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12bh7 for a 12au7

post #1 of 37
Thread Starter 
I was reading that 12bh7's sound better than the 12au7. I was wondering if you can put these in a soha with no problems.
post #2 of 37
Haven't tried it, but Runeight would be the one to know for sure. It appears that the typical plate voltage is even higher (250V) than a "normal" 12AU7 (200V). So, it may not be a good match for the SOHA.

With so many 12AU7 variants out there (more than any except the 12AX7), I'm not sure that it would be as fruitful to look outside the family as with other tubes. Here are some very good references on the types of 12au7 tubes available:
Brent Jesse Recording on the 12AU7
SND Tube Sales on 12AU7

Those pages include:
12AU7
12AU7A
5814
5963
6189
6680
7316
7730
ECC82
ECC802
There are others, too - and that's not even counting the variance among brands. Even then, there are "triple-mica's," different style getters, "5 Stars," JAN's, and many unknown brands (National?). I have about 1-2 dozen 12au7-type tubes so far, and only 2-3 are actually 12AU7's.
post #3 of 37
Thread Starter 
I was just wondering. I tried an german rft in my soha yesterday then tried an rca cleartop and I could hear quite a difference. But, I haven't had a lot of time to really try things yet. The german brand did have a better sound but it was running for a few hours and the cleartop was just plugged in.I am getting a little excited with tube rolling I think.
post #4 of 37
Quote:
Originally Posted by headphonejunkie View Post
... I am getting a little excited with tube rolling I think.
No kidding. Keep in mind that it can take hours - even a couple of days - of burning before a new tube assumes its "permanent" sound. I've had some Millett RCA's blow the doors off with bass, but no highs. I left them plugged in for a day or two, enjoying the bass just for kicks (literally). Lo and behold, they lost the boom and ended up pretty detailed. They're now well-rounded sounding tubes.
post #5 of 37
Thread Starter 
Like I said I had just plugged the cleartop in quickly before I ran upstairs. The rft has only a couple of hours on it too. The rca had two minutes maybe.Its hard. The wife doesn't like me downstairs as much as I am.
post #6 of 37
Definitely true. I've been burning in an Electro-Harmonix 12AU7 tube and after a few days it's losing the shrill highs and getting some better bass response. Quite the opposite of the JJ, but that one went from good to amazing in about 2 weeks.
post #7 of 37
Thread Starter 
One thing I noticed about the rft is when I power up the amp it lights up for a second. The rca's I have do not do that. Also, the rft is about 1 1/2 times as wide as the rca's.
post #8 of 37
I personally like the 12bh7 better than all the 12au7's I have tried. There are some good 12au7/5814a's like the early 1950's Raytheon and Hytron D getter, 2 mica tubes. But the 12bh7 is more neutral, dynamic and resolving in my amps. The 12bh7 should work fine as long as the amp can handle the additional heater current draw of the 12bh7 tube.
post #9 of 37
Quote:
Originally Posted by sacd lover View Post
The 12bh7 should work fine as long as the amp can handle the additional heater current draw of the 12bh7 tube.
So what is the bottleneck of SOHA. The current output of the toroid? According to datasheets 12BH7 draws twice as much as 12AU7.
post #10 of 37
Quote:
Originally Posted by Yen View Post
So what is the bottleneck of SOHA. The current output of the toroid? According to datasheets 12BH7 draws twice as much as 12AU7.
The LM337 can handle 1.5A, which is plenty, but it may mean a heavy-duty extruded heat sink - something much bigger than will fit on the present board.

No offense to the other poster, but the DIY SOHA is quite a bit different than just rolling tubes in a retail amp. It's been stated many times: the SOHA does not follow normal tube preferences with regard to the 12AU7. This is all because the SOHA's plate voltage is set for ~40V. Typical 12AU7's are in the 100-200V range (except the 5963: 60-70V, my favorite so far). To be honest, Blooze is the only one I've read that preferred the black plates and/or clear tops. There are specific posts by Batman that say just the opposite, and go on to say that tubes many dismiss such as the ubiquitous JAN's might work really well, too. It may be because Blooze used the mu-follower CCS, which as we have found out - hasn't been tried too many times.

Regardless, if you're set on trying the 12BH7, give it a go - that's what DIY is all about. You may discover something all the rest of us will start using, but keep a thermometer on the LM337 just in case.
post #11 of 37
Thread Starter 
I always seem to start something . I am just curious and new to this so I am exploring all avenues.Maybe, the reason I see a difference between these higher end tubes is because I am using a follower circuit too. Maybe the follower circuit is the preferable ciruit to use.
post #12 of 37
Of course, as you say, tube rolling is great - try 'em all. Perhaps a little review from SOHA history may help with some ideas:

Quote:
Originally Posted by Blooze, 1/9/2006
I have two NOS Sylvania JHS-6189's from 1966. A GE JAN-5814A from 1967 and a used GE 5814A five star.

The Sylvania's sound especially nice in the mids and highs. The highs are not peaky at all and may actually be a bit rolled off, but just enough to take the sharp edge off. The drawback to them, if you can call it that, is that the bass is just HUGE. Sometimes overwhelming at low volumes, but seems to even out and tighten up as you increase volume. I can't believe someone wanted to put a bass-boost circuit in this! I think this tube will sound nice with the slightly higher impedence of the AKG's.

The 5814A's both sound very similar. Although it seems the midrange may seem a little flat at times with the highs being a bit shrill. I was running these at 39 volts, but think they may like a slightly lower voltage?? (I was getting 20V-60V adjustment range on them which is way more than the 6189's). I haven't really listened to them enough to make a good judgement on them. Any suggestions?

Quote:
Originally Posted by Batman, 2/22/06
Tube rolling with this thing is fun and there are no rules. We were surprised at how good the SOHA sounded and one of the most amazing things about this cheap little amp is that it actually is good enough to allow one to hear the diffferences between tubes.

I've just spent this week rolling about a dozen tubes through my SOHA. The tubes that have sounded the worst have been the "audiophile" ones, the various black plates and clear tops. For some reason they sound too detailed and lack bass.

The best sounding tubes have been the ones with long gray plates. My favorites are a GE 5963 and an RCA 5963 and a Raytheon 12AU7

My second favorite tubes are a Mullard copy 5963 made by BEL in India and a OEM labeled Mullard. These two have shorter (13mm) plates.

In the last group are the new production 12AU7 tubes. Best of these is the ElectroHarmonix, followed by the JJ. The EI was rather bland.

I've not tried any of the JAN's cause I don't have any. This amp breaks a lot of rules so it wouldn't surprise me if the JANS's sounded great I'm betting that the 5963 with the long gray plates (second from the left in your picture) and perhaps the Amperex next to it sound the best.
Quote:
Originally Posted by Blooze, 2/22/06
I'm just the opposite as I didn't like the RCA grey plate 5963's, but am really enjoying the black plate RCA 5963 and RCA BP 12AU7. The black plate RCA 5814 I had wasn't bad either. Lacked in the bass if I remember right, but had great depth. I think I tried some Sylvania JAN 6189's at first, but wasn't impressed after hearing some others.
Quote:
Originally Posted by mrdon, 5/19/2006
About tubes...I went to a Vintage Radio swap meet last week and picked up a slew of NOS 12au7's and 5963's at bargain basement prices. In fact, with one 12au7 I actually struck NOS European tube gold - an RCA branded but Siemens OEM for $5 After trying the much loved GE and RCA 5963's, my ears are addicted to this RCA branded Siemens manufactured 12au7 with o-getter. I have yet to look up the date codes but with my HD-600's the resolution, detail, and depth is incredible. I have heard things in recordings I have never heard before such as Diana Krall's piano bench creaking on quiet passages from the Love Scenes SACD. In comparison with the two 5963's, the sibiliance (sp.?) is non-existant; that is the "S's" are not harsh and gritty but smooth. Of course all this detail and resolution does not sacrifice the midrange warmth and bass extension. If you can get your hands on a Siemens 12au7, I would pop it immediately in your SOHA. You will not regret it.
Quote:
Originally Posted by Batman, 5/10/2006
My three favorite tubes were all 5963's with gray plates; one was a GE one was an RCA and the third was a Westinghouse that actually is a Mullard copy made by BEL in India.

As good as the SOHA sounds, I would be surprised if typical audiophile tweaks will improve it. I would save them for more complex designs. Just my 2 Ohms
Here's the one I guess I was referring to earlier:
Quote:
Originally Posted by Batman, 5/9/2006
There's a lot of synergy going on between the tube and the cans, hence different folks (with different cans) seem to prefer different tubes (eg YMMV). What's interesting is that with HD-600 cans, both mains_hum and I preferred the same tubes in genreral. We found generally that many tubes had extended HF at the expense of bass or generous bass at the expense of the HF. The good tubes had decent quantities of both.
Of the tubes that tomb mentions which I have tried, I would rank them about the same. The best tube I have has been the GE 5963 but the RCA (gra plate) 5963 has been pretty good as well.

Of the new production tubes, I liked the Electroharmonix 12AU7EH best although some might find it metallic. The JJ was pretty good and the EI was boring to my ears.

I absoulutely hated the traditional audiophile members of this family, the various black plates and clear tops. They all sounded too metallic for my ears and these are tubes that I love in my Foreplay preamp...go figure.
There's a lot of enjoyable reading in the original SOHA thread:
http://headwize.com/ubb/showpage.php?fnum=3&tid=5896

Keep in mind that in some of these cases, they weren't even regulating the heater supply. So, it may be that these comments aren't completely applicable to the Digi SOHA board, YMMV.

P.S. (This is all in addition to the other thread posted that reviewed about ten different tubes.)
post #13 of 37
Thread Starter 
I don't think I can afford to buy all the tubes I would want to try. Right now I have three tubes; An NOS rft,An NOS RCA cleartop ,And A NOS rca blackplate marked united on the box. I will have to find some cheap tubes on ebay. Right now, these tubes will have to hold me for say six months? I could see myself getting caught up in this and spending a lot of money!?!?No matter what amp I had.
post #14 of 37
Quote:
Originally Posted by headphonejunkie View Post
I don't think I can afford to buy all the tubes I would want to try. Right now I have three tubes; An NOS rft,An NOS RCA cleartop ,And A NOS rca blackplate marked united on the box. I will have to find some cheap tubes on ebay. Right now, these tubes will have to hold me for say six months? I could see myself getting caught up in this and spending a lot of money!?!?No matter what amp I had.
What's that old saying ... "Welcome to Head-Fi, sorry about your wallet."

BTW, you might be better off with a recognized retailer instead of e-bay. Many, if not most, of the e-bay retailers don't test their tubes. Those that do are often selling used tubes, not NOS.

If you stay away from boutique (ample reasons listed in the previous post for the SOHA), most 12AU7's are less than $10. Almost all are less than $12. As stated many times, the 5963 is $4 at most places. Recognized tube vendors will give you as good - or better - deals than e-bay most of the time.

Antique Electronic Supply, Vaccum Tubes.Net, and the Tube Depot have very good deals - there are many others, such as Radio Electric Supply, VacuumTubesinc.com, etc. The best dealers will respond gradiously to your e-mail questions about various brands/construction of different tubes. I recently spent a few hours rummaging through the tube bins at Tube Depot:
Tube Depot in Person. I was shocked at how many really good, name-brand tubes they have available in types that are not judged "boutique".
post #15 of 37
Quote:
Originally Posted by headphonejunkie View Post
One thing I noticed about the rft is when I power up the amp it lights up for a second. The rca's I have do not do that.
I am not sure of the Eastern tubes but this is a characteristic of Euro tubes - noticed in many times on my Siemens tubes. Can't tell you why though. ( I also recall reading somewhere that the East German RFT's were sold as Telefunken?? don't quote me )and as for buying tubes, it is as much an addiction as buidling amps. As Tomb pointed out "welcome to head-fi......" , now you need to get a couple of Steinchen's buffers and really start having some fun ..dB
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