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Jeffrey D. Medwin

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About Jeffrey D. Medwin

  • Rank
    Forum Veteran
  • Birthday 11/27/1944

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  • Gender
  • Location
    50 miles East of Kansas City, MO.
  • Interests
    Audio, music, and the stock market, ..............is there anything else ?
  • My System
    Two stage Direct Coupled DIY triode amps, careful wiring, very lightly-modded professional - use speakers.
  • See My System

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  1. Jeffrey D. Medwin

    KT-88 vs 6550

    Deeper bass ?? The design of the amplifier has about 10 to 15 times more profound effect on the quality of the bass, than switching output tube brands will produce. Additionally, well thought-out wiring of an audio system - amp to driver voice coils, can also have a larger effect on a high efficiency speaker's bass presentation,...... moreso than swapping tubes. Jeff Medwin
  2. Jeffrey D. Medwin

    KT-88 vs 6550

    Glad some folks like that. Jac is one of THE best. After building Direct Coupled two stage tube SE amps the last dozen years, ( JJ 2A3-40s, Type 45 ( NG ) and 6005s ) I have recently gotten interested in doing an all-out SE DC KT88 amp design. Attached is Master Schematic for you to see. VERY simple, elegant, all-tube design. KISS rules. I start the build this weekend. Ordered some great 9 Pin Noval tube sockets for the Input stage tube - just this afternoon from " Jakeband ", the Italian tube socket maker who supposedly beats what Jac offers, in Yammomoto sockets, at a few Euro's less in price. LOOK at his all-out product designs, ...see : http://www.jakeband.it/index.html If 'ya want to use the best tube socket, these from Italy may be "it" today! My design's Input / Driver tube has a mu of 100, so its going to have the best possible parts implementation I can do, to retain full-fidelity, with minimal loss per stage. Jeffrey Medwin KT88 MASTER SCHEMATIC.pdf
  3. Jeffrey D. Medwin

    KT-88 vs 6550

    See what Jac Music in Germany says about all of these tubes, very experienced audio parts dealer is Jac !! Enjoy . http://www.jacmusic.com/KT88/kt88.htm Jeffrey Medwin
  4. Jeffrey D. Medwin

    Western Electric and Belden 8402 wire

    Matt, The tone of your response won't get you far. Very disrespectful of another human being. Insulting. I wanted to discuss some things privately with you. I'll do it now instead. The following is where you have made novice mistakes, that I can see ......without even seeing a schematic : 1) 2A3 amps, with extra filament transformers needed, are best made as Mono Blocks IF you want to have any sort of decent layout, design, and build quality. 2) You never EVER use a 100 Ohm choke in a 2A3 amp, ( Hammond 159Q) Never !!! That choke simply RUINS the dynamics and timing of the entire music presentation. Chokes have to be 20 Ohms or less, ( it was the first thing I have known about 2A3 amps, since way-back in 1979 ). Notice, my post above, I use two 6 Ohm Ls in 2019 ( 159ZA ). L1/C1/L2/C2. What will charge a Finals circuit quicker and better, 6+6 or 12 Ohms of series resistance to the Finals, or 100 Ohms of series resistance ?? The amp you show us was a "goner", / doomed, the moment you selected a 100 Ohm choke !! 3) You never use a "C" input filter, after the rectifier. You always want to use a "L" input filter, which is superior, even a Non-Critical "L". A "C" input filter, after the rectifier, has less control over the diodes, and it puts spikes on the B+. 4) You never build a tube amp and locate the RCA jacks at the rear of the chassis !! This is the lowest signal level in the entire amp. RCA jacks on the back of the amp are in proximity of AC fields from the 120VAC power cord, and to the fields of the output jacks,. WHY do that ??. Additionally, rear-of-chassis RCA jack placement dictates that you run the lowest signal level through a LONG wire, with attendant losses due to (a) the unnecessary length of that wire and (b) the fields the wire picks up, going past all the components, output transformers, etc., below deck. RCA Jacks need to be placed such that there is no more than a 2 inch run, from the RCA jack to the grid of the Input tube. I like to use two Polished Silver Cardas 19 AWG runs in parallel for that 2 inch run, to preserve bass. 5) You never EVER put a volume Pot in an amp, especially BEFORE the lowest level signal gets to the Input tube. Again, this is the LOWEST level of signal in the entire amp, and you are NEEDLESSLY degrading that low level signal, by putting it through a pot. The pot has a resistive element and a wiper arm, the interface of the two creates a diode-like effect on the signal, PRIOR to amplification. The Pot is a mistake, the Japanese amplifiers do this a lot. Use an active preamp to control system volume, or a highest-quality system-wide passive attenuator/source-selector, before the power amp !! 6) Your choice of an input tube in a two stage 2A3 amp is sub-optimal. It needs to be a Mu of 100 in a two-stage amp. Not just for proper gain, ( there will actually be excessive gain ), but, ONLY this mu will make for a lively and fun-to-listen-to / alert music presentation. Even a Mu of 70, a 6SL7 triode "won't cut it" compared to a GOOD mu of 100 Input / driver tube in a two stage amp.. The lower mu tubes will sound dull, lack alertness and livelyness, dead, and will need to be "pushed" all the time. Not so - when the mu is 100 !! 7) It appears, from the photo, ( and your "rude attitude / comments above" ), that you use a capacitor couple between the two triode stages. Of the three ways to couple two stages, that cap couple is the worst way, fidelity-wise, because film caps are IMperfect. Transformer coupling would be a better way. The best possible way to connect two stages is a direct couple, from the plate of the Input tube to the grid of the Output tube. Its hard to beat a triple run of Cardas Polished Silver 19 AWG wire, fidelity-wise, to connect two tube stages !! What makes an amp good is not all that costly engraving you spent money for on a face plate - to impress the inexperienced, but the quality of thinking in all the important design and lay-out choices, many of which, are performance gains gotten for free. That is just a start - to critique your build. When you settle-down some day, clean up your mouth / mind, contact me privately and we can discuss DIY amps. Jeff Medwin
  5. Jeffrey D. Medwin

    Western Electric and Belden 8402 wire

    Hello Matt, Very cool to see. Looks impressive if one didn't know better. There are some things you could do to vastly improve that build . Is there any way you can contact me, or vice versa, through Klipsch Forum Private Mail system, so we can exchange phone numbers and email addresses - and we can talk one-on-one, SE 2A3 amp design ?? Jeff Medwin
  6. Jeffrey D. Medwin

    Western Electric and Belden 8402 wire

    That, and the wire in a choke, we have little control over. ( in 2019, I use 6 Ohm DCR chokes for L1 and L2, Hammond 159ZA ). But I get real gains replacing the stock leads in and out of Transformers and Chokes with appropriately-chosen Mil Spec wiring. It all adds up to better DYNAMICS, and more listening fun. Jeff
  7. Jeffrey D. Medwin

    Western Electric and Belden 8402 wire

    Basically, always only a two-stage tube SE amplifier, first tube MUST be a Mu of 100 triode with a Shunt Regulated B+ supply, directly coupled with heavy pure silver wiring to : ( one of only three Finals tubes ) : the grid of a JJ 2A3-40 or a 6005 ( very low Power, triode-connected ), or to the grid of a KT-88 run as a Pentode with its own separate Shunt Regulated B+ supply for it's Screens. Always Zero Feedback. LSES power supply, which stands for Low Storage Effect Power Supply, ala the Serious Stereo 2A3 monoblocks. ( Look them up on line. 'Best commercial amps, sonically and in design, I know of . ) I use only directly heated tube rectification, L1/C1/L2/C2 B+ filters, with all power supply filter inductors VERY importantly being 10 Ohms or less in DCR, and all Cs being Film Caps only, not exceeding 50 uF per location ( a FAST reacting supply ). I also ( uniquely ) bypass my C1 and C2 film caps - going to the Finals - with GTO film caps, capable of doing 1.500 Amperes peak instantaneous. Careful attention is paid to wiring, using either multiple duos or "trios" of Mil Spec ( 12+12+14 M22759/11 on grounds ) or multiple runs of Polished Cardas SIlver 19 AWG in a few locations. Very careful attention to layout. RCA jacks always within 2 inches of the grid of the Input / Driver tube, two Cardas Silver runs for this short two inch input tube run. Direct Couple uses three Cardas Silver runs in parallel. All my tube op points are VERY carefully chosen to conservatively run a tube, for maximum sonic performance and maximum life span. I use Golden Ratio plate dissipations, 62%. So, a 10 Watt rated plate I will run at 6.2 Watts dissipation, by reducing current across the tube, but not necessarily voltage across the tube. I make extensive use of multiple film cap bypassing in key capacitor positions, values selected by ear. I also design for maximum DYNAMIC contrasting with my amps. Here is a two stage stereo 6005 prototype I did in 2018, plays lovely in its ( very low - less than one Watt ) output power range. 14 gauge welded steel chassis, powder coated. The 2A3 Finals tube will be 2 or 3 watts of Power Output, the KT88 5 to 7 Watts of Power Output. Jeff
  8. Correct Karlson3, two lengths are 9.52 feet, but RWF never offered that double increment in a terminated form. He did a 1Xs, 3Xs, 6Xs and 12 Xs offerings, in Brown or Gold. There were two iterations of Gold, the second being even beefier, lower in AWG. Wm.Z.Johnson used to demo his ARC gear with RWF's cables I have read. The first time I ever heard of "bi-wiring" was via RWF, 1978.. I once hosted a Fulton Seminar in L.A.'s Sutro Auditorium, early 1980s, where RWF talked about the need for good wiring for audio components, and he gave us a demo there also. Tetra-wired. Fun event.
  9. Boys, Honestly, I don't care about your Formula at all. What if your theory does not apply to RWF's Lab work, which I suspect is the case? Its called "barking up the wrong tree". You are just guessing without REALLY knowing whats going on . I don't have to always know why, just SHOW me what works !! The University's Lab animals, all returned to health, normalcy, when RWF was done !! Jeff Medwin
  10. Alexander, The lab-studied wire was copper stranded and tin plated, in Mr. Fulton's time, no silver content . In 2019, "I" use wire with silver content because its an excellent conductor, and has a wider bandwidth than plain copper, or copper tin plated. You are asking me questions, but yet, you seem to already KNOW what is of value and what is not. That is awesome. Jeff Medwin
  11. In a SET audio amp, any PC board is a degrade - versus what can be done with point to point wiring. We use pure silver wire 18 or 19 AWG in parallel, for key spans, like the RCA jack to the grid of the input tube, or the plate of the input tube, to the grid of the Finals tube ( the direct couple). My favorite treatment for the direct couple is three Polished 19 AWG runs of Cardas pure silver, sourced from Percy. For B+ runs and grounds, we employ paralleled runs of Mil Spec, copper stranded, silver plated m22759/11 in various gauges, as needed, There is no way, IME/IMHO, that a PC board can compete with the above-mentioned techniques, on a performance basis. Wire leads from components often need to be reworked also, as pictured to optimize dynamic contrasting. Jeff Medwin
  12. Hi Alexander, That length was developed from the Lab of Mr. Robert W. Fulton, back in the 1970s, when the Minneapolis University brought him in as a Consultant to find out why the Lab Animals ( baboons ) were getting sick after they upped their test frequencies to the 60 khZ range. I have NO idea how he derived it. He felt it important enough to develop Audio's first complete line of wiring, ( speaker wiring and interconnects ) and everything he put out was 57 1/8th, or a multiple of it. Inside speakers, he had his shop do divisors of 57 1/8th, for some of the short runs. The tripled-up wire ( green ) on my crossover wiring photo I showed you all, 8 AWG, was 14 1/4 inches long. See this, and the HOME page also : http://fultonmusicalindustries.com/biography.html For the last 6 years of his life, he was studying audio with a 2 Gig Tek scope. Robert Fulton was a gifted and he KNEW how to do EE stuff in his LAB. See his bio. Jeff Medwin
  13. Dean, Its not nonsense at all. Anything I post I have experienced directly though experimentation, and through listening. As a result of this thread, there has been one Forum Member so far, who has privately contacted me, and asked for sourcing details to build a 12+12+14 AWG trio of wires., 9.52 feet long ( two 57 1/8th inch increments). If this Forum individual follows up, and makes and compares the wire on his system, to whatever he was using before, then perhaps we will have someone you have all known for awhile, and are trusting of their judgement, add to this topic. I sure hopes he follows through. What if he, like me, is blown away by 8 AWG Mil Spec wire, and reports on it here?? It is easier for me to hear and understand the full impact of this wiring, because I have it throughout my DIY amplifier, (8 AWG equivalents on grounds now, an inch out of the Power Transformer's High Voltage Center Tap winding ), all the way through my passive crossover and to my 15 inch driver's voice coil terminals. Wideband wiring ( the silver helps with bandwidth ) that is used, allows one to easily ascertain differences in cap polarity, time alignments of drivers, etc. The below-deck photos ( Page 28 ) of the blue prototype amp show that I have run wires, bundled and unbundled, preferring the later. Have a nice evening. Jeff Medwin
  14. Sir, so you think, and you are entitled to your thinking, but I Know from my actual building and listening experience, you are totally incorrect !! Jeff Medwin.