henry4841

Sure you can but it is not something I care to do. Just me being old school probably.

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.

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.

Great work, thanks for taking the time to do so. CL-90 works as it is supposed to do from your test.

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.

Around 60 years ago. McIntosh ditching a tube rectifier says a lot.

When did McIntosh go with SS rectification in their tube amplifiers ?

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.

Here are some pictures in Arta distortion software of the SE KT-88 amplifier after replacing the Psvane 12AT-7 with an NOS GE 12AT7. The distortion at 1khz 1 watt was cut in more than half by just changing the input tube. Distortion numbers of .26% THD and .27% THD+N at 1 watt is something I am proud of seeing in this SET tube amplifier. Left and right shots of the screens. Notice the 2nd harmonics and touch of 3rd and not much of anything else of the fundamental signal of 1Khz. The 4th harmonic is 73db down from the fundamental which is basically not heard along with a 5th harmonic 80db down. Good looking distortion profile for a SET in my book. Just what I expected and desired when building this amplifier. Some SET 2nd harmonics and a touch of 3rd is exactly what many consider makes an amplifier sound best. Some big name SS amplifiers introduce or build their amplifiers to have exactly the same stats as a good SET amplifier.

Asking and selling are two entirely different things. Classic Audio Prattville, Ala last month had a pair of Heresy's for $600. Not sure if they still have them but they looked nice to me.

Looking at the screen shot of the Arta on the Sweetie I honestly believe a choke in the PS section would clean up the hump at 500hz. I looked to see if I had any chokes in my stash and I do not. Used my last one on the KT-88 build. The cheapest ones I see at I could use at Mouser are $13.40 apiece raising the cost $26.80 to make this amp look better on the bench and during test with no benefit to my ears when listening to music. For curiosities sake I may purchase a couple of chokes just to satisfy my curiosity. I do not think there is a problem in the build or parts being this amp is built as mono's and both channels look almost identical on the screen. Look forward to hearing Maynard's opinion.

I decided to check how much was distortion in the .66% and .67% eliminating the noise number and the figures are .56% and .54% for just distortion, which is dominant 2nd harmonic by the way. The kind of distortion one expects to see in a SET amplifier. I would expect some chokes in the PS section would make it look much better on this Arta software but why would you. This amplifier is quite on my LaScala's with my ear next to the speakers and it sounds wonderful to my ears just as it is. Also curious on what Maynard thinks is the cause of the peak between 300hz and 700hz. Looks to me like that is what is carrying on further up the frequency range. Fascinating not seeing any 3rd harmonics to speak of on this amplifier on Arta. Curious to hear what Maynard thinks is why. This maybe is what makes this amplifier stand out from the crowd of SET's.

I decided to run Arta on the Sweetie today. Got my curiosity up. This is what I found, first picture left channel. When I first tried to take pictures I was measuring .59% left and .62% distortion and noise at .250mw. Respectable numbers in my book for a 1 watt amplifier. I certainly would not add any feedback to my Sweetie. One thing I notice in the profile is no or very little 3rd harmonics from this amplifier. One can see a lot going on from the 4th harmonic that my KT-88 build do not have. Nothing to be concerned about being the noise or whatever it is, is well below the fundamental. Another thing I like to see is there are no or almost minute spurs on the fundamental signal which my KT-88 amplifiers do have.

Poor choice of words on my part Maynard. For a SET amplifier at 250mv the distortion is not anything to worry about. I was referring to a good SS or say the SE KT-88 I just built amplifier distortion profile on Arta software. When I find time next week I will look at the Arta profile and see exactly what the number is. Arta does state in as distortion or distortion and noise. I can look at it each way. In fact I can take a picture of the screen and post it as well. I do remember when looking at the profile there was a lot more going on down low, something like 80 or 90db down from the fundamental. In other words nothing one should hear.

CWelsh on the Pictures of your Tube amp thread where I posted pictures of my latest build a SE KT-88 asked how did the KT-88 compare to the sound of the Sweetie. This morning I decided to do some comparisons between some of my other amps to this new one the KT-88. I decided to post results here instead of on a thread about pictures of tube amplifiers. The Sweetie will hold it's own with the KT-88 I just built and a First Watt Aleph J clone I built many years ago. Some may even prefer the Sweetie. This week I did some distortion testing with the Arta distortion software. The KT-88 amplifier has a really clean signal, much like many SS amplifiers, with some 2nd harmonics and a touch of 3rd which many consider what makes an amplifier sound best. The Sweetie has the same 2nd and 3rd harmonics but distortion numbers are not what one would call good. I tested my personal KT-88 along with this one I just finished with the intentions of selling somewhere and the Sweetie. The KT-88's were tested at 1Khz 1 watt. I would not test the Sweetie at 1 watt because that is all the power it makes at clipping. Would not be fair, but even at 250mw of power the distortion numbers were not what one would call good. All that being said the Sweetie is one amazing sounding amplifier. SET amplifiers are known not to measure well on the bench but sound outstanding to many people. Trying to sell a 1 watt SET amplifier would have a very limited market and a tough sell except to knowledgeable audiophiles. The SE Kt-88 is a great sounding single ended amplifier with more expense but a broader market with the more common 6 or 7 watts one expects from a SET amplifier. One would certainly need Heritage type speakers to even consider a 1 watt Sweetie but they would be rewarded with some truly outstanding sound.

I was planning on detailing the time and work I put into this amplifier at some date. The case is solid 7/8" cherry wood with dovetails joints I personally cut myself. Aluminum is 1/8" plate. The design is a proven one close to if not over 20 years old with hundreds made and tested. In other words a solid design that I designed to be conservatively biased and operated and not hot rodded to produce better numbers that shorten the life of the tubes. A tube is somewhat like an old type light bulb with a wattage rating that has nothing to do with the output to the speakers. The JJ KT-84's are rated at 42 watts and I am running the tubes at less than 30 watts which is below the 80% l like to run all my builds at meaning one should expect a long tube life. One of my personal EL-34 amplifiers, which was my build before this one, is one I played around with the many different tubes in the EL-34 family which includes but not limited to the 6L6's, EL-34's, KT-77's and KT-88 with some others I do not have in stock that can be used. After doing many hours of listening and biasing the tubes I have there is no doubt in my mind the KT-88's are the best sounding of the family. Big and expensive but worth the cost in my limited experience. I actually started this build with the intention of using some EL-34's and actually bought a new set of JJ EL-34's for this build but after listening to the differences between the KT-88's and EL-34's I decided to bias this amplifier for the KT-88's. I have not done an A/B comparison between this build and the Sweetie. The Sweetie is one of my favorite sounding amplifiers and it has a tone I love. The Sweetie is limited in it's power more in line of the Decware Zen which it should be compared to. A SE KT-88 makes much more power, this one depending on the set of tubes is capable of 7 or more watts. This is a big amplifier. Right now with the tubes I have in it the amplifier is putting out an average of 6 watts per channel. One channel slightly over and one slightly less than 6 watts. This is typical power one can expect from a properly designed SET amplifier in the family of the EL-34 tubes. And for that matter a SET 300B amplifier. The KT-88 is a big tube that handles higher voltages and more current than a 300B. In my opinion the sound can be compared to a SET 300B without the hassle of dealing with a directly heated cathode. In other words much easier to build a quite amplifier. I ran a distortion analysis on this amplifier and the sound floor is 70db down from the main signal. In other works quite with your ear against my 103db LaScala's. Comparing the KT-88 tube to an EL-34, the ones I own, the bass is way better with a more pleasant vocal sound as well. This amplifier is built with slightly over 3lb OPT's instead of the 1 or 2 lbs ones you usually see being used that are offered for sale in most amplifiers of this type. With larger OPT's the sound becomes cleaner and clearer to my old ears with still a lovely SET sound. The output tubes are biased at around 70ma of current equaling 140ma for a pair with a few more ma's from the rest of the circuits and I am using a Hammond PS rated for 201ma's so one can expect a long life from this amplifier. I did a lot of testing inside this amplifier to determine if the higher wattage parts are operating within their rating. Also did some comparison on the input tubes. I knew there is normally a 20% tolerance in tube manufacturing but did not realize this also is true with a dual triode input tube. In one tube there can be a difference of 20% or more in the voltage and current between the two sections. I had to go through 4 12AT-7's before finding one that was closely matched inside the tube. Yesterday I received two Psvane 12AT-7's from tubesandmore and one of them had a difference in plate voltage between the pair of triodes of 30v's. The other was matched much better with just a slight difference between the two. I am sure most never realize the imbalance in the dual triode preamp tube they now have in their amplifier. Chances are one will never notice the difference in volume between the two. Yes one channel will always be stronger than the other if you have a 20% imbalance between the channels. That and one channel is going to put out more power at clipping than the other. One will never know when changing dual triode input tubes unless one checks the two triodes on the bench. This is just one step I took when building this amplifier. Right now it has JJ KT-88's which sound really good. They are the less expensive KT-88's being offered now that are in stock. After a few hours listening with the Psvane 12AT-7 tube last night for a few hours I like the vocals this tube produces and I do not think I would change it. It is being very conservatively biased with balanced triodes so I would not consider changing it.

And two more pictures. I have some more testing and listening to do but for the most part I am finished with it. I do have a bottom plate to cover the electronics from curious fingers made of plywood I am going to install when I am satisfied with what I have done. Could possible be in the garage section at a later date if there is any interest.

My latest build, a single ended KT-88 with zero feedback.

After giving this some more thought what I really think I meant is to bring back the old PA, club LaScala that made a home model desirable to audiophiles. Surely Klipsch can make a profit selling it roughly in the middle price between a Cornwall and a LaScala by just spraying some black paint on MDF. The look of the 70 LaScala with the new drivers. Other than that possibly a bass design that is real close sonically to the LaScala with the horns and drivers of the new LaScala. Surely possible with new technology, bass speakers, horn and drivers. Lot's of interest in open baffle bass these days. Open baffle bass or something similar with modern LaScala horns and drivers. In other words getting away from the labor involved in building a LaScala bass bin. Anything in the works Roy to fill in the gap between the Cornwall and LaScala? I am almost positive your design team has given this some thought.

I expect this thread to get out of bounds real quickly if it has not already but since the mid elections are over I expect the price of fuel to increase again increasing the cost of everything. The old saying "if you got it a truck brought it" is going to ring true.

There is a big difference in price from a Cornwall to a LaScala roughly $6,600 with nothing in between in the Heritage line. This was not the case just a few years ago. I can understand why, LaScala is now dressed up to look nice in most buyers rooms. Lots more veneered wood needed to look nice in the open horn of the LaScala. When I bought my LaScala's in '86 the difference in price from LaScala to K-horn was close to double. Why not offer a LaScala like the old days, built from dyed birch plywood or painted MDF and not from expensive veneers. Klipsch may have good reasons for not doing so but I do believe there would be a market for a stripped down LaScala. With the price now really close to the price of a K-horn Klipsch loses a big market of buyers who would love to own LaScala's but cannot fit one into their budget. May not be profitable for Klipsch but it is a shame more cannot own a remarkable speaker like the LaScala. I posted this here with the hope Roy sees this post and possible will comment.

Tubes and Klipsch go together like peas and carrots. Especially SET tube amplifiers. With their low power output they need efficient speakers to enjoy the most linear of all the classes of amplification. The best sounding speakers deserve the best sounding amplifier. Those that equate loud with best will never understand.

I have to live with an amp and speakers for a few weeks or longer and then go back to what replaced them to really decide myself. Initial impressions, if new product is just different sounding, can be deceiving. I personally like both SS and tube sound but lean more to tubes.

Measure across the inductors and the measurements should be accurate if you have a good inductor measurer on a circuit as simple as a crossover network. Unhook from speakers if you choose to.