John Warren Posted April 11, 2020 Author Share Posted April 11, 2020 And here's the Toroidal output transformer version of the amplifier. I had the transformers wound specifically for this project. The output modules are a wee bit different (DC balance and feedback circuits) for both stable operation and enhanced bandwidth. The transformer are also sized for 60W. 2 Quote Link to comment Share on other sites More sharing options...
John Warren Posted May 25, 2020 Author Share Posted May 25, 2020 Webpage describing break-out and testing. A Wuhan Flu project of sorts. http://www.northreadingeng.com/LK-72A/LK-72A.htm 3 Quote Link to comment Share on other sites More sharing options...
Edgar Posted May 25, 2020 Share Posted May 25, 2020 I just completed my second week of furlough from work, during which time I rebuilt and modified two solid state amps, so I'm a little weary of breathing solder smoke at the moment. But someday I hope to build a multichannel (more than 2) 7591 amp. LK-72 is one of the nicest sounding amps I've heard. My father left me his, but unfortunately it is gathering dust in my basement at the moment. Quote Link to comment Share on other sites More sharing options...
Schu Posted May 25, 2020 Share Posted May 25, 2020 🤜🤛 Quote Link to comment Share on other sites More sharing options...
John Warren Posted May 25, 2020 Author Share Posted May 25, 2020 On 5/25/2020 at 1:21 PM, Edgar said: LK-72 is one of the nicest sounding amps I've heard. My father left me his, but unfortunately it is gathering dust in my basement at the moment. I've been listening to the one described above for about five weeks now and I'm quite pleased with it, even with the low end tubes I'm using. I have a chassis design that is 1/4" thick Aluminum plate that everything bolts on to. I sent the plate out to get clear anodized, and will look awesome! I machined it to accept either the Hammond, Scott or the Transcendar output transfformers. Still lots of bits and pieces to attend to but it's coming along. 1 Quote Link to comment Share on other sites More sharing options...
John Warren Posted July 5, 2020 Author Share Posted July 5, 2020 The chassis plate for the LK-72A clone and will be shipped from the machine shop in a few weeks. The plate is machined from a 1/4" plate of Aluminum alloy. PC boards and transformer locations are shown in the layout. The PC boards will be mounted to the plate using standoffs. The boards will be enclosed in a cage (red outline in the layout). 3 Quote Link to comment Share on other sites More sharing options...
Schu Posted July 7, 2020 Share Posted July 7, 2020 You should offer a copper plate upgrade... Quote Link to comment Share on other sites More sharing options...
John Warren Posted July 8, 2020 Author Share Posted July 8, 2020 Dear God man I haven't even got the prototype built and we're already "upgrading" the design. That said, there really no advantage to going Cu on this particular part but I like your spunk. 1 1 Quote Link to comment Share on other sites More sharing options...
Moderators Travis In Austin Posted July 10, 2020 Moderators Share Posted July 10, 2020 On 7/8/2020 at 4:26 PM, John Warren said: Dear God man I haven't even got the prototype built and we're already "upgrading" the design. That said, there really no advantage to going Cu on this particular part but I like your spunk. I was thinking about maybe something simple DIY, maybe a phono-pre, saw this, I give up, LOL. Beautiful. In addition to the copper option I would like a matching Klipsch wood option. 1 Quote Link to comment Share on other sites More sharing options...
John Warren Posted August 29, 2020 Author Share Posted August 29, 2020 So back at it. I order 5 chassis plates from the machine shop and, due to COVID had to deal with a slip in delivery of about 6wks. First, installing transformers. Here, the Hammond OTs and the Scott LK72 power supply transformer. On the next unit, I'll be using the Heyboer LK72A replacement PS transformer and Transcendar LK72A clone OTs. In this build, it's the amp alone. Potentiometers are CHA and CHB level adjust, center channel level adjust and balance. RCA jacks are Amphenol, CHA and CHB input and center channel out are shown above the pots. 1 Quote Link to comment Share on other sites More sharing options...
John Warren Posted August 29, 2020 Author Share Posted August 29, 2020 The support "legs" are high voltage standoffs used in switch gear. Not part of the amplifier design but useful during assembly. 2 1 Quote Link to comment Share on other sites More sharing options...
Moderators Travis In Austin Posted August 29, 2020 Moderators Share Posted August 29, 2020 So you need to add a photo to the "post a photo to your bench thread" in this Talkin Tubes section thread please. 1 Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted August 29, 2020 Share Posted August 29, 2020 On 7/10/2020 at 5:54 PM, dwilawyer said: Beautiful. Meh. Printed circuit. We all know point to point with silver mil spec wire is where its at. 1 Quote Link to comment Share on other sites More sharing options...
Edgar Posted August 29, 2020 Share Posted August 29, 2020 1 hour ago, CECAA850 said: Meh. Printed circuit. We all know point to point with silver mil spec wire is where its at. Are two wires in parallel better than one that is 1.414x the diameter? 1 Quote Link to comment Share on other sites More sharing options...
codewritinfool Posted August 29, 2020 Share Posted August 29, 2020 13 minutes ago, Edgar said: Are two wires in parallel better than one that is 1.414x the diameter? You know better than this @Edgar. As detailed in a different post, paralleled resistors sound better. What are wires? Resistors! When you start getting into parallel theory, though, you can't use 1.414x, you have to switch to the golden mean. "Golden mean or gold wire, your choice!" is what I always heard. But I'm known for hearing things, so use caution with my advice. 1 Quote Link to comment Share on other sites More sharing options...
Edgar Posted August 29, 2020 Share Posted August 29, 2020 33 minutes ago, codewritinfool said: You know better than this @Edgar. These memes pop up every so often in totally unrelated threads, and I pity the newcomer to the Forum who has no idea where they come from or what they are about. Now if I can just find my stash of black zip ties ... 1 Quote Link to comment Share on other sites More sharing options...
John Warren Posted August 29, 2020 Author Share Posted August 29, 2020 1 hour ago, codewritinfool said: You know better than this @Edgar. As detailed in a different post, paralleled resistors sound better. What are wires? Resistors! When you start getting into parallel theory, though, you can't use 1.414x, you have to switch to the golden mean. "Golden mean or gold wire, your choice!" is what I always heard. huh? Quote Link to comment Share on other sites More sharing options...
Moderators Travis In Austin Posted August 29, 2020 Moderators Share Posted August 29, 2020 14 minutes ago, John Warren said: huh? Hey John, nice to see you. It's in reference to other threads and posts in the Talkin' Tube section where some (1) one claim there is an audible difference (and distinct advantage) in using two resistors in parallel over one. It's sore of an inside running joke. Always nice ot see your creations. Please post a photo of your bench in the "Post a photo of your bench" tread in this section. Quote Link to comment Share on other sites More sharing options...
Moderators Travis In Austin Posted August 29, 2020 Moderators Share Posted August 29, 2020 Don't know if this is way off topic or not. Are there standards, like from AES, or CTA, for specifications for amplifiers? Like what protocols, standards should be used to come up with power rating, THD, THD + N, etc.? There are specific protocols and standards from IEC and AES on how to test for speaker specifications. It there the same for amplifiers? Quote Link to comment Share on other sites More sharing options...
John Warren Posted August 30, 2020 Author Share Posted August 30, 2020 10 hours ago, dwilawyer said: Don't know if this is way off topic or not. Are there standards, like from AES, or CTA, for specifications for amplifiers? Like what protocols, standards should be used to come up with power rating, THD, THD + N, etc.? There are specific protocols and standards from IEC and AES on how to test for speaker specifications. It there the same for amplifiers? There are methods described in CEA standards (Consumer Electronics Association) and amplifiers can be certified to meet those standards. If they're compliant it will be listed in the product datasheet. Audio analyzers (CLIO, NTI, Keysight, AP) are capable of measuring to the standards. 1 Quote Link to comment Share on other sites More sharing options...
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