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In doing somw research for a tweeter amp it seems like 6V6 was very popular as a guitar amp tube and EL84's were the choice for HiFi amps. I realize 6V6's were widely used in HiFi too but not so much since the late 1940s. After that the choice seems to be EL84.Is the EL84 a better HiFi tube or stick with 6V6's?
Follow Ups:
I have had very good results with the 6V6 (in triode) for hi-fi. Haven't tried the 6BQ5, but it may be good as well. It's easier to drive, a little, and a pentode; so you can try various trix with the supressor.I would guess that 90% of it is in the design, implementation, development; you can probably get transcendent results with either of them.
In triode, of course. Gotta be triodes.
Aloha,
Poinz
I'm not as hung on using them in triode as Poinz. But go look at the plate curves of a 6V6 in triode. Gaaah! They're simply gorgeous!! Why this tube isn't used for audio more than it is boils down to the generalizations about "guitar" vs. "audio" tubes.Poinz and I definitely agree on something else too - the current crop of 6V6 is VERY good! The Tung-Sol reissues kill, and the EH are right there too.
Wander over to the Decware forum and read about "El-Cheapo". It BEGS for a bit more B+ and a nice pair of 6V6 Tung-Sols triode connected.
If you want to experiment with a pair of 6V6s that would be a great starting point. Of course Eric makes some killer stuff too, but if you need to watch the budget then check out "El-Cheapo". BTW, electrically 6AQ5 = 6V6 almost exactly.
We sure do agree on that. As far as I am concerned, they are the best 6V6 type ever made, with the EH not too far behind. Both these also have very low heater-cathode leakage, so they're very quiet; the best of the old tube I've heard, RCA and Bendix, were a lot hummier.Jim, the Machine started life as a DIY project, and still is:
Here's How A lot more of them have been built than bought, and it may in the end be a simpler project than El Cheapo, I dunno.
Best,
Poinz
Another crummy amp by Poinz! ;-)If you haven't looked yet, the El-Cheapo uses cathode bias and has a WAY overbuilt power supply, as well as a CCS for the phase inverter/driver. It also uses a 6AL5/diode hybrid bridge for the - supply for the CCS.
Eli and I wanted El-Cheapo to be scalable with just a change of iron and output tubes essentially. We think it would make the basis for a KILLER 7591A amp if the 6V6 can't make enough power for a particular person's needs. And of course, we wanted it to be CHEAP! The parts (other than the chassis, the iron and a few odds and ends) come to just over $100.00.
As well, we often used parts that I use in my kits since the economies of scale made the price competitive with lower grade parts.
All kidding aside, that's a darn nice amp you put together there!
The Machine is in some respects more complex than El Cheapo (170v negative supply, bias supply), and in other respects simpler (no current sources, no caps in the cathode circuits). I would expect that the parts costs would be about the same for equivalent quality.I'm thinking of some sort of sand discreet or chip CCS for the tail, and just build a mongo bias supply to provide for it and the tail; the tail supply has proven remarkably noninfluential to the sound, in my experimentation. As it is, the 5965s draw 3mA each (6mA for the whole amp), so a resistor and cheap toroid is viable. As we discussed privately, I'm eventually going to VHF single triodes for the front end, and they like 5-10mA each, so a very long tail becomes impractical. This is something I got to get after.
I'm not sure what the final design of EC is, Jim. The only place I knew of to reference it was a mongerously long thread over on the other forum, and I didn't have time to wade that far downstream. Is there a more practical way to have a look at it?
Aloha,
Poinz
Poinz,A link to the most current EC schematic is provided below.
At this time, the only change I'm considering is replacing the "Rat Shack" filament trafo with a Triad VPS241800. The Triad trafo's 2X 1.8 A/12 VAC secondaries would provide for both heater power and the B+ boost Jim McShane recommends. The VPS241800 comes with some "baggage": an extra pair of ferrite beads and a change in the 'AQ5 bias resistor value to 350 Ohms.
Eli D.
Speaking of trafo subs, what is the secondary voltage of the Allied 6K27VF used for B- supply?
Eli D.
I was hoping you'd show up here.Listen, if you want to put E C up as a DIY article, I have lots of space on my server, at your disposal. You (or somebody) will have to exposit a rational, um, exposition, and arrange schems and photos, and like that. I can help you. We can put it up on the 'Projects' side of the site. At least then I'll be able to chew on your ankles more efficiently.
:^)
Poinz
I was always under the impression that the 6V6 gets overlooked in modern gear because it was not used as often as EL84/ 7189's in vintage gear. Seems to me much of the retail tube audio market was quite derivative of the vintage market until just 5 or 6 six years ago (with some notable exceptions). In the DIY world, the 6V6 has a reputation for not doing much under 100Hz. I would suggest that this owes much to amp design and less to the tube, but a at least the vintage make tubes that I have heard can be a bit soft. I am told that the new makes actually sound better. All this said, in my view, the 6V6 has the best mid range of all the more common beam tubes and pentodes, even when the screen grid is not tied top the plate.Rodney
Hmmm, I hadn't heard that. Funny considering it was loved for a guitar amp. Anyhow my experiences are totally opposite. I think the 6V6 kicks serious ass on bass. I never spent much time using NOS tubes so maybe that is why. But still I found your comment interesting considering what my ears tell me.I always assumed it wasn't as popular since it has less power than the el84.
My amp did so good in the bass I was convinced I had a grid choke/coupling cap problem. But when I finally got around to measuring it the sucker was close to ruler flat. Results are posted on diy tube. Search for "Voltage measurements on amp with grid chokes " if you are interested.
Russ
the vintage amps and tubes than the tube make itself. I cna I should not repeat the "reputation" of the tube, as it really has less to do with my experience and more the comments of "others" with whom I have spoken regarding output tubes for DIY. That said, my most extensive experience came from some Radio Craftsmen amps (with RCA ouptut tubes) which sounded quite beautiful in the mids, but I must admit were a bit soft on the low end. Yet, I would never build an amp with that circuit or power supply, so it is not surprising that 6V6 amps with more robust power supplies and better circuits sound better. Moreover, given what I heard to this point from that tube...Rodney
The hi-fi guys would have liked the 6BQ because it was easier to drive and physically small. By that time, they were seriously cheaping out on their mid-market gear, and you can build a nice compact little amp with pentode EL84s, driven by a single stage from line level, and advertise it as a 35w piece. I started doing this stuff gleaning iron and other parts from old receivers and amps, and so many corners were cut in the design and implementation of those later low-line pieces it's amazing.I first heard 6V6s in a guitar amp, and that's why I decided to use it. I think the guitar guys liked them because they're rugged. That said, the iron for my first example Machine was from a Harmon Kardon hi-fi receiver. Lousy iron, by the way; output transformers about the size of a ST-70 choke.
An interesting point about the bass, I hadn't heard that; I just a few weeks ago measured the first new-iteration commercial Machine, and it's 1dB down at 10Hz, so there's definitely no problem with bass capability in the device, if the other circuit components are up to snuff.
Aloha,
Poinz
and are reported to sound the same. But I have run inot the "bass" remarks from a few, often hedged by "but I have not heard an all out design." Perhaps some of this is due to the vintage tubes and their ample midrange energy... or vintage "cheap skate" iron...I think it was a "Voice of Music" or similiar amp that got me hip to 6V6s. I actually have a pretty large collection of vintage tubes. Perhaps one day I will get around to building something for them.
Rodney
I will sometimes install 6V6's in my AES Superamp wired for triode operation. They sound very good but slightly underpowered compared to the other tubes it can use.
Poinz,I'm with you. The 6V6 and its "equivalents" are more linear than other 12 W. types when wired as triodes. Harman/Kardon built PLENTY of units that used the 'V6 in pentode mode and they functioned well. The 'V6 and "equivalents" are GOOD HIFI tubes. 12 W. multi-grid power O/P tubes, as a class, are pretty darn special.
Unlike like its big brother, the EL34, the EL84's suppressor grid is hard wired to the cathode internally. So, "games" are not possible.
Eli D.
Too bad. The discreetness (is that a word?) of the suppressor in the EL34 allows various options in triode:wire to the cathode, normally,
wire to the plate (in my case so far, directly),
wire to the screen, which is wired to the plate, through any of several resistor/diode/zener combinations. This is an avenue of considerable experimentation, which I am just now undertaking on an EL34 dedicated Machine, to be attached to the tail of a similarly dedicated Mœbius. The hard supressor connection is a disappointment, but has not proven to be a killing disadvantage in beam tubes like the 6V6, so there we go. Onward.
Howzit, Eli?
Poinz
Check out Poinz' creation. You'll find him regularly at the tube diy forum.
Much better than the old one. No ads, much more recent data, lots of stuff. Thanks for the reference.
AudioTropic.net Aloha,
Poinz
It's actually on a finished chassis. I need three however for my tube LCR theater system. I also need three KT88 units for the mids but that's anothet discussion.Your design works just as advertised but I want to try some others as well. What about a tuce CCS in place of that 25K cathode resistor? I'll try that tonight with an EF86.
Gus
Try everything.I haven't used a CCS on the tail of the input amp because the 5965 only needs ~3mA/device (6mA/amp) to hit the sweet spot, so a resistor works fine, and is simple. I'm now looking at improved devices for the front end that need 5/10mA/device to rock'n'roll, so a CCS is looking much more attractive to me, as well as ultimately simpler (I can just build the bias supply from Hell, and use it for the tail supply too). I'm not sure the CCS needs to be tube, I have tried several types of resistor, from dirty ol' metal oxides to fab Kiwames in the tail, and could hear no difference whatever , so maybe a pretty quiet chip or discreet sand CCS would be 'jus' as mo'bettah'.
There are places in this circuit that are critical, the tail supply/implementation has proven, so far, to be not one of them.
Mahalo,
Poinz
I was measuring 6.2ma at the 5965 cathodes. No measurable distortion difference between the CCS and the 25K resistor. I was using a 6AU6 and I also regulated the -140 at 150v with an 0A2.Now I really need to get rid of that -150v supply. Reason I am tapping bias voltage from it and the drop to 32volts is too great. I want to keep it at two power tranneys. So tonights test is a solid state CCS using a pair of 2n2222 and an LED fed with -12v. This way I can have a more reasonable bias supply that also feeds the CCS.
I considered regulating the +300 to the 5965 plate loads but with a CCS in the cathodes, it makes little sense, don't you think?
Gus
Gus,One of the reasons we went with self bias in "El Cheapo" was to avoid the hassle of adjusting both CCSes and bias.
Can you "goose" your B+ rail voltage up some? If so, changing from "fixed" to self bias might be beneficial.
Eli D.
it's all in the implementation of whichever tube you decide to use. 6V6 can sound amazing in the right circuit.roN
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