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henry4841

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Everything posted by henry4841

  1. First let me check my stock of tubes and see if I already have some. I've bought a number of tubes over the years without ever using them. My favorite non-audio tube is the GU-50. Built a couple of SE amps with them and they sound great.
  2. Unless I am mistaken Roy mentioned doing the very same thing to PWK before he died and got disciplined for asking such a question being PWK said he had already tried it decades ago with no improvement. As CBH just said you should not believe everything you read on net. That and always consider who it is say something. Do they hold an engineer degree like PWK.
  3. And the larger the cone the more air you are going to move.
  4. This amplifier has evolved into a SE KT-88 one. Why, because to me this design sounds best biased for the Kt-88 tubes after doing a lot of testing and listening. I have been playing with different bias setting for the tubes using scope and Arta distortion analyzer software and I have found that reducing the current through the KT-88 tubes from the reference setting produces the best results as far as output power vs distortion. I've reduced the current in the output tube from 78ma to 64ma at 406v's from K-P. The dissipation of the tube now is 26 watts on a Electro-Harmonix Kt-88 rated for 44 watts. This is where the output power is much the same as when being run at 78ma but with better distortion numbers. This means the tubes should last many hours running around 1/2 of it's maximum rating. From a couple of popular SE KT-88 designs that are similar as far as V's and current being run in the output tubes the more common value for the cathode resistor is between 470r and 560r. I have found using a 680r resistor has the best results and that is what is going to stay in this amplifier. I've bought 7 12AT7's and some JJ-EL34 tubes and some JJ-Kt-88 tubes before settling on what looks and sounds best on the bench. The spares will go in stock for possible use in the future. The EL-34 tubes in this amplifier do sound really nice and really cannot be faulted it is just the KT-88 tube sounds somewhat better as far as sound stage and vocals with a much better bass response that is almost as good as a good SS amplifier. I said almost as good but that is only going to apply to horn speakers capable of using the 6 or 7 watts this amplifier produces.
  5. I spent some time this week changing the voltages and current on the input tube seeing if any value changes made any difference. Nothing significant came from testing on the input tube. The power tube is running at 80% and I see no reason to change anything there. In other words I am confident Maynard hit the nail on the head when he published this design. If not the head of the nail real close. Sure you can start manipulating the signal with feedback lowering the 2nd harmonics making it sound more like a pentode amplifier or a SS one but why. Certainly not me having multiple SS amps and one pentode and one PP tube amplifier to hear that kind of sound with. I favor single ended amplifiers, not that I do not like the other kinds of amplification as well but what really makes me smile is a simple circuit 2 stage single ended tube amplifier. Right now the signal in this amplifier goes through this amplifier with as little manipulation as possible other than amplification which is what you want. One is hearing the sound of the tube at least as reasonable possible in a SET amplifier. Certainly anyone is welcome to play with the circuit however they desire. The only point to be made is build one and see what all the fuss is about. Then you can tailor the sound to suit you.
  6. I feel your loss having lost my best friend 2 years ago to covid.
  7. I think the design, circuit, is fine. Any limitations is in the tubes themselves is my feelings. Exactly why I like simple two stage circuits. One gets to hear what the tube sounds like without, or at least little manipulation, of the sound. No simple simple 2 stage amplifier such as this is going to shine on the bench. They just for some reason sound gorgeous for many of us. I like what I see on the scope and on the Arta distortion analyzer software. In my opinion it is doing what it is supposed to do, sound sweet in the mids and on vocals especially. I have built 2 SE KT-88's since building this amplifier. I just recently had time to play with my new signal generator that has distortion numbers low enough to use Arta is the only reason I decided to put this amp back on the bench and do some testing. Passed with flying colors when I finally figured out how to get 1/4 watt on the output. The distortion number you see is 2nd harmonic, what one builds a SET amplifier for. There are ways to lower the 2nd harmonic as Captain has been discussing but I like hearing the charm of the 6Y6 tube as my Great Grandpa heard it in his day. I am moving on with another project now. I have a First Watt Aleph J I built in my test chassis that I built for testing first watt designs that I need to put in a proper chassis I bought many months ago. Built the PS section yesterday. Life is good.
  8. Did not bother this morning, but did one day last week. Looked good to me. Surprising to me is the excellent bass response for just one watt of power. Best some of my other amps with better numbers sonically.
  9. I do not consider the roll off at such a high frequency to be a problem other than for those that like to chase numbers. I consider 2db down at 18Khz to be very respectable. I can not hear that high anyways nor can most over 50.
  10. I ran some test using Arta this morning at 1/4 watt output and I am seeing approximately 2db down on one channel and 2 1/2db down on the other at 18khz with 1khz as a reference. This is on the Premium Sweetie build. I feel like most that would even consider this amplifier are like myself now limited on just how high a frequency they can hear. I did not notice an appreciable loss at 10k worth mentioning. Excellent numbers for frequency response in my world on a tube build.
  11. I forgot George has already ran some test on Hammond 125 series transformers. The numbers speak for themselves. I talk to George on occasion and he is talking about taking his site down. I would hate to see that happen but I can understand why. below is what he found on the Hammond 125Cse's at his website. Quote, Hammond 125CSE These have been the best choice in low cost transformers. Best sound is achieved at 70mA. This transformer makes about 1 watt more above 100Hz than the Electra-Print. Specs at 1 watt: frequency response is 11.7Hz to 42.9KHz with 50mA, and 10.4Hz to 44.2KHz with 70 mA. Distortion is .65% with 70mA (mostly 2nd harmonic). Distortion is 2.6% at 6.0 watts. Low frequency effects at 5 watts: Visible saturation can be seen on the scope for any frequency below 77 Hz at 50 mA, 64Hz at 80mA. clipping was observed at any frequency below 130Hz with 80mA, but none was noted at 50 mA. Low frequency distortion tests at 1 watt: 100Hz lowest distortion was 1.01% with 63 Ma. At 36 HZ .66% occurs with 58mA.
  12. But then you will defeat the purpose of the build. Those Lundahl transformers are expensive. I plan on doing some more test today to see when the high frequencies are down 3db using the Hammond 125Dse's like the ones used on this build. I really like the sound of the Hammond 125 series of transformers I have tried of late over the Edcor's. I have two Sweeties right now, one with Hammond OPT's and the other with Edcor to compare the sound with. The one with the Edcor's is a stereo version whereas the premium Sweetie is dual mono's on one chassis though. Should not make any difference in frequency range test though. One can always improve any amplifier to some degree by throwing expensive parts at it. The goal of the Sweetie was a really good sounding amplifier for the lowest cost using good quality parts. I honestly think the Sweetie as designed by Maynard fulfils that goal as a good inexpensive forum amplifier project. One thing I like is the lower voltage it operates on making it more appealing for a beginner to build. That and no adjustments are necessary if one follows the build guide.
  13. Sure, go ahead. Personally I like the circuit as it was designed by Maynard. The last few days, almost a week now, I have played with some changes in the circuit just because. Nothing I tried improved the circuit to any significant degree. I think Maynard got it right the first time many years ago. I have not tried feedback being I see no reason to reduce the amount of 2nd harmonics. That is about the only distortion seen on Arta and I like seeing it in a SET amplifier. That is why I build SET amplifiers. All I can add is if and when someone builds this amplifier they can play with it all they want and publish their findings here or on another thread. I do not think I am going to play with this circuit anymore myself. I like what I hear. This build is about as cheap one can build a quality amplifier and I do not believe you will be disappointed. The original Sweetie project that is. No need to go to the extreme I did on this premium build. Yes the premium may sound somewhat better but not enough to get excited about. The original sounds plenty good enough. Just use good Digi-key or Mouser parts.
  14. It's entertainment not rocket science. I am sure that not everyone would take to the Sweetie with it's generous amounts of 2nd harmonics. For me it is what gives it it's charm and makes it different. Nelson Pass when discussing First Watt products often says he just wants to hear the transistor clapping. Much could be said for those that like simple SET tube amplifiers with few parts. I love the sound of that old 6Y6 tube. By the way, it is surprising to me how good the bass is for such an anemic little amplifier, 1 watt.
  15. None taken. Doing what sounds best to you is the best part of building amplifiers. As you may know I have lots of amplifiers, around 25 working ones both SS and tube. Most are class A, my preference. My music choice does play a role in what I enjoy but most that come to my house and listen with me consider my listening level is too loud. I am definitely in the league of simple circuits with few parts and no feedback. With no feedback in a SET amplifier you are listening to what the tube sounds like without any manipulation. I have plenty of SS amplifiers that do have feedback in their design and for a change I can enjoy them but my preference is a good SET amplifier without any feedback. For rockers and modern music one would probably prefer some feedback but then they are not a large market for a 5 to 7 watt SET amplifier. Most of them look for mega watt amplifiers with horn speakers needing only a few milliwatts of power to play too loud. Right now class D is all the range and I only expect it to be the norm for the masses in the future.
  16. That and the only significant distortion I see on the graph is 2nd harmonic so with feedback you will be reducing the amount of 2nd harmonics. I like the sound of this amplifier probably because of it's 2nd harmonic signature. Also I think the lack of the typical touch of 3rd harmonic that is absent in this SET contributes to it's pleasing sound I like as well. All in all at 250mw I like what I am seeing on the graph. Certainly if one wants to play some with this 1 watt amplifier you could install a switch and change back and forth between feedback or not. You would have to play around with the amount of feedback till you are satisfied with what you see and hear.
  17. Sure you can but it is not something I care to do. Just me being old school probably.
  18. The error I made is in my math finding 250mw at 8 ohms. As most on this forum know 2.83vs into 8 ohms =1 watt. The number is what you see used to measure efficiency of a speaker at 1 meter. So I just used simple math thinking if I divide 2.83vs by 4 I will have the volts needed at my 8 ohm load to achieve 1/4 watt, wrong. That is the amount of voltage, .7 I was raising the volume control to see at 8 ohms thinking I had 1/4watt. I should have used ohms law and I would have found that 1.4vs at 8 ohms was what was needed to achieve 1/4 watt, 250mw. In other words the old previous graphs were at .06 watts instead of .250 watts. Just a simple ohms law calculation error on my part. https://ohmslawcalculator.com/ohms-law-calculator I had rather not use feedback in a SET amplifier. Sure it will produce better numbers but at what cost. I have nothing against feedback, just not in a SET.
  19. I made a mistake calculating 1/4 watt into 8 ohms into voltage at resistor. The correct voltage for 1/4 watt into an 8 ohm load is 1.414v's and I was using a much lower voltage previously. Sorry Maynard. My only excuse is never tested using Arta at 1/4 watt. That aside with the correct 1/4watt into 8 ohms the graph looks like this. For a 1 watt amplifier this graph looks great to me. One has to remember the 6Y6 tube is a very old tube design when 1 watt was the norm. As I have stated many times about the Sweetie it has a tone that sends me back to the era of my childhood. The sound from a backelite radio my mother played while doing her morning housework. Lovely sounding little amplifier with just enough power for any of the Heritage speakers. For most that is.
  20. Great work, thanks for taking the time to do so. CL-90 works as it is supposed to do from your test.
  21. It could be, more likely, you like the amplification design in the MC30 and not the type of rectification. I probably love the sound of one amplifier that others would not like at all. Reason for so many different types of amplifiers on the market. This hobby is entertainment and not all science.
  22. Around 60 years ago. McIntosh ditching a tube rectifier says a lot.
  23. When did McIntosh go with SS rectification in their tube amplifiers ?
  24. It appears the Chinese do not have the ability, at least Psvane, to produce really low noise, matched internally for dual triodes, tubes consistently as the giants in tube manufacturing era did years ago.
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