Chinese 811A "Power Amplifier" Tube from Amazon ??

Discussion in 'Amateur Radio Amplifiers' started by K4ZOT, Dec 20, 2018.

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  1. VE3PP

    VE3PP XML Subscriber QRZ Page

    Do the cheap tubes work? The question will be for how long.
  2. KA9JLM

    KA9JLM Ham Member QRZ Page

    If Amazon sells them, They have to work for at least 30 days. :rolleyes:
  3. N8FVJ

    N8FVJ Ham Member QRZ Page

  4. N2IIE

    N2IIE XML Subscriber QRZ Page

    I've installed 4 Penta 811A tubes from eBay in August of 2018 for my AL-811H and am still getting good power. I paid $104 at the time.
  5. KM1H

    KM1H Ham Member QRZ Page

    Are those current or old date codes?

    Penta has a long history of selling (they do not make them) Chinese tubes with better reliability than others Ive evaluated.

    The original Penta was a US company from CA but they are long gone.

  6. KM1H

    KM1H Ham Member QRZ Page

    The difference is that the Russians DO NOT claim they are 811A's as do the Chinese. Those Amazon tubes have the Shuguang logo so dont expect miracles based on their past 811"A" and 572B problems.

    The vertical fins are there to stiffen the thin sheet metal anode, compare them to a USA version. I have seen no actual claim to any additional dissipation over a late US 811.

  7. KA9JLM

    KA9JLM Ham Member QRZ Page

    Many tubes had a problem running in a horizontal position.

    I think Dentron mounted them like that to make a small desktop amp.
  8. KM1H

    KM1H Ham Member QRZ Page

    Dentron 811A/572B, Hunter (572B), Collins (811A/572B user selected), Gonset (both) and others used them horizontal becuz RCA had the filaments aligned with the pins so they would be vertical in the sockets. Early Russians and Chinese mounted them any which way since they were "supposed" to be installed vertically. Ameritron wasnt taking any chances.

    KA9JLM likes this.
  9. KA9JLM

    KA9JLM Ham Member QRZ Page

    Would you happen to have a link to a "Buy it now" ?

    I do not care to play the bid game.

    Thank You.
  10. K6LPM

    K6LPM Ham Member QRZ Page

    While I havent had an opportunity to sample any current production RF types of valves, I have been using a variety of different modern production audio valves. I still have a preference and I will often choose a NOS (does such things really exist) or vintage tube and pay a premium. Regardless, I must admit that the current production audio electron tubes coming out of all three or four of the modern production factories based overseas have really been getting better and better. I believe that no matter whose name is branded on recent production valves, there really is in fact only three or so OEM manufacturers. That would be China, Russia and Yugoslavia. It appears that they have all really stepped up their game as far as the quality, consistiency and overall performance. Over the course of about a decade it seems that the quality of the Chinese tubes have been having a bit of a competition between Russia and China. They continue to try and out do one and another.
    While current production isnt beating out tubes built forty or fifty years ago, in many instances they are getting close.
    This is just my opinion based on my own anecdotal observations and experiences with audio output and audio preamp tubes. Notable new production Chinese tubes that have impressed me include varieties of 6L6GC, 6550, 300B, KT88 . The Chinese have been known for making some particularly very strong 12ax7 types for very cheap. While you used to have had to weed out many microphonic and noisier tubes. At bulk wholesale prices of under $4USD, it is cost effective for distributors to purchase such bulk tubes and grade thru them, Brand them as a premium audiophool component and list them for $25-$30+ dollars and then resell the rejects in bulk to various other jobbers that perhaps market them online and at swapmeets or hamfests?
    I doubt it is too far a stretch of my creative imagination to assume similar is happening in the world of RF tube manufacturer and distribution. Such an industry serves a very small market share.
    Perhaps such inferior 811's that couldnt withstand such plate voltages and cut the mustard are in fact second tier merchandise and being marketed elsewhere? 811 is a very unique tube for all but the most esoteric modern audiophool applications.
    While many of the earlier production runs of thermonic products from China probably did suck quite bad, it has obviously been getting better and better as they keep going at it.
    I have said before that it isnt that for the most part Chinese manufacture is inferior. It is more about what the end consumer demands. The demand has traditionally been for rock bottom cheapest cost cutting economical products. They have served that demand very well. At the same time they have discovered a benign way for the state to sponsor an economic strategy that manipulates the capitalistic western parts of the world, by beating us at our own game! They are more and more capable of producing many products of premium quality if that is what the marketplace demands they will tool up meet the demand and eventually leverage it. Much to their advantage. but also to the advantage of us getting good tubes too! (Is the glass half full or half empty? Sorry. I intend not for this to be a political/economic discussion but just a few
    points and opinions based on nothing substantiated or understood too well by my own layperson...
    frankly I dont feel very much well when these discussions take on any adversarial type of tone or spirit; where it is likely "us" and "them",,,,, whoever the heck "them" actually is and with whom do you speak of regarding "us" ? Rather petty, immature and seemingly not appearing very smart is it? )
    Once again this is only my opinion. I am not an expert, an economist or engineer but just a regular Joe consumer that has experience using similar unique products.
    If new production audio tubes are getting correct, it seems RF tubes shouldnt be too far behind! As long as there is a demand and the larger specialty distributors Such as RF parts, MFJ, and the likes of Antique Electronic Supply/Amplified Parts/CED can provide the the vehicle the logistics and make the deal happen, we will eventually get the good stuff.
    One final note: I mentioned that there are only a very few production plants throughout the world. Russia Yugoslavia and China. These manufactures are pretty much the only suppliers and will do production runs for just about anyone that has enough seed money. They operate without enforcement of trademarks, copyrights or patent infringement enforcement. They have all been known in the past to produce fakes/counterfeits/copies of some of the most popular devices of the past. Also many new distributors also might elude to the fact they manufacture their own devices however no matter the brand name, label or colorful package, they are in fact all the same tubes and not any better than the other,,,, just a different production run is all perhaps.
    Deal with suppliers that will honor a warranty and have the customer service you can accept.
    Lets hope that the whole myriad of new production thermonic devices for RF applications continues to grow in quality and performance. Just as it is has within the audio community.

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