Tickling The Dragon's Tail 

Thank you. I just enjoy sharing this stuff. I know I am communicating with real people - the RU-vid community has been a wonderful experience for me just sharing what I experience without too much personal opinion on my part. After my review of the video, I see I make mistakes in what I say as I am moving so fast. It is a tense moment as it can go "Bang" really quick or do - Nothing... but have to keep moving.

@@ElPasoTubeAmps I man, i want to modify my amp adding it more gain ,i got a Rivera M100 and Peavey 6505+112 plus combo. Can you give me some advice?

@@isolirionband7300 Here is a schematic for your amplifier. www.thetubestore.com/lib/thetubestore/schematics/Peavey/Peavey-6505PLUS-112-Schematic.pdf I am not suggesting you make this change but if you want more gain out of the input stage tube, V1, you can see that the plate load resistor for the 12AX7 is R38 and it is 220K ohms. This load resistor determines the voltage gain of the tube so - if you really want to do this - you might want to change it to a slightly higher value like, maybe 270K or go as high as 470K. This should give you a bit more gain in the first stage. Not sure what it will do to distortion or the rest of the sound or it may become unstable and start oscillating, etc. so, do this at your own risk and always give yourself a way to back-out and go back to original. Hope this helps.

Wow... 50, 1625's. That aught to do it for an amplifier or two. I think the only tubes I have many of one kind is 6SN7 and 12AU7. If you need some, let me know. The Williamsom amplifiers built with 807's or 1625's and running the Acrosound transformers are some of the best performing amplifiers I have ever tested and built. I still have a voltage doubler with 866A built as a module but got lazy and went with those 20KV, 2A epoxy blocks in this amplifier. But the MV rectifiers are charming and very powerful - I see them as kind of the SS rectifiers of the 1920's 🙂

@@ElPasoTubeAmps really appreciate the offer I’m pretty set for 6SN7, only reason I got that many 1625s is I made a low offer on the lot from the fella selling them and he accepted it, got extras in case I kill a few. You are right about those 866s or any MV rectifier, they are such a beautiful blue that you need to see in person to appreciate and 15v drop is great, I’ve never used them in a power supply yet on something I built just played with them here and there, you put that perfectly saying the SS rectifier of the 20s. I’ll likely be up until 4 am playing now haha, if we don’t speak again before then you sir have a great Christmas!

@@ElPasoTubeAmps Hey there David happy 2024 to you and hope your year started good, do you know of any store or website that has the bigger 7 pin bases for sale that fit the 1625? The last few lots I got off eBay were listed wrong by the seller and were the smaller 7 once they got here. I’d rather not buy the Chinese ones if I can help it.

Yes, thank you. Since I have a DPDT relay, I should put one across each contact. Also across the contacts of the smaller relay that operates the large DPDT relay. Thanks.

Merry Christmas, Dave.

Yes, the reversed biased diode across the DC relay coil prevents a huge inductive voltage spike from coming back down the line that could damage whatever is controlling the relay, nowadays usually a solid state tranceiver. Years ago I build a simple 2N2222 circuit with relay and the first time I actuated it, the transistor shorted. So I changed the transistor - next time, did the same thing - finally I figured out what was happening and put the diode across the coil and it worked perfectly. Also might prevent a "pop" in a receiver during release.

One more thing that you might find interesting. I had forgotten about the possible time delay of the release of the relay because of the reverse biased diode. I use ChatGPT a good bit so I thought I would ask its opinion on the subject. You might enjoy what it has to say. I pasted the conversation in below. Thanks again... User In building equipment and using conventional relays, in this particular case, a relay with a DC coil, I always put a reverse biased diode across the DC relay coil so that when the voltage is removed from the coil, the reverse polarity collapsing field will be snubbed by the diode. Some say this changes the time the relay contacts open or close. Would adding the diode change the pick-up time or release time of the relay? ChatGPT Adding a reverse-biased diode across a DC relay coil, also known as a flyback diode, is a common practice to protect circuit components from voltage spikes caused by the collapsing magnetic field when the coil is de-energized. The diode provides a path for the current generated by the collapsing field, preventing high-voltage spikes that can damage other components in the circuit. Regarding the impact on the pick-up or release time of the relay: Pick-Up Time: The pick-up time of a relay, the time it takes for the contacts to close after the coil is energized, is generally not affected by the presence of a flyback diode. When the relay is energized, the diode is reverse-biased and does not conduct. Therefore, it does not impact the magnetic field's build-up in the coil that leads to the closing of the contacts. Release Time: The release time, the time it takes for the contacts to open after de-energizing the coil, can be slightly affected by the diode. When the relay is de-energized, the collapsing magnetic field generates a current in the opposite direction, which is conducted through the diode. This can extend the time it takes for the magnetic field to fully collapse, potentially causing a small delay in the opening of the contacts. However, this delay is usually minimal and may not be significant in many applications. In summary, the impact of a flyback diode on the operation of a relay is typically minimal with regard to the pick-up time, and it may slightly extend the release time. However, the protection it offers against voltage spikes is often more critical, making it a recommended practice in most DC relay applications.

@@ElPasoTubeAmps I can't locate the reference but I believe the concern was relay contact life when switching higher voltage and current DC loads. Unless manufacturer installed and tested the diode in the life expectancy test the relay may fail somewhat prematurely. I can live with that much better than the pops and surges its absence causes. Just one of those odd factoids that clutters one's mind!

I am laughing at the, cluttering of one's mind. So true. think that is what keeps us going. We can drive ourselves crazy and sometimes the ones around us because of our passions... If it was too simple, it wouldn't be fun... 🙂

Can't get enough of it... I love audio and want to build a 500 watt amplifier, just for the channel, using a pair of 4-125A and a huge OPT I have. I had two of the large OPT - meant to run 810 tubes - and built the 810 amplifier using one of them with the help of a friend from Denver. He took it to Denver and now it is his but looking at the specs of the 810 and 4-125A, they are similar enough in plate-to-plate Z that it should work pretty good. I feel I owe another audio amplifier project to my audio fans and subscribers.

Forgot to mention - congratulations on getting your general class license. I see you have established your QRZ account. I have filled mine up with lots of pictures. I hope we meet soon on 20 or 40M. 73 WA4QGA

Thank you. I plan on putting some shrink tubing over the pins just to dress it up. With all that HV in the area I don't think it matters a lot concerning safety... I mention this often in my videos that I use, Goop, to stick things like that down to the metal. Did the same thing with the two relays. Goop is good stuff - it won't come lose or fall off but it can be removed if necessary. I like to do a sufficient and proper job in the first stage of building to get things up and running and afterwards go back over it - sometimes for years - doing little things to dress it up. Always good to hear from you.

Totally agree with the issue of DC on relay contacts. It can be a real problem. Got plenty of little things to take care yet, including the shrink on the walwart. A few years ago I used a small relay to apply screen voltage to a pair of 4-125A tubes. What I did not realize concerning the contacts is with DC, even when the contacts open, the DC current may "follow" and keep arcing, and it did, and not allow the contacts to open and break the circuit. I noticed a light coming from under the chassis and knew that was not right. Had to put the modulator on the bench to find out what was wrong. I use the bias voltage supply to control screen and HV and had to change the relay contact to the AC primary side of of the screen supply transformer. We live and learn, don't we. Thank you for your comments.

@@ElPasoTubeAmps We live and learn indeed... you wouldnt be able to learn otherwise

Agree. That little wall wart in the video is used just as you suggest to operate the small relay and provide protection and isolation for any external control device, like a tranceiver. 🙂

The dragon lives on 40 meters. An awesome 4-1000A amplifier. All is well. I have some thoughts for videos but just haven't taken the time to do any. Thanks for thinking of me.

Thanks - I am hoping to post another exciting ☺ video of this amplifier tonight with the 3-1000Z and also testing a pair of 4-1000A - hopefully... tonight.

@@ElPasoTubeAmps I can't wait to see it!

That is the HV coming on. At voltages that high there can be a slight blue glow around the inside of the glass envelope. I like to use ChatGPT sometimes as it gives really nice answers. Here is my question and its answer. User In high voltage vacuum tubes running at 3500 VDC or above, there is sometimes a very light and thin blue glow that appears to be around the inside of the envelope. It is normal as long as the whole inside of the tube does not turn deep blue. What do you think causes this phenomena? ChatGPT The light blue glow you observe in high voltage vacuum tubes, like those operating at 3500 VDC or above, is a phenomenon known as "fluorescence" caused by the impact of electrons on the glass envelope of the tube. In vacuum tubes, electrons are emitted from the cathode and accelerated by the high voltage towards the anode. When the voltage is sufficiently high, some of these electrons can miss the anode or other intended targets and strike the glass envelope of the tube. The energy from these high-speed electrons excites the atoms in the glass, causing them to emit light as they return to their normal state. This emission of light is what you see as the blue glow. The type of glass used in the tube can affect the color of the glow. Some glasses contain impurities or additives that can fluoresce under electron bombardment, resulting in the characteristic blue glow. This is similar to how certain materials fluoresce under ultraviolet light. It's important to note that while a faint blue glow is normal and often harmless in vacuum tubes, a more intense or widespread glow might indicate a problem, such as gas contamination inside the tube or excessive electron bombardment of the glass. This could lead to reduced tube life or failure. However, as long as the glow remains light and thin, it is typically considered a normal byproduct of high-voltage operation in vacuum tubes.

Thank you for thinking of me. Yes, I am doing better. In one month it will be two years from my wife's passing but when the time is right, I know she will come for me. I do work at being productive and have six cats now ... they are my little family. I have to make sure all my homebrew equipment is cat-safe so they can't get inside. 🙂 Got a few ideas for some simple videos that I need to get busy on. You all on RU-vid have been very kind and caring. I really appreciate that and it does make a difference. Stay safe and thank you. David Beard

@@ElPasoTubeAmps Thanks for replying! Glad to hear you’re doing well and hanging in there. Sorry for your loss, it’s difficult to move forward sometimes when such a big piece of life is suddenly not there anymore. All you can do is what you’re doing though, being productive and having your family! Animals are fantastic. They’re just like people in many ways, and occasionally devious little things… cats especially. I’ve had a 72-pound dog companion for about a year and a half now and can’t imagine life without him. My folks have two cats with big personalities too. I’m looking to downsize my electronics collection. I have a lot of audio tubes, a few Thordarsson transformers, DuKane amplifiers, MV rectifiers and thyratrons (672A) and selenium diodes. Would you have any interest in acquiring some of these? I work sometimes in Phoenix and El Paso, I’d be happy to get them to you. I’m really happy to hear that the followers and comments on RU-vid lift your spirits. I sincerely look forward to your videos and hope you’re doing well, seems I’m in good company with the rest of the folks who watch your stuff on here.

I wish I could help but that is over my head... I am not a musician so all I could offer would be an analytical measurement of the transformer. With that said, there does seem to be something magical added to audio by "iron" so, unless the price of the transformer is prohibitive, it might be worth a try.

I do appreciate your concern for me. There is no issue of X-ray as my voltages are well below any level that would cause gamma rays to be emitted. Also, RF radiation at HF frequencies (3MHz to 30MHz) is not a concern at my power levels. I could be killed by electrocution but I am experienced and careful. What would I do for excitement if I stopped this hobby? I might have to take up hunting Texas rattle snakes at night - that would be fun. I promise I will be very careful. I have six kitty cats that depend on me. ♥

@@ElPasoTubeAmps that is good news. I just concerned about you. Merry Christmas.