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I see at least one guy here bought some Ebay Tubes and is having trouble with what I understand is a fairly reliable tube AND brand.
Are there COUNTERFEIT Tubes on the market? Or tubes bought as 'seconds' and sold as new / good?
Any vendors to simply AVOID?
Too much is never enough
Follow Ups:
from sellers that appeared to handle some volume. Each tube about $35-$50, signal tubes, all brand name, although I don't remember if all the boxes were branded or not (I think you'll want branded).
Anyway, so far, happy with the purchase. Went from $15 tubes to $45 tubes and the change was a noticeable improvement in sound. Hoping they last much longer, too. I don't think there are many worthwhile $15 tubes unless you just want to see if your equipment works.
In Europe on eBay you frequently see photos of the tube in question in the tube tester. Particularly in Germany vendors are good at recording actual test results. A lot of vendors have tube testers, and if they won't give youth results as a percentage of new it's up to you to buy or look elsewhere. "Tests good" only means 60% upwards, and 60% isn't great. You would usually be looking for 80% and above. And if you see a vendor with a tester (look at other tubes he's selling) saying "filaments good" it's a good bet he tested the tube and got a low result.
This doesn't address the question of rebranding tubes, but it addresses the question of whether you're getting a strong tube or not (80% or over). I'd prefer a reliably tested used tube to a "new" boxed tube. You can get all kinds of tubes in what looks like their original boxes.
I have been using this tactic too when shopping for tubes at Ebay. At times, you would notice some "not so nice" sellers trying to dump garbage in Ebay by the way how they listed their tubes. These are the sellers I always avoid. Another kind is even more pathetic, they listed with a single picture, a short description stating tested OK, then a long description of their company and how big is their warehouse or inventory...priceless.
I've successfully bought several dozen 6AS7 (or Russian equivalent) tubes off EBay from Russia. I've had no failures, and all that I've used have lasted well over 3 years.
For phono and driver (6SN7) tubes I use one of a couple US tube vendors and have had great results.
I purchased several NOS 6AS7GA tubes from a well-known US vendor and had 30% fall out, which they replaced free.
Those kinds of tubes last a long time, right? I couldn't imagine having a single amp using atrio of thsee guys needing 20 or more 'spares'.....
Too much is never enough
I get about 5 years of life out of my 6AS7 tubes in my AtmaSphere M60 amps. There are 8 per amp so a total of 16.
I go through periodic acquisition fits when I get nervous about supply or an itch to try something new. I just learned my most recent binge purchasing NOS 6AS7GA tubes was not a good move as these don't have long life in the AtmaSphere amps.
I probably have 60 new and still-good used tubes "in stock".
My incoming MA1s will have 14 6AS7s per side for a total of 28. I'm not crazy about the heat, energy use, or retubing cost, but the reliability and sound quality make up for the downsides.
You mention heat? In 90+ weather? I don't see the AC keeping up. In winter you might not need to run the central heat...
Have you ever bothered to measure power consumption?
Too much is never enough
Well the M60 consumes about 300W per channel. The MA1 consumes about 500W per channel. Not all of this is heat, and is probably only when all the tubes are running at high volume, but it's kinda like having a hair dryer going, so definitely adds a little load for the AC to compensate.
One reason I'm considering Class D or a Benchmark Class A/B/H amps in the summer. It hasn't been a huge issue so far, however, even in 100 degree heat.
Just a thought......
An amp making NO SOUND thru a speaker and drawing a couple hundred watts???
It is ALL HEAT. You are doing No Work.
'D' is cool. Highly efficient PS, and OVERAL efficiency at full power can run Over 90%.
Efficiency drops as a function of power, reaching ZERO at Zero output. Maybe a little better than an AB amp at similar powers. Depends on some other things.
But keep in mind that your SPEAKER will not (probably) exceed about 5% which puts and UPPER LIMIT on overall efficiency. Speaker voice coils can get darn hot. And change with heat. Not necessarily 'for the better'......
Still and all? Your heat load TO the AC is a LOT. A person might be about 100 watts equivient each.
So while you are adding heat to your house, the AC is running at some low efficiency REMOVING such heat. It's all downhill!
If I go tube? I'll take some readings at both normal listening levels AND at idle.....
Too much is never enough
Can't argue with Class D. Efficiency. Or A/B for that matter. But there is something magical about the OTL sound that overcomes thoughts about efficiency.
what you LIKE overwhelms any thoughts of efficiency.
I gave up a D amp and went back to a more conventional A/B amp....
Too bad my speakers are Lo-80s sensitivity and OTL is simply not going to drive 'em at anything over headphone level.....
I'm contemplating a big change of direction. After owning panels for 3 decades or more, I'm going to migrate up to LA and listen to some klipsch. If that's a go? Send off for the Latino ST70 which should be enough power for 96db speakers and build me a KIT AMP.......
Too much is never enough
I wouldnt rule out eBay, especially now with the amount of estate lots finding their way to 'collectors'. I've picked up probably 200 NOS tubes recently which look to have been kept together for some time. Desirable 50's and 60's types. Crisp boxes, perfect logos and test as they should. They'll end up through eBay and into private hands. Why sell them to a vendor so he can take his cut?.
"Are there COUNTERFEIT Tubes on the market? Or tubes bought as 'seconds' and sold as new / good?"
Yes and yes.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
thanks. Tube market is a 'buyer beware' situation, apparently, unless you go with a first tier seller.
Too much is never enough
I have just started to collect vintage tubes no more than 4 months ago. IMO, if you are an experienced online shopper and a fast learner like me (yes, I dont know $h1t about vintage tubes 4 months ago though I have been playing SS amps for more than 30 years, and I have been buying online for more than 20 years. Ebay, Amazon, AliExpres, TaoBao, TMall, etc...you name it), I would rather shop at Ebay for tubes instead of buying from tube vendors.
I bought my first NIB vintage tube, a RCA 5691, from a reputable vendor (always got mentioned here) for US$200 about 4 months ago. What I get is a relabeled Sylvania 5691 in a white box!!! Not to mention it took almost a month to arrive in Singapore from the US. Yeah right, buy from vendors. No, thank you.
Now, I have about 60-70 tubes in my collection, about 80% are NOS or very lightly used and I bought most of them at very reasonable prices. Yes, you can get a very decent RCA 5691 for about $100 at Ebay if you shop around patiently. I got my next two pairs of NOS 5691 (RCA & Sylvania) for about $220/pair in their original boxes. Nevertheless, I got burned one time out of more than 40 purchases from Ebay, not due to the seller but becos of my lack of recognizing a pair of tube, and overbid on them. No big deal, I took it as a learning lesson. You just need to be careful and know what to look for and avoid. Good luck.
P.S. I am not directing anything towards any vendors, please dont take it as an offence; I am just sharing a newbie's experience.
There are quite a few ways people get burned when buying tubes on fleabay (in addition to the obvious misrepresentation/bait and switch/etc.):
1- Really good fakes of NOS tubes - even if you have a lot of experience, it's hard to tell.
2- Marginal tubes sold as NOS, and matched tubes that are not so.
3- Tubes tested only for gm, but are noisy and microphonic. Many years ago I brought (not through fleabay) a bunch of 40's Sylvania VT-231's (6SN7's) for cheap. I didn't have any equipment then that uses that tube but now I do. Each tube still test better than NOS regarding mutual transconductance and looks perfect, but they noisy and microphonic as heck - things that consumer level tube testers cannot test for.
So, more or less, it is about who you are buying the tubes from. What are the differences between buying from a reputable vendor and an Ebay seller, whose account might be over 10 years, with thousands of positive feedback and a rating near 99%? BTW, I also bought from private sellers with 100% feedback. Yes, I always avoid listings with unclear pictures, incomplete or questionable descriptions as well as sellers from high risk countries like China, Hong Kong, Vietnam, etc...So, I dont see where is the problem of buying from Ebay as long as you practice some simple rules. It is not like all tube vendors are saints...LOL
Warning not to buy vintage tubes from Ebay is just over-exaggerated, IMO.
FYI, for the last 4 months, I managed to acquire the followings from Ebay:
3 matched pairs of Sylvania VT-231 (~$40/pcs - 1 DOA on first test)
2 matched pairs plus 1 pcs of Ken Rad VT-231 (~$70/pcs)
4 pairs plus 1 pcs of Mullard ECC35 (~$200-250/pcs - bought one at $100 with a loose base and 90% print gone but very light emission mark)
2 pairs of Mullard ECC33 (~$220-250/pcs)
4 pairs of NU 6SN7GT (~$40/pcs)
2 pairs of Raytheon 6SN7GT (~$35/pcs)
2 pairs of RCA 5691 (~$110/pcs)
1 pair of Sylvania 6SN7W (~$140/pcs)
3 pcs of Brimar 6SL7GT (~$90/pcs)
1 pair of Tung-Sol 6SU7GTY (~$100/pcs)
Except the one DOA Sylvania, all are tested strong and quiet on my tube amp, they are either NIB (original box) or very lightly used with no or very fade emission mark on top of glass. Please let me know where can I get these prices from a tube vendor.
Shop smart!!!
People can buy from wherever/whomever they choose - and I couldn't care less if from fleabay or tube dealer/reseller, not my money. Just pointing out different ways how people CAN get burned - not saying you WILL get burned.
Good for you getting those tubes for the prices paid, enjoy.
Accountant
Dentist
Auto mechanic
Tube Vendor
Hey, you missed out lawyers...lol
Originally I had Lawyer. But not working anymore I felt that the general public would need the services of an Accountant more than legal advice. When I was working that would have been my first choice.
But yes, you a Lawyer is on the list
"Any vendors to simply AVOID?"
I've said this dozens of times.
DON'T buy tubes off eBay.
I have at least 20 customers who got burned.
Dan Santoni
Sounds like 'sound' advice.
I wouldn't even buy spark plugs or ANY car parts, either.....
Too much is never enough
As long as there is a market and money to be made, there is counterfeit anything - especially on fleabay. There is a very large market for old/rare tubes.
Since you are 'new' to tubes, as others have suggested, start with new production tubes just to test the waters. If you decide to continue on, then start rolling with old tubes from trusted sellers. You might be paying a little more but at least you know they are 'vested' and you won't get burned.
good idea.
IF I buy an amp....probably the VTA kit amp, It'll come with tubes. Though upgrades ARE possible, in that ecosystem.
Too much is never enough
Rather than try to figure out the moving target of unscrupulous ebay sellers, simply cultivate a life long relationship with one of the known, and trusted, tube purveyors, many have been mentioned in this thread. They stand behind their products and you will have no worries.
Makes perfect sense.
Too much is never enough
Yes and yes. eBay as a whole is a crapshoot.
Tubesandmore, tubedepot, jim mcshane have good tubes, new and old, at very reasonable prices, and you don't need to worry about what you are getting.
Others also, just search here.
Thanks.
What got me started was I saw some posts about tubes which SHOULD have lasted a normal time, going for onlly a few months. EBAY Purchase.
Buyers on Amazon complain frequentlly about 'fake' or 'counterfeit' goods. I could save 5$ per spaarkplug for my car (needs NGK / OEM) but most of the 1 star complaiints are about FAKE.
So REAL stores are both welcome and worth of business.
Too much is never enough
The Tubestore and Upscale Audio are also reliable, Upscale has a great selection but gets pretty pricey.
Yes, there are counterfeits, and yes there are sellers that either knowingly or not, sell sketchy tubes of questionable provenance.
If I was just getting into tubes, I'd probably not bother chasing NOS stuff because it's such a crap shoot these days. People have already hoarded the good NOS stuff, so not much but the dregs nowadays. If you're open to buying used and competently tested tubes that's a different matter.
It might help to know what it is you're looking for. With a few more specifics, the advice you get might actually be worth more than what you paid for it.
Thank you so much for what is NOW a perfect answer.
I'm just thinking output tubes for now. the Latino amps use anything from the EL34 family on up to KT 120 on the big mono bloc.
I doubt I'd ever go for NOS.
Too much is never enough
There is a forum sponsored by VTA. You could go over there and ask what tubes are working out best with what ever model you end up with.
I have the VTA ST70 that also has a broad choice of tubes. Just because you CAN use a particular output tube, doesn't mean it's going to be the best choice. An example is I can use a KT88 in my ST70. Great tube, but in my amp, not so good.
I've looked at the VTA material......And yes, people have tried all SORTS of things.
But only some consensus.
As a first amp? I'll 100% 'keep it simple'.....
Too much is never enough
. The KT 66 is also a good tube in the ST70. Then there is 6p3se/6n3ce also. The 7581 is akin to the KT66 but at a lesser price...about $85-90. Pretty blue lights too.
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You paid HOW MUCH for that electrical receptacle?!!! Are YOU nuts?
Edits: 08/12/21 08/12/21
"The KT 66 is also a good tube in the ST70. Then there is 6p3se/6n3ce also. The 7581 is akin to the KT66"
None of these tubes perform optimally into the low-Z load presented by the Dynaco transformers. 6.6K is their sweet spot, as published in the manufacturers' original data. The 6P3S-E may be even higher. The EL34 is the best match for this amp.
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Buy Chinese. Bury freedom.
"The primary impedance on the original Dynaco A-470 output transformers was 4300 ohms. This works out well for EL34, 6L6, KT66, KT77, KT88 or 6550 output tubes."
The above is a quote from Bob Latino. I think that is the source of the confusion.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Mike Samra was a big advocate of using a 6L6 in VTA's version of the ST-70 (link to but one post, below).
I put their (stuffed with parts by me) 12AU7 board into one of my ST-70s years ago, and was never in love with it. I describe the sound as "too solid-stateish" and have been told by more than a few that the non-linear 12AU7 was the prime suspect. I tried 12BH7s, but that was largely a lateral move.
After reading Mike's frequent recommendations, I bought some 6P3S-E from Jim McShane, back when he still sold them. I'm not going to claim the amp was "transformed", but it certainly was a bit more pleasant to listen to music with than with the (original but used) Mullard EL-34 or reissue Gold Lion KT-77 I tried.
I'll leave it to those with more circuit knowledge than me to explain it (Canceling distortions? He asks, very tongue in cheek) but whatever it was, I liked the VTA better with the Soviet 6L6 variant.
"I tried 12BH7s, but that was largely a lateral move."
IMO the 6cg7 would have been a better choice. The 6cg7 is just as linear as a 6sn7, one of the most linear signal tubes ever made outside of some direct heated signal tubes.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Apparently I didn't do enough research. Since the 6CG7 isn't a direct plug 'n play replacement for a 12AU7, I must have missed posts recommending it.
I did some more homework just now and found a couple of comments on the 12AU7. One, by former Inmate Neff (who I always appreciated) said, "As I stated the only worse thing [than] having a 12AU7 in an amp is a chassis fire." which brought me a good laugh over my morning coffee. I was aware that the 12AU7 wasn't a respected tube, but humor like that almost always gets my attention.
The second comment was by Mike Samra, who wrote, "I will tell you and I know others feel this way, I don't like the 12au7 in an amplifier, period! The 6cg7 is so much better and it's more or less a drop in replacement for a 12au7 by just moving the filament wires when you have a 6.3v fil source. The tube is much more linear and makes more power and the end result is lower distortion with a more detailed and open sound.
For the life of me i can't understand why any manufacturer or builder would still use the 12au7 and the only thing I can think of is, they are cheap, and available."
End quote. (link to Mike's post below)
My unenthusiastic idea was to convert the amp to 12A77s, since it only involves a few resistor changes, and because I have five NOS JAN 12AT7s sitting here, doing nothing. Triode Kingdom informed me that the 12AT7 would only be marginally better than the 12AU7 though, hence the lack of enthusiasm.
Converting the VTA board to 6CG7s will require cutting and rewiring a few filament traces, but I had thought about hacking into it anyway, to add the CCS they now use, and eliminating the AC balance pots. I've got nothing to lose, since the amp's just been sitting here collecting dust for a long time.
Once again Tre', thanks for the recommendation. You brought some hope and possibilities to an amp I had no idea what to do with, and it's always nice to have a plan.
.
Have Fun and Enjoy the Music
"Still Working the Problem"
Tre', have you tried any of the reissue 6CG7s? I wonder if they're as linear as NOS.
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Buy Chinese. Bury freedom.
I have a good stock of NOS and OS and my system doesn't use them anymore.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
I'm also going to email Jim McShane to see what his recommendations are.
On the other hand, NOS 6CG7s and 6FQ7s are still somewhat available. This issue of using better tube types and other parts is exactly why I hate PCBs. You and I have discussed this in the past. If I had a ST-70, I would do everything possible to replace that board with an aluminum panel that could be wired point-to-point. Dynaco used PCBs in their products to save production cost and make kit building easier. We don't have those priorities. :)
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Buy Chinese. Bury freedom.
Edits: 08/14/21
"Hacking" PCBs isn't the best way to go, long term. But, on the other hand, it's easy enough to do, and the 6CG7s should give me an idea of whether or not I'd be moving in the right direction.
If I feel it's enough of an improvement, then I could make a turret board, perhaps with octal sockets for 6SN7s, which would enlarge my tube choices.
Don't tell anybody but I once took a hole punch to a Citation II and put a 6sn7 based Williamson front end with low NFB. I up-tapped the output transformer to get a higher impedance for the triode strapped 6550s.
Less power but it's a great sounding amp in a bi-amped situation (crossover at 100Hz) with the lows filtered out at the input. (when you up-tap an output transformer the reflected impedance goes up but the primary inductance doesn't change so the LF -3db point goes up an octave)
My cousin still uses that amp and loves it.
Looking back, I could have just built the thing with 6cg7s and kept the value instead of "cutting up" the chassis but at the time Cit IIs weren't worth that much. I think I paid $100 for that one. I owned 4 of them at one point.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
I think I felt a collective chill from all the Citation II fans while reading your post.
That might make an interesting thread, asking "What did you wreck [or devalue] in an attempt to improve things?". I'm betting there's some early Marantz or other tube gear out there with holes where they don't belong or a chassis painted red.
I was going to tear into my Audio Research SP3-A-1 preamp around thirty years ago, and the advice I got was "Leave it alone". Given what they're going for now on ebay, it was good advice.
There are a number of things I'd like to change in my Citation V. Much of it would be hidden, like the use of larger PS caps and maybe the addition of a screen choke. However, rewiring a socket for a different tube type hurts resale value, even when socket size stays the same. The mod I want most - a front panel power switch - would really kill its market value, no matter how professionally it's done. Wish I had bought a dozen of these back when they were $100 each. That's the only way I could justify making one of them "my own."
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Buy Chinese. Bury freedom.
I had a running Cit.ii and a pair of W6m carcasses...I kept the Heathkits and sold the restored Cit.ii. Too much money got waved under my nose.
Cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
Ain't that the truth? Pre internet, I got to see a lot of great old hi-fi equipment. But being a Rust Belt dweller at the time, I had little disposable cash to buy any of it.
That was when I bought my modest Dynaco collection, and even that has increased in value.
There's more to life than money. :-)
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
That's true, and I probably should have left the monitary value out of my comment.
My other interest, in addition to hi-fi, has always been motorcycles. Finding an old, 1940s original paint and parts Harley or Indian is rare. Everybody was customizing them in the 1960s/1970s, not thinking a thing about it. But now, finding one in its original state is a thing of beauty.
I'd be happy to find a modified Marantz 8B, some extra holes drilled in its chassis, but I'd be a lot happier to find one that hasn't been touched, simply for its aesthetic value.
In the summer of 1974 my good friend Ron Finuf one year out of high school, while working for David "Huggy Bear" Hansen at "The Shop" bought an old police bike. I think it was a pan head. He ripped it apart and chopped it finishing it just in time to ride it to Idaho to watch Evil do his thing.
Huggy Bear and a bunch of other guys from The Shop were going but changed their minds at the last minute and headed off in a different direction. Ron rode all the way there and back solo.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
We have a legendary Harley drag racer named Pete Hill from the area I now live. Pete was in his seventies when he jumped on a rigid frame (no rear shocks) Harley Knucklehead (which preceded Panheads) and rode it to Sturgis SD and back to SC, about 3300 miles, round trip.
That was back in the days when men were men, and sheep were nervous, as the old saying goes.
I've ridden bikes all over Texas, Colorado, Pennsylvania and upstate New York, but I don't have any stories like that to tell. Except maybe the time I rode from Colorado Springs to Dallas on New Year's Day when it was 12 degrees and a foot of new snow on the ground. It was so bad, I didn't ride for nearly ten years after that experience. :(
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Buy Chinese. Bury freedom.
Punch that 12 ºF into a wind chill calculator on line, add your average speed, and it's no wonder you weren't anxious to get back in the saddle, not to mention the potential for ice on the road. Hypothermia is a very real thing on a bike.
My most grueling ride was when a few of us left for New Hampshire about six years ago. We did 1003 miles in 17 hours that first day. We'd have pushed further, but one guy's eyes were so beat up by pollen that he was having trouble seeing, so we stopped for the night and finished the run the next morning.
Wow...and I thought riding 100 miles in 7 hours was pretty sweet. It was in the summer...lots of fun in -7F with studded snow tires, riding trails and rivers. Best epic ride ever.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
can't say that I did not occasionally get jealous of the motorized folks...LOL
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
.
Have Fun and Enjoy the Music
"Still Working the Problem"
.
Have Fun and Enjoy the Music
"Still Working the Problem"
That was prior to the release of the 6sn7 board which is what is in my Don Sachs amp which is the custom version of the ST-120.
=========================
You paid HOW MUCH for that electrical receptacle?!!! Are YOU nuts?
when Mike wrote that he must have been using the high gain version driver board using 12AT7's. Not the newer low gain 12AU7 board.
What leads you to assume that it was the earlier, 12AT7 version Mike was talking about?
Below is a link to one of his 12AU7 VTA posts, but a search will turn up others. If I had to speculate, I think Mike had tried both, because in one post he listed the resistors to change to convert the circuit from the AT7 to the AU7.
He's not correct, the EL34 that these were designed for is absolutely the best match. Thats true from the standpoint of both output power and distortion. This doesn't mean the other tubes can't be used in a pinch, but the design of these amps is really optimized for the EL34
.
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Buy Chinese. Bury freedom.
.
Have Fun and Enjoy the Music
"Still Working the Problem"
the VTA ST-70 which is what I have. I have used all these tubes
=========================
You paid HOW MUCH for that electrical receptacle?!!! Are YOU nuts?
I looked at the tube4hifi website and there is no indication that the new output transformers for the VTA ST70 are a different primary impedance than the old ones.
"The A-470 output transformers are brand new USA made custom production transformers. They use the same interleaved/layer winding
technique as the original cloth lead A-470's and incorporate the same high quality M-6 grain oriented laminations.
They are dimensionally accurate to the original design and have a durable heat resistant black epoxy finish."
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Recomended the KT-66. That was 12 or so yrs ago. I can only tell you of my experience with the VTA ST-70 and Bob's recommendations. Others May prefer the El34. It becomes a matter of tastes.
=========================
You paid HOW MUCH for that electrical receptacle?!!! Are YOU nuts?
It's not a matter of taste in terms of maximizing the tube's performance. Like the 6L6 family, the KT66 performs optimally with an a-a load around 6.6K or 7K. It really makes no sense to use anything other than the EL34 in the ST-70.
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Buy Chinese. Bury freedom.
I did that in the 80's and it was the worst purchaser I have ever made. Lesson learned. Good #'s do not necessarily add upo to good sound.
=========================
You paid HOW MUCH for that electrical receptacle?!!! Are YOU nuts?
"Good #'s do not necessarily add upo to good sound."
That's true, but changing the operating conditions so a particular tube produces worse performance is not a recipe for success.
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Buy Chinese. Bury freedom.
at 4300 ohms the power is down and the distortions are up. But some people like distortion so a person can say "it's a matter of taste". I wouldn't be one of those people. :-)
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
I've been wrangling with this problem myself due to the older HK amps I'm rebuilding. The transformers are 3.6K to 3.8K, non-UL, and they weren't meant for the EL34. The original tube was a beam power type, no longer available, and the EL34 is now the only tube that matches. Unfortunately, because it's a true pentode, the screen requirements of the EL34 in pentode mode are very challenging. You can't just use a dropping resistor and a bypass cap as is usually done with 6L6 types. I have at least four amps like this to "re-create", and it's giving me headaches and serious heartburn. :(
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Buy Chinese. Bury freedom.
So are you saying that they are best used with a EL34 output tube?
Honestly, I'm thinking of replacing the driver board and going back to the stock version with a 7643 driver tube.
4300 ohms matches up with a el34. The KT66 needs a higher impedance."Honestly, I'm thinking of replacing the driver board and going back to the stock version with a 7643 driver tube."
OK, now you've got me confused. The original ST 70 used a 7199.
I assume the "original" aftermarket driver board used a 7643?
edit. I see. the 7643 is a sub for a 7199.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 08/12/21
Where did you see that info. Tre'? My understanding is that there is no direct substitute for the 7199.
Inmate Cleantimestream reports that the 7643 is a sub for the 6GH8A, as does Airtime, using it in his Sherwood S5000, which he converted from the original 7199.
I'm only pointing that out so that someone doesn't invest in the 7643, thinking it's a direct substitute for the 7199, unless you found info to the contrary.
You are correct. There are no direct subs for the 7199. I just didn't know about the 7643 being used (with a rewire) in place of a 7199. That's new information to me.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
"perhaps the best 9 pin pentode/triode ever... {Opinion}." (link to post below)
ask Jim McShane what tube would he use if it was his stereo. That's the extent of my vast tube knowledge - ask Jim.
I'm throwing myself a party.
.
Have Fun and Enjoy the Music
"Still Working the Problem"
and the new a470 output transformer is 4300 ohms primary just like the old one.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
I'm looking at the VTA line.... How would I find the impedance of the transformer for the ST120 or the MONO M125?
Each of these amps has multiple tube choices LISTED but like the ST70, one or another may actually be a better match....
Bob Latino has RETIRED and is either messing about in his shop or out fishing......???
Too much is never enough
I find the GL KT66 and the TungSol EL34B's work the best in the VTA ST70.
As for driver tubes, that's where you can go crazy trying stuff.
So I've read. I'd only change the middle tube......and keep it simple at first.
Too much is never enough
You are fortunate in that you have an almost dizzying abundance of types that fall between EL34 and the KT120. That's also the curse. So much to experiment with ...- and that's just the current manufacture stuff. Add in used vintage, and NOS (such as it is today) and you might never exhaust all the variations. But what fun trying as long as the money lasts.
for a FIRST tube amp purchase? I'll go with whatever the amp comes with.....though I may ask for a slight upgrade to the output tubes.......KT66, perhaps on the ST70, that sort of thing.
I'm not wealthy enough to open my own tube store, either. I asked one guy who posted a PICTURE of about 20 (in 4 or 5 different brands) of the 6SN7, a premap tube for the optional OCTAL board for the ST70 ST120 from VTA. We're talkin' a LIFETIME supply. There are some 'collectors' with a steamer trunk FULL of all sorts of good tubes.
I wonder If I can get tubes for my 1950s Zenith Transoceanic. ???
Too much is never enough
"I wonder If I can get tubes for my 1950s Zenith Transoceanic. ???"Yes, radio and TV tubes are abundant and cheap. There was much more demand for them than audio tubes, therefore many more were manufactured.
I have huge boxes of radio/TV tubes that I bought just because there were a few audio tubes in the lot that I wanted.
Do an Ebay search tor "Tube Lot". You will find many such box lots.
Edits: 08/11/21
I don't remember the tube numbers, but nothing I associate with audio......Some really odd stuff.
Too much is never enough
Not trying to be rude or denigrating but where have you been the last 30 years? Do search and you'll find lots of posts like the one you referenced going back a long time.
It sucks to get old. It really sucks to get old and bitter.
Edits: 08/10/21
Please be plain, if you can....
I'm farly new to tubes. Except when I was younger and did the tube check thing up at the local drug store or where the tube checker lived. I had custody of a GE X-Ray Machine that had a couple shoping bags of tubes in it. I real PIA if if went bad for a tube.
So what? What is your point? Want me to parse something YOU say for veracity or duplication?
And yes, If you ARE getting 'old and bitter', you are also losing the ability to self-filter. Fine.....Just take it out on someone else.
I'd apologize if I offended you, but I really think that'd be going too far.
Too much is never enough
What's the matter with you? He said, "Not trying to be rude or denigrating ..." And he's right, everything you asked can be answered for yourself with just a couple rudimentary searches.
--------------------------
Buy Chinese. Bury freedom.
Right. I'll simply stop asking questions, even though I have several more. And not quite enough time for the research.The tube question IS fairly easy, too. And if I thought about it, obvious. Though I'll never be wealthy enough to afford NOS anything. I wouldn't buy anything from Ebay OR Amazon any more.
Too much fake in ALL categores. Though someone wanting a Coach or Gucci ANYTHING for 20$ should already know.But you should see how much research I've already done. and on some weird trails in tube-Land. Like why do tube amps have so little capacitance compared to SS amps? Why don't they use toroids? Just stuff I'm curious about now.......
One day soon, I'll go listen t the Klipsch I am considering and than decide on a path forward.
Apologies to all.
Too much is never enough
Edits: 08/10/21
"why do tube amps have so little capacitance compared to SS amps"
Solid state amps use relatively low voltages, tube amps use higher voltages. 100uf at 500 volts is the same amount of Joules as 10000uf at 50 volts.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Yep......I had already figured that out.....by going to a 'Capacitor Energy Calculator'.....online.
Tube amps apparently always present full PS voltage (500v or so?) TO the tube at all times.....
Too much is never enough
"Tube amps apparently always present full PS voltage (500v or so?) TO the tube at all times....."
I'm not sure I understand what you mean by that. I'm not sure you understand what you mean by that.
Every amplifier has it's own design. Every amplifier uses the voltages it uses based on the designer.
I designed a single ended 300b amplifier and it uses 465 volts on the plate of the 300b. The 300b is cathode biased and draws 64ma of current at idle. There is 80 volts at the cathode so that means there is 385 volts across the tube (plate to cathode). These details will be different for a different design.
You say the above as if you think that transistor amplifiers don't always present voltage to the transistors. If that's what you think then you are wrong. Transistors run on lower voltages than tubes but the B+ voltage is always presents at the collectors in a SS amp, just as it is (to the plates) in a tube amp.
I hope that helps.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Yes....all tube amps will be different to a greater or lesser degree.
Point is that they ALL share high voltage TO the tube at all times....
I think that's one advantage ot a tube amp.
Too much is never enough
I am tripping over your use of the term "at all times".All amplifying devices (tubes or transistors) are supplied operating voltage, at levels appropriate to the device (and the circuit design), at all times while in operation.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 08/11/21 08/11/21
My bad......But I had already figured out the capacitor question.
the ENERGY part of it is highly voltage driven.....
But coming from a SS background, I must admit that seeing an amp with only a couple hundred MFD total is a little weird....
Too much is never enough
"But coming from a SS background, I must admit that seeing an amp with only a couple hundred MFD total is a little weird...."
I can understand that.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
And when you get into integrated circuits? Capacitors of a few volts and Nano values.
you cant' make much given maybe 5000angstroms wide (1/2 micron) and 1000A thick.....
Too much is never enough
Power supply filter capacitors need to be large in value. Signal capacitors don't necessarily need to be large in value.Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 08/13/21
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