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| Romy the Cat's
personal site dedicated to advanced audio and evolved music reproduction
techniques
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I am having a LOT of microphonic trouble with the 7788s in a high gain stage. I run a 40mV input signal into a 7788 triode at 15mA CCS. Plenty of gain, nicel output. But dang, if I bump the tube or board or chassis, the grids inside...
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Maybe if you didn't try to pull the caps down so fast. Why the hurry? Maybe a 500 ohm or 5k ohm resistor would be a more kind bleeder. I think the peak current spike is not such a good thing for the capacitor. You are also at ...
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I stumbled upon this. And noticed the extra 6.8mH balun ahead of the diodes. Hmmm, I wonder if this can help snap that diode off? Seems very counterintuitive. Or maybe it is wired up not as a common mode choke? Need to t...
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Snubbers are more effective when there is no inductor - just a diode/capacitor rectification. That's when they become useful. To snub out the ringing caused by leakage inductance. Keeps the "buzz" from coupling to other areas of the...
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Looks to me like the horizontal and vertical steps in the waveform are due to the diode switching. One diode turns off while the other turns on. Storage time on the diodes is normally short. But it depends on the test setup! T...
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Looks way cool. You have 30mA bleeder for each output? Seems like a lot of draw. What brand polyprops make a 200uF? jh...
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[quote]I need juts one amps and one speaker[/quote]I don't design amplifiers for myself. I design them for others. And I am always on the lookout for something new or different or any possible improvement. Not all customers wan...
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Yes, it is an E55L. I wonder how stable it is. Interesting to me how many of these "uber-tubes" are designed for RF operation. Should make a wonderful oscillator. The other find I came across was a pair of 6CL6. Makes me...
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I was rummaging through a pile of tubes and came across a pair of 8233. Medium size tube, gold pins, PQ. I think it might have been a video output tube for an old Tek scope. So I looked it up on Duncanamps. 10W plate dissipati...
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[quote]the subject of the intermediation is kind of complex[/quote]It's difficult for me to guess exactly what the possible sonic effects of the ripples would be. I see a tube operating at a fixed point, having a particular distortion spectrum....
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The issue I see is that of intermodulation distortion on the biasing of the output tube. It will effectively change HF operating point per supply ripple. Easy to understand if one imagines a gross ripple of 50V. Same thing happ...
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I have not experienced any ill effects from ferrite beads myself. That is why I asked. Some report sonic degradation issues (like CH at Ayre). Some say they can get magnetized. Listening to the masses I am unable to put togeth...
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So what is with the ferrite beads? Do you find they are necessary? Seems to me the resistors right on the socket would be good enough. Especially with the grounding of the center pins. I run beads all the time in my digital si...
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The 6sn7 is a fine amplification tube for use in preamps or gain stages, but it has way too high of an output impedance for driving power tubes. This is my personal preference. It also depends greatly on the topology. Maybe George u...
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Romy, I tried out a 6e5p as a driver tube in a PP 2a3 amp (was using a 7788 for driver). Well, knock my socks off! The amp went from 6 watts to 8 watts! Distortion dropped a tad, but mostly it was more signal swing. I could dr...
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[quote]This is very bogus notion[/quote]Well I am glad to see you feel that way. You never know - some people cry foul when such happens. "Hey, that was my idea! And now this guy stole it and put into his own product." It happ...
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[quote user="Romy"]why don’t not you try my 6E5P?[/quote]I didn't want to steal any of your ideas. Although, admittedly it was my backup plan. No question the 6ep5 makes for a superb driver tube. Had not really looked into who has s...
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Ok, once I got pin 8 connected to pin 1, the curves came out straight. Here is the true pentode plot at 200V screen, 0.5V/step:[img]http://www.hagtech.com/blog/images/7788-04.jpg[/img]And here is my new data sheet plot for triode mode:[img]http...
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Ok, so it took me awhile. I finally got around to doing a design around this tube, believe it or not, as a driver for a 2A3. It just seemed right. Bought some 60's vintage(?) Amperex "PQ" on eBay. Well, here's what it looks li...
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[quote]...responsibility is SHARED, and lies as much with "the people" as with their CHOSEN leader...[/quote]Aw crap. Does that mean I'm responsible for everything Bush does?[quote]...kids are staffed with historic BS about the horrible uncle-A...
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I think Jack Eliano of Electraprint can custom wind something for you. Or maybe Mike at Magnequest. At under 5W, the core does not need to be very big, so cost of exotic materials go down and bandwidth and magnetic coupling go up.jh...
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For a single driver, looks to me like you need an input signal of at least 3Vrms. A lot of linestages can do that, so a single tube power amp seems both reasonable and interesting. Yes, I was looking at wrong data sheet. You kn...
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With this tube I would think cathode emission limits lifetime. Stepping back a moment, I'm guessing this tube is designed for radar operation. Maybe in an aircraft. The spec sheet definately talks only about pulse mode of opera...
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How about some sort of composite? You need the strength of steel, these parts weigh a lot. But maybe a different approach. Maybe something like plywood glued to a sheet of aluminum? That would give you the solidity and conduct...
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Started building a test board for the "composite" 6c33. Then I realize I could not hook up the grids separately. They be connected internally. So no way to do this test. Not with this tube anyway.jh...
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[quote]Is this one of those shining moments?[/quote]It could have been. The theory seems pretty reasonable to me at the moment. Time will tell. I'll make up a new adapter card that runs both sections and add a pot to negatively...
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[quote]do two tubes at once then it make sense to have one selected reference tube[/quote]I see. Yes, the digital scope option would work. I have one, might try it out. With a 6c33, the VacuTrace has only enough power to trace ...
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It's hard to predict how the anomaly will sound. Sort of like a dynamic bias shift in the tube. That's why I think IMD. The shift moves around at LF rates, so the HF reproduction can fall on any number of load lines (within loop are...
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[quote]I really do not understand what conclusion you make by shutting the tube down.[/quote]I make no conclusion. It's just an interesting thing to watch. A good experiment. I was hoping it would be a clue for everyone here.Since t...
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Sorry for making that video so large. Here it is again but 1/10th the number of bits. Compression can be a useful thing.http://www.hagtech.com/blog/media/6c33.wmvjh...
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