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tube fanatic

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Everything posted by tube fanatic

  1. The “Little Tater” SET : Maynard
  2. Jeffrey—as my friend Ari says, “gey gezunterheyt” if doing that makes you happy. Maynard
  3. Jeffrey, I seem to recall you advocating the use of different color tie wraps as a means of tuning the sound of an amplifier. As to using them, it all depends on what the tied wires are carrying. If used appropriately, they have no effect at all. Maynard
  4. A detailed description of the listening room, listening level, proximity to the speakers when listening, types of music listened to, etc. would be helpful in terms of making recommendations. Maynard
  5. A “few” of the demo units: Maynard
  6. The “Super Amp 1” parallel SEP: Maynard
  7. The “Little Joy” ultra flea power SEP spud: Maynard
  8. Is Sal still restoring amps? I heard he is only selling parts now. Maynard
  9. A clipped sine wave does not have a dc component. I would be more concerned with a SS amp which has a very high dc offset. The latter is easily measured. Maynard
  10. From 1948..... Maynard
  11. Here is what Augspurger and Murphy had to say about this very interesting subject: https://butleraudio.com/damping1.php Maynard
  12. Well stated. Yet, having an output impedance of 30+ ohms, as is often found with SEPs when no voltage fb is used, seems to make little or no difference when used with many speakers. Maynard
  13. The DC resistance of the secondary is of no consequence in general. The output impedance is a different matter. I have used high output impedance as well as low output impedance amps with Khorns and have gotten excellent results with both. Again, you would need to experience different amps yourself and choose what you find most pleasing. No one can tell you what will be best for your ears. Maynard
  14. It depends on your definition of satisfactory. Some users like very low DF SEPs, often with less than 1 wpc, while others prefer 60 or more wpc. The only way for you to make a determination is to try various tube amps and draw your own conclusions. Maynard
  15. What problems are you having with the A300? It is not a difficult amp to service. Maynard
  16. No. It requires a totally different operating point as well as other changes..... Maynard
  17. The “Little Surprise” mono parallel SEP spud amp. Maynard
  18. Found this in a Radio Maintenance magazine from 1951. Maynard
  19. The easiest solution is to order some JJ 12dw7s from Tube Depot for $12.95 each. Maynard
  20. There are 2 ways to reduce distortion in SEP amps. One is to use it at a fraction of its maximum output power, and the other is to use nfb. I prefer the latter (as voltage fb) as it reduces the typically high output impedance as well as increasing the bandwidth. If applied within reason, it does not ruin the resultant sound in my experience. In fact, it can provide a very triode like experience in some systems. Maynard
  21. Class AB refers to a specific set of operating conditions which are usually somewhere between class A and class B. So unless the amp has provision to change that, it is running in AB at idle through its maximum power output. It combines the advantages of both classes while minimizing their respective disadvantages. Maynard
  22. Here is the perspective of an EE from the Steve Hoffman forum. I agree with him. I believe that using multiple caps in parallel, regardless of type or price, craps up the sound. My ENT doc friend showed me some frequency response plots of typical males in their mid to late 70s which have convinced me that some of what we believe we hear is wishful thinking. Also, the nonlinearity of the human auditory system is so great, and so varied from one person to the next, that universal recommendations about audio components are worthless. Maynard John DysonForum Resident Location: Fishers, Indiana If I was making the decision for myself, I wouldn't change the cap unless I had a concrete reason to do so. Some people like to change things -- and that is fine also, perhaps part of the enjoyment. Put my EE hat on (I am an EE RF/Audio/Systems, SW Operating Systems/DSP -- and generally pretty good at all of them ), so here is a quick (back of scrap pad of paper) analysis of the situation: Lets see -- cathode resistor/capacitor (I dont know the tube, so I'll guess a gm of about 2mmhos or 2mS.) That would imply an effective resistance of about 500ohms at the cathode (without bypass.) With an electrolytic with perhaps 0.1ohms of ESR, lets guess at 10% of that is nonlinearity. That would mean a delta of 0.01ohms with a 500ohm impedance at the node... The additional amount of distortion caused by the electrolytic changing by the 0.01ohms would be less (much less than) 0.002% additional distortion, and I am guessing VERY, VERY HIGH. In reality, the amount of distortion caused by the nonlinearity of the resistance would be pretty small. Now, we have an issue about the nonlinearity of the capacitance of the capacitor, and the best success there is to make sure that the capacitance has a reactance that is very small (relative to the lowest audio frequency) in relation to 500ohms. Also, unless the tube/valve is in a negative feedback circuit, the changing gm will totally swamp the nonlinearity of the capacitor (either the resistive or the capacitive reactance nonlinearity.) If I was making a design decision, I would simply try to choose a reasonably high quality capacitor with fairly low ESR -- the rest will take care of itself. The difference in distortion of a reasonably good electrolytic vs a perfect capacitor will be vanishingly small, and probably not even measurable. Of all of the things that might need to be improved (other than as a failed/degraded parts replacement) I don't think that changing the capacitor would be all that helpful. Audio source material and transducers (speakers, headphones, microphones, etc) are much more important. John Dyson, Apr 25, 2018
  23. Here’s what Rozenblit had to say about OTL output capacitors on the Transcendent forum: Maynard Bruce Rozenblit03/29/04 There seems to be a lot of confusion about what an OTL is on other message boards. OTL stands for output transformerless. The idea is to eliminate the output transformer from the signal path. That's what I do. It is a very difficult task because of the impedance mismatch between tubes and speakers. There also seems to be a great deal of resistance to the use of an output capacitor. Many people for some unexplained reason, have gotten the idea that an output capacitor will greatly injure the signal. That is baloney. A transformer is about 1000 times more injurious to a signal than a capacitor. Most tube amps have output transformers but that is OK. Most speakers have internal coupling capacitors but that is OK. When an amp has an output capacitor, its the end of the world. I don't get it. Many people have spent a couple of hundred dollars to replace the stock caps in the SE OTL with black gates and all have reported back that there was no improvement. All have wasted their time and money. There is a big difference between conceptual idealistic notions and what works in the physical world. I concern my designs with what works in the physical world. The T16 is direct coupled and the SE OTL sounds even better but it has an output capacitor. Its the results that matter, not the concept. QUOTE
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