Maniac

I actually have experience with the exact same stepper in C2C, about 5~6 years ago. It used to be all the rage here in Taiwan, with cheap kits that allow you to build it yourself, and yes I did build a couple of it, and no, I hated the thing. However, since I'm also selling similar products, I felt it is best if I keep it to myself, or else people would likely assuming that I'm slinging mud with baseless claim to attack a competitor. The ladder type circuit often used will produce also a "boom" when you change volume, and if you change the volume often, it WILL die rather quickly due to the spring losing tension. (People have reported that their stepper dies in about 8 ~ 10 month) Why they hell am I thinking about dropping a stepper volume control in our HA-006? Well, it is because I've found another different design that is closely based on Pot type technology than switch type technology. For example, instead of a real spring loaded switch contact that compress and relaxes as it go in and out of contacts, our stepper uses a wiper assembly with constant pressure just like what you see in pots, and the tactile feedback is done with additional mechanism instead of using the contact to create the stepped feedback to your hand. Without a switch contact that tighten and loosen when you turn it through the steps, it will not lose tension in such a short time. Also, the circuit is based on 1% precision SMD resistors in series, it will NOT produce a loud boom when you change volume, it will create a very small audible artifacts when going between steps as you turn. However, those audible artifacts is not harsh or loud, and one gets used to it rather quickly. (It's like a soft mid freq pop that is mixed into the music, you might not even notice it if you aren't looking for it.)

Hummm, I'm thinking, what about modifying the locking socket so that it does not require as much effort to insert and remove plugs? I guess I can tamper with the locking spring in there to make it submit somehow.

Unfortunately the locking jack is designed into the case, and there just isn't any easy way of replacing it with a regular jack. But I will definitely consider getting rid of it once we have gone through the current batch of cases. As for the upped version, the no-name locking jack will be replaced with a Neutrik locking jack that have silver plated contacts. As for the stepper, I understand your concern, but the one I'll be using (I'm using it right now on test rigs) does seem to have struck a nice balance between range and step size. As well, for the high end version, the gain of the unit can be specified by the user from anywhere between 1 to 11x. It won't be the exact number that the user requested, but it will be quite close. Thanks David

Just wondering, how's everyone's take on a higher end version of HA-006+ (Might just call it HA-006++)? Basically it would use better parts all around, including stepped attenuator for volume pot. I'm thinking the price would be around $450 USD, I'm beginning to test some variations of it, and hopefully will have more conclusive results soon. (All of them are not even close to proper break-in period, so I won't comment of the actual differences, but does appear promising...) Thanks David

Well... the result was quicker than I had expected... I changed -15V rail to about -10V, the output DC's bias changed 5mV when I did that. That's done without a load, which would mean that if you got something like a 32ohm load attached, it would have dropped it down to nothing. (Well, 5mV is pretty close to nothing too.) And yes, it is done with both servo removed to ensure that servo is not trying to fix any possible imbalance. IMHO, I think the reason that the DC bias changed is not due to the fact that this is a DC coupled amp, but the effect of rail voltage on the input JFET, which have quite an effect on the output DC bias.

Well, I actually have a HA-006+ on my bench, it's about half way though the "+" upgrade and it should be good for a bit of test with imbalanced power. Lemme grab some gears and get it setup.

Personally speaking, I don't really feel that there's a true need for a tracking power supply. Power wise, a properly done (non-tracking) power supply would not have much in the way of imbalance between the positive rail and negative rail. Secondly, with most amps, you actually won't find a lot of difference even when the power rail is slightly imbalanced, and about the only time you will know that it have an imbalanced power rail is when you open it up and measure it live with a multi-meter. Sound wise and output measurement wise, unless it is so badly imbalanced, it should actually be extremely hard for user to notice the difference even if you have the chance to A-B compare one with imbalanced rails and a precisely balanced one. I reckon it would have to have one of the rail off by at least 10% or more to have a noticeable effect, but if any of the regulated power rail is off by 3 percent from factory setting, you'd have more problem to worry about than just sound quality. I'll have to say that I have not tested an amp with rail intensionally imbalanced, and have never really saw any +/- rail power going out of whack from all the machines that I've opened up or modded myself. (I do mod a few equipments that I use for the fun of it.) Thanks David

I wonder if your setup can allow you to try no attenuation on the computer side and see if there's any difference? I have not really tried foobar's volume control, but most others me and some of my customers had tried has been that as long as there SOME digital attenuation, the damage will be there, doesn't matter how much you attenuate it.

Due to the nature of pot manufacturing, and the log curve required makes it very difficult to make the first section of the pot uniformly as they (or we) liked. However, from what I found out, if there's not much imbalance, the pot actually does not degrade the sound that much. If you use digital volume control on your computer, it will actually cause it to degrade a lot more than that. That's one of the reason that quality stepped attenuator and quality pots are asking for big bucks.

Actually I thought about that too, but I've found out that there are a lot of sources that can't put out 2VRMS for various reasons. DynaLo should be able to put out a bit more than 15V P-P, I can't recall the exact figure, but I think I saw something in the 20ish zone when I was driving it to clipping on my scope. You know, as often as there are good rules and habits, there are manufacturers that breaks it for one reason or another. That's one of the problem that I've seen some user have, and of course, there are sources with nutty RCA output level of over 5VRMS. It would be perfect if everyone can tailor their setup themselves to exactly fit their need, but to be honest, even I get tired of building stuff for my own use. Thanks David

If they do not understand gain, then they would just go for default, since it got "bigger" gain, appears more powerful and does not cost a penny extra.

Nah, there are some headphones that REALLY needs the gain. If I claim the gain is low when it is actually high, people with sensitive phones is still gonna be pissed that they are stuck at 7~8 o'clock position. If I claim the gain is 11 while it is like 3, users of K240DF, K271 and such might wonder why they can't hear much even with the volume turn up to the max. IMHO, honesty here is the way to go, as most users are knowledgeable about their preferences and choices. I briefly thought about selectable gain, but decided against it. As the current design does not have any easy way to add it without LONG wires to connect it to a switch somewhere. Might as well have it soldered in properly. Thanks David

Hummm, I think I will have an option of 3x and 5x as optional. And have 11x as standard, as others posted above had said. It's best to have uninformed customer getting what they wanted, because I do see a LOT of comments about "This amp is not powerful, cuz I had to turn the volume up." in a few forums. Most of them just don't have the concept of gain and actual potential max power of the amp. Since those who KNOW and understand the advantage of lower gain know exactly what they wanted, I think they will pick what they wanted from the option instead of going with default. I will think about the exact gain value offered, and the parts that I'll be using, and then post it on the web shop as well as here.

Just wondering about one setting on DynaLo, originally I believe it is set at a gain of 11, and since that might be a bit much for some of the more sensitive ear/headphones, what would you guys recommend as an "optional" lower gain setting? I'm considering adding it as a option that you can choose at the time of purchase. (The option would cost around $5USD for parts and labor) Basically it would involve paralleling a resistor over the original gain resistor, so that adding this option would not take much time and won't require me to stock a load of dynalo boards with different gain settings. Thanks David

A few posts back, someone mentioned about "improved on the original", basically it meant improved on the original HA-006 to the current HA-006+. Not improving on the DynaLo, as it is the original concept and we don't plan to change too much of that.

Hello luvdunhill, thank you for the offer. I had saw that dual JFET a few years ago when I started building my Beta 22, but LinearSystems never seem to make the 2SJ side of the Dual FET, if they do make the other side, we will definitely consider using it. Possibly using the SMD version for small/entry level version and the metal canned one for higher end version. However, that's only gonna happen if they decide to make the 2SJ side of the transistor. For the moment, it is hand matched to very very low DC bias at the output (normally below 5mV without DC servo, rarely above 10mV). Thanks David

Woops, I shipped out on the 6th not 5th, sorry for the incorrect on the previous post...

Hello everyone, I'd like to put in a few words regarding the HA-006+ The original Gilmore DynaLo design uses dual FET that is next to impossible to acquire in large quantity at reasonable price. (I used to be able to get a pair for around 8 USD, now I found someone selling them for $28 a piece) That was replaced with hand matched single FET. That is all the change regarding transistor selection. During the Christmas/New Year, we were working on lowering the overall noise floor of the HA-006+, while it is very quiet with high impedance load, it starts humming softly with 32ohm or lower load (eg: Grados, some Sonys). We were probing and prodding the unit for quite a while before replacing the transformer with an ultra low noise Toroidal transformer. Which lower the overall noise massively, and does not really show any sort of noise at all, even with Grados and other sensitive headphones. All those who have purchased HA-006+ from me is entitled to a free upgrade that includes round-trip shipping. All those who ordered during the Christmas season had their order put on hold until the upgrade is ready (which was then shipped on Jan 5th). If you guys have any question regarding the unit, please feel free to ask.

Thank you, we try to keep the top as clean as possible for both aesthetic and layout concerns, and some of the components are placed on the bottom for optinum layout and placement considerings. The side effect is the top sometimes gets a bit barren.

Thanks for the compliments, The It is because we want to line up the center line of the jack and knob horizontally. Otherwise we'd have to lower the jack's position and make it look lopsided. The white wire you see connecting to the jack and RCA sockets are Belden silver plated copper wire with Teflon insulation. It's one of the better wires around that don't cost some crazy price. As for topology, it uses KECES Gen2 power supply that had been evolving for some time. It takes up the bottom part and left part of the baord in the internal photo. The part with the two blue pots is the precision voltage reference, and the left half of heatsink cools the two transistors controlled by the voltage reference. The whole power supply took up like 2/3 of the board space. The actual amp, uses National's LME49710 OP amp for voltage gain and LME49600 for current gain. It is a very simple circuit that is one hell of a devil to optimize, we had dozens of prototype board sitting there doing nothing because earlier designs didn't meet our requirements of performance. The black box you see near the pot is for gain control, which will make it a lot simpler for headphone users, as headphones comes in so many different sensitivity, and is very hard to pick a single gain setting that can suit them all. Anything else you would like to know?

We always check customer's location and pre-set the unit to the proper voltage, and include the proper power cable for the region. (We have American NEMA type, Euro Schuko type, Brit type and Aussie/Kiwi type of power cable in stock here...) We feel that including the cable is going to make it more convenient for most people, as for RCA/Coax/Toslink cables, we opt not to do so as most have their own preferred cable.

I'm certainly considering that, any recommended member? A few reviewers I had previously were less than ideal, some dragged on for 3~6 month, and some simply vanish not too long after they have decided that they'd like to keep the unit. I think neither me or the community would really want to see either happen, as it not only deter us from providing the review sample, it also deprive everyone the information that they had waited so long to see. Thanks David

The top is the same as the other's in using a translucent acrylic cover. Both output are always on, by slaved to the headphone output, I mean pre-out output the same volume as the headphone output. Innards view: To satisfy the pixel peepers inside all of us. Click for large 5 mega pixel photo if you REALLY want to see the details. Anything you'd like me to elaborate about on the photo? The relay in the back is for input select, and the one near the volume pot is for gain selection. Thanks

It's alright, thanks.

Will post some internal photos in a few hours, need to get my shooting rig setup so that I can take a more detailed photo.