nikongod

Thanks to everyone who participated in this little loan circuit! Im happy it sounds like most of you liked the headphones, good stuff. I snapped some pics of the mods I did to the Grados. I blacked out the mesh on the drivers least these fall into the hands of the enemy. Im not really sure who that is though. The good stuff. If you hold a Grado driver up to a good light source you can see that there are little circular vents under the black material. I arranged the little strips of dynomat so that they did not interfere with the vents. I dynomatted the back of the magnet, and dynomatted the magnet to the frame. This probably didnt do anything. But I did it anyways.

Happy Birthday!

I had not seen this. Every SP I have seen an internal picture of or poked around in has a dedicated star ground point and no obvious other chassis grounds. Mikhail did always tie signal ground HARD to chassis ground though. Just to make sure, you measured impedance between the various chassis, and got something other than 0? Call Craig.

There are a few schools of thought & "styles" at play here. If you want to get techy I'l pick the other side and well duke it out until we come to an agreement, which will be never. Woo amps have a very right angle design. EVERYTHING is at right angles. They all use ground bus bars (no star grounds). The amp you have follows what apperas to be the "shortest wire" design. It looks like there is a star ground point although more of a "x-mas tree" style ground system. pros & cons. Having all of your components layed out at right angles makes the layout of the amp a decent bit cleaner looking (visually...) and is MUCH easier to assemble. This is key when the realities of mass production are concerned. taking 10% less time to build its 1 amp more a day in some cases... That is important. The "shortest wire" camp argues that the shorter wires have lower parallel capacitances, lower inductances, and generally work more like ideal wires than not. The downside is that these amps are MUCH harder to layout and build. They also take more wire to build. A STRONG advantage to this camp is that the layouts easily accommodate modifications on the fly. "hard right angle" layouts are generally too dense to modify mid production or as a custom option. For sure it can be done, just not was easily. The "ground bus" camp lives and runs on efficiency and "good enough". A well thought out ground bus amp saves a TON of wire which consequentially lowers cost and reduces build time. The Star ground camp argues that there is 1 ground in the amp. 1, and only one. The star ground point. There are conditions which will throw a ground bus out of whack that have NO effect on star grounds. heh. The downside is that star grounds require a metric assload of wire (half of the wires in a SP amp are grounds) and a ton of time to build. Somewhere in the middle of those 2 is what is called a Christmas tree ground. Its basically a cross between those 2 ground schools. It tends to act more like a star ground than a ground bus while saving a little wire. On a production piece it is common to see what you can group together without screwing up the amp in the prototyping phase and going from there.

Try it at a bunch of loads. You are not going to damage anything. From what I have read elsewhere the word "within" on cartridge data sheets is loosely translated from Japanese which really means "around" or "approximately."

I dont think I have photos of my first headphone rig, but here is some of my old shit for you to laugh at. CHA-47 Allesandro MS-2 Creative Nomad Zen/80gb. I had a govibe at some point High voltage tubes! I may have actually built this BEFORE the CHA-47. The first balanced amp I built. good stuff.

I still want to see a FR graph at 120 ohms that can be plotted against the same beyer cans driven from ~0 ohms. We can argue theory of what amps and headphones do when run a certain way until we hate eachother, but can a FR graph be argued? I guess it could, but maybe it shows that there is no change.

Series resistance is totally fine for lowering damping factors if that is the goal. I dont see the difference between an amp with a 120ohm output impedance by its nature (an OTL amp, or a high impedance transformer) and an amp with a very low output impedance by nature with a big output resistor as far as the headphones are concerned. I think that is entirely a matter of perspective and focuses too heavily on the amp without regard to the headphone. Looking only at the amp and the theoretical goal of very low output impedance & improving electrical damping factor adding an output resistor like this is madness, but by the perspective of what the headphones seem to want it makes the amp better. I think that gear should be compared at its best, and with such an easy guess at how to get there why shouldnt it?

The no global feedback OTL tube camp would strongly disagree. Perhaps its the problem of looking at only the people on the headphone boards, but they were considered reference grade for a LONG time. None of these do better than an output impedance of about 60ohms, solder another 60-100 ohms into the cable and you are doing exactly what the MFR expects. But electrical damping can not control all driver resonances. The designers are still stuck messing around with acoustical damping and other fun stuff. At the end of the day, I think its within the rights of the MFR to say that they want their headphone driven by a 120 ohm output impedance. If they can only make something great that way, thats fine. Nobody complains that high performance engines need 94 or better fuel, why should anyone complain that they need specially made amps to drive high performance headphones? The amp does not even need to be specially made, if you have an amp with a low output impedance get an impedance dongle like the Etymotic "P to S" cable but with 120 ohms. I could not tell if it was sarcasm (I hope not, it sounds fun to me!) but you mentioned wanting to measure stuff like this for the next 20 years. If it wasnt sarcasm, I would be VERY interested to see how beyers measure driven from various source impedances. Some (most) headphones work better 1 way, others another. Nobody can agree on which is right. The majority camp says thats how modern amps are built, the minority camp says thats what the standards dictate. The problem is that when there are 2 standards the wrong one will inevitably be used. When only a few people really use the one standard the odds of the wrong standard being misused increase greatly. Perhaps by a reviewer. At that point the gear that works great the way it was designed to work dosnt even sound decent. Although I think they sound GREAT driven from high output impedance amps, beyer inevitably pokes themselves in the butt for clinging to that standard. If you run them wrong they dont sound right at all.

Happy Birthday!

Happy Birthday!

The legend I have heard for the popularization of the 600ohm drivers by AKG & others was that they could be plugged into a 600-ohm output on a studio console. Looking at the output impedance of older consoles with transformers, and newer stuff with protection resistors on the outputs, 120 ohms is a pretty good average guess for output impedance. I think its well within the MFR's right to still follow this, and it makes perfect sense that they do in light of that. The question is do any reviews of the gear apply when they are not made using the product according to the MFR's best usage guidelines? The MFR has given you the benefit of telling you how they think they run best why not follow that? Would you expect truly agressive summer tires to work in the snow? The argument that the headphones should work from anything comes up. That clearly ignores professionals who only have 120ish ohm output impedance sources or the average home user with an integrated amp with a high impedance out for the headphones. You wonder how headphones designed for 0 ohm output impedances sound on 120ohm sources. I'l tell you, its crap.

Id try it, but I have no idea how it will work Depending on your mood regarding the redoing them balanced.... Taking the HP1000 apart is easy. I'd probably do that rather than hacking up a good vintage cable. Put the real cable back on later

Happy Birthday!

I spent some more time looking at the 6C45pi tube curves. It is very attractive for its absurdly absurd absurdity. I really like how linear it looks into a 6.6Kohm load (40 ohm load on the 18ct:1 setting) at 150v/30ma idle. I am a little put off by its very high gain and input capacitances because of miller effect though. I think this tube would work really well if a 10K:600ohm input transformer were used with a low impedance attenuator between it and the tubes, but Im petty set on the attenuator I have coming. For a later date How do people hook up the cathodes of the 6c45 in a longish tail pair? The bias point above only needs Vgk of ~1.4V which dosnt buy much in the way of a shared cathode resistor after the stopper resistors are considered. I considered a CCS to a negative supply, but that prevents the use of a CCS to feed the CT of the transformer. Maybe a big fat plate choke for up there. Moar iron=moar better? Maybe its just superfluous in a forced balanced amp. I'd certainly appreciate more info on this. I found the circuit I was trying to describe BTW. Im going to actually bread-board this one like a good boy, and I guess I'l decide then what Im going to do with the cathodes. Im sticking with the 6h30 for this one, but I do appreciate the help and advice.

I have been reading more about this, and from what I have found the impedance seen by the tube depends whether its in class-A or class-B. class-A gets 1/2 of the whole primary, class-B gets 1/4. I thought some more about the gain & amp in general, and Im not sure where to go there. My plan at the moment is to use a CCS to feed the center tap of the transformer (with no shunt reg, I dont think it will be necessary here), with each triode set up as a common cathode with its own resistor and cap. This will buy me a little gain compared to my original boring plan of a differential pair with the CCS tying the 2 cathodes together. Im not sure I like cathode LED's but I'l probably try them too. a headphone sized red-light-district amp could be fun. I thought about the 6c45 but I am frankly afraid of them. I got TVC's with +6, +12db taps from an estate sale. I hope I have gain covered.

Happy birthday naamanf! Have a great one!

Have you considered the PS for the Cavalli Bijou? It has clearly proven its self for a single HV supply headphone amp application. Isnt the Exstata PS dual rail? I would make the (possibly very poorly informed) guess that the bijou PS is overkill for the Akido though. One of the original design goals of the Akido was good to outstanding PSR. Overkill is nice, but you can always upgrade the PS later if you need to. It was digger945's LV akido I heard. If I recall it had a Tangent TREAD running everything. He replaced the LM-317 output devices with dn2540 or 10M45 too I think its all in the LV akido thread on head-fi

Indeed! I had the LV akido on loan a while ago. I liked the amp quite a bit, although I cant compare to the EHHA, as I have not heard one much. My impressions of the amp (compared to the Melos SHA-Gold eargasmatron) are that the LV akido was a bit more detailed & controlled than the Melos but at the same time still had a littttle tube "sweetness" to it. I would not call this amp warm, as I think wam is a more fuzzy and undefined sound (specifically being drunk in front of a fire, thats a warm sound) I think sweet is better here. Sweetness is a gentle smoothness to me, but is not fuzzy like warmth. It is well defined, but begs for you to listen to more.

did you account for the input impedance of the volt-meter loading down the output impedance of the bias supply? Every STAX amp i have measured (attempted to...) measure bias on at the jack says ~200-260V (its been a while)

Happy Birthday!

Happy Birthday!

Happy Birthday Colin!

Happy Birthday!