Gr eat video. I have d 104 about 70 yo. No bottom on base and no switch on stand. I need to update mic. How is this possible without everything it doesnt have? Harry, w3wkx
I think you need another base and switch assembly that you can take parts off of to save your heirloom microphone. They are not too expensive on Ebay. I have one similar that was bought for me in 1963 when I got my general class license - 61 years old - and is special to me. I keep them going and have acquired several heads to experiment with different mic elements. I have also found that the inexpensive condenser mics sold on Ebay and Amazon have a QC problem. Some work much better than others so a simple method of evaluating them would be good. I just ordered some more... 🙂 and will work on a method to sort the good ones from the weak ones and plan on making a video. Thanks for your comments. I hope you can save your 70 yo microphone for another 100 years. 73 WA4QGA
Today is June 26, 2024, and I've been working on these D-104 heads again. I’ve found a great solution by placing three small, inexpensive microphones in a triangular pattern inside the D-104 head. By wiring the three positive terminals in parallel and the three negative terminals in parallel, treating them as one microphone, it works marvelously. I now have two heads set up this way and consistently receive unsolicited compliments on the audio quality. There are no other changes in the setup, just wiring the three mic elements together. This setup works beautifully with my KWM-2A and 32S-1. However, when I wired one of the mic stands with an 8-pin connector for my Icom 7300, it didn’t work well at all. Despite my efforts, I haven’t found a better microphone for the 7300 than the stock mobile-style hand mic it came with. I continue to receive wonderful compliments on the audio quality of the 7300 with its stock mic. I also want to take a moment to thank all of you for your kind comments and good wishes. 2022 was a tough year. Not only did my two cats pass away, but the love of my life, my wife Marilu, who I was married to for 45 years, came down with pancreatic cancer and passed on June 19, 2022. It has been a difficult journey. I now have six cats, and I believe Marilu sent them to me because she knew I needed them. I am deeply grateful for your kindness and support. God bless you all. I’ve been posting since 2008 and have met so many wonderful people through this RU-vid channel. 73, WA4QGA.
Thank you. You are very kind. Here are a couple of additional videos when I got more serious about it. Yes, the antennas are very directional and need a good size tripod to mount them on. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-KLhxggZbsVc.html ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-SDLm1N10fTI.html
I can't remember all these measurements without reviewing the video or remeasuring but I would say 3 mV out of, 450-500 volts for the plate supply is excellent. I don't know if I mentioned it in this video but I have found an important and fundamental design to be most effective in reducing hum in audio amplifiers and that is to keep all power supply components, including the choke and especially the main electrolytic capacitors in one corner of the chassis away from the input connections. There is indeed, current flowing thru the chassis between the CT (or negative chassis ground) of the power transformer and the electrolytic power supply capacitors that will be picked up by the input circuits if the currents are flowing thru the input portion of the chassis. If the chassis layout is not proper with the PS isolated from the inputs, no amount of adding capacitors or anything else will fix it. Thanks for your comments.
Pretty cool… I’m looking to build a reverb unit to go with MY 1955 Electromatic Artist and found this! Side note: my friend found it in his grandparents attic, and gave it to me. And I believe I watched Uncle Doug’s video on that amp to learn a bit more about the amp.
Thank you for your comments. I emailed Doug the other day and he is doing good - but getting old like me. I think he is rebuilding something exotic and will, hopefully, post soon.
Is the frequency of the transformer 50 or 60 Hz? I have to wonder if the Hantek was actually right if you convert frequency to half. If it's 50-60 Hz actually, then 100.8Hz would line up with that right too. I wonder if it's within the linear parameters at the small current that you injected in, of a mostly non linear curve? Thank you for sharing. I could be wrong of course, too.
When I started exploring inductance measurement, I realized there was a steep learning curve, and I'm still learning. Certain inductors, like the 1000 Henry UTC audio chokes, are designed for minimal current flow, primarily to generate grid voltage for the subsequent stage. Power supply inductors need to be tested at relatively higher currents, such as 500 mA, aligning with the ratings of power supply chokes. When measuring vacuum tube output transformers with inductance values around 20H, I found that a small current of about 10mA was crucial. This is because at microamp levels, mere movement of the transformer on the bench can alter the surrounding magnetic fields, drastically affecting the measurements. As for the testing frequency, power supply chokes should be measured at the line frequency or twice that for full-wave rectification, whereas 1kHz is more suitable for audio inductors. While inductance theoretically isn’t affected by frequency, practical measurement prove otherwise. Measurements of an inductor without specifying the frequency and current level involved might end up being unreliable. I hope this explanation is helpful. Thanks for your comments.
-20dB=1/10 or 10% distortion, -40dB=1/100 or 1% distortion, -60dB=1/1000 or 0,1% distortion, -80dB=1/10000 or 0,01% distortion. I don't understand the talk about 10th of a million etc. etc. What do I miss? -55dB down is 0.178% of distortion and barely detectable with human ear that detects 3rd harmonic around 0,2-0,25% distortion. I wouldn't consider 60Hz fundamental that is -70dB below full signal level a problem. Can you hear it when putting your ear to the loudspeaker? It's 0,03% of intermodulation distortion and should not be audible since it's a single tone with a few harmonics at a lower level. Complex signals like music is, can however create a lot of more distortion (Read Nelson Pass paper on distortion). Thumb of rule about 10 times or 20dB higher. So that 0,2% 3rd hamonic for single tone can be several percent during music listening, and that, I suspect, will give a bright and harsh character to this amplifier. Expect this amplifier to start sound quite bad when pushed hard.
That is a big discussion you have going there. As for global negative feed back (GNFB) often times just called NFB, is taking some of the output of the amplifier right off the speaker terminals of the amplifier and feeding it back, out of phase, to the first stage of the amplifier. I have found over and over that more than about 16 dB of NFB can start to cause instabilities in the amplifier like motor-boating at a very low frequency. As for S/N ratio in dB, anything better than about -75 dB will likely not be heard coming out of the most efficient speakers with our ear right at the speaker. High quality amplifiers usually boast -90 dB S/N compared at their rated output. 90 dB is a ratio of one billion to one... so, if you have 100 watts of power and the noise is -90 dB down, the noise is 10 nano watts or 0.1 microwatts, however you want to look at it. At say, -60 dB down from 100 watts, the noise is 0.1 milli watts and you actually may be able to hear that out of high efficienty speakers. Remember that for every 10 dB, the power is changed by a factor of 10 so the difference between 90 and 60 dB is 30 dB or a power factor of 1000 times - louder or softer - depending if the power is increased or decreased. Hope this helps.
@@ElPasoTubeAmps OK, you are talking about power and not gain. Shouldn't you consider the difference as gain ? The level of detection is basically only compared in voltage or amplitude and not power. Attenuation in a volume control is never specified in power, only as a voltage divider. A spectrum analyzer only analyze voltage and amplitude not current or power. The NFB is also specified as a amplitude and voltage level and then this is valid: 20dB = Gain of 10 40dB = Gain of 100 60dB = Gain of 1000 Noise is also quantified in amplitude and voltage. So, as I see it every change of 20dB is a factor of 10 and not 100. 16dB of NFB is not critical in it self for oscillation. You just happend to run into phase problem at that level of negative feedback. Your feedback loop have a higher frequency pole than the first gain stage so the feedback loop that are supposed to come back 180 degree out of phase have a pole creating more phase shift and when hitting more than 90 degree phase shift it comes back more IN phase than OUT of phase and then you have a negative feedback loop that will make the first gain stage to add low frequency gain, and then it come into low frequency oscillation. Many transistor amplifiers can have NFB of 40dB or more. Just have control over low and high frequency poles of the first gain stage and you will be able to have more feedback without the risk of run into oscillation. Personally I do not like negative feedback and avoid it as much as possible. My own designs most often ends with a little bit of feedback like 3-9dB just to even out amplitude over the frequency response I try to have. To much global negative feedback kills and changes harmonics to much which make sound monotonic and with a collapsed soundstage. IMHO.
I agree the 16 dB of feedback is not any fixed critical level for oscillation but that seems to be a good limit for vacuum tube amplifiers. I think the amplifiers that have the 40 dB level of NFB are solid state without an output inductor. It is that OPT in tube amps that causes some instabilities in many cases and some also need RC circuits with a pole around 75KHz to keep parasitic suppressed. I see the RC circuits in different places, usually around the OPT or in the case of Williamson amplifiers at the plate of the first stage. I use a power meter to adjust NFB - usually setting the power to a clean level, say 5W, with no NFB, then adjusting NFB to a determined level, in my case of 16 dB of FB to about 130 mW. I do this with a pot and then measure the pot and install a fixed resistor. Converting those figures to voltage gives approximately 6.32 volts for 5W into 8 ohms and 1.02 volts for 130 mW. The results turn out the same. Lots of NFB does indeed give an amplifier a compressed sound when compared side-by-side with an amplifier with no NFB, but the gain in power can't be ignored when NFB is employed. A clean 5W amplifier with no NFB can (maybe) be turned into a very nice 30W amplifier with, in my case, around 16 dB of NFB. I have one stereo SET with 300B and as you mentioned, I have a switch for (I can't remember exactly) about 5-6 dB of NFB and the other position of the switch for no NFB. I like the sound of SET with no NFB but, as already stated, the power is often very low.
I am planning, when it cools off this afternoon... to replace the RG-58 in my truck for my mobile station, with the RG-400. RG-58 is good cable but honestly, I sometimes use it as a lossy connection between an exciter driving an amplifier but I don't need loss in my mobile setup. 🙂 Thanks for your comments. 73 WA4QGA
Hi Andrew, Good to hear from you. You have done some marvelous work on GHz level antennas. I have watched many of your videos. I never advanced past 2.4 GHz as far as building my own antennas. I put up store-bought 5 GHz dishes on my house and share my Internet with two AirBnB properties I have near by and only have to have one fiber account. I did build a 1.4 GHz antenna for a radio telescope and use SDR and a PC to view the resonate hydrogen line in nebule. That was about a year ago. You mention the o-rings in your N connectors and another gentleman said he got Teflon washers in some of his PL-259 connectors so apparently some good manufacturers of these so called, UHF PL-259 connectors realized the problem with the shield shorting long ago. I did test these connections shown in this video with a megger and it would withstand 2.5 KV so It seems the o-rings I used are Ok and don't have too much carbon as mentioned in a comment below.... Anyway, take care and stay safe.
Hey David so good to see you again! I hope you have been doing great and thanks for another video and that’s a great tip! It’s always nice when we get another one from you. I finished those Williamson amplifiers with the 1625s I went off the Stancor schematic and let me tell you they sound amazing, you were the reason I wanted to build Williamson and I do not regret it so thanks! I’d love to show you them maybe I could email you? Take care my friend
I would like to see your 1625 Williamson amplifier. As far as I am concerned, they are as good a power amplifier as any, regardless of the design and price. Mine runs 12-15 hours a day in my backhouse with KT66. TheAudioShop@SBCGlobal.Net
Hi Dave, Here's a video on the method I have been using with great success. However I did discover that those silver plated shells did not screw onto an SO-239 completely before getting tight. I had to order a special tap to clean the threads. Maybe the tried and true Amphenol connectors might have been a better choice. 73 WJ3U ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-O3u05ZTTTr4.html
Hi Don, Indeed, the USA made Amphenol connectors are by far the best even if the dielectric is not PTFE. I have had new PL-259 and SO-239 connectors that simply will not tighten up the threads because of loose and-way-out-of-tolerance, conditions. Junk is what it is called. I just thought it might be helpful to someone going thru what I went thru, even with RG-58, to have the shield shorting to the center conductor because of the new PL-259 connectors and have some sort of solution. The new connectors (some) are actually quite good for LMR-400 size dielectric but, as the video shows, not so good for other uses. Amazing how a tiny design modification can change things in ways unseen at the time. No doubt, in my mind, designs, as seemingly simple as a PL-259 connector, were much better planned and thought-out many years ago. 73 WA4QGA PS - I did watch the BBI video. Can't say his method is bad but I don't see it necessary in most cases - maybe as he said, in rain and weather conditions on a vehicle, his method is probably better.
Hi Dave. I've been frigging with these frigging things for 60 years, since the days of the Belling-Lee 75 ohm PAL connectors for TV and FM. Did one the other day actually. I have always thought this style of thing where you fold over the braid and ram it home a terrible design, although I understand the design constraints, and now they seem to have made it worse! Best EJP
It is just that I followed prescribed directions and it always ended up shorted... what's wrong with this picture. A close visual inspection started making sense. For the large coax like LMR-400, for example, the dielectric presses right up against the center pin, covers it, and it works perfect. If one looks up connectors for RG-400, it is a completely different and new, screw on connector - oh well... so much for using the reducers - but it got me thinking how it used to work great and an inspection of the older connectors made it obvious. I normally use the large and stiff LMR-400 but sometimes that is like plumbing a house with 3/4 inch copper when you only need a small plastic tube like on a refrigerator. Anyway, good to hear from you. I have a few more idea for short videos. Since Microsoft took away the video editor that I used to concatenated videos, I prefer to just make one short one and post instead of going thru learning another video editor. Stay safe...
I didn't think about that. Thanks. Maybe the nylon washers are the best and leave out the o-ring? Since the only thing soldered is the center pin, I will likely take my main RF line apart tonight and just insert the nylon washer.
You got me going - I just went and measured the o-rings I have with a megger going to 5KV and I think mine are going to be OK. Still 20G ohm or better until I get it so close that it just arcs across in air. Still something to keep in mind. Thanks again...
Hello, I am in desperate need of some old 6b4g tubes and im in Texas. If you can spare a pair for the going rate? Ebay has been not too kind with tubes!
I might remind you that the original 6B4G tube is a genuine direct heated cathode where as the JAN 6B4G is an indirect heated cathode with its cathode connection on pin 8 just like a 6L6. This is important to keep in mind when building the cathode circuit.
I agree that Ebay prices are over the top but they mostly always have been. Also, tubes are a real risk so it is best to buy from someone that will allow returns, in my opinion. Here are some listings - the ones from Canada might deserve a good look - www.ebay.com/sch/i.html?_from=R40&_trksid=p4432023.m570.l1313&_nkw=6B4G+tube&_sacat=0 As for schematics, I built the amplifier exactly as Collins Radio did for their KW-1 transmitter. Here is the schematic and full manual. collinsradio.org/archives/manuals/KW-1-(01-52).pdf Good building with your amplifier. Nothing like turning on our homebrew equipment and seeing it operate perfectly... 🙂
Here is a much better schematic of the audio section of the Collins KW-1 collinsradio.org/wp-content/uploads/2019/06/KW-1-March-53-Edition-Main-Schematic.pdf
Thats all you need for an epic concert venue, portable, perfect sound replication. And, all in a single chassis, would be about as compact and effective as solid state, but the quality would be 10, 50 or 100 times superior. Then, you just have big old baffles, they can be left and right, and have like 50 full range speakers all connected in series, so you dont even need an output transformer in that case, if its impedance matched definetly. It would be loud, so loud, bad, but this would be for impedance matching and lower distortion and higher sensitivity. I cannot imagine what 1200w would do, Im playing with 5w. You have all of it phased and tuned and pre determined, then the set up is actually set up instead of just thrown out on the stage, where you actually have competent techs. The whole thing can just be 2 squares or rectangles, and streched over is lightweight grill cloth that is black, but you then add a projector in front or laser show or both. This could be set up as stereo with 2 separate channels or even, 1 unit still in stereo but l and r is toed out but obviously separation is needed for best quality. You can always add a sub, and I think those are just needing a large heavy box, but have not investigated. If the 50 speakers are all moving in unison and the baffle doesnt vibrate to cancel it out you could actually have very good low bass with a single full range driver system no bloody box and crossover. With a large single moving wavefront. I dont know if there would be too many sources for high and mid frequency to jumble up the sound, but i think they would all work in harmony. Aaagghhhhh all the missed out on potential!!!!
A man after my own heart... I always had the pipe-dream of building such an amplifier(s) for AC/DC or the like bands but probably not anymore. It would require a fully competent tech to keep someone from getting killed from the 3500 volts but it would light up the venue - for sure... 🙂
@@ElPasoTubeAmps Some concerts i am just completely confused, how they have all this new expensive equipment, but it still sounds like a really loud cheap boombox. Have you been to Greune Hall ever? They have a really neat old system I assume, they are an example in how a/v tech Should be, it looks like full range and a box baffle hybrid and probably tube amplifiers, not sure though. Thats kindof what Ive been trying to emulate with all of my doing. Youre a fountain of knowledge! I try to catch up on your chanel, but its just an ongoing lesson, thank you again for all the professional tips!
I buy them mostly off Ebay as I do the LMR-400 . I am careful to buy from a reputable dealer and make sure the connectors are silver plated and PTFE (Teflon) dielectric. There is also, www.mouser.com where you can be sure to get genuine USA made connectors, if you choose, but they cost $$$. Hope that helps.
