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I am looking to build a 6V6 SE amp but I wasn't able to use this chassis I already have lying around. It is a bit too small for the entire amp with power supply on the same chassis. Thoughts on building it as I always do when I build a preamp. The power supply on a separate chassis.
Thanks!
Follow Ups:
I'm so happy with my PSE 4P1L amp I haven't built anything in 2 years. Stocked up on the tube when they were cheap. But I use filament bias, and that's more complex in terms of power supplies - certainly a 2 chassis job. I simplify the filament supplies by using Thurlby Thandar 30v 2A bench supplies - get them cheap on ebay and they sound great into Rod Coleman's filament boards.
The triode 6V6 is similar to the 4P1L in terms of gain and power. You could use them in PSE for instance. But what you can do fairly painlessly is use a 4P1L driver stage in filament bias. With sensitive speakers and 2v in from a DAC or similar then 2 stages should be enough - it is for me with Mark Audio Alpair 10s and a 2v ES9023 DAC running off batteries off my Mac Mini.
I use LL1660/25mA interstage but the Hammond 126 is also pretty good - lacks the last level of detail but good sound and bifilar wound. I have the C model at 15mA but the B model at 30mA would probably be better for a 4P1L.
With DHTs and filament bias you don't need the cathode bypass cap, and since I loathe them that's enough motivation for me. With 6V6 you'd have to choose between a cathode bypass cap and fixed bias. Since I didn't fancy either I used 4P1Ls in the output. But the 6V6 is a decent sounding tube - not a DHT but OK for what it is, and the good thing is the gain of around 10 allows you to use 2 stages.
I have never had a problem making an amplifier DEAD quiet {learned over time through proper implementation and grounding schemes with due credit to Will Vincent}. My speakers are Khorn bass bins with JBL 2360/2445 compression drivers 2 way set up with sensitivity around 104 db.
Love the sound of 6V6 and the ones I built were mono-block triode wired and took the form of 6005 tubes {electrically identical to 6V6 but can't handle quite as high voltage} I would identify with separating the power supply for a phone stage, maybe even a pre-amp; but even my SETs are dead quiet with hiss only heard about 12 inches away from the 31 inch square Horn. Since 10 watts will part your hair, don't need much power.
The Mind has No Firewall~ U.S. Army War College.
Here is my little 6V6 amp. Chassis is about 12X10 and it is silent.
6V6 amps get away with small iron.
I built an amplifier of this type some years ago. It consists of two mono amps and two separate power supplies (including power transformers) on one chassis. Each channel uses a 6X5 rectifier, EF86 preamp and 6V6 output. The EF86 and 6V6 both operate as pentodes. I believe the output power is about four watts per channel. THD and IM are very respectable.
I tried a number of other combinations along the way, including a 12AX7 front end (didn't like the sound) and several other pentode outputs, as well as 6V6 in triode (not enough power for my speakers). I settled on the EF86/6V6 pentode as being the only combination capable of producing the magic I was looking for. The 6BQ5 would probably do as well, but I wanted the octal for esthetics. The sound quality of this amp greatly exceeded my expectations, and I ended up using it as a primary amplifier. It's particularly revealing with my Grado headphones. The two together have a significant synergy, and the result is easily the equal of many systems costing north of five figures. In fact, it was this system that led me down the road to ruin, staying up until all hours of the night. I just can't get enough of this sound...
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Buy Chinese. Bury freedom.
I know what you mean. I just bought a Citation V amp from a guy Don Sachs and I am in the same dilemma. Can't shut it off!
If you use pentode mode, the 6V6 has rather high distortion - 8% to 12%, according to the RCA specs. That pretty much means that feed back is a must. I haven't found any specs on distortion in triode mode, so that is an unknown. The plate resistance is triode mode (1960 Ohms) is reasonably low, however.
A DHT triode (45, 46, or 2A3) will give you better performance. That said, 45s are crazy expensive, 46 are becoming more popular and therefore more expensive, and 2A3s are approaching the cost of mid grade 300Bs. I'm in the design stage for a flea power headphone amp, and am toying with the idea of using a 12B4A, which has an Rp of 1030 Ohms.
Good luck with your project.
DHT's. Just want a simple amp. Other suggestions would be nice!
O.K. Getting back to your original question, I usually separate the power supply from the amp using separate chassis, and interconnect them with a cable of less then 3 feet in length. Unless you can find a magnetically shielded power transformer, the fields around it can couple into other components (e.g., output and interstage transformers). I've done it both ways, but prefer separate chassis. I built a stereo amp with separate power transformers\chokes for each channel on a single large chassis. It weighed a ton and got really hot.
The speakers you settle on have an ENORMOUS influence on everything else.
I gave you some ideas for a no GNFB triode wired design. It will sound fine, but 2 WPC is all there is. If you employ speakers whose sensitivity is in the 94 to 96 dB. range, look to a full pentode setup that uses regulated g2 B+ and employs both Schade and global NFB. The bulk of the NFB should be in the short, Schade, loop. Only a few dB. will be needed in the outer, global, loop.
Whenever GNFB is employed, use a 1 pole high pass filter that "corners" in the 15 to 18 Hz. range, to gain protection against O/P trafo core saturation. Suppress infrasonic trash! Also, employ high gm small signal types. High gm provides resistance to HF error correction signal induced slew limiting.
Eli D.
I built a push-pull 6V6 ultralinear amp with used Dynaco Z-565 outputs and a single, current-sourced, long-tail differential 6SL7 driver. I used some 0.22uF Facon paper-in-oil coupling capacitors.
There's barely enough excess gain to provide any negative feedback. The amplifier has a nice midrange but sounds pretty shut-in. I might try changing to poly coupling caps to see if it opens up a bit. The amp makes about 11 Watts per channel.
This was a junkbox project and I've never tried to optimize it. It was supposed to be a loose adaptation of Poindexter's "Musical Machine."
IMHO, not really a success. Listenable, but not extraordinary. I know, not what you were looking for, but sometimes it's good to have a data point, even if it's not a positive one.
I think adding another stage of gain would lower the distortion and give a more incisive sound. If you're going to run almost pure open-loop, you probably want a very linear output stage. And a more robust driver tube.
LOL.
-Henry
Henry, that's a very clean layout. A shame to see it sitting idle just because the first rendition didn't wake up. Have you made basic measurements like frequency response and the like? Much as I like octals, I believe 6BQ5s produce better dynamics than 6V6 in PP designs. Can't prove that, it's just my gut feel after years of hearing both.
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Buy Chinese. Bury freedom.
Thanks. The amps haven't gone to waste. I sold them to my friend, Bryan who was using them in his system which is notably more high-end than mine. About a year ago I brought my new solid-state amplifier over to his house and it sounded so much better I took pity on him and gave it to him on semi-permanent loan. I use the tube amps to watch movies on my TV.
The amps aren't horrible, they just don't have that "sparkle" or "see-through transparency" of the solid-state amp.
-Henry
Mikey
The 12B4A are nice tubes but
6AH4 and 6EM7 are better sounding.
DanL
Short of #45 DHTs, triode wired 6V6 family tubes are the best bet in this power range, for GOOD sound. Obviously, highly efficient speakers are needed, when approx. 2 WPC is the power yield.
A 12AV7 or 5965 will provide all the drive needed in a RC coupled setup.
If the OP includes substantial amounts of reservoir capacitance on the amp's chassis, along with using a shielded umbilical between the chassis pair, I don't have objections to separating the amp from the power "iron", rectifiers, and some filtering elements.
BTW, a good performing, low cost, B+ PSU for the project, can be built around a Triad N-68X isolation transformer and a pair of Cree C3D02060F 600 PIV Schottky diodes. "Full wave" doubler topology would be employed working into very substantial stack capacitance, a "hash" filter, an "ordinary" filter choke, and reservoir capacitance.
Eli D.
I agree with Eli. 6V6 plate curves look great in triode connected.
Two immediate thoughts for you to consider.
(1) Don't do a SE 6V6, use a 6AQ5 / 6005 instead, sounds better, better spacing inside the tube envelope.
(2) Don't do a separate chassis. Its a mistake. Wiring gets to be way way too long.
The power supply is PART of the audio circuit in a SE amp, and as such, it needs to be properly laid out with as minimum a lead lengths as possible, to sound its best !
Contrary to what some here "think they know" and think audio is narrow band .... every single inch of wire length saved in a good SE amp translates into better sonics. Of course, one must pay attention to fields also, as part of the spacing / layout design process.
One inch of bad wire can ruin the musical experience.
Jeff Medwin
Last Christmas I traveled the 5.5 hours to NY City down Rt 95 in heavy bumper to bumper traffic traveling at 70 – 80 MPH in our Passat wagon with my wife driving. The trip is tedious, stressful and boring and I spent a good deal of my time as a passenger looking for a decent radio station as we passed from one station to the next down the coast. The Passat has a basic radio with 4 speakers in the doors and two “ear lasers” in the dashboard, so the “treble” control is attenuated a good 45 deg. Between the road noise, the wind noise, and the engine noise there is not much bandwidth left to hear the radio, but I picked up a classical station as we approached New Haven and could just make out the announcer saying Beethoven’s “Pastoral” Sonata was coming up next.
As the meltingly beautiful opening stanzas of the melody unfolded through the thick haze of noise, my mind was drawn to the music. For the next 20 minutes I was transfixed by the distant and distorted, but ever so familiar music, that the road and the sensations of it became secondary to my consciousness. As I “sang" along in my head with the distant piano as it swelled, receded, and faded entirely for seconds at a time I never missed a note and never lost my place. I was captivated by Beethoven, spellbound by his genius, and seduced by the beauty of Sonata No. 15. As the radio station faded away along with the final notes of the Sonata, I found myself at Stanford having lost myself in a profound “musical experience.”
The power supply is PART of the audio circuit in a SE amp, and as such, it needs to be properly laid out with as minimum a lead lengths as possible, to sound its best !
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~!
The Mind has No Firewall~ U.S. Army War College.
My house has three huge transformers
on a pole behind my house.
I am the first house on my grid.
I know - lucky me 8^D
DanL
had to old school joke!
Absolutely! Don't use wire that's green and wet. Everything else is just fine.
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Buy Chinese. Bury freedom.
Not sure what kinds of thoughts you're looking for. Will this be PP? SE? What kind of output transformer? Are you wanting to use feedback, or no? Integrated, or just a power amp?
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