Hi Kornbread. PM me your name and home address. I have some NOS tubes I'll mail you.
12AX7 12AZ7 12AU7 12AT7
Some of them are labeled as "Admiral" brand, which was just a company that rebranded tubes from RCA, GE, Toshiba, Sylvania, Mullard, etc and sold to TV/audio repair men back in the 1950/60's. They are unused and most likely better than the new tubes produced by EH, JJ, TungSol, etc.
Interesting - thanks for the shootout. I wonder if that 12AT7 is on it's way out or if that's just the character of the tube? I have read guitarists sometimes drop one in a preamp stage to mellow out a Marshall, but thought it was just the amplification factor that was causing the change. I have never used the 12AX7 in a hifi application, but I may have to try some. I love the 12BH7 - seems to do most things right. Definitely one to try if you have the opportunity.
The holidays are officially over for me, back to work 4am sharp (probably be a while before I get a day off) and schoolwork continues, free time has come to a screeching halt.
Man that was nice having free time!!!
I will get to the 12ay7 (have to buy one, you recommend a certain brand?) eventually, don't know when. Don't trust me on what I 'think' I hear cause I don't trust me either. I'm no 'golden ear'. The 12at7 just felt right in the mids, bottom was week, top bit soft, background was blacker? but both tubes lacked the macro-dynamics and resolution the SS gear had but the tubes lacked the harshness. W/tubes you could hear further into the music and they sounded more right??? Odd.
John, not to disappoint, but it was whatever version Spotify had. Spotify keeps me entertained by cheaply allowing me to sample new music and gives a general feel for changes in the system. Then I'll listen to some old cd's on lossless flac>foobar>aune dac/pre, or in this case aune dac> tube pre to get a feel for the changes.
Tom, I've been doing a looooot of reading on these glowy things lately and eventually it always leads to a Marshall/Fender/Mesa cite. I don't know if those guitar guys are after the same things us audio guys are after.
Not sure what I was thinking - major brain fart! It won't work in that circuit at all. Heaters are 6.3v and B+ is way too high. But I do like the 6DJ8 and I have a bunch of them!
GE 12au7a. Not much time to do any real listening. Quick impression; it is more linear in frequency response, the highs are there and so are the lows, bass digs nicely, has a bit of slap to the bass, similar in sound to the 12ax7 but with less gain and what feels like a blacker background (lower noise?). I'll have to compare the ax7 and au7a more closely at some date. The 12at7 sounds a lot different that either of these. Bad or not, the 12at7 is the king of the mids.
Got the 12a_7 tubes Craig sent. Opened the box and bam ... a Mullard!
Thinking to myself that this Craig dude is one hell of a guy to be sending me a Mullard.
Opened the box to see what that baby looked like ...and it's an RCA clear top w/side getter ...
All kidding aside, thanks for the tubes Craig. It has taken a chunk out of my homework time, but I 'think' I have figured out what most of the Admiral branded tubes are except the 12ax7a. RCA, GE and Sylvania seem to be the predominate tube makers here but they're sooooo many variations. Tube id must be an art form.
That Mullard ... I mean RCA 12au7a sounds ok. Balanced more like the ax7; sounds fairly linear top to bottom, maybe pulls a bit more detail out of the mix, balanced a bit more towards top end?, backgrounds are still blacker than ax7, oddly it has good bottom but male vocals seem to have lost a little chestiness?
I think how a tube sounds can vary by application. I wasn’t nuts about the cleartops in my bravo headphone amp or the front end of my Primaluna PL4, but they sound incredible in the tube section of my Rogue Sphinx.
After listening to another 12at7, I think the first one, the one that did everything wrong except the beautiful middle, must be on the fritz. This one has some of the same characteristics; it's not as soft but still a tad soft on top, the deep bass feels lighter but not as light, and the middle is fine but nothing like the first one. Maybe that's the thing with tubes, they don't measure as well as a lot of good ss stuff but their distortion makes them sound more real to us?
I have had very little time to do any real listening so all of this could change given time to actually listen. On top of that, my old ears aren't what they use to be, not that they ever were, so take the eval at face value.
Sorry tajanes. Let me get some time on this at7 and I'll do the ay7 next.
@tajanes sorry but it looks like there is no 12ay7 in the bunch.
Sent a message and a link to the 4sUniversal pre info page, asking TubeDepot what 12**7 tube they recommended. Eric quickly responded that "bar-none" his favorite was the nos GE 12au7 and with no prompting, he also recommended almost the same mods as Craig; resistor changes moving the tube into a more linear area of its curve and moving the potentiometer to the input side. There 12au7's range from $399- $9.95, his recommended was $29. After this mod the preamp will be 12au7 only.
Dale resistors, Solen fast caps, Sprague 715 orange drop, Mullard (new produciton), GE and TungSol 12au7's, some 18ga. 'Aerospace Grade' wire, and a green jewel light to replace the nonfunctional ground lift switch.
My bum is sore, my eyes bloodshot, and my temper short. This class, corporate finance, is kicking me square in the knuts. Time for a short reprieve.
I have been saving the mods of placing the volume pot in the input side before the tube and swapping values of resistors (and quality) that PWRRYD and TubeDepot suggested until I have enough time to do everything at once. But I did have time to order another batch of cheap 12au7s' from TubeDepot.
I'll have a decent selection of low priced tubes to roll between this pre and a bravo headphone amp to get their feel.
In total, this makes about a dozen tubes to play with. It appears everyone has their take on how a 12au7 should be made. Every one of these budget tubes has a different internal structure.
It's funny that back in the day when I ran tube gear GE tubes were my least favorite although they were the easiest availability. I always went for the Telefunken , Mullard or Phillips tubes. Sylvania s were good too.
Finally got around to the mods Craig and Eric from https://www.tubedepot.com/ recommended. These mods are optimized for the 12au7 so the 4Suniversal preamp http://diyaudioprojects.com/Tubes/Universal-Tube-Preamplifier/ that can run about a half dozen 9 pin dual triodes, can now run only 12au7. .22uf Orange drops (was .47 Audyn) were recommended for their sound on the output (are these caps considered blocking caps?). The rest of the mods involved swapping out various resistor values, moving the volume pot from the output to the input side of the tube, and adding a 22uf f&t caps to increase gain. (cathode bypass?). Also ordered a few more cheap tubes to row.
@Tom_S since the volume pot now resides between J2 and R3, you mentioned R4 1m. resistor, is redundant and if the preamp was not connected to an amp, it would be easier on the tube if R4 was placed between C1 and J3. I kind of forgot. Is that ok or does that need to be corrected first?
Hooked it up to a chip amp and speakers. It does work. Worried about 288v and uneven heater circuits. No measurable difference between the cathode and plate vs plate to ground. Is this because of the bypass cap on the cathode?
Trying to learn how to do a loadline. If this is correct, isn't it pretty far off? 288v/(82,000ohm+1200ohm)=.00346=3.46ma
Messed up. That last load line chart is wrong. The 12ax7 plate current ranges from 0 - 3.5 ma and I assumed the 12au7 was similar and someone forgot to put a decimal point in the ma range. Nope. The 12au7 plate current goes to 35ma. The plate current requirements between tubes in a family are quite a bit different. The 12bh7 plate current goes to 50ma.
So the load lines look more like this ... fingers crossed no more mistakes.
Got some work to do. Craig suggested a 20k plate and 470Ω cathode resistor. Ordered a bunch of various sized resistors, but have no 20k. on hand right now. Can make a 30 or 24.2k so had to do some ciphering. 278/30k + 470Ω=9.1ma, 278/24.2k+470Ω=11.3ma with the cathode and plate load lines meeting between -2 and -4 volt grid lines. Scratching head, can it be moved just a bit to the right, should it, and how? 20k plate + 1k cathode give the 13.4 load line and the 1k cathode load line.
Cannot stand having a bunch of time on my hands and not being able to do anything.
Craig mentioned with the increased current to the plate, a 20k. plate resistor might get hot, if, the power supply can handle it. More than likely it will be sometime mid week before the assortment of resistors arrive since shipping is a little slow, but hey, I completely understand. That got me to worrying about just one ½ watt plate resistor, or adding another in series to get 30 or 24k. I was thinking about. Went digging and found more 82.5k. Dales so I simply paralleled that with the other 82.5k plate resistor already on there for 41.25k. and bonus for increased power handling. Left the 1.2k. cathode resistor alone, for now. That started moving the load lines in the right direction.
Take it with a grain of salt cause my ears are made of aluminum foil, but it's back. Man did that one small change make a big difference. Listening to the previous modifications was like forcing down a cold bowl of oatmeal with no milk, everything was just mush. Not entertaining at all. Now it's actually decent sounding. Not the most bestest and all that stuff, but much better than before. Spent about three hours in the trailer listening to Colter Wall, Krall, Nora Jones, and a potload of 80's ballads. It also mated well with the recent crossover alteration on the sadie (FaitalPro fe120/xt25) build. Not the latest or greatest in detail retrieval or bass, the very top is a bit shy, and at this time, staging could be better, but the vocals are definitely getting there. Fingers crossed that continuing to move that tube towards its happy spot yields more large scale improvements.
And the refreshments weren't bad either. Rum with a light initial taste, light body, and some flavor on the tail end blended with a light corn and rye whiskey which was on medium toasted, medium charred white oak at 120proof for two years. Things could have gotten interesting if they hadn't interrupted the listening session and drug me into the house for dinner.
Things may change after getting this circuit lined out but a quad of cheap 12au7 tubes got rolled, rowed, or whatever today. Definitely some differences between the same tube model and different brands/manufacturer, even among rebranded tubes from the same manufacturer. With a 5" driver, the Sadies are bass shy (need a good 8 or 10 bass bin) so no comment on real bass. All the tubes sounded good on vocals and portrayed a palpable stage between the speakers.
It appears there are currently 3 major tube manufactures which others like Mesa, Ruby, TAD, Groove Tubes, PM
Components, Valve Art, Peavy, Fender, and probably more, rebrand as their own.
In Sino China: Sino, Shuguang, Golden Dragon.
In Slovakia, JJ electronics: JJ and Telefunken.
Reflektor Corp. in Saratov, Russia: New Sensor, Electro Hormonix, Mullard and Tung Sol reissue, Sovtek, Genelax Gold Lion, and Svetlana.
Least favorite was the Slovakian JJ ecc82 $10. Images were a bit larger than life, diffuse comes to mind, but sounds that should have been unattached and outside the speakers never really unattached themselves. Perhaps a bit of whispiness to female voices and not as much chestiness to male vocals as I would have preferred. It almost completely lost some faint brush strokes on a cymbal. It struck me oddly that this tube's highest treble was rolled off while the lower/mid treble was a bit splashy.
The Electro Harmonix $13, and Tung Sol were the better imaging of the lot. The EH more precise in placement, the TS more diffuse. In Liability, the EH placed Lordesmack dab in center, in sharper focus, and just a touch in front of the other tubes. Sss were a bit highlighted, but like the JJ, the very top was rolled off, just not as much. Nora Jones sounded better through these than the JJ but her voice still lacked just a bit of weight.
I liked how the Tung Sol $22, tended to add some heft or bite to vocals. They sounded more gruffy and full. Lower/mid treble was still a bit splashy with the very top a bit rolled off kin to the EH, with neither the EH or TS being as rolled off at the very top as the JJ.
It is said that Reflektor bought the Mullard name with intentions of cashing in on the name and imitating the popular Mullard sound. No idea if they succeeded or not as I have never owned a 'real' one but the $23 Mullard was the smoothest of the quad. Sometimes I felt voices were a little further back in the mix while at other times they were more forward, but vocals were fuller, not chestier, just fuller and smoother. Treble was not as splashy as the others, and unlike the others, brushed cymbals were not lost in the mix. This preamp is not now, nor do I figure it ever will be for those wanting to hear everything in a recording but I could hear more stuff in the recording with the TS and yes, the smoother Mullard, than the other tubes. Really wanted to like this more 'refined' tube but its ability to place images was behind both the EH and TS and I preferred the grit the TS added to vocals, especially Nora Jones and Colter Wall's voice.
Still have another half dozen tubes to roll, row, or whatever; Sylvania 5963 $20 and GE $30 nos, and RCA side ghetter clear top, GE, and Daystrom Nichimen (rebranded Hitachi?) pulls from Tom.
The Sylvania is a nos 5963, which, as far as I can tell, is a 12au7 sub intended for long life in a computer. Feels odd thinking about tubes in a computer so here is a tubed calculator. Definitely not a pocket calculator!
Anyhow, bland comes to mind. It was not bright, nor to much bass, nor too much anything. Best way I can describe it is if you were sitting way back in the audience and everybody else was taller than you.
After that is the RCA clear top side ghetter. One of the several pulls that Tom was kind enough to send. As far as imaging, this tube is up there with the Electro and TungSol. Things are where they should be and I 'think' appropriately sized. While I feel this tube does good on both male and female voice and at first glance appears to pull information out of the treble range, if a recording or piece of gear is hot in the treble, this tube will show you. It's not bad at all, but, it's a bit harder to relax and just listen with this one. So far, I'd say these last two tubes are at opposing ends; way back in the audience or right there in your face.
For a $50 order, Mouser uprated shipping to next day air in order get a few cheap parts here on time. Color me impressed.
Bottom left corner are a couple flea sized Vishay ½watt 470k. resistors. A much larger brown ½watt 22.1k. Dale laying across them. A grey 2watt metal oxide Ohmite to the right of the tube with a pair of 12watt Brown Devil and 11watt Ohmite wirewound resistors flanking the power switch. Supposedly, wirewound is quieter and a resistor close to its wattage can be noisier. Craig mentioned the lighter resistors might get warm so they got upgraded.
After extended listening with multiple systems, I still enjoy this preamp's presentation, but am starting to notice how much information it may not present. Not the most revealing pre ever. An example would be Phil Collin's In The Air Tonight 2015 Remaster. At 2:13 there is a male voice adding some texture to Phil's voice, while this voice is easily distinguished from Phil's using the modded Bravo headamp and Grado phones, the only way I know it is there using the 4s on the Orgones or Sadies, is because I already know it's there. Although not as distinguishable as with the head setup, it is clearly there using the Aune pre on the main notakhanspire house system. Of course, the house amps are Acurus, the Sadies use the Carver 705x, and the Orgons use a Sure 300x2 t-amp so not exactly an apples to apples comparison.
I'll have to start swapping the Aune pre into the other systems and report back.
Can you hear the same difference with the 4s in front o the Bravo? Any other headphone amps that you could use to add more comparisons?
I really should mod my Bravo as well...
Haven't tried that.
Quick listen with the same phones, the Aune x1 dac/pre/head amp does pull this voice out of the mix even better, sounds 'cleaner?', upper mid/lower treble bit more forward, bass tighter less 'rubbery?', and to rehash some audiophile verbiage, the background is definitely darker ... but I still find the modded Bravo more enjoyable. You need to mod that Bravo.
Quickie impressions. YMMV, $.02, IMO, Objects in the rear view mirror are closet than they appear, etc..
4s vs Aune x1with the Orgons and t-amp using iphone 3s line-out.
Aune: tighter focus on images, sounds are more free of speakers, female vocals more wispy, bit more initial attack of note, slightly more emphasis on upper mid/lower treble, bit more extension on very top, midbass/bass interplay different not sure why.
4s: noticed female voice that was point your finger spot on is now larger and spread out yet some of the sounds that were totally free of the speakers are now hanging around the speakers, wispy female voice is fuller, bit less extension at the top, bass seems just as tight but something's different, upper mid/lower treble nice, upper treble sweet.
The Aune was slightly better at pulling the support singer @2:13 from the mix, but not by much. Have to wonder about the difference of using the iphone 3s line-out vs the computer usb>dac and if the iphone supports the same 320k as the computer, even though it is set to highest quality.
Largest differences between the two are imaging, the way they recreate female voice, bass/midbass interplay.
Comments
12AX7
12AZ7
12AU7
12AT7
Some of them are labeled as "Admiral" brand, which was just a company that rebranded tubes from RCA, GE, Toshiba, Sylvania, Mullard, etc and sold to TV/audio repair men back in the 1950/60's. They are unused and most likely better than the new tubes produced by EH, JJ, TungSol, etc.
Craig
I think how a tube sounds can vary by application. I wasn’t nuts about the cleartops in my bravo headphone amp or the front end of my Primaluna PL4, but they sound incredible in the tube section of my Rogue Sphinx.
After extended listening with multiple systems, I still enjoy this preamp's presentation, but am starting to notice how much information it may not present. Not the most revealing pre ever. An example would be Phil Collin's In The Air Tonight 2015 Remaster. At 2:13 there is a male voice adding some texture to Phil's voice, while this voice is easily distinguished from Phil's using the modded Bravo headamp and Grado phones, the only way I know it is there using the 4s on the Orgones or Sadies, is because I already know it's there. Although not as distinguishable as with the head setup, it is clearly there using the Aune pre on the main notakhanspire house system. Of course, the house amps are Acurus, the Sadies use the Carver 705x, and the Orgons use a Sure 300x2 t-amp so not exactly an apples to apples comparison.
I'll have to start swapping the Aune pre into the other systems and report back.
Can you hear the same difference with the 4s in front o the Bravo? Any other headphone amps that you could use to add more comparisons?
I really should mod my Bravo as well...
Haven't tried that.
Quick listen with the same phones, the Aune x1 dac/pre/head amp does pull this voice out of the mix even better, sounds 'cleaner?', upper mid/lower treble bit more forward, bass tighter less 'rubbery?', and to rehash some audiophile verbiage, the background is definitely darker ... but I still find the modded Bravo more enjoyable. You need to mod that Bravo.
Quickie impressions. YMMV, $.02, IMO, Objects in the rear view mirror are closet than they appear, etc..
4s vs Aune x1with the Orgons and t-amp using iphone 3s line-out.
Aune: tighter focus on images, sounds are more free of speakers, female vocals more wispy, bit more initial attack of note, slightly more emphasis on upper mid/lower treble, bit more extension on very top, midbass/bass interplay different not sure why.
4s: noticed female voice that was point your finger spot on is now larger and spread out yet some of the sounds that were totally free of the speakers are now hanging around the speakers, wispy female voice is fuller, bit less extension at the top, bass seems just as tight but something's different, upper mid/lower treble nice, upper treble sweet.
The Aune was slightly better at pulling the support singer @2:13 from the mix, but not by much. Have to wonder about the difference of using the iphone 3s line-out vs the computer usb>dac and if the iphone supports the same 320k as the computer, even though it is set to highest quality.
Largest differences between the two are imaging, the way they recreate female voice, bass/midbass interplay.