What's the Best Regen Tube?

Before we tackle the KORG NuTube in the Twinplex Regenerative Receiver, just how critical are Tube Health and Tube Type, when you are doing a build?

[@wadepatton2433]

The Mullard is no tube ol' chap, but a valve! It was dramatic, thank for the demo.

[@MIKROWAVE1]

I thought they were TUUUUUBES Mate.

[@wadepatton2433]

@@MIKROWAVE1 aye, but those Brits with Marshall amplifiers tend to think otherwise. I'm only a Yank funnin' ya. W1ADE here. Thanks for the electronics education you're sharing with us. 73

[@zachreyhelmberger894]

I love exhaustive stuff like this!

[@MIKROWAVE1]

Thanks Zachrey! I'm exhausted too, by the way.

[@snarfusmaximus]

The first regen I built was a Twinplex as I had a type 19 in my stash. Years later I modified it slightly to work with a set of four Octo-Coils I purchased from eBay which gave me a tuning range from 1 to 18MHz. Gotta say, I love that radio and can see why it's so popular.

[@MIKROWAVE1]

Wow.

[@seanross1732]

I sold a set of OctoCoils back around 2011/ 2013. wish I still had them.

[@karlschulte9231]

My second regen was twinplex with 6sl7. Also can use 6sn7. It works great with my big siler velvet vernier dial.

[@NebukedNezzer]

in recent history I have a regenerative receiver with a 6sk7 remote cut off pentode. it works nice with smooth regeneration control.

[@julianvalenti]

nice article. it is intresting how to select by testing it the best tube of the junkbox, best wishes and 73's!

[@MIKROWAVE1]

Geeze maybe I should test them!

[@mikemaben7485]

My old twin reverb fender tube amp. Had a increadable unique sound. Nothing sounds like a tube amplifier.

[@MIKROWAVE1]

Truth.

[@submarineradioman5535]

I replaced the 6U8’s in my Conar 500 regen with 6EA8’s and it significantly improved overall performance…

[@MIKROWAVE1]

You souped it up!

[@DAVIDGREGORYKERR]

if a 3V on the heater maybe a 1K+100PF might de-couple the heater from negative, it should now work.

[@gregsimopoulos4708]

Hello Mike...? With regard to the increased number of turns in the tickler coil... I was wondering if reducing the value of the 470 pF capacitor in the "throttle capacitor" position would have a similar or complimentary effect as increasing the number of turns on the tickler coil...? (perhaps you would like experiment with that...? :) I would be very curious... Thanks again for all of your great works, Michael...! Best regards...!

[@MIKROWAVE1]

Increasing the bypass cap value increases the feedback like adding turns to some extent. Typically you mess with three things to get "perfect smooth regen" The Operating Voltage, the Tickler and the Bypass (throttle) Cap value. For most triodes, 25 VDC is a good place to start this cycle of madness.

[@francoisdastardly4405]

The 807 pentode work very well as low voltage regenerative detector.

[@MIKROWAVE1]

Anathema! Ye Gods! Ah I guess almost any valve will work great in the regen but you have scored big with your 807. Good work. Geeze the filament would draw more than most radios today.

[@Crosley-1520]

Power tubes do make very good regen detectors, with the smoothest transition in/out oscillation. The QST "Novice Special" receiver from the mid-50s used two 6AQ5 tubes and it was a very good performer. I've seen designs where a 6V6 was used as detector and a 6SN7 for audio output, the opposite as one would expect. The only drawback is that you can end up radiating a few watts of power via the antenna when the detector is oscillating!

[@kensmith5694]

You really should use a weak station and somehow judge the SNR to rate tubes. One of the advantages of the regen over the crystal set is that you can listen to the weak stations.

[@MIKROWAVE1]

SNR is a good, but hard thing to judge. Other factors include how well they perform for getting into the high Q area, CW performance, AM demodulation fidelity, voltage range, hum and gain.

[@kensmith5694]

@@MIKROWAVE1 Your squelch circuit actually was measuring the effective SNR of the receiver. Picking off high frequencies from the demodulated signal largely gives you a measure of the noise without the signal getting into it,

[@psnpacific]

👍

[@zachreyhelmberger894]

Is it possible to use the regen to drive an RF power amp so you can transmit CW at the frequency you are receiving?

[@MIKROWAVE1]

These types of one and two valve XCVR circuits did exist - but you need to have a switch that can make the changeover connections without causing the frequency to get too misaligned, Regens operate best at critical feedback for reception, but while in the transmit mode the oscillator is put into heavy feedback, for stability. This is even simpler! onetuberadio.com/2020/05/11/1920-one-tube-transmitter-receiver/

[@jimw7ry]

13:28 The dirty Englishman! Indeed! LOL! 73, W7RY

[@tubeDude48]

At 1:56, where do you get those coil-forms from? And the socket.

[@EngineeringVignettes]

Go on eBay and type in "ham radio coil form" (or similar without "ham radio"). Lots of them for sale there... Cheers,

[@coltronex]

I 3D print mine ans use an old tube base

[@MIKROWAVE1]

Nice.

[@johnnytacokleinschmidt515]

Hi, Mike. Can you leave the titling up about 3 or 4 times longer. For slow guys like me! Thanks and great video and content.

[@MIKROWAVE1]

Guilty as charged. Will do.

[@johnnytacokleinschmidt515]

@@MIKROWAVE1 Thank-you! You're a fantastic educator and seem both very knowledgeable and enthusiastic about radio electronics. The crystal set videos and regeneratives are amazing. I'm slowly working my way in. Recently procured an early regenerative set from the radio museum swap meet. I think it looks commercially built. Not able so far to figure out what it is. I have extended family out your way. If you ever come to the Nutmeg State I'd be happy to have you as a special guest at the museum. I'll buy you lunch! 😆 Be well and God Bless!

[@jimw7ry]

Simply use the pause button mate! J.

[@alnorman6846]

For the nutube Can the interelectrode capacitance be determined or the upper frequency limit be determined?

[@MIKROWAVE1]

Wow that is unknown, but I would imagine that the impedances of the terminals could be measured by a bridge or Network Analyzer with bias if you were careful.

[@user-up1cb3xh3o]

Под прилагаемой схеме нас аналог советский аналог пойдет 6н2п двойной триод. Спасибо за видео.

[@MIKROWAVE1]

Да, я знаком с 6Н2П, но не держу его в руках. Спасибо за просмотр!

[@user-up1cb3xh3o]

@@MIKROWAVE1 Hello ! little request. in the following videos in the comments write the names of books and authors. very interesting. thanks for your hard work!

[@tomstrum6259]

Maybe you could do a "Best Low voltage (12v) Tube" Regen Test using various Pentode Tubes with Variable Screen bias Voltage for Regen control.... Are Small signal Pentodes better than Beam Power pentodes ?? ....Also using Extreme Low noise High-Gain audio amp, which Pentode or Triode Is Quietest Input Noise voltage (Best Sig to Noise) regen Detector is Best ??

[@MIKROWAVE1]

The beauty is that the regen can make the worst tube or semiconductor work! Finding the best takes more instrumentation than I have!

[@DAVIDGREGORYKERR]

Don't you think it would be nice to have a pocket radio that you might want to listen to.

[@sinisatrlin840]

E90CC computer tube works great in Twinplex. It is cheap and it is 10.000 hour tube. Heater has to be DC

[@MIKROWAVE1]

When I started at Motorola in 1980, we were still making SELCAL boxes for the Boeing 747's all 12AU7 valve. Never had a failure. Why upgrade?

[@sinisatrlin840]

@@MIKROWAVE1 12AU7 itself is "upgrade" from 6SN7 which is made from two 6J5 elements and its roots are in venerable 27 (27,37, 56, 76, 6C5 and 6J5). I do not consider E90CC as ugrade, only as cheaper option. E90CC is lousy as audio tube candidate and NOS can be found for few $. NOS 12AU7 i try to save as investment beacouse i am a avid tube collector and i know that shue box of NOS 5 star 5814A (Or E82CC) is now worth as mid sized car. Computer tubes are financially worthless, and any attempt to give them another life is worth trying, they are much cheaper (last time i purchased sleeve of them) than modern 12AU7 from eastern production. Also when tube in your Twinplex has green Amperex sign on it, it looks and feels little bit better than Sovtek or Sino.

[@Oggabooga-ce9dr]

I use a type 27

[@MIKROWAVE1]

The 27 is a wonderful bottle. And it has a Cathode which makes things go easier.

[@NebukedNezzer]

1963 I am a student in high school electronics class. our instructor wanted us to build a regenerative receiver with the 1H5 tube. I told him it will not work could I please use a 6sn7. ok, well guess what. all the others failed and mine worked fine. he was left scratching his head. how did I know? as I told him I had tried to build a 1H5 regenerative circuit and it failed. it matters what tube you choose.

[@MIKROWAVE1]

The 1H5 tube is a high Mu Triode and diode in one tube. Its not ideal compared to say a 6J5, but it will work fine in a classic Regen circuit. However with the high gain, the feedback will need to be less, so fewer turns on the tickler. Just use the Triode connections and ignore or short to cathode, the diode pins. And don't forget to try reversing the tickler as always!

[@NebukedNezzer]

my teacher and the other students in my 1963 high school electronics class tried every trick but could not make the 1h5 regenerate. why I do not know. I used half a 6sn7 and it worked fine in the same circuit. sometimes things do not work out.

[@MIKROWAVE1]

@NebukedNezzer oh now you have our attention. If you remember the Star Trek episode where Spock proves that they are not in reality because a circuit that has to work, does not function. 1H5 is on order.

[@NebukedNezzer]

Best of luck with this project. none of us in the electronics class could make it work. I had tried the 1H5 at home with no luck. I don't remember the circuit but it was the classic tickler feedback kind of circuit. @@MIKROWAVE1

[@MIKROWAVE1]

OMG I lost that bet. What a piece of work that 1H5 is! I took a standard regen with a 6J5 / 6C5 from my shelf. Rewired it for a 1H4 medium Mu Triode. Excellent, probably better than the 6J5 with only a little more feedback needed. Then I added the grid cap and stuck in your 1H5. First of all it sounded so tinny that I knew something was wrong right off. It did pick up a few stations but never did get it to oscillate properly before I threw it across the room. Something is very weird about this tube. Oh and if you put your finger on the grid cap - ALL KINDS OF GAIN AND HUM. How can it be such a good audio amplifier and not work as a regen?

[@XPFTP]

hahhah ai know that voice on the am 75 hahhaa

[@MIKROWAVE1]

Ah Yes. the Timtron.

[@karlschulte9231]

Except diodes!😂