aerius

The last time you might've heard my amp was last summer. There have been many many changes since then, the most important ones being the improved biasing & new operating points on the ECC40 along with the grid neutralization for output tubes. Slightly more gain, but a lot cleaner and it won't distort or do anything funny at high volume like it did before. Everything else is also a lot better.

Automatic colour balance on my digital camera was fooled by the glowing tube filaments. Soundwise it's up there, it's probably limited by the output tubes and transformers but it's still handily beaten every commercially available design I've heard so far. It'll squash a PPX3 Slam like a bug, the proof of concept build which used crappier transformers and a far less optimized design & layout with crappier output tubes was still dead even with that Singlepower. Why? Why??!! It's a complete waste of a 45 or 2A3. All you'll hear is the sound of a 6SN7 straining to drive the output tube along with the sound of the output transformer. For the $500-700 budget you're not going to be able to afford good output transformers either seeing how there's also a bunch of chokes and likely a custom power transformer which also needs to be bought. At the very least use a 5687 family tube which has better drive capabilities. The 6SN7 has a plate impedance of nearly 8k Ohms, it's simply not going to be a good driver tube for any power triode. Use the 6SN7 for what it does best, either as an input tube or a driver for Pentodes and other easy to drive tubes.

I just noticed I now have a custom title. It fucking rocks.

I think you're onto something here. It's as if the headphone, and especially the headphone amp industry is moving towards the planned obsolescence model of the computer industry, except unlike computers which keep getting faster and cheaper the headphone amps for the most part just get different and more expensive. Hooray for the free market and unrestrained capitalism, it's almost like manufacturers are trying to spam the market with as many products as they can in the minimum amount of time, gotta keep up with the Jones's and all that. I can't say I'm surprised though, it happens in many markets once things hit a critical mass and people realize how much money there is to be made. The problem is people are going to get disillusioned and pissed, and that ain't good for the industry in the long run.

There's probably at least a dozen of them floating around on Headwize, but I can't vouch for the goodness of any of them since I haven't built them. Anyways, quick correction to the schematic. Use a red LED instead of the blue one. I used a blue one at first siince it dropped about the same amount of voltage as the cathode resistor I had in there before. However this runs the tube too close to cut-off and the sound suffers a bit compared to a red LED. My particular LED runs at a bit over 1.8V, and is rated for 20mA and 1400mcd. From my research on DIYaudio.com, brighter is bad because of higher impedance, so look for a lower mcd number. If possible, try to get an LED where the bias current of the circuit is in the upper half of the LED's current rating, apparently the LED is more linear when run that way.

I just had another crackpot idea. Take the Espressivo Headphone Amp as a starting point, building it with the 6C45Pi tubes. Instead of the costly multi-tapped autoformer, substitute one of the cheap Amveco donuts, the 62081 or 62082 looks about right. For further cheapness, find an LED that can handle 30-40mA (or parallel a couple 20mA ones together) and biases at the required ~2.2V, this allows you to get rid of the bypass cap altogether. The Gary Pimm Current Source can be found here. If you use the MOSFET only one, I think it only drops around 20V so the B+ can be lowered accordingly and you can omit the cap & resistors to the left of the CCS. From what I've read, the 6C45Pi is a rather fiddly tube so you'll need short neat wiring and good grounding to keep it from oscillating and doing stupid stuff.

Schematics, transformer hookup diagram, and PSU. The 50uF cap near the transformer is a 240VAC motor run capacitor. Bypass with a fancy cap if it makes you feel better. The 4pF caps are 500V silver mica caps. These are the neutralization caps and should be soldered right to the tube socket tabs. You want them to hang off the underside of the socket with the shortest leads possible. 0.22uF caps are any decent polypropylene film & foil cap. Best if rated for 250V or more. Wima FKP or Sprague Orange Drops work nicely enough, but feel free to go nuts if you feel like it. If you're using the 6BL7 output tube, then use the 820R resistor. If using the BX7, use the 1k resistor. Finding rimlock sockets for the ECC40 could be a bit of an adventure. There's usually some on Ebay and European tube vendors usually have them. ECC40 tubes are also pretty common on Ebay. Try to keep your wiring short & neat or the ECC40's might decide to oscillate on you. Power supply voltage isn't that critical, anything between 260V & 300V works fine. You probably want to run the tube heaters on DC, some tubes hum, others don't, but you might as well play it safe. How to hook up the Amveco 62080 transformer. This is a toroidal power transformer available for about $20 each on Digikey. Yes, it works really well as an output transformer. Power supply is a 240V transformer followed by a 8uF film cap, a choke from 20-50H, a 220uF cap, 100R resistor, then 2 75uF motor run caps in parallel. Run a wire from here to the 6BL7's. Then a 500R resistor and another 75uF motor run cap, then run a wire to the ECC40's. I probably missed a few things, so if you have any questions just ask.

I'll have to draw up the latest revisions of the schematic, but yes, it will easily beat the performance of a PPX3 Slam. You'll have to do the whole thing point to point as there is no PCB for my amp design. Not hard though as the circuit is quite simple.

Output transformers are great, but I have to question the quality of the transformers in the WA 5. $3000 with all that fancy casework and so forth doesn't exactly leave much of a budget for good transformers. And if good transformers were used, then something else was most likely compromised.

I can't say I'm surprised by the report of lackluster sound. A 2-chassis 300B amp with output transformers as well is going to be severely compromised somewhere, and that somewhere is going to be the circuit design and sound. I can't say I'm surprised that it sounds just like every other under-driven 6SN7 300B amp. BUT HEY EVERYBODY LOOK AT THE FUCKING BEAUTIFUL CHASSIS WITH SEPARATE POWER SUPPLY!!!!

I'd actually go for the Nottingham Anna Log. I've heard the Dais which is one model down from the Anna Log and it is freakin' amazing.

Honestly now, does it look like I give a shit about looks?

I'm torn between complete indifference and couldn't care less. Whoopdedo, another 6SN7 300B amp, to go with the other 10,000 6SN7 300B amps. Give me something different like the Wavelength Audio designs, which use fun tubes like the 6C45Pi and WE437A to drive the 300B.

No, it needs MORE COWBELL!!!

You could always sell one of your kidneys. I've heard that some places will also pay you for a partial liver donation, and unlike your kidney, your liver will grow back after they cut a chunk off it.

In your case the K340 is the woman you married.

My GF's sister read about 20-30 pages before giving up in disgust and returning the book to the library.

As many Head-fiers know, digital is digital and bits is bits, and every CD player and DAC sounds the same anyway as long as it's not broken. Therefore the comparison was totally fair.

To me the HP-2 and PS-1 are very different, other than being metal, hideously expensive, made by Grado, and having a similar soundstage and high level of detail & resolution, there's not too much in common. I think the best way is to use an analogy. The HP-2 is a sexy hot chick, but she's a perfectionist temperamental bitch and if you accidentally do one tiny thing wrong she flips out, calls you stupid, gives you the cold shoulder and refuses to sleep with you. The PS-1 is a sexy cute chick, you can goof with her and make fart jokes and she'll laugh with you and give you a great time in bed.

BUT IT PLUGS INTO IPOD!!!

Because it's small and it's cute, and HOLY SHIT IT PLUGS INTO AN IPOD!!!!!

Or when you're searching the 'net for schematics of the gear before you even buy it. "No, I do not want yet another 300B amp using a 6SL7 input with a 6SN7 cathode follower!"

I've run into a few more since the meet, I still haven't heard a properly working one and frankly I'm not holding my breath.

I wouldn't touch either one of them, the build quality and QC on those cheap Chinese amps is pure utter shit, as of now I've run across more than a dozen of them at meets and so forth, there's maybe 3 or 4 which worked properly. The rest had crapped out pots, linear instead of log pots, massive hum, massive channel imbalances, and a bunch of other problems. The working ones, well, frankly I wasn't impressed by the sound at all, just the usual mushy bloated tubey crap. To me they're pretty much worthless unless you want to gut the entire amp and use the case to build your own project.

I need the fine control of a standard pot, or failing that a stepped attenuator with somewhere between 70-100+ steps. Unfortunately, SA's with that many steps are rather large and ludicrously expensive.