Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Jalmeida on September 22, 2023, 11:00:23 am
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Happy friday. Not to throw a Molotov cocktail out here, but i am admittedly finding myself reeling from prices of some NOS and vintage tubes(cough cough Mullards). This all started on my 1964 AC50/2 smallbox I snagged recently that is slowly being returned to original state after some questionable past repairs. And with that I thought, why not throw some Mullard EL34 and pre-amp tubes in. :l2:
I have to say I am not really a mojo guy. I have never got into vintage tube unless absolutely necessary. But I do believe there were some things just made better at some places and certain times. But I must say I have gone down the rabbit hole searching topics with discussions seeing some differing views on this even in some amp technician circles. And I am admittedly terrified at the thought of burning up a $500 pair of Mullards on an amp because I left it on one night.
So, worth the expense?? Or mojo only?
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I would be more concerned with ruining output and power transformers due to internal shorts residing in a potentially bad old tube. NOS tubes have been picked through for the last 30 or so years. The remaining stock is mostly comprised of culls. My two cents; buy burned in and tested new production tubes at a fraction of the cost.
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a $500 pair of Mullards
:huh: I don't want to spend that much on a complete amp! :icon_biggrin:
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For me it has mostly depended on the tube.
I like some of the new production 6L6, 6V6, and EL84 tubes and would not pay extra for NOS.
6BM8 and 6cz5 (6973 subs) I find the NOS tubes better and available for reasonable $.
JJ has good preamp tubes IMO.
Tube dealers now want a lot of $ for NOS. I do not blame them, but I am too thrifty to pay that price. If I go to a yard sale, I always ask. Sometimes I get lucky and a box of tubes is found in the basement.
I also used to do energy audits at military bases. Storage facilities still have cases of JAN tubes. As one manager at a 4 million sq ft storage facility told me," what we do is store stuff until it is completely worthless and then auction it off." Maybe most of those have been auctioned off by now.
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I recently bought two match used 6V6gt's from TubeDepot. I hardly have a dozen hours on them, but so far they have been solid. Time will tell. They cost $24.95ea. That's less than just about everything but JJ new.
But, no I can't justify (or, afford) $150+ a piece for NOS 6V6's. And, I don't own a recording studio where I'm trying to draw in clientele with rare, mystical equipment. :icon_biggrin:
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a $500 pair of Mullards
:huh: I don't want to spend that much on a complete amp! :icon_biggrin:
Yeah, pretty silly pricing. And my thoughts are that some of that pricing is mojo/hype markup. I won’t spend that much for NOS consumable power tubes.
So then sub-question. Is is best to be running NOS pre-amp tubes? Say in the V1 positions?
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So then sub-question. Is is best to be running NOS pre-amp tubes? Say in the V1 positions?
good question. I have some good old RCA, GE, etc. 12AX7s and AY7s and I use them. But rather than pay a high price for more of them, I buy JJ 5751s and find them to be really good preamp tubes. But I typically do not like AX7s in V1. I recently bought some new Russian Tungsol 12AX7s and half of them were too noisy for the v1 position. YMMV. In general tubes are inconsistent; NOS and new production IMO.
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I think bmccowan has it right.
It's definitely more about noise than tone in V1 for me. Every time I've swapped tubes in that position, I've done it to make things quieter.
I'm convinced that, aside from capacitor/resistor frequency shaping, "tube tone" is mostly determined by the last gain stage before the PI. How that tube is biased has historically been a defining point in many amps.
But, lower gain at the input, i.e., a 5751, can sometimes be just the right thing, too.
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NOS/Vintage tubes worth it??
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So, worth the expense?? Or mojo only?
Like most things, "worth the expense" depends on how much it trips your trigger & how deep your pockets are.
No-feedback power sections like your AC50 are the best opportunity to hear differences among power tubes, but mainly after you get the amp pushed beyond "clean."
And I disagree with others; I'd say the Input stage is where I hear the most difference for a preamp tube change. Again, it matters whether there is local negative feedback, as that will tend to squash differences among tubes.
Audible differences tend to be small compared to a speaker-change, etc.
While you can still very occasionally get lucky (I have 2-3 times over the past 4-5 years), I feel the window for accumulating old American or European tubes was mostly 20-30 years ago.
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I feel the window for accumulating old American or European tubes was mostly 20-30 years ago
That's when I saw all those cases of JAN tubes in military warehouses, along with outdated PCs and miles of manila rope. :icon_biggrin:
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... I feel the window for accumulating old American or European tubes was mostly 20-30 years ago.
That's when I saw all those cases of JAN tubes in military warehouses ...
Yeah, the JAN 6L6WGBs were being sold at guitar shows (after being sold at DRMO auctions) in the late 1990s.
By the time I went into the military in 2000, I couldn't find a vacuum tube anywhere (despite being in an electronics career field).
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> went into the military in 2000, I couldn't find a vacuum tube anywhere
Word on a street was that B-52 still had tubes in some recent year. Maybe not this century. And of course few techs got near the B-52s. Probably their manuals are restricted?
B-52 is slated to fly until 2050. Probably at least one will fly 2052-2054 to mark a full century of flight. The Bear Tu-95 is similar vintage said to fly to 2040, maybe longer. Even if the B-52 is tube-free, I bet a buck against a ruble there are tubes in Tu-95 spares.
I salvaged one of Ampex's first rotary-head "Quad" video recorders and it had two HUGE power amps to turn motors at odd speeds. Bucketfuls of 6550. I also have one 6550 reputed to be from the last batch at the old KenRad (then G.E.) works, to be the military's "Lifetime Buy".
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> went into the military in 2000, I couldn't find a vacuum tube anywhere
Word on a street was that B-52 still had tubes in some recent year. Maybe not this century. And of course few techs got near the B-52s. Probably their manuals are restricted?
B-52 is slated to fly until 2050. ...
That's the example everyone uses.
However, fighter aircraft that first entered service in the 1970s (and was all solid-state) already got decommissioned in the early 2000s. Talking about the F-14.
I looked for tubes in San Diego military bases, I looked for tubes in Virgina military bases. Never found a single one, not even in installation scrap auctions. There might be a few hiding somewhere, but I bet the other ones left in the 21st century are microwave/radar frequency (and even that stuff is being supplanted by solid-state).
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I know there's still lots of DeHavilland Beavers and Otters in service. I believe they were originally from the late 40's/ early 50's. They're very sought after, although the avionics have all been upgraded, no more tubes. I'm sure several will still be airworthy for their centennial flight.
No different than early cessnas, privately owned and maintained, I have no doubt several will be around for their centennial. Helicopters as well. That stuff doesn't really go bad, per se, as long as there's a market for maintaining them. That particular technology hasn't really changed much.
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And yet, of the 12,000+ B-17s made for WWII, only SIX still fly. A bunch have been "under restoration", most for a long time. I took the ride in one, and what is really going to cripple it is engines. "Mine" was using a Studebaker-made engine instead of the Wright it was designed for. The young FAA guy did not know that and wanted to cite the 'wrong engine'; the B-17 community of experts told him Studie made a LOT of WWII Wright radials, and maybe better than Wright. But both have been out of that business a very long time, and as HBP can say, the old storehouses get scoured. Aircraft engines MUST be rebuilt every so many hours, with certified parts. There are a few engines which got "new makers": I think the WACO at the strip up here has FAA certed Jacobs-replacement parts. (like this (https://www.radialengines.com/)) But a 1,200HP engine is very much bigger than a 300 horse job like Cessna 190, even the 450HP of the DHC-2.
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That's the whole point. Joe Blow can't afford to maintain a B-17, never mind keep fuel in it. Same goes for basically any turbine engine.
I doubt you could find a beaver nowadays for under a million dollars, that's because they were arguably the best plane ever built for what they do. But a cessna from the 1960's for 150k buy in? That's affordable for someone with some extra change. Throw on some floats, and you can actually see the stars from time to time. Maintenance on a fixed wing plane, depending on the hours you put on in a year isn't astronomical.
A piston engine hughes 300 which can be bought for 100k ish? Yeah, the maintenance increases drastically with a helicopter, but you can still do a day trip picnic for a couple hundred dollars, if you can fork out the bottom line for maintenance. Hardly anybody could afford to start a jet ranger or A star, never mind leisure travel. Plus, you're looking into the millions for a buy in. They sure are a nice ride though.
This is why war time planes and jets end up in museums, while private runabouts end up in hangers.
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I was avionics in the USAF. The F-106 was a tube aircraft and got upgraded to solid state in the 60s to transistor. So the technology was definitely transitioning before the 70s. I worked F-16 but knew lots of guys from the F-106 and F-4 era. The russians still use alot of tubes on their aircraft in service. They found that nuclear EMP wouldn’t destroy the tubes where the early technology Transistors would get destroyed.
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I've a lot of NOS tubes but only purchased 2 or 3 at NOS prices (I can't afford high prices), I purchased it at flea market ham fest and some received exchanging with other things
If you have enough patience and to invest in tubes also when you don't have to use it in a brief time isn't a problem you can find good affairs
Franco
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I've a lot of NOS tubes but only purchased 2 or 3 at NOS prices (I can't afford high prices), I purchased it at ...
I probably have a lifetime supply. Maybe 800-1000 tubes?
- I had a large number from decades of buying a little at a time since the 1990s as deals showed up.
- I found one "NOS" deal when I bought the stock left over from a TV repair shop (sold by the shop owner's son, decades after the shop closed). Gave away 900 or so tubes to keep the 30 or so that were actually usable to me. That deal only worked because the seller acknowledged my buying price reflected what I was willing to pay for those 30 tubes, divided by the total number of tubes he was selling. Overall, I was a buyer at 10¢ per tube.
- I found one situation where a very-odd guy had many "pulls" that apparently came from a repairman in the area. Thousands upon thousands of tubes, no telling what their condition might be. We agreed on a fairly low price per-tube, to offset the risk of duds or worn-out tubes in the buy. Still cost me a few-thousand, as I bought several-hundred US and European tubes. I've been lucky to find only 2-3 outright dead tubes in that batch; most have tested & performed quite well.
While possible, I don't expect to bump in to either of those last 2 situations again.