HT 1 help

Discussion - HT-1 amplifiers
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Classicplayer
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Sat Jan 10, 2015 2:04 am

How long did the original tubes last you. Sometimes I wonder if this HT1R is a bit hard on tubes. It could be my imagination though.

Classicplayer

Luckyrabbit2015
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Sat Jan 10, 2015 2:58 pm

Now there,s the question,
I purchased the head s/h from a guy who just used it for studio work, after around 6 months it went down whilst not being used, went to fire it up and nothing, good bet a tube had blown so replaced both and have used it just about every day now for over a year. Old tubes of Chinese origin, new ones are Phillips US Military spec. sold under "Phil Kit" from Watford Valves.

Regards

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Classicplayer
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Sat Jan 10, 2015 5:23 pm

My HT1R combo has Tung-Sols in both preamp and a 12AU7 as a power tube. Not so long ago, my tech told me that today's vacume tubes are made on "decades-old " equipment that was sold to the companies around the world now providing them for the market. He's an electronic engineer as a profession and has a few patents under his name, so I guess he's qualified to speak to the subject.

Classicplayer

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thephantum
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Sat Jan 10, 2015 6:55 pm

Classicplayer wrote:Not so long ago, my tech told me that today's vacume tubes are made on "decades-old " equipment that was sold to the companies around the world now providing them for the market. He's an electronic engineer as a profession and has a few patents under his name, so I guess he's qualified to speak to the subject.

Classicplayer
That's very true. But it's not just the equipment, it's also the expertise. When the US, UK and W.German tube makers sold of their manufacturing gear in the 80's, the folks who operated it all did not go with it. It's like taking the welder out of the hands of a guy with 50 years welding experience and putting in it the hands of someone with zero experience. All that knowledge has been lost....

Here's a perfect example: A few months back I acquired a lot of 12 old 12BH7A tubes. They were untested so I got them on the cheap. I have an old B&K 707 tube tester (was my dad's) so I tested each tube. Out of the lot, I got 9 strong tubes: 3 TungSol's, 3 Sylvania's, 2 RCA's and 1 GE.

Anyway, I already had the tester out so, just for sh*ts and giggles, I tested two brand new EH 12BH7A's as well. My particular tester does not give an actual gm reading (trans-conductance), rather it gives you a range: under 65 is bad, over 65 is good. The two, brand new, EH tubes read 90 on both triodes. So both are good and well balanced. However, by comparison the lowest readings I got on the old tubes was 100 (the GE). The three TungSol 12BH7A's pegged the meter at 120+.

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Classicplayer
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Sat Jan 10, 2015 7:37 pm

Phantum,

That's one reason why I elected to go with a decently rated smallish' tube amp (my HT1R) with as simple a tube compliment as this amp has. The cost and quality of tubes put me off getting anything bigger as well as the need for a practice-recording unit designed for home use. My results with this amp exceeded my expectations and when it comes time to re-tube, I can deal with the dollar outlay....well worth it just to keep this little gem purring along.

Classicplayer

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thephantum
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Sat Jan 10, 2015 7:51 pm

I hear you. That's exactly why I did the same thing...except I went HT-5 for practice/recording and HT-20 for jamming/recording/light gigging. I just got tired of feeding matched quads of power tubes to amps at a $100+ a pop.

I know we are getting off topic, but I'm still curious about your's eating 12AU7's. Do you have access to someone with a tube tester? I'd love to see what a tube reads before you put it in and then again after you feel it's lost it's edge....

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Classicplayer
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Sat Jan 10, 2015 9:40 pm

My tech probably has a tester, but he's an hour's ride away. I wouldn't claim the the HT1R eats the tubes because, I am still learning the "feel" of the amp now that I have the Celestion in it. Some reviews of this amp consider it "warm" sounding. That warm sound might be attributed to the fact that once tubes get sufficiently warmed up, they shed some of the brightness (so I've read). They smooth out. There is not bright switch of course, but with judicial use of the gain, volume and ISF and tweaking my guitar's pickups, I manage to get some of those highs back. Still, your idea is a good one and next time I visit the tech's shop, I will find out if he can test a prior 12AU7 that I took out of the amp. Do you detect premature tube aging in your HT5?

Classicplayer

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thephantum
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Sun Jan 11, 2015 9:29 pm

If the HT-1 is anything like the HT-5 (and I believe they are similar in design), it's pushing the power tube pretty hard. Just as an example, a 12BH7A is rated to run at an absolute maximum plate voltage of 450v. Bone stock, mine was running at right at 450v. At that plate voltage, optimum bias (70% plate dissipation) would have been 5.45mV. Again, bone stock mine was set to 6.2mV (80%). So B* runs the bottle right at it's maximum and runs it hot.

Maximum plate voltage of a 12AU7 is 300v. I've got a nickel that says the HT-1 is either running it at that plate voltage or even a little over. I've got another nickel that says it's running at 7mV bias or higher...which is hot (6.5 would be optimal).

Regarding tube wear in mine, I would say yes. After a little less than a year the original EH 12BH7 did sound like it was losing some edge. It wasn't completely flat or lifeless or anything, it still sounded damn good...but it seemed to have lost some higher order harmonics. At least to my ears. When I was testing all the other tubes, I also popped it in the B&K and compared it to a new EH, it had lost a little trans-conductance, but not much (like 85 compared to 90). So there is evidence that the tube had worn out a bit in less than a year.

Thing is, I never even tried to A/B it against a new EH to confirm that sonically. Once I realized that all the vintage tubes had much higher trans-conductance than the new EH's, I only rolled those vintage ones across it. I settled on one of the TungSol's...made in mid 1957.

All this makes me wonder though: with the exception of the Artisan series (which are Class A), every one of B*'s tube amps are straight up Class AB, fixed bias amps....except for the HT-1 which is cathode biased. So maybe they knew the 12AU7 would start losing edge quicker and made it cathode biased so you could change the power tube quickly without having to go through the whole bias procedure? Just a thought....

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Classicplayer
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Sun Jan 11, 2015 10:15 pm

Darn good thought, it is! It would be interesting to know (and I'm guessing BS would never reveal) the method they use to get optimal tone from the HT line of amps. My sense tells me BS is more concerned with tone than tube life in such a competitive amp market? I do know in a quick discussion with my amp/guitar tech, he did tell me that he re-tubes his Fender Deluxe RI about yearly. He does does play out but not nightly, but perhaps once or twice a month. That's not a lot of use in my opinion, but maybe it is a lot considering the quality of today's tube offerings. As I wrote, I found a "work-a-round" for my HT1R combo.

I know we sort of hijacked the thread, but it does deal, with BS and their tube amps; plus your input is quite interesting and thoughtful.

Classicplayer

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thephantum
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Sun Jan 11, 2015 10:57 pm

A lot of it also depends on how hard you use the amp as well. Even if you are only gigging once or twice a month, there's a lot of stress being placed on the power tube(s)...not just by being played hard, but also by being transported and bounced around. A lot of times you don't have the option of letting the tubes fully cool down before you move the amp as well. In a case like that, yea, even if they still sounded awesome, I would probably change tubes once a year as well...maybe even every 6-9 months.

I'm not gigging on a regular basis anymore. I have a couple of folks I jam with occasionally, but mainly I play to the basement walls. So if I'm in the middle of playing and a tube goes...yea, it's going to be annoying and inconvenient and I'm going to mutter under my breath about it, but it's not a show stopper like it would be if it was a gig.

...and you're right, we not only hijacked this thread....we kidnapped it and tied it up in the cellar. :lol:

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