Building the Audio Note Kit 1 SET amp...
Following up on my previous posts about the resistor value non-issue, I've found myself sufficiently captivated by all of this unfolding drama to complete a careful look at all of the photos at Rebbi's blog, looking for anything that might account for the problem. I found nothing. As might be expected, everything looks to have been done meticulously and accurately. I even checked all resistor values against the schematics which are available on the Internet, with the exception of the four resistors on the filament supply board (those don't seem to appear on any of the schematics I found; apparently they were introduced during a relatively recent revision of the design). I did note what MIGHT be a bit of heat damage on R21 of the driver board, but looking at the schematic I don't see how that could account for the specific symptoms in this case. And in any event that resistor would only affect one channel. One possibility that seems very remote but I wouldn't totally rule out at this point is that the output transformers were manufactured with the wrong color coding on the wires. I say that in part because most (but not all) versions of the Kit 1 for which photos appear on the net have transformers which used a different set of colors for their secondaries than the green-blue-yellow colors of the ones that were supplied to Rebbi. And of course if the colors were mixed up such that the 4 ohm tap is being used, or the speaker connections are being made BETWEEN the 4 ohm and 8 ohm taps, that would easily account for the problem. The tech could probably verify the color coding by measuring resistances between the different possible combinations of the three wires. Best regards, -- Al |
Al, Thanks for all that meticulous attention and for the kind, positive comments about my build. I hand't worked with a soldering iron in a few years but once I got the cobwebs out I LOVED the building experience and have really caught the DIY bug. Brian overnighted some tubes and new caps for the Power Supply PCB. The technician has them now and will be working on the amp tomorrow morning. I should know something tomorrow afternoon at the latest. I'm hoping it's something simple. Yes, you are correct (and very observant, by the way) about the output transformers. The color of the wiring has changed since earlier versions of the kit and I had to ask Brian what the correct colors were. He told me that green is 0 (ground), blue is 4 ohm and yellow is 8 ohm. (I think that the earlier versions had a purple wire for the 8 ohm tap.) I deliberately didn't cut the unused, 4 ohm leads but bundled and shrink-tubed them in case I ever want to run a 4 ohm speaker. The most challenging aspect of the build was that I was working with the previous version of the Assembly Manual, supplemented by a "beta" version of the latest Manual edition. Most of the design changes in the 2014 version of the Kit 1 have not been radical, although, as you noted, the Filament PCB has changed quite a bit (the whole heat sink configuration is quite different) and things like the lead colors on the OPT's have changed, too. So I corresponded with Brian whenever I had questions and, when I was uncertain at all, I tried to be extra careful not to solder anything until I was totally sure I had it right (although I'd have done that, anyway, given how slowly I tend to work). By the way, a very pretty, updated manual is almost completed. I offered to send suggestions for the new edition to Brian and he accepted. I told him he could use photos from the blog if any of them are useful. So the bottom line is that future builders of this amp will have VERY nice, clear instructions to follow! I don't think I mentioned this earlier, but the tech said that the amp wasn't putting out anything close to 8 watts, so there's something very funky going on with the power section. Again, I'm hoping it's simple! |
Saki, Yes, when I think of it, I've started some doozy threads. The one about Ohm Walsh Micro Talls has run to over 2000 posts, last I checked. :-) Of course, when I start thinking about all the productive work I could've accomplished when I was spending precious time posting to audiophile geek message boards, I'm not quite as happy with myself. ;-) |
Thanks very much, Jeff, Rob, & Rebbi. I should add to my previous post that one thing that couldn't be verified from the photos, in many cases, is that polarized electrolytic capacitors were installed with the proper polarity. But given the accuracy of everything that could be verified, including the polarity of some of those capacitors, I suspect that too was accomplished with perfect accuracy. Best regards, -- Al |
Well, Friends, no joy just yet. The technician, with guidance from Brian, was unable to troubleshoot the problem, even with the complement of new tubes. So, Brian and I will Skype early next week to see if we can troubleshoot the issue in that way in real time. If not, Brian's going to get the amp shipped to Digital Pete, the fellow in Florida who does assembly of certain ANK products for those who (like Roxy54) want to buy a kit preassembled at extra cost. (Roxy has the 10th Anniversary Edition of the Kit 1 with the AN Copper Foil caps and the C-Core trannies.) Pete's a real artist. Some of his assembly work is featured on the ANK website and it's gorgeous. And if by some bizarre chance I got something like a bad transformer (which, given that they're all pretested before shipping, shouldn't be the case) he'll know and be able to swap it right there. My hope, of course, is that Brian and I can figure this out on our own. This seems to be one of those one-in-a-million things. Brian told me that he sold two Kit 1's not long after mine and they turned out perfectly. Go figure! I'll keep y'all posted! |
There aren't many companies who offer this kind of support. I was impressed from the first time I called Brian, and Pete Fulton is just great. It is so good to know that a company isn't just taking your money and letting you drift. It will surely all be sorted out in the end, but I'm sorry that you have to go through the hassle. |
Hi, folks, Well, I got a personal message from one of you asking what's going on, so here's the latest. Brian and I spent a total of about an hour and a half on Skype yesterday, spread over a couple of sessions. We went through all the static AC and DC voltages as well as some resistance measurements and everything that we checked looks good, except for one value (can't remember which one) that seems to drop precipitously after being measured. I don't remember exactly what we concluded about that one  sometimes it's just not easy to get a good reading on a solder joint. We also tried putting a speaker load on one channel to check some AC voltages as the volume potentiometer is moved with a CD playing. I have a few more measurements to do. Brian sent me a file of a sine wave (pure tone) that I have burned to a CD so I can play it while taking some measurements and adjusting the volume control. Brian explained to me, again, that everything in the driver stage looks good. But when the technician here in Austin to whom I had sent the amplifier measured the output voltage with his scope, everything looked "squashed." "Like an elephant was sitting on the waveform," Brian said. So something weird is going on with the power stage not putting out full power. If we cannot sort this out ourselves in another day or two, Brian is going to pay to have the amp shipped to Digital Pete, his assembly guy in Florida. Pete has built and done troubleshooting a bunch of these kits (and others) and has all the parts on hand. If, for example, I have a bad transformer or a bad 300B tube, he will be able to swap it then and there. As much as I am eager to get back to listening to music again, I am again grateful to Sebrof for giving me the opportunity to use his speakers and determine that a speaker mismatch was not the issue. I am also very, very grateful to Brian, whose customer service is above and beyond amazing. He clearly gets a kick out of working on these things and keeping his customers happy. And in the category of making lemonade out of lemons, so to speak, I am learning even more about electronics and how this amplifier works through this process. I'll be kind of disappointed if Brian and I can't figure it out long-distance, but as I said, I am also eager to get back to hearing that beautiful music. Brian said that Pete will turn it around really quickly if we do end up sending it to him. When I run the additional tests, I'll let you know what I find. And I am hoping to see all of this resolved within the next week or so. |
Oh, I also want to mention, for those of you who are interested, that Brian said that he is super curious to figure out what's going on because this is not typical of a build problem. Usually, he told me, either the amp is working fine or there's something really pronounced that goes wrong, like one very noisy channel or the amp frying due to a major wiring error or reversed electrolytic capacitor. But having an amp that "almost" or "sort of" works is just plain weird. I'm sure we're going to get to the bottom of it, though. |
I wonder if Brian at A-Note could send you an amp that he knows is working properly to see if it does work with the Decapos. If it does work, then you know you'll still need to troubleshoot, if it doesn't, then you could save everyone a lot of time and trouble trying to diagnose a problem that may not exist. Like most of us here, I'm pulling for you to get this sorted out to the point where when it's all over, you are absolutely thrilled with the outcome. Best of luck and thanks for keeping us all in the loop. |
Reb, does Brian agree at this point that the test you did with the problem tracks at Sebrof's with yours versus his amps confirms a problem? They are two different amp/designs for example. Frequency response differences in teh lower octaves alone for example might account for that if teh AN is attempting to put out more power at lower frequencies for example. Seikosha's idea comparing apples and apples amps sounds like a good one to me. I'm not sure that output power ratings alone tell the whole story in regards to what to expect necessarily. Also I would guess someone familiar with the amp like the AN tech or Brian could identify if the sonic effects of the amps clipping, which is undoubtedly bound to occur at some point, is as expected. For example, assuming soft clipping, teh volume might stop going up well before audible clipping occurs. Just some more food for thought FWIW. Sounds like the best thing is for an expert in your particular amp to give it a once over in person, which is where you are heading. |
REb, one other question I am curious about. Did your amp go louder at Sebrofs before clipping than at home with the Ref 3as? I would expect at least that assuming use with the more efficient speakers. Whether or not one amp rated a few watts higher than another would actually go as loud or louder in any particular case is a little greyer for me. |
Seikosha and Mapman, Everybody agrees that this amp isn't working properly. The tech actually sent Brian video of his scope readings and they confirmed a problem. I played some bass heavy music for Brian and even over Skype he could hear the distortion when the volume went up. I think the experiment at Sebrof's confirmed that this isn't a speaker mismatch problem - we heard the same effects there. We're just not yet sure what's causing the amp to misbehave in this way and not put out its rated power. But I'm confident we'll figure it out one way or another. |
I'm hard pressed to see how it could be called a good match if truly not that efficient in the bass but may only need match to a certain extent depending on listening volume requirements and room size mainly. Its not working properly currently would seem to be the consensus so there is still a chance. |
FWIW, regarding what can be expected from a SET architecure as opposed to other tube based designs, my understanding about SETs in general, based purely on what I read, which is consistent with what I have heard to-date, is that its their midrange that make them special. They can do well on the extremes as well but it takes a fairly specialized approach to component matching with high efficiency speakers in particular for them to be able to "do it all", especially in the bass. Of course a smaller room helps to enable doing all that is needed practically in many cases. I hope it works out with the Decapos. I'm still thinking there is a good chance from what I hear once the technical issues with teh newborn amp are sorted out. |
So, After three separate Skype sessions with Brian leading me through test procedures as well as some voltage meter checks on my own, putting a sine wave through the amp and taking a variety of measurements on the 300 B tubes, here's what we know: We have verified that one suspect  that the volume pot might have been wired incorrectly (it's actually a somewhat complicated procedure involving six separate connections)  is fine. The volume pot wiring is good. Most of the AC and DC voltages look perfect, even better than usual. But there is some odd behavior with a few of the AC voltages vis-à -vis how things react when the volume pot is raised or lowered. We also discovered that I have four ceramic capacitors soldered in the wrong position on the driver board, although these are not in the signal path and would not be causing the symptoms we've been hearing. (Brian is going to send me a set of replacement capacitors.) At this point, Brian is pretty convinced that there is a problem with the driver board passing along a clipped or distorted signal. So we're going to do another Skype session and he will lead me through a step-by-step series of voltage checks on each stage of the driver board. We should be getting there soon! |
We also discovered that I have four ceramic capacitors soldered in the wrong position on the driver board, although these are not in the signal path and would not be causing the symptoms we've been hearing. (Brian is going to send me a set of replacement capacitors.)Rebbi, I don't quite understand that. The ceramic capacitors I see on the driver board in this photo from your blog are C1, C2, C3, and C4, and they all appear to be in the correct locations per the markings on the board. Where is Brian saying they should be located? Best regards, -- Al |
fwiw i had a defective input board on one of my ref1000m amps not long after i acquired them . The foil or conductive material on the board had separated from the board resulting in substantial distortion at all volumes. Replacing the board resolved the problem. So a defective circuit board is certainly a logical candidate assuming all else checks out properly. Am interested also in whats wrong with how those capacitors are installed. Looks good in the pic. |
OK, I just noticed in this photo that there are printed circuit connections visible within the board forming a direct connection between what I (and you) had believed were the two pads/holes for C1, and likewise for C4. Given that, it becomes apparent that the uppermost ends of C1 through C4 should go to the pads at the top of the board that are adjacent to (and connected to) W20 through W23, respectively. And the reason you need replacements for the capacitors, of course, is that the leads on the original ones were trimmed for mounting in the more closely spaced holes, and will no longer reach the correct locations. Wow! An understandable and easy to make error, if ever there was one. Best regards, -- Al |
GSM, why the comment? If you are not the kind of person who wants to build, learn, test, fiix and understand your gear, then no you would never do this regardless of the outcome. Testing and trouble shooting gear is part of the process of learning and DIY. Cannot separate it. It comes with the turf as they say. |
Rebbi I am impressed with your patience and dedication to the understanding and building of your amp. I have had to trouble shoot several of my projects of late and was forced to learn. One was particularly difficult to sort out, but I learned so much. You will conquer this gremlin and along the way learn a great deal about tube amps. Forge on you brave and capable tube amp pioneer! |
Grannyring, Yes, I am certainly learning a lot. It's a good feeling to know that I can take the bottom of the chassis off and fix or upgrade anything I want. Like, on a trivial letter, when I got the amp back from the local "repair" shop (sorry for the sarcasm), the speaker binding posts and input selector switch were both loose. On a factory built amp, I'd have been all upset. On my Kit 1, I just took the chassis bottom cover off and tightened a few lock nuts. What a nice feeling! Almarg, You are amazing: bingo and bingo! What Brian explained to me is that the ceramic caps (C1, 2, 3 and 4) perform some sort of filtering function and aren't in the signal path at all. The reason there are two sets of pads in the PCB is that the PCB (which is an original Audio Note design) can accommodate more than one size/type of cap in that position, and the two sets of holes take two different kinds of caps. As they are right now, they're shorted out and not doing anything, but that doesn't effect the troubleshooting we're doing. |
A super cool thing about DIY that I have found most enjoyable is the subtle and not so subtle changes in sound when I change out one part for another. If one wants a bit more "old school" warmth in their system, dont go out and buy a new speaker cable or interconnect, put in an oil cap and Allen Bradley resistor in cathode of your driver tube. One guy I know has a seriously upgraded AN DAC and he loaded the circuit with Allen Bradley resistors. He loves the sound and I got to hear it and yes it is way cool sounding. He took a point of view and went with it and can always undo it later on if the mood strikes. Look under the hood of a Ken Shindo amp or preamp...you will find all sorts of vintage parts. I got lots of ideas after googling Shindo and viewing the innards. To much warmth in your system? Try an Audio Note Tantalum or Vichay Nude Resistor in the driver cathode. I settled on AN Tants on my driver tube. They gave me all of the musicality of the Allen Bradley's with a bit less warmth. Some amps have electrolytic caps in their power supplies. Replace one or two of them with oils and listen to how smooth and liquid your amp will sound. I am currently experimenting with hi quality Wima caps in my power supply. Dont get me started on coupling caps :) Lots of fun to be had with them. Being able to change out parts in a SET amp yields very interesting changes in sound since they have so few parts to begin with and it is very empowering to have so much control and spending so little money. So much of this hobby is very expensive...cost come way down and satisfaction goes way up when one enters the DIY arena. |
Jet, you are so right and I so do that! Let me share with you my most recent find for the power supply of tube amps and preamps. I have used the large computer grade electrolytics and recently tried the oil types from GE & ASC. I like the oil types and have mixed them with Mundorf MLytics when more capacitance is needed. However, nothing prepared me for the sonic breakthrough that resulted when I placed 100% Clarity TC film caps in my Preamp. Oh my. Go look at Parts Connextion and see the TC 600 series of film power supply caps. With no electrolytics in my preamp and these killer TC caps things really opened up and the life like sound of voice and instrument is SOTA. They are large and you need room under the hood so some gear won't accommodate them unfortunately. TC caps come in 600vdc values with up to 500uf of capacitance. They simply sound spectacular. Since my preamp is tube voltage regulated, and I cannot overstate the importance of tube regulation done right, I was not sure how much these TC film caps would help over the computer grade electrolytics. The bottom line is they are really a sonic joy. These are the sorts of improvements only DIY initiatives and curiosity will uncover. Since starting my DIY journey I am happy to say the sonic gains in my system are unprecedented and I have learned so much. Lots of great gear out there designed by brilliant folks and companies. They can often times be brought to the next level with DIY initiative and passion. |
Ronnjay, here is a Kit 1 schematic which I believe corresponds pretty closely if not exactly to the configuration supplied to Rebbi. (See page 3 of the pdf for a clear presentation of the schematic, although you will have to refer to the first two pages for the reference designations of the components). As you will see, C1 through C4 provide noise filtering and decoupling for the B+ that is supplied to the small signal stages. Consistent with Rebbi's explanation of the reason for the two holes and pads at one end of the capacitors, it appears that some versions of the kit were provided with physically large 0.015 uf capacitors (see Section 7 of the manual), and others (including Rebbi's) with smaller capacitors which are 4700 pf according to the schematic. Both values seem to me to be within reason, with the choice depending on the range of frequencies that are considered to be most likely in need of being filtered. Rebbi & Mapman, thanks for the nice comments. Best regards, -- Al |
Al, thanks, I see that pages 4&5 of section 7 of the manual that you referenced above show physically larger caps in the C1-C4 positions. Without rereading a lot of the thread, I don't know what symptoms are being experienced other than guessing that an oscillation could be present by those caps being electrically missing. |
Almarg, Right. If you go to the product page of the Kit 1 8th anniversary edition (not the C-Core 10th anniversary edition) and you click the download manual tab at the bottom of the page, you'll find photos in the manual of the populated driver board, using the older style, much larger caps. They would have used the top and bottom holes. The smaller sized caps being delivered with the kit these days for C1-C4 use the middle and upper holes, as Al pointed out. On another note, Brian and I did more testing last night via Skype and confirmed that there are some very wonky AC voltage values on my driver board, so something is wrong there. That seems to be the source of the sonic problems I've heard! It's not impossible that I have some bad solder joints connecting the valve bases to the PCB, so I'm going to go through those and see if adding solder fixes the problem. But in the meantime, Brian is having Digital Pete, his builder in Florida, send me a finished driver board to replace mine in case I can't get mine sorted. I think the one he's sending has the standard Mundorf Supreme caps, but if the board fixes the problem, I'll replace them with my Silver/Gold/Oil caps. Again, AN Kits customer service has been above and beyond. Although I'll have to swallow some pride to use Digital Pete's driver board in place of my own if I can't get mine sorted, it'll be a quick way of getting the amp in order! |
I have enjoyed this thread more than any I can recall here on Audiogon. The comments by Jetrexpro, Grannyring, and others ( and the incomparable insight contributed by Almarg), gives so much validity to the DIY approach. Even though my skills pale in comparison to those mentioned, my sense of musical enjoyment would be greatly impaired without even my limited DIY minstrations. Which is why this thread is so enjoyable. I think back on some of my own projects, which all seemed to come with their own set of problems, mistakes, and mishaps, it seems to add to the overall audio, and DIY, experience. I wouldn't have it any other way. My very best regards to all, Dan |
I dont know about that Dan. You have taught us a thing or two while making us drool over your DIY Garrard 401 plinth and I will not forget your Class D amp I am storing that note away for future reference. Grannyring-Thanks for the Clarity Cap tip. I did not know about them. I am contemplating building a 2nd amp and thinking about the power supply so your tip is timely. Best to Rebbi-a crazy journey but well worth it. Once the problem is solved there will be some serious music making :) |
