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Performing DIY tube amps or tweaking an existing amp requires careful selection of tubes for peak performance. Although tubes vary regarding the sonic signature in different circuits, I believe a list of known great performers has value here for new DIYers.
My favorites are:
Sylvania 6SN7GTA 'Y' plate- Great value, lower cost in the GTA series.
Tung Sol 6P5GT/76- Very linear tube in a preamp & the Tung Sol is a stellar performer.
GE 6BQ5/EL84- Great audio tube always perfomed well. Much prefer GE brand.
6V6GT- Various brands. Perhaps one of the best for triode connected amps without the seperate filament transformer requirement of a real triode tube.
2A3 or 6A3- Various brands. A very good sounding triode and more power output than a 45 tube.
Amperex E80CC/6085. Great replacement in vintage amps were a lowly 12AU7 exists and a socket change to 6SN7 is too space restricted. I find the 12DW7 a poor performer and usually a cascode E80CC still has enough gain to replace it.
Mullard EZ81/6CA4. Great sounding rectifier that has high enough current capacity for PP EL84 amps.
Mullard EZ80. Lower output current version of a EZ81. Same sonic signature of the Mullard EZ81. Great tube for preamps or even a SE EL84 or 6AQ5.
Mullard GZ34. Excellent for amplifiers that produce more power than EL84 amps.
RCA 5U4G or Tung Sol 5U4GB- Both are excellent tubes in the 5U4 design.
Sylvania 5R4GYB- Best sounding in my tests. Excellent for higher voltage B+. RCA 5R4G are also very good in the larger glass.
Mullard 12AX7 long plate. One of the best sounding 12AX7s ever.
Brimar 13D5. If 12AU7 must be used, this is the best sounding 12AU7 I heard. Newver heard Mullard 'box plate' types that are likely a good replacement.
Raytheon 6CG7 black plate with center shield. Best of this family of tubes per my tests.
As for FM tuner tubes:
Like an amplifier, quality tuners require best tubes. The problem with tuners are the much more complicated circuits compared to a rather simple audio amplifier. It requires a lot of experience to modify a tuner and most do not have that experience. Another issue is alignment. The final step in alignment after instrumentation is that 1-2 degree tweak on the I.F. cans.
The statement 'when in doubt, use RCA' is so true in tuners per my experience. I find RCA outperforms any Mullard, GE & Sylvania in the common 6BA6, 6AU6 & 6BE6 group in a high performance FM tuner. The 6BE6 is an AM frequency band converter tube, so if one has a new tube other than RCA, use it. Some exceptions to RCA are the Mullard 6AL5 & Tung Sol 6AL5. A modified for peak performance tuner will easily determine the best 6AL5- no kidding as you will not hear a difference in most stock tuners. As for that common 6AQ8/ECC85 RF amp tube, Telefunken is the best period.
Feel free to add to the list above as I am more of a low power amp nut.
Follow Ups:
6EA7/6EM7's...
And anything with thoriated tungsten filaments :)
Outputs
45
2a3
300b
Outputs if you don't mind DIY high voltage
845
211
813
Drivers
10Y
71A
46
Input tubes
26
201A
Cheap alternatives - these will make a stonkingly good amp VERY cheaply.
Outputs
813 low voltage
845 Chinese - low voltage
2a3 Chinese
Drivers
31
Input tubes
3a5
Andy,
I know that you STRONGLY favor DH types. However, triode wired 6V6 family tubes are stunningly linear and also easy to drive. Power O/P is slightly less than a 2A3 delivers.
Being in "Old Blighty", you might be able to source Mullard made EL90s. Try those with your favorite DH driver. You might get a very pleasant surprise.
Eli D.
I know that you STRONGLY favor DH types.> >
Hi Eli! Don't worry, I get flak from all my fellow tube users except the two others I know that won't touch indirectly heated tubes. But the thing is this - I've been using an all-DHT setup for nearly 2 years now. Every now and then I put in an indirectly heated amp or preamp or such. Now, every time I feel I lose that ultimate transparency. There's just a subtle thickening and rounding of the tone. The zing goes out of cymbals, the breathy intake out of singers. That's as best as I can describe it - just a rounding and thickening of the tone.
Now, what most tube builders do is the opposite - they start with indirectly heated tubes and then stick in a 45 or 2a3 and say "mmmm - that's nice" Maybe you can only hear the effect if your normal system is all-DHT and then you switch IN the indirectly heated tubes?
> > However, triode wired 6V6 family tubes are stunningly linear and also easy to drive. Power O/P is slightly less than a 2A3 delivers.> >
The last amp I built before my DHT period was PPP 6V6, actually 7C5s. At the time I thought it sounded great. Haven't revisited that amp, since I sold it. I actually think it may be more important to use DHT small tubes, so might look again at 7C5 outputs. Very easy to drive as you say.
> > Being in "Old Blighty", you might be able to source Mullard made EL90s. Try those with your favorite DH driver. You might get a very pleasant surprise.> >
I fear I'm out of indirectly heated tubes. I've stockpiled about 100 of 10Y and 24 of 813, so I think that's the driver and output of the future - thoriated filaments!!! Nice!!! Should take me well into retirement turning out prototypes of those with different iron and input tubes. Though I still have the odd quad of 300b and 845 to use up for variety. I felt 813 was going up in price so I bagged some, same with 10Y. Haven't used the 813 yet - hope it sounds as good as people say!
Andy
Dude,
You are overlooking a valuble resource, NOS Locktal based tubes. The 7Z4 will go where a 6V4/EZ80 goes. The 7Y4 goes where a 6X4 goes. The 7N7 is electrically equivalent to the 6SN7. The 7F7 is electrically equivalent to the 6SL7. The 7AF7 is another terrific medium mu twin triode, with a smaller heater draw than the 6SN7 family. The "14" series Locktals, with their "12" V. heaters, are even less costly than the "7" series tubes.
I fully agree with your assessment of the 6V6, in triode mode. The entire family: Octal, Loctal, Noval, and 7 pin mini tubes are a superb resource. Aside from the NOS, New Sensor offers 2 FINE current production 6V6 varieties, that carry the EH and TungSol labels. BTW, the 6V6 family is highly satisfactory in UL and pentode modes, as well as triode mode.
Eli D.
Yep, My PP 300B, 45, etc, sit quietly while I amaze myself at what the 6v6 in triode offers with a cool driver. While I am sure 1w is pushing it in my system now, it has been a month or so & really don't turn the dang thing off. 27 as driver & 3/4 done with a IT coupled version that has Hashimoto H-20-7U installed & awaiting O'Netics level II from Bud P, for the IT. Into some modded JBL SR4725's. The RC version has the best electric guitar tone I have ever heard. I feel I might have broke free from 300B etc....I'll be bringing this simple little amp to VSAC next year & run it without embarrassment.
J & G
Hi Eli,
I would like to ask who currently makes a good 6V6 amp. You guys have my interest up. Thanks.
Search for Poindexter.
His amp is supposed to be not just a great 6V6 amps, but one of the better amps around (in ANY kind of a reasonable price range).
I built a variation of the music machine. I changed the input tube to a Sylvania 6SN7. My version used four inexpensive PPP 6AQ5 per channel for about 10 watts output with 280 volts on the 6AQ5 plates or a little over spec.
> > I would like to ask who currently makes a good 6V6 amp. < <
Poindexter's "Musical Machine" is a very serious assault on "state of the art" performance. If you have the requisite coin of the realm, build a "Machine" yourself or commission Poinz to do it for you.
A much more budget conscious design is "El Cheapo". EC yields lots of good sound, for surprisingly little money. Are you ready to "sling" solder? :> ))
Eli D.
Old 1940s era 7C5 are a great option for 6V6GT tubes that can be expensive.
Screen grid fragility makes the 7C5 awfully close to the 6AQ5.
Google El Leako to see a Leak Stereo 20 converted into an "El Cheapo" style amp. SHiFTY did some very nice work. He used 7C5s as the O/P tubes. ;> )
Eli D.
Google El Leako to see a Leak Stereo 20 converted into an "El Cheapo" style amp. SHiFTY did some very nice work. He used 7C5s as the O/P tubes. ;> ) > >
I tried to find a picture, but no luck. You can do a lot with a Stereo 20 - mine has PPP 6S4 outputs and an ECC40 driver!! Next one will go all-DHT. May use 1624 outputs for that, but you really need something thinner to fit the chassis. Maybe 7C5 outputs and 3a5 in. That should be tasty, but would need a preamp.
Andy,
SHiFTY posted some pictures in the "El Cheapo" saga. A direct link is provided below. Notice the "gorilla" of a filter choke that was added to the OEM "iron" set. IIRC, our "Kiwi" friend also posted photos over on DIY Audio.
The low mu and low gm of the 3A5 argue against it being used as a LTP. However, the amount of loop NFB needed here is low. Linearizing the O/P trafo is the principal target. Perhaps Williamson style circuitry using the 3A5 after the "concertina" phase splitter is indicated. You're the expert on DH types, not me. Is there a good sounding single, modest mu, small signal DHT in your "pile"? I'm thinking of a strange, but likely palatable, "cocktail". DHT voltage gain DC coupled to a (SIC) ZVN0545A "split load" phase splitter holds the bottle count down to a reasonable level.
Eli D.
Notice the "gorilla" of a filter choke that was added to the OEM "iron" set. > > >
Absolutely gross - destroys the look. Yuk!
<>
I don't use loop feedback.
<>
Morgan Jones has a clever rewiring scheme for the OPT to make it sound better - hard wires the secondaries for 4 ohms.
< < < Perhaps Williamson style circuitry using the 3A5 after the "concertina" phase splitter is indicated.> >
I like to have a balanced in option, so I use a diff pair with CCS under it. I use the ECC40 if I need more gain and only have room for one stage, or I rely on some gain in the preamp if I just use DHTs.
< < You're the expert on DH types, not me. Is there a good sounding single, modest mu, small signal DHT in your "pile"? I'm thinking of a strange, but likely palatable, "cocktail". DHT voltage gain DC coupled to a (SIC) ZVN0545A "split load" phase splitter holds the bottle count down to a reasonable level.> >
Not really - there are a few DHTs with higher gain but the plate resistance gets silly - see 1H5, 3a/142A, 3a/108, DC80, 826, 1G6G. No - the thing to do is just use three stages in the amp, like 01A, 10Y, 300b. It's a predictable combination but it sure as hell works! Andy
I did not know that about 7C5 marginal screens. I have run trioded 7C5s fairly hard with 340 volts plate & 35 ma plate current. I did not see a glowing screen as I always take a peek inside power tubes. Perhaps the difficult angle prevented that on the 7C5 due to large top getter.
I am a complete 6v6 triode convert in my amps
27
26
Both of thesse 2 as drivers in flea 2 stagers are magic
Agree on the 6CG7 & E80cc
I also really think a lowley 6l6G has all I would ever need in a 2 stager amp. My 300B PPP amp will not get re-tubed. I can build a equally or better amp for almost the price of re-tube.
I did just go all out on a 27/6v6 strapped amp with Hashimoto H-20-7U OT's & O-Netics Level II IT's. All for the glory of a wappin 1w, but the RC version I have now is the best I have ever heard in small wattage amp DHT of not. Never would have thought. PS is huge & seperate, & just the way I like em.
10 is a special tube for DIY but getting stupid expensive & no way to justify cost in my world.
J & G
I suspected it was, thanks for the confirmation.
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