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Posts by wakibaki

Yes, I've got a couple of irons in the fire as far as development is concerned.   These things seem to be multiplying...     I'm still interested in this design, so I'm experimenting with what can be achieved at the lowest cost (hence the reverb transformers) and with the greatest simplicity, but also seeing what the best performance obtainable is without pushing up the price too much.     I've got quite a lot of components for this on hand including...
I did some more sims. I improved the transformer model, I've put in some parasitic resistances, tweaked the coupling (leakage). I need a transformer spare in my hand to measure.   Then I put in some 6SN7's and optimized. 6SN7's have a couple of things going in their favour.   1) They're better at lower currents than the russian tubes. The tubes are best >= 8mA I read, but the CCS's help the linearity, the sim works best at the values shown, and I like the fact...
  Seldom is good enough, you just have to increase your work rate...
As a general rule, yes. If it graphs bad then it is bad.   Some people like to wriggle on this point, somebody always wants to quote some amplifier that 'everybody' thought sounded wonderful that had crap measurements, and it's very difficult, even for a convinced engineer, to stand up against the enormous weight of antiscientific sentiment that seems to have found expression in the audio arena. You only have to look at the huge mass of contributed material on...
Google:   karaoke tracks   but you'll have to pay for them...   You can use Audacity or any other free music software for playback/record, but it won't split the backing from the vocals using a regular recording AFAIK, but I did find this:- http://www.youtube.com/watch?v=JEjzdurnJhw. - which apparently explains how to do it, although I didn't watch it.   w
The AD5204/6 are pretty good, but they are linear pots. You really need logarithmic for volume controls. They also have THD ~0.004%, whereas you can get devices like the PGA2310, 11, 20 etc. chips from TI which are intended as volume controls and have THD better by about a factor of 10. Or look at the Cirrus CS3318 if you need 8 channels in a single package.   You can run linear digipots as fake logarithmic pots by skipping values, but everybody who's into digital...
There have been a lot of formulas bandied around here to no great effect.   What can we actually do with formulas?   Here are a couple of very basic ones...   1) V = I x R   2) P = I x V   ...rearranging (1)...   I = V / R   ...and substituting into (2)...   3) P = (V x V) / R   This tells us the voltage required to produce a given power in a given resistance.   Harmful is one thing, desirable is another.   So let's think about...
There's a live thread over on DiyAudio about a DHT SET headphone amp:- http://www.diyaudio.com/forums/tubes-valves/228625-all-dht-set-headphone-amp.html   The stated object in the DiyA thread is ~9vrms into 600R (AKG Sextet), 7vrms into 38R (Hifiman HE-500) and hum <-80dB @ 0.4vrms.   It's wandered all over the place without really producing a design yet, however. It's got an ideological bias too because they want to go with DHTs, which everybody is insisting is...
Just fiddling around, listening to this amplifier as I have built it, I started tapping on one of the tubes, suddenly the volume level jumped up quite a lot, accompanied with a loss of fidelity. Gave me quite a fright.   Debugging these things is so much more difficult than solid state, because you can't just poke around in there with quite the same degree of freedom. I hate dangerous voltages. Tubes get hot.   It seems there's some kind of wiring problem in...
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