tube fanatic Posted April 2, 2017 Share Posted April 2, 2017 It's no secret that my obsession is designing low cost, low power, tube amps for use with Klipsch speakers in small or medium size rooms. The combination is so amazing that the locals (with the exception of the guy down the road) have given up on large room systems completely. The Delights are the third members (the Little Smoothies and Little Taters are the first two) of what is being called the "nice, adorable, little amp collection," a series (eventually there will be about a dozen) of low and flea power mono SETs and SEPs constructed on the small, 6 X 8, Hammond chassis. In keeping with my philosophy, they use inexpensive and abundant radio/tv type tubes which no one else would give a second look! This series will be a bit unique in that I will only build one pair of each (some locals decided that they want an element of exclusivity). However, the schematic is posted below for those with the experience to build their own (it's a pdf between the second and third pictures. (William and I went over it in detail looking for errors, but if you see anything weird, let me know immediately!). Power output is a little over 1 W, which is more than enough to cleanly drive most Klipsch speakers to more than reasonable levels. The amps are completely configurable for the desired characteristics in each system- they feature variable bass enhancement for use with bass-deficient speakers like LSs and Heresys, as well as adjustable high frequency rolloff (my "famous" ear bleed filter) to tame speakers which seem too bright (as many have complained of with the Reference II speakers). It's easy to tailor the sound to suit almost any listening environment and personal taste. As to sound, well, they are simply delightful! The bottom end is very potent and clean (see the 320Hz square wave below), and the midrange and top end is exceedingly smooth. Being individual mono amps, the soundstage size is limited solely by that of the source material. With a good recording it is huge. So, that's the scoop. Next up on the agenda are the "Little DC Delights", a variation of this amp using different tubes, a dc filament supply, and a very novel power supply arrangement. Stay tuned in the fall. REMEMBER THAT THIS AMP USES VOLTAGES WHICH CAN KILL YOU!!! DO NOT ATTEMPT TO BUILD YOUR OWN UNLESS YOU HAVE THE EXPERIENCE TO WORK WITH SUCH VOLTAGES IN A SAFE MANNER. Maynard Little-Delight.pdf 3 Quote Link to comment Share on other sites More sharing options...
mike stehr Posted April 2, 2017 Share Posted April 2, 2017 3 hours ago, tube fanatic said: The amps are completely configurable for the desired characteristics in each system- they feature variable bass enhancement for use with bass-deficient speakers like LSs and Heresys Nice! Quote Link to comment Share on other sites More sharing options...
Seraphim6801 Posted April 3, 2017 Share Posted April 3, 2017 Man that's really cool!!Sent from my VS986 using Tapatalk Quote Link to comment Share on other sites More sharing options...
Tom Mobley Posted April 3, 2017 Share Posted April 3, 2017 where's the stuff for the adjustable bass output and screech filter? Is that the knob on the right front? Quote Link to comment Share on other sites More sharing options...
davesans Posted April 4, 2017 Share Posted April 4, 2017 Very nice work Maynard Quote Link to comment Share on other sites More sharing options...
tube fanatic Posted April 4, 2017 Author Share Posted April 4, 2017 14 hours ago, Tom Mobley said: where's the stuff for the adjustable bass output and screech filter? Is that the knob on the right front? The front panel knob is on the volume control (these are integrated amps). Frequency response is adjusted with the blue, multi-turn, trimmers evident in the under-chassis pics. Conventional pots can be used instead for those who want to have the adjustments available on the outside. Maynard Quote Link to comment Share on other sites More sharing options...
Tom Mobley Posted April 5, 2017 Share Posted April 5, 2017 Thanks for taking time to reply. Quote Link to comment Share on other sites More sharing options...
JL Sargent Posted April 5, 2017 Share Posted April 5, 2017 The little blue trim pots are perfect! Beautiful work Maynard. Lets see a picture of your workbench. Quote Link to comment Share on other sites More sharing options...
tube fanatic Posted April 5, 2017 Author Share Posted April 5, 2017 3 hours ago, wdecho said: What type of resistors are you using Maynard, specifically the big blue ones, carbon or film? Just curious. The large resistors are metal oxide power resistors. I use that type in the p/s, for filament dropping, and on the cathode of the output tube. 1 hour ago, JL Sargent said: Lets see a picture of your workbench. Sure- here's a picture of part of the shop 5 Quote Link to comment Share on other sites More sharing options...
JL Sargent Posted April 5, 2017 Share Posted April 5, 2017 That's great. Thanks for sharing. I like the way you have your pliers organized. Quote Link to comment Share on other sites More sharing options...
The Dude Posted April 5, 2017 Share Posted April 5, 2017 Are you willing to share the BOM and where you acquired the parts? I am looking for some monos for my Heresies in a 10'x9' room with a tube preamp. Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted April 5, 2017 Share Posted April 5, 2017 I love the Christmas Story lamp Maynard. Nice touch to an otherwise sterile looking environment. Quote Link to comment Share on other sites More sharing options...
Marvel Posted April 6, 2017 Share Posted April 6, 2017 Those are beautiful, Maynard. Could one get a little more high end with different output trannies or is it expecting too much from this circuit. I'm thinking of tweeters only. Your workspace puts me to shame! Bruce Quote Link to comment Share on other sites More sharing options...
tube fanatic Posted April 6, 2017 Author Share Posted April 6, 2017 22 hours ago, The Dude said: Are you willing to share the BOM and where you acquired the parts? I am looking for some monos for my Heresies in a 10'x9' room with a tube preamp. Unfortunately, I don't have a BOM made up for these. However, except for the tubes and sockets, Mouser has everything you need. 11 hours ago, Marvel said: Those are beautiful, Maynard. Could one get a little more high end with different output trannies or is it expecting too much from this circuit. I'm thinking of tweeters only. Your workspace puts me to shame! Bruce Thanks for the compliments on the bench area. It's still a work in progress, but it's getting there! As to other opts being better, that would be a personal judgment. I think the top end of the Hammond SE series xfmrs is excellent. As far as using these for tweeters only, are you planning on feeding a full range signal, or using an active crossover? If all you need is hf output from the amps, I would change some of the operating parameters based on the frequencies you would want them to deal with. If you go that route, let me know and I'll tell you what to change. Maynard 1 Quote Link to comment Share on other sites More sharing options...
thebes Posted April 6, 2017 Share Posted April 6, 2017 Another first class build Maynard! I can personally attest to the sonic wonders of Maynard's work. Sound and performance that is hard to beat. Anyone contemplating building an amp should do one of Maynard's. Quote Link to comment Share on other sites More sharing options...
mike stehr Posted April 7, 2017 Share Posted April 7, 2017 On 4/5/2017 at 6:52 AM, The Dude said: Are you willing to share the BOM The list of parts is on the right side of the schematic in the pdf file. 1 Quote Link to comment Share on other sites More sharing options...
The Dude Posted April 8, 2017 Share Posted April 8, 2017 On 4/4/2017 at 4:31 AM, wdecho said: Ask yourself how often do you listen at rock concert levels anymore. Only late at night when I am drinking. However, there is something magical about a great sound at lower levels. That being said I am intrigued by these and the Little Sweetie. From what I understand, SEP is single ended pentode and SET is single ended triode. Is the 6ca5 a triode tube wired as a pentode, maybe not a triode or pentode, maybe just how you wire it? I have a book on all of this stuff, maybe I should read it. Yesterday when I should have been working I was mapping out all of the components to try to identify which were which. I have attached said map, which has each component labeled. I had some troubles deciphering some of the resistors as it is hard to read the color codes. If someone could verify, I would greatly appreciate it. What I like about these, is I have all parts minus the tube sockets and tubes, and only at $250.00 for the components. The last thing I need to figure out is the tube sockets. It appears that both of these tubes are 7 pin tubes. So one would figure that they need 7 pin tube sockets. However, they appear they have different diameter bases. If someone could explain this I would my appreciate it. Once I finalize the bom at mouser, (which yes you can obtain all of these parts from Mouser), I will share it here via Excel spread sheet if you would like. After re reading this, I need to go back and correct some of my resistors (type wise). Also R7 does not have a wattage rating, I could assume 2 watt however I noticed R8 is a 4 watt. Either wattage rating is hard to locate at Mouser, any suggestions? Quote Link to comment Share on other sites More sharing options...
mike stehr Posted April 8, 2017 Share Posted April 8, 2017 Familiarize the schematic, and break it down into sections. Such as power supply, input/preamp and finals...or output. You will see which resistors go where with the schematic and parts list. You don't really have to look at the color codes of the resistors in the images. You can pick up sockets from eBay or AES or another vender. The one socket looks like a 9 pin socket in the photo, I dunno... If you can't find the exact wattage rating for a value resistor, you can step up to a higher wattage rating. Mouser has a vast list of parts. Unless you ask Maynard for a particular part stock # from Mouser, it's a bit of a challenge to find the exact parts he ordered. I think I had to ask him about the big grey X/Y cap across the power switch, to get the proper part number. I recall asking for stock numbers for more than one part. I built Maynard's 6AQ5 SEPP circuit using James HS6123 OPTs. (single-ended parallel pentode) In the event if I had to throw away all my tube amps except two, I would keep the 2A3 stereo SET amp, and 6AQ5 SEPP. I think if you build it, you'll like it. 1 Quote Link to comment Share on other sites More sharing options...
tube fanatic Posted April 9, 2017 Author Share Posted April 9, 2017 Regarding the driver tube socket, it depends on which tube you decide to use. There are 7 and 9 pin options in the parts list, and all are electrically identical. As specified in the parts list, R7 is 1/2 watt. This serves as a limiter on the maximum amount of nfb which can be applied (the amount is not overly critical), as well as setting the highest corner freq. of the filter (approx. 65 Hz). R8 can be created by a pair of 1.6k/2-3W resistors in parallel, a pair of 390 ohm/2-3W resistors in series, or a single 820 ohm/5W metal oxide or cement power resistor. The 20 ohm difference on either side is not of concern. I'm sure others would very much appreciate your posting of a BOM from Mouser as well as your starting a build thread if you have the time. Maynard 1 Quote Link to comment Share on other sites More sharing options...
The Dude Posted May 8, 2017 Share Posted May 8, 2017 Is it possible to run these with a passive pre or is there a need for a pre amp? Quote Link to comment Share on other sites More sharing options...
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