gepardcv

Got any more details on that? Based on the LL teardown, I concluded that, while the build quality left much to be desired, so did the circuit. I then heard a LL2T at a meet, and while it worked fine with a 009, it sounded ghastly with a 007 (or maybe that 007 was broken — the sound was dull to the point that it made Audeze headphones seem bright and lively in comparison). Are these other amps really worth the effort of reverse-engineering and building?

I had the misfortune of hearing an iESL (plugged into an iCAN) unit several months ago. It was a joke. It had a 009 plugged into it, which I wasn't super interested in (in retrospect, a mistake), so I double-checked all the dials for the right bias setting, etc., and plugged in my 007. With the volume turned all the way up, it barely made a sound. I don't blast my music, but this thing at max reached about the same loudness as a Carbon with the volume pot at 8:30-9:00. Then I remembered that I have no reason to trust iFi to know about the 5M bias ballast resistor, had no way to check, and proceeded to yank out my headphones before anything bad happened to them. Then I fled the room, with a rictus grin frozen on my face. I now wish I stayed long enough to find out if it actually worked with the 009. For iFi's sake, I hope this was an early unit with problems which have since been fixed. If not, then buying the iESL to power Stax headphones is absurd. The SRM-252S costs a fraction of its price, and has the desirable property of actually working.

Your hum problem sounds awfully familiar. I posted about this a few weeks ago, see https://www.head-case.org/forums/topic/12840-technical-assistanceadvice-thread/?do=findComment&comment=772776. A few things I have found helpful in eliminating noise: 1. Do not attach volume pot grounds to anything. Makes things horrible. 2. Attach input XLR pin 1s to the chassis near the input. Many Neutrik jacks have a special pin or other feature to do this painlessly. (Check continuity to be sure.) Do not run grounds from the XLR inputs anywhere else. If you have loop-out XLRs, also tie their pin 1s to the chassis. 3. The safety earth should be separate from the star ground, and needs to use tooth washers and locking nuts, since it's the critical electrical safety feature. I have found that it does need to be tied to the star ground. 4. Do not allow any audio signal wires in any direction to run close to the transformer. 5. Do not allow any AC wires from the transformer (including heaters) to touch any signal wires. 6. With the mini-BH PSU, you may hear some hum with no input plugged in and the volume control turned up. I've empirically found that the mini-BH PSU hums in this situation and the GRHV does not. There should be no hum with a source plugged in, for any position on the volume pot. Note that in my builds, I attach the amp boards to the PSU, rather than to the star ground. I have found it to makes no audible difference with amps using the mini-BH, GRHV, or GRLV PSUs (i.e., dead silence). YMMV.

I have built a KGSSHV and a KGST using mini BH PSUs, and a Carbon with the GRHV. Though I have not used an oscilloscope to check the builds, I’m pretty sure the GRHV is quieter. Just my impression, anyway...

Right. This is why I'm suggesting "cloud" -> mobile app -> DAC. More details on the three pieces: 1. "Cloud" needs to be your own service account. Amazon is unlikely to pull the plug on S3, whereas some random company building a service on top of S3 can go belly-up, or change its service or terms-of-use, at any time, taking your precious data with it. (Assuming Amazon does not fail, no EMP hits its data centers, etc. etc. etc.) You copy media files into it normally, not in some proprietary block format, so they can be trivially read. 2. Mobile app: assume an app exists which can talk to the "cloud" account and output to the mobile device's audio out interface. Meaning the Lightning port on iOS devices, plus whatever Android uses. It should support Bluetooth out, since I expect sound quality there to improve over time. Integrated amps with Bluetooth inputs are already on the market. 3. In a common use case, this means using a Lightning-to-USB cable from the iOS device going into the DAC. The DAC connection pretty much has to be USB, unless you use something like an Eitr (in which case you're still on USB from device to the DDC). For the hardcore anti-USB crowd, that pretty much makes this set-up a non-starter . (Missing pieces include streaming from S3, which is non-trivial and incurs additional cost. A problem to solve, for certain.)

@blubliss: Could something tempt you to move away from your NAS box to an off-site service you control? I mean move your media to your own Amazon Drive or S3 account? Assume that a good playback interface to your DAC exists. The basic pro-et-contra are not replacing failing drives, or migrating to new storage appliances in the future versus trusting Amazon with your data.

My physical media collection was in the basement level of a house which flooded in Hurricane Sandy. All vinyl lost. CD paper and booklets destroyed. The disks themselves survived, just needed a good cleaning. So I put them in large sleeve folios. Those folios don’t take up much room, and the media are all still there if I ever want. Pure streaming from 3rd party services isn’t an option for me personally. I listen to too much old, obscure, and international stuff which doesn’t exist on Tidal, and never will. I’ve been thinking about a way to put media files on Amazon Drive or S3, and put together an iOS app that can stream them (maybe something like that already exists). Then connect an iPad to a DAC. Seems more elegant and future-proof to me than buying an expensive dedicated streamer box which will become obsolete when Tidal goes out of business.

It's probably still around, but I've never received a reply to any email I sent that way. I don't think it's interested in business coming through email. Not sure what dimensions you're looking for, but Fischer Elektronik makes excellent heatsinks in various sizes. They're somewhat available at various places (I've had intermittent luck with finding stock at Newark Electronics and TME, https://www.tme.eu/en/).

Check out the Head-Fi "for sale" section. The site itself is unusable, but some guy built a slick search engine for its content: https://devbrada.com/classifieds/ — please note that you might not be able to sell on there if you don't have an established reputation.

The SDR mod for the HD800 brings it close to the 800S at a fraction of the price. I never compared the 800+SDR to the 800S directly, though, so don’t know for certain. Re: optical out and connecting your DAC. That discussion is a can of worms. Supposedly a high-end interface card can make things better (e.g., a Lynx AES16e or whatever it’s called — you’ll need a breakout cable and connect your DAC through its SPDIF input, or AES if it has one). I don’t know, never heard one. Check the used market — people started dumping them since Schiit released the Eitr USB-to-SPDIF converter and gen5 USB. You could also send your Bifrost to Schiit for a couple of upgrades: $250 for multibit, which most people seem to like, and $150 for gen5 USB, which will upgrade its USB interface to one with all kinds of fancy isolation electronics. FWIW, I upgraded my Gungnir Multibit to gen5 to keep up its resale value, but can’t say I hear much difference.

Is going to a meet an option for you? Major cities often host a couple every year. Look around on Head-Fi for announcements. It'll give you the opportunity to try a whole lot of different things. Just remember that show conditions can be noisy and difficult. Also, keep your bullshit detector on. I've had people at meets try to convince me of some staggeringly dumb things. Also, seconding the advice to refresh your HD650: replace the earpads and headband pad, and it'll look and feel good as new. The SR-007A is my favorite headphone, but that price you're quoting sounds too good to be true. If it's a grey market import, keep in mind that you'll have warranty service problems (which, granted, are unlikely to be needed; also, Stax has stingy warranties; anyway, asking for help here on HC will be more effective for some problems). The 252S amp is pretty good, but you might find yourself looking to upgrade to a KG amp, which will never be cheap, since they're all DIY (though not difficult to find). It makes for a pretty expensive system, but it can definitely be that "setup for 20 years" that you're looking for. As a really nice alternative which doesn't require exotic amplification, the HD800 can be found for $800 or less on the used market in excellent condition. I've even seen it for around $1000 new, depending on holiday deals at various retailers. Add the (easy to install) SDR mod for another $30 or so. It's an excellent headphone, with much, much less bass roll-off than the HD650. It takes well to equalization, so you can give it just a touch to make it sound even better to your ears. Dynamic amps are tough to recommend. I've never been a fan of Schiit amps for numerous reasons, but I don't have great or inexpensive suggestions that don't involve DIY. There's a lot of popular garbage on the market. As for DACs, ask yourself: can you hear a difference between your current DAC and the audio output of an iPhone or iPad (with volume turned to the max) plugged into your amplifier? The answer should be enlightening.

Thanks, @sorenb! That was exactly what I needed. I think I have it sorted out now. Didn't find any hair or dust, but just disassembling and reassembling the cup down to the driver helped for some reason.

I started getting a rattle in the right channel of an SR-207. It's only audible in lower frequencies, like the bass shaker test on Audio Check. When the same thing happened to my HD600, I disassembled it and removed a hair from the driver, which fixed the problem. A little searching the threads here hasn't turned up disassembly instructions for Lambda-type headphones. Repair suggestions, please?

Searching on HF for "009 headband replacement" brings up instructions for a nice mod on the first hit. Not the same user name as here, but I'm guessing it's yours. Pretty sure that anyone capable of doing that mod will have thought of doing that search.

I ordered the Phoenix "PT 1,5" series terminal blocks which we discussed earlier. While it's nice that they have plastic along the bottoms, I'm not convinced they would help prevent arcing if a trace passes beneath the attached wire. (1) There is still no plastic right where the trace would run. (2) There is no plastic directly beneath the wire attachment. It's beyond me why there just isn't a fully-enclosed plastic housing here. Maybe it's another Phoenix part number which I haven't found yet. Photo attached.

The datasheet for Phoenix part 1935174 says the following: Rated voltage (III/3) 250 V Rated voltage (III/2) 400 V Rated voltage (II/2) 630 V What does that mean, and how do you know it's not just good for 250V? (The Mouser page for the product says 250V, but I don't trust it.)

Interesting. Using a 5-position connector as a starting point, I ran a Mouser search for a TE Dynamics connector (link) which found a 600V wire housing and receptacle pair. The datasheet for the receptacle says it's 34.32mm wide, but a comparable Phoenix (datasheet) is about 10mm smaller. I don't think the TE unit fits on most of Kevin's boards. (I also haven't looked to see how much an appropriate crimping tool costs. Prices on those things are usually eye-watering.)

It certainly seems like almost everyone uses these connectors, and there must be dozens of amps built with them by regulars and lurkers here by now. This is only the second report of this failure mode. Not good, certainly, and it would be nice to find a better alternative. I wanted to switch to Molex or something similar, but couldn't find parts with sufficiently high voltage ratings.

You guys rock. Disconnecting the pot grounds from everything did the trick. The amp is now dead silent. I'll edit my other post to show the exact grounding scheme I ended up with.

All the 400V-rated ones I bought from Mouser have been green. Never seen those things in black. A few from another vendor (forgot which one) had part numbers which matched 400V on data sheets came in bags which said 250V, but looked identical to the supposedly 400V parts.

How did you make the trafo shields? Or were they off-the-shelf (in which case part numbers, please).

Yes, I've tried pots to star ground. No change. Input grounds are connected to the chassis (using the Neutrik connection pin), and not to the pot or star ground. I read that it's supposedly the Right Way in the famous Rane Note. (Unless I brutally misunderstood what I read).

UPDATED 2017-08-21: Thanks to hints from @Laowei and @MLA as well as suggestions to double-check the entire scheme from @mypasswordis and @Whitigir, I figured out what happened. See edits below. I have a question about volume pots and hum. On my builds, there's a faint hum which begins when the volume pot reaches 11:30 o'clock, gets louder and tracks to the right channel until 3 o'clock, then disappears at max. This happens with all pots I tried, several TKD601s and an RK50. Any suggestions about what might cause this? I have a feeling I'm making a mistake in grounding, but (1) I tried a few variations cobbled from suggestions on various threads here without success, and (2) wouldn't a bad grounding scheme imply that there should be more consistent noise all the time? Likely related to this, I have found that there is much louder hum across more of the pot range whenever there is no source plugged in. For example, my Carbon (split PSU) is grounded as follows: IEC earth to chassis (through IEC module) and star ground Transformer 0 to star ground PSU board 1 to star ground PSU board 2 to star ground Amp board 1 to PSU board 1 Amp board 2 to PSU board 2 EDIT: Pot output ground 1 to amp board 1 (this caused problems) EDIT: Pot output ground 2 to amp board 2 (this caused problems) FWIW, I have always made one-box builds so far, and I imagine the transformer contributes to this, but I don't get why only part of the volume pot range manifests the problem. Like I said, the hum is pretty faint with nothing plugged in so doesn't matter much with music playing at reasonable levels, but I'd still like to understand what is going on.

FWIW, my understanding of the Soekris DSD implementation is that it just converts to PCM, pretty much the same as a software player. I've nothing against that approach, and I like the features and performance of the dac1541 which I received about a week ago, but the extra formats don't seem to have much practical effect.

No clue about OP's specific headphones, but I have definitely found that a lot of amps hiss with high-sensitivity low-impedance loads. I test with a JH13. In the inexpensive range, consider an Emotiva Big or Little Ego. Not dead silent, but close and much better than the original DragonFly (no idea about newer versions). Also an O2+ODAC, though they are often built with way too much gain, which may make problems of its own. The best performing devices, with zero hiss audible to me with sensitive IEMs, in my experience have been Apple iPhones and iPads, and the new Soekris dac1541 (though the latter doesn't quite kill all sound at minimum volume; it's not a big deal though).