EL84 and 12AX7 Options
- Thread starter sKiZo
- Start date
sKiZo
Hates received: 92644 43.20°N 85.50°W
Another neet feature on the amp ... you can still find information on it!
Got me a nice tasty copy of the original build manual with all the test voltages, troubleshooting, and evarthang!!
PS ... I'm thinking an SV83 would get pushed pretty hard in this rig, and not all that sure it'd be stable in this configuration. As mentioned earlier, these lil beasties do NOT like to be modded.
Got me a nice tasty copy of the original build manual with all the test voltages, troubleshooting, and evarthang!!
PS ... I'm thinking an SV83 would get pushed pretty hard in this rig, and not all that sure it'd be stable in this configuration. As mentioned earlier, these lil beasties do NOT like to be modded.
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sKiZo
Hates received: 92644 43.20°N 85.50°W
Well ... just pulled the trigger and went with these.
The biggest issue with these amps is microphonics, and these get great reviews for that. The Sovtek is also spiral wound - highly recommended in the first stage. It shouldn't have any issues with the required tube shield either, unlike the TAD 7025's - those have thick glass and could be a tight fit.
The 7025-WA's are supposed to be a 12AX7 on steroids ... higher gain with a full midrange and smooth top to bottom. Guess I'll see.
And ya ... yall talked me into the TAD power tubes. If nothing else all the exposed logos will match! ;-}
The biggest issue with these amps is microphonics, and these get great reviews for that. The Sovtek is also spiral wound - highly recommended in the first stage. It shouldn't have any issues with the required tube shield either, unlike the TAD 7025's - those have thick glass and could be a tight fit.
The 7025-WA's are supposed to be a 12AX7 on steroids ... higher gain with a full midrange and smooth top to bottom. Guess I'll see.
And ya ... yall talked me into the TAD power tubes. If nothing else all the exposed logos will match! ;-}
jaymanaa
RIP 1961-2018
Well ... just pulled the trigger and went with these.
The biggest issue with these amps is microphonics, and these get great reviews for that. The Sovtek is also spiral wound - highly recommended in the first stage. It shouldn't have any issues with the required tube shield either, unlike the TAD 7025's - those have thick glass and could be a tight fit.
The 7025-WA's are supposed to be a 12AX7 on steroids ... higher gain with a full midrange and smooth top to bottom. Guess I'll see.
And ya ... yall talked me into the TAD power tubes. If nothing else all the exposed logos will match! ;-}
7025 indicates spiral filament low noise tube, the "W" is for vibration resistant, and the "A" is controlled warm up time (11 seconds). Gain should be same as 12AX7.
Yes, transistor regulator, I'll post the schematic soon as I can find it, it's on my other computer. It works great, and can be built adjustable or fixed voltage out. And the voltage out is super clean, a great spot to take your phono voltage from too. I use a 1N4007 diode at the take off when I do that.
sKiZo
Hates received: 92644 43.20°N 85.50°W
So, did I do good?
On the regulator, be interesting to see if it's something that would be easily reversed if necessary. I'm a bit wary about damaging the iron ... the PT on these things is apparently some serious weirdness and almost impossible to find replacements for. I may just err on the side of caution there.
PS ... I still expect the Sovtek was a good choice in the shielded socket, as the TADs do have that thicker glass that can be a tight squeeze ...
On the regulator, be interesting to see if it's something that would be easily reversed if necessary. I'm a bit wary about damaging the iron ... the PT on these things is apparently some serious weirdness and almost impossible to find replacements for. I may just err on the side of caution there.
PS ... I still expect the Sovtek was a good choice in the shielded socket, as the TADs do have that thicker glass that can be a tight squeeze ...
SoundOfSound
Super Member
Whenever I suggest a tube I always get shot down by someone who's had a bad experience with them so my recommandation : if you buy re-branded tubes such as Groove Tubes or Ruby make sure you know what brand you're actually getting. These folks generally buy tubes and test them and match them where needed than charge you a bit extra for their work. Make sure you're getting a decent brand before you hit the BUY button. BTW, I'm quite happy with my 12AX7 and EL84 JJ's.
sKiZo
Hates received: 92644 43.20°N 85.50°W
Yeah ... like TAD's a brand, eh. <G>
From what I understand, they're built by Shuguang to TAD's specs, and TAD also does final QC and selection before branding them. It's the little design tweaks that make them special.
Nothing new really ... even RCA sourced out half their catalog.
Fun fact ... the standard EL84 is 20mm diameter. The EL84STR is 22.5 mm. Internal envelope is the same ... The difference is in the glass.
PS ... off topic, but I see TAD also has a 12BH7A-STR in the lineup now. Build is similar to the vaunted RCA black plates. I may have to get me some of those for the Latino ...
From what I understand, they're built by Shuguang to TAD's specs, and TAD also does final QC and selection before branding them. It's the little design tweaks that make them special.
Nothing new really ... even RCA sourced out half their catalog.
Fun fact ... the standard EL84 is 20mm diameter. The EL84STR is 22.5 mm. Internal envelope is the same ... The difference is in the glass.
PS ... off topic, but I see TAD also has a 12BH7A-STR in the lineup now. Build is similar to the vaunted RCA black plates. I may have to get me some of those for the Latino ...
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PR Audio
Super Member
Yup ...
I'll post back with the results, but I'm prepared to be amazed ...
Nice...As previously mentioned in other posts, I rolled various EL84 in my Heathkit SA-2, but in my SA-2 and my ears, nothing like the sound of the STR's.
I miss that SA-2, my current CJ MV75 had EI KT90, now has EH KT90, and though more powerful and sounds nicer than my SS amps and receivers, the SA-2 with EL84-STR simply had a "magic" in its sound that made it more enjoyable. We tend to use words like magic, sweet, warm, luscious, etc. and sounds weird and kind of stupid at first, but once you hear it you recognize it and can relate.
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Tom Bombadil
AK Member
When I've researched EL84s across the web, this is what I always find too. There are always posts declaring that whatever tube you are leaning toward, is the worst tube they tried.
Plus this is an area where the opinions of guitar amp users can be very different from those of audio amp users.
My Cary SLA-30 uses 8 EL84/6BQ5 tubes. If I had to retube it right now, I'm not sure what I would go with. But it likely wouldn't be one of the highly recommended NOS tubes as that could cost me $500+.
jaymanaa
RIP 1961-2018
I wonder if there are any truly matched octets left of a lot of the higher end EL84s? I would think it would take a whole bunch of say RCA solid getter 6BQ5s to make a truly matched octet. Not saying your amp requires matched, as I'm not familiar with it, just thinking out loud. I put together a "fairly" matched quad of real GEC KT77s a few years ago, and it was a lot of work, and a lot of money. I hate to admit it, but now I don't even run them because other tubes are plenty good for my old ears.
sKiZo
Hates received: 92644 43.20°N 85.50°W
That Leslie I mentioned earlier has been relisted. Supposed to be an original octet of RCAs in it. For the money, might be worth it just for the tubes?
http://www.ebay.com/itm/leslie-tube...189-4-12AU7-tubes-all-usa-made-/321828352100?
http://www.ebay.com/itm/leslie-tube...189-4-12AU7-tubes-all-usa-made-/321828352100?
Tom Bombadil
AK Member
Might be.
Right now I'm running a matched octet of pre-war EI EL84s which have less than 100 hours on them. And have a matched octet of Made in West Germany tubes which were rebranded but tested well. Not sure who made them. May try to figure that out at some point. Got those from Upscale Audio several years ago. Still NIB. So I think I'm set for many years.
thedelihaus
Nocturnal transmissions
Really appreciating this thread. I have grabbed a few 6U8a, 6678 and ECF82s (and two pair GB-1252s) for an AudioDon restored Dynaco A-70 and will start eyeing the rectifier tubes and output tubes next.
Currently have 6CA7s but wouldn't mind a few spare sets of tubes for future use- KT-77s and possibly some EL-34s.
Currently have 6CA7s but wouldn't mind a few spare sets of tubes for future use- KT-77s and possibly some EL-34s.
jaymanaa
RIP 1961-2018
I've been very happy with a pair of Orange Globe Amperex 6U8As in a 433 on my test bench. I'll see if I can figure out who made them. They took a little "edge" off the top of what I can hear, making the amp more fun to listen to.
Tom Bombadil
AK Member
I recently did a lot of research on 6CA7 / KT-77 tubes. Read many, many opinions and reviews. Had a thread here.
I found a lot of positive feedback on some current tubes. Opinions tended to be very good for the Electro Harmonix 6CA7EH, which run about $20 a tube. Opinions were very, very good for the current Genalex KT-77s, which run around $45/tube. And several people said good things about the JJ KT-77, which is cheaper than the Gen.
However I ended up purchasing several slightly used 1970s GE 6CA7 big bottles, which I were able to find for $30/tube. I already had a duet of them, so I was leaning that way. They do sound beautiful.
The EH 6CA7s may be one of the best buys out there, of the current tubes. $80 for a matched quad. That's only $13 in 1970 dollars.
thedelihaus
Nocturnal transmissions
Thank you- I bookmarked that thread and followed it with earnest.
Your GE 6CA7 deal- so very nice.
I currently have Sylvania fat bottle 6CA7s now. Any further purchase is for future use and backup.