possibly other who read and have the same questions / concern as I do, and remember, this is for educational purposes. *** I started this thread with a question: Why no KG class AB ? because my perspective was that if done right, class AB could sound as good as class A but retain a better efficiency. Not that I made that clear in the first entry, at least it was in the back of my mind and I wanted to check for explanations from other more enlightened head-case members who could explain things in a way I could not. I am still learning and the information which I have come over in the past few day is an eye opener. Yes yes I know, for most of you the information I will present is old news, no brainer or perhaps jaw dropping. No matter, I've had a blast, learned things I did know would transpire and also made it very clear how things should be done from now on. So lets get going. Edited reply's for the convenience of this entry, but you can always go up and read the full statement(s). JimL; 1) - So basically, until Mark Levinson and Krell came along, pretty much all amplifiers were class AB because nobody thought that there was a big enough market to support a class A commercial amp. Class AB was considered the best compromise between cost, efficiency and sound quality. It was never considered the best, just that Class A was considered too expensive. 2) - The first Mark Levinson Class A amp was rated at 25 watts (but was reportedly class A down to 2 ohms, at which point it was a 100 watt amp), was mono, and was big, heavy and cost a few thousand dollars - I think you could have bought over 100 NAD3020 integrated amps for the same money, and the 3020 was stereo, had roughly the same power rating, and included a phono section. But, it turned out that there was a market for it, and Krell came out with stereo class A amps that had more power and generated more heat. And it's gone on from there. The limiting factors for speaker amps is basically how much power do you need and how much money (and size, and heat) do you want to spend getting it. 3) - For non-electrostatic headphone amps it is significantly different. Here, you only need a few watts at most, into higher impedances than speakers have. So low to moderate voltages (say 15 volts at most)and relatively low currents (an amp or so at most). Based on specs, the least efficient non-electrostatic headphone is the HFM Susvara, and 5 watts into that should produce 120 dB, which is enough to give you hearing damage in minutes if sustained. So in theory, a class A headphone rated at 5 watts into the Susvara's impedance should do the trick. Which means that an amp that draws 25-30 watts from the wall should be able get you close to the threshold of pain In that case, there isn't a lot to be gained by dropping back to class AB. That said, some cheap headphone amps ARE run in class AB because the manufacturer doesn't want to lay out money for heatsinks. Every penny counts. 4) - One other detail is how the push-pull output stage is biased. This is basically what determines whether an amp is Class B, AB or A. For class B, the output stage is biased at zero, meaning with no signal there is no current running through the output devices. 5) - In class AB, there is some current running through the output devices with no signal, but when a signal is sent through the amp, each of the two output devices only reproduce half plus a bit more of the output, and the combination of both devices is needed to produce the whole signal. In reality the output devices are turning on and off during the output, which can produce crossover distortion, which is a transient that occurs when the device turns on or off. The problem is that this distortion actually gets worse as a proportion of the output was you go to lower power, until you get down to the point where the signal is small enough that the turn on and turn off does not occur. 6) - Now with most music other than the compressed crap that some modern producers are putting out (i.e. loud all the time), the fact is that much of music is at a volume that is 10-20 dB below maximum, so that an amp is usually running a 1-10% of max power. 7) - Now for true class A, there is enough current running that both devices output some signal current at all times. In theory this should only matter for music peaks. In reality, since active devices (tubes, transistors) are more linear in the middle of their operating range rather compared to their limits, this decrease distortion at all levels. So far so good right. I sat down an made a cup of coffee with a thought in the back of my mind: Remember, KG Dynalo and Dynahi is push-pull (PP) class A amplifier. The PP class A was new to me because I viewed class A as single ended and push-pull as class AB. Class A: – The amplifiers single output transistor conducts for the full 360o of the cycle of the input waveform. Class B: – The amplifiers two output transistors only conduct for one-half, that is, 180o of the input waveform. Class AB: – The amplifiers two output transistors conduct somewhere between 180o and 360o of the input waveform. Clarification: AB which use a minimum of two transistors conduct 0o to 180o for the positive cycle and 180o to 360o for the negative cycle. Class A: The most commonly used type of power amplifier configuration is the Class A Amplifier. The Class A amplifier is the simplest form of power amplifier that uses a single switching transistor in the standard common emitter circuit configuration as seen previously to produce an inverted output. The transistor is always biased “ON” so that it conducts during one complete cycle of the input signal waveform producing minimum distortion and maximum amplitude of the output signal. This means then that the Class A Amplifier configuration is the ideal operating mode, because there can be no crossover or switch-off distortion to the output waveform even during the negative half of the cycle. Class A power amplifier output stages may use a single power transistor or pairs of transistors connected together to share the high load current. This is the simplest type of Class A power amplifier circuit. It uses a single-ended transistor for its output stage with the resistive load connected directly to the Collector terminal. When the transistor switches “ON” it sinks the output current through the Collector resulting in an inevitable voltage drop across the Emitter resistance thereby limiting the negative output capability. The efficiency of this type of circuit is very low (less than 30%) and delivers small power outputs for a large drain on the DC power supply. A Class A amplifier stage passes the same load current even when no input signal is applied so large heatsinks are needed for the output transistors. However, another simple way to increase the current handling capacity of the circuit while at the same time obtain a greater power gain is to replace the single output transistor with a Darlington Transistor. These types of devices are basically two transistors within a single package, one small “pilot” transistor and another larger “switching” transistor. The big advantage of these devices are that the input impedance is suitably large while the output impedance is relatively low, thereby reducing the power loss and therefore the heat within the switching device. It is possible to obtain greater power output and efficiency than that of the Class A amplifier by using two complementary transistors in the output stage with one transistor being an NPN or N-channel type while the other transistor is a PNP or P-channel (the complement) type connected in what is called a “push-pull” configuration. This type of power amplifier configuration is generally called a Class B Amplifier and is another type of audio amplifier circuit that we will look at in the next tutorial. Class B: To improve the full power efficiency of the previous Class A amplifier by reducing the wasted power in the form of heat, it is possible to design the power amplifier circuit with two transistors in its output stage producing what is commonly termed as a Class B Amplifier also known as a push-pull amplifier configuration. Push-pull amplifiers use two “complementary” or matching transistors, one being an NPN-type and the other being a PNP-type with both power transistors receiving the same input signal together that is equal in magnitude, but in opposite phase to each other. This results in one transistor only amplifying one half or 180o of the input waveform cycle while the other transistor amplifies the other half or remaining 180o of the input waveform cycle with the resulting “two-halves” being put back together again at the output terminal. Then the conduction angle for this type of amplifier circuit is only 180o or 50% of the input signal. This pushing and pulling effect of the alternating half cycles by the transistors gives this type of circuit its amusing “push-pull” name, but are more generally known as the Class B Amplifier. The Class B Amplifier has the big advantage over their Class A amplifier cousins in that no current flows through the transistors when they are in their quiescent state (ie, with no input signal), therefore no power is dissipated in the output transistors or transformer when there is no signal present unlike Class A amplifier stages that require significant base bias thereby dissipating lots of heat – even with no input signal present. So the overall conversion efficiency ( η ) of the amplifier is greater than that of the equivalent Class A with efficiencies reaching as high as 70% possible resulting in nearly all modern types of push-pull amplifiers operated in this Class B mode. The Class B amplifier circuit above uses complimentary transistors for each half of the waveform and while Class B amplifiers have a much high gain than the Class A types, one of the main disadvantages of class B type push-pull amplifiers is that they suffer from an effect known commonly as crossover distortion. Hopefully we remember from our tutorials about Transistors that it takes approximately 0.7 volts (measured from base to emitter) to get a bipolar transistor to start conducting. In a pure class B amplifier, the output transistors are not “pre-biased” to an “ON” state of operation. This means that the part of the output waveform which falls below this 0.7 volt window will not be reproduced accurately as the transition between the two transistors (when they are switching over from one transistor to the other), the transistors do not stop or start conducting exactly at the zero crossover point even if they are specially matched pairs. The output transistors for each half of the waveform (positive and negative) will each have a 0.7 volt area in which they are not conducting. The result is that both transistors are turned “OFF” at exactly the same time. A simple way to eliminate crossover distortion in a Class B amplifier is to add two small voltage sources to the circuit to bias both the transistors at a point slightly above their cut-off point. This then would give us what is commonly called an Class AB Amplifier circuit. However, it is impractical to add additional voltage sources to the amplifier circuit so PN-junctions are used to provide the additional bias in the form of silicon diodes. The Class AB Amplifier: We know that we need the base-emitter voltage to be greater than 0.7v for a silicon bipolar transistor to start conducting, so if we were to replace the two voltage divider biasing resistors connected to the base terminals of the transistors with two silicon Diodes. The biasing voltage applied to the transistors would now be equal to the forward voltage drop of these diodes. These two diodes are generally called Biasing Diodes or Compensating Diodes and are chosen to match the characteristics of the matching transistors. The Class AB Amplifier circuit is a compromise between the Class A and the Class B configurations. This very small diode biasing voltage causes both transistors to slightly conduct even when no input signal is present. An input signal waveform will cause the transistors to operate as normal in their active region thereby eliminating any crossover distortion present in pure Class B amplifier designs. A small collector current will flow when there is no input signal but it is much less than that for the Class A amplifier configuration. This means then that the transistor will be “ON” for more than half a cycle of the waveform but much less than a full cycle giving a conduction angle of between 180o to 360o or 50% to 100% of the input signal depending upon the amount of additional biasing used. The amount of diode biasing voltage present at the base terminal of the transistor can be increased in multiples by adding additional diodes in series. Class B amplifiers are greatly preferred over Class A designs for high-power applications such as audio power amplifiers and PA systems. Like the class-A amplifier circuit, one way to greatly boost the current gain ( Ai ) of a Class B push-pull amplifier is to use Darlington transistors pairs instead of single transistors in its output circuitry. This section is the most interesting and important one. For Class A amplifier operation the switching transistors Q-point is located near to the center of the output characteristic load line of the transistor and within the linear region. This allows the transistor to conduct for the complete 360o so the output signal varies over the full cycle of the input signal. The main advantage of Class A is that the output signal will always be an exact reproduction of the input signal reducing distortion. However it suffers from poor efficiency, because to bias the transistor in the center of the load line there must always be a suitable DC quiescent current flowing through the switching transistor even if there is no input signal to amplify. For Class B amplifier operation, two complimentary switching transistors are used with the Q-point (that is its biasing point) of each transistor located at its cut-off point. This allows for one transistor to amplify the signal over one half of the input waveform, while the other transistor amplifies the other half. These two amplified halves are then combined together at the load to produce one full waveform cycle. This NPN-PNP complimentary pair is also known as a push-pull configuration. Because of the cut-off biasing, the quiescent current is zero when there is no input signal, therefore no power is dissipated or wasted when the transistors are in the quiescent condition, increasing the overall efficiency of a Class B amplifier with respect to Class A. However, as the Class B amplifier is biased so that the output current flows through each transistor for only half of the input cycle, the output waveform is therefore not an exact replica of the input waveform since the output signal is distorted. This distortion occurs at every zero-crossing of the input signal producing what is generally called cross-over distortion as the two transistors switch “ON” between themselves. This distortion problem can be easily overcome by locating the biasing point of the transistor slightly above cut-off. By biasing the transistor slightly above its cut-off point but much below the centre Q-point of the class A amplifier, we can create a Class AB amplifier circuit. Then the basic purpose of a Class AB amplifier is to preserve the basic Class B configuration while at the same time improving its linearity by biasing each switching transistor slightly above threshold. End of article entry. Conclusion - Bias, bias and some more bias. So now that we have a grasp of the difference between class A, B and AB, how do we tie together class AB and push-pull class A ? We do so by adjusting the bias to the transistors quiescent point or Q-point to the linear portion. The transistor is a linear device in the active region and nonlinear in its cutoff and saturation region. - That's it. This is the answer and "secret" wo why Kevin Gilmore use push-pull class A in his dynamic headphone amplifiers. "For now I have seen the light". We can ofc achieve the same performance via single ended but we are power limited, by using several transistors in a chain we can obtain a much higher output power but maintain in class A the whole time. That's it. I don't think I have anything els to add here. I totally get why KG is only interested in push-pull class A. - Oneminde Sources: 1. https://www.electronics-tutorials.ws/amplifier/amp_5.html 2. https://www.electronics-tutorials.ws/amplifier/amp_6.html 3. https://www.electronics-tutorials.ws/amplifier/class-ab-amplifier.html