cotdt

I made a mistake on the booster triode on Post #11, on where the resistor goes. The 10R resistor is already part of the schematics, so it should be clear, anyway. Here is the correct version:

Here is my improved circuit for the Doge 6210. Let me know if you find any improvements. Seems to sound better without capacitors in the cathode bias, which the Doge originally used. I know it's a strange circuit.

Sure, but I need to find a way to draw the schematics on my computer. right now i have to draw schematics by hand and take a picture, which doesn't come out so clear.

drauthurwells is going nuts on the Doge thread on head-fi. It's a good read, and very entertaining. I stopped replying because his claims are so out of this world. The story is that Mr. Wells contacted Earl by PM, to sell him a Doge amp. Earl agreed to buy it based on the good previous experience with the EL84 tube. Well, Earl said the amp did not work and the knobs were completely loose and falling apart. He returned the amp for another one from Mr. Wells, and that one didn't work either. It arched Earl's NOS tubes, in fact. This time, Mr. Wells refused to allow the return, claiming that Earl's agenda was to damage his reputation to help Singlepower. This ignores the fact that it was Mr. Wells who was the one who contacted Earl to sell him the amp, not the other way around. After much argument with Earl, Mr. Wells offered to give a HALF refund for return of the amp, but this offer is not acceptable to any sane person. So Earl and I was talking about it and Earl wondered if I can fix it, and I said "yeah, i have a working version of this amp, so i should be able to do it." So he sent me his broken amp and the build quality was horrible. The tube sockets were loose, and the chassis itself was twisted and would not sit on all four legs. In contrast, my Doge from Pacific Valve was very well-built. I did not even test Earl's amp since I was sure it would destroy my nice Russian 6P14P tubes. I proceeded to rebuild the entire amp from stratch with premium parts and it now works wonderfully. The stock amp used Pin 1 as a binding post, so NOS 6BQ5s did not work with the amp unless you snipped off Pin 1. This and the loose parts could have been the problem with Earl's amp(s). 6BQ5 and EL84 are not the same tube, because the 6BQ5 uses Pin 1 internally, but they are otherwise swappable. Mr. Wells is still accusing me about lying that anything was wrong with Earl's amp. He still claims the amps were working perfectly, and that Earl should have returned it to him, forgetting the fact that Mr. Wells refused the full return money.

maybe not the best, but it should be a pretty good amp based on what i've been told. if you make a clone, you have access to better parts so it should sound better than stock. i've also got the schematics to the Doge 6210, and also my "improved" circuit, which uses the booster triode trick and removes global feedback.

I did a Darkvoice 337 versus Doge 6210 shootout writeup on head-fi. I threw in the M^3 w/STEPS just for fun. In short, both these amps walked all over the M^3. I was surprised that these simple tube circuits work so well, even compared to more modern solid state designs.

aerius, you're disagreeing with me but you are basically saying the same thing that I am. strange post.

anyone knows where i can get conductive plastic?

oops my mistake. i meant power transformer for the sigma22. i've dabbled in tube audio for too long, it has stolen a portion of my identity.

yes, jeff's kit for the B22 includes the output transformer. the total cost of the balanced B22 including all the parts can be done under $600, but I went for premium parts and it ended up costing significantly more. i got the matched transistors from amb, and the rest from jeff. i did not have to get parts from anywhere else, except for the screws and hex standoffs. and the usual, like solder and wire, and a Par-Metal 20-series case. not sure how much MisterX charges to build one, but I know how much I would charge. At a casual rate, it takes about 6 hours to stuff all of the 5 boards (1 PSU and 4 amp boards), but the casework takes longer. Then there are nifty little things like a gain switch (at the input level). I got a big case for mine in case I wanted to add an extra power supply board. Impressions coming soon!

the slow and mushy tube sound is typically associated with the 300B, but they say that the TJ 300B mesh tubes don't have this typical 300B sound and is has much better clarity reminescent of the 45. So probably tube-rolling the 300B would solve the slowness problem. Not sure if the 6SN7 is the best driver choice. Personally I would use a power tube as the driver tube. what surprises me about the reports on the woo5 is that it is quiet. it's hard to make DHTs quiet, especially the 300B. so that's quite impressive. i've found that cheap output transformers sound really good. i don't see any point in investing $800 on a pair of output transformers when my $10 output transformers already sound so good.

you will lose output capability. well, adding a resistor in series is commonly done for the Koss KSC35. Since you increase output impedance, for some amps you'll get tighter bass and better clarity. But good amps should already drive them to their max potential without such tricks.

that PSU designer tool looks useful. I'll eventually use it for my future tube amp, but it will be a while before I have the funds for it. Impedance does not need to be matched. You just want the output impedance to be sufficiently low relative to the headphones. The output impedance being 10 times lower than the headphone's impedance is good, more would be even better. It's only when the output impedance is significantly higher than your headphone's impedance that you get the effects aerius mentioned. A good SS amp has an output impedance of 0.1 ohms, about 4-16 ohms for a transformer-coupled tube amp, and 30+ ohms for an OTL tube amp.

I don't see why the SS-1 and the B52 cannot be compared. They are both headphone amps, and while the B52 uses tubes, it sound signature is closer to a Solid State amp. I wouldn't be surprised if they sounded similar. In that case, it would be interesting to compare. It is interesting even to compare very different amps, like a complex SS amp with lots of global feedback versus a simple SET amp with no global feedback. But yeah, I mentioned B22 (not B52) which is a high end solid state headphone amp designed by Amb Labs. The circuit is designed for extreme high performance and transparency, and can deliver probably 60W into 8ohms. Basically, the current two top SS amps are the balanced B22 and SS-1. They should be compared to see what the cutting edge of SS amps have to offer.

Actually, it's not only $15k, but it's not even finished yet. There is still the crossfeed and some other circuits that need to be worked on. It will probably end up around $20k. I'd like to hear it, but also A/B compare it against other amps using the same DAC. In a few months I might be around the area and will ask Sleestack about auditioning it. I'm sure it'll be amazing, but I want to find out just how amazing it is by doing direct comparisons, say against a balanced B22.

Those wires tend to be 20ohms per feet, which is useful, but not universal. I use a lot of 10K resistors. In that case, what should I use?

If the PPX3 SLAM has an output impedance of 30 ohms, then bass will be loose and flabby. High output impedance actually boosts bass response for most headphones, but it won't be high quality bass.

I should note that the resistor should be durable and reliable.

what software is that, aerius?

How would you make your own resistor of any arbitrary value? What natural material works well? I've made my own inductors out of tin foil, then capacitors out of mineral oil, and would like to move on to resistors. Any advice would be grateful.

Clean DC power should be better than AC. I tried battery powering the filaments on my indirectly heated triode, and the 60Hz hum dropped by 20dB compared to AC. Unfortunately, I had other noises coming from my B+ supply that was a greater issue, so I went back to AC for convenience. In the future, I will revisit DC battery powering the entire amp.

Nice work, aerius, but why are the tubes glowing purple? I bet the amp sounds nice. Seems like overkill for a headphone amp, though. Nanoha, here is a design using 6SN7:

spanks!

I bought a 24-step stepped attenuator but I dont' see any benefits to justify the price. 24 steps are not nearly enough for me, unless it's an amp where I can set the gain really low. I would much rather use a good potentiometer like a TKD. The pots "feel" better since the turning is much smoother than a stepped attenuator, which feel notchy. Pots are better and cheaper in my opinion, as long as it's a well-matched one using conductive plastic or film. The carbon pots degrade the sound and have shorter life spans.