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Anonymous
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Building amplifiers seems to have become the hot activity for me..... after discovering the great sound of triodes this year, and trying the mosfet comparison, I'm sticking with tubes and trying more things (this hobby has become as much fun for me as telescope building!).
My latest experiment was to build a single channel PP (push-pull) triode amp using the same tubes as my SE (single-ended) amp, for comparison. I was impressed enough to convert the SE amp to PP using better quality transformers.
Why? More power, but even better, tighter bass and more detail overall. The SE does have a more "laidback" presentation and seemingly more depth, but it seemed to lose some other things as well (pretty good on some things, but not so great on others). The PP just seems to do well on everything.
It probably helped that there were no coupling caps anywhere, I used transformers for interstage as well as output coupling. This allowed me to apply needed voltages directly, and make the simplest possible circuit. Triodes are biased on full Class A, with no feedback needed.
I have been enjoying my CD's all over again. I just wish the studios would use less echo on some vocals.... one song on this setup seemed to stretch the echo all the way across the room.... too much!
Kent
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BluewaterObserva
Postmaster
Reged: 05/18/04
Posts: 5748
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Dang Kent... I'm jealous you get to experiment in this manner. I gave up on it all, long ago. But, you sure have me re-considering my choices for amplification. lol
So what sort of sustained power you getting out of those tubes -vs- their ratings?
Vocal processing has gotten way out of control these days for sure. Funny it doesn't seem as distracting on instruments as it is on vocals.
Funny, if you watch live shows these days of the bigger pop stars, they most always have a different mic to talk to the crowd than they do for their singing vocals. This is because most run so much crud these days, they would sound rediculous talking through all that garbage / dsp they have going on.
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Anonymous
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I haven't made any measurements yet.... there's several watts per channel there.... guess I should measure it. I have only been looking at tube voltages to get these biased up right. Then I'm in a rush to listen to it! I can tell you that it will drive an efficient 8" 2-way quite loudly!
Yea, I can understand using a little echo, using compression to keep from clipping, and maybe some EQ.... but it's getting way too easy to get carried away and make voices sound really weird!
I used to believe that some sort of correction (like neg. feedback) was necessary in any amplifier, but now I find that if you run truly linear devices in Class A, you just don't need correction of any kind, and you have better overall performance to boot! This is quite an education for me, and I'm glad you're getting something out of all this too.
I think I'm going to stick with PP tube amps from now on, even if I do make a serious effort at building a good mosfet amp sometime. But building a tube amp is actually pretty easy. This one has few resistors and caps, mostly tubes, transformers, and power supply. Most transistor amps are much more complex!
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Rusty
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Reged: 08/06/03
Posts: 19246
Loc: Brooker, FL
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You're making me feel old - as We diddled with triodes in college electronics (mainly because transisors had just gotten to the FET stage). Of course, Real Men played with pentodes... 
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N11GPS Fastar//TOA-130S//MK66 Std//AT6RC//Vintage C5//Megrez II 80mm APO//SolarMax 40
NJP Temma II//Sirius EQ-G
Too Many Astro-Cameras//Mallincam Color Hyper Plus
Two not-spoiled Golden Retrievers - Casey and Nelson
Lot 19 Deerlick Astronomy Village (Canis Major)
Sometimes I think we're alone in the universe, and sometimes I think we're not. In either case the idea is quite staggering. - Arthur C. Clarke
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BluewaterObserva
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Reged: 05/18/04
Posts: 5748
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"Real men played with pentodes".. That is to funny on so many levels.....
You know, Quality Class A tube amps, don't cost as much as thought they did. I'm actually going to go down to one of the snooty audio shops and audition a few....
I have had a long dream for my home theater... In essence tri-amping (well bi-amping, and using a powered sub anyways)
I would like to use a gnarly tube amp for all my base drivers. (7 channels) and use my Denon power amps for the mids and highs. (once again 7 channels) I guess for now the 800watt Velodyne 15" sub would stay as is. I had figured the 7 channels of tube would just be way over the top on cost. The audio store guy is telling me, he can get me into 7 channels of serious tube amplification for only around $1500. (Of course I have to wire a dedicated circuit for it all too)
I'll post back after I audition some of the stuff. He wheeled off some names, I have barely even heard of. But I am not so up on high end audio these days.
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Anonymous
Unregistered
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I'm really not too aware of what's out there anymore either. And when you build your own, there's no incentive to find out. If I can build a good tube amp on my first try, just about any tube amp has gotta sound pretty good!
You go listening around to tube amps and you might not want any transistors in your system! Although I still use a non-tube amp in my bedroom, they're okay for background music....
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Anonymous
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Hey Rusty! You still keep any pentodes lit up? 6L6's maybe?
Surely you still have some of that around!
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Rusty
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Reged: 08/06/03
Posts: 19246
Loc: Brooker, FL
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Ich ben haben nich pentodes - in fact I've sold all my valves...the bottom line is that while tubes render things more better, my ears don't. So I have only solid-state gear...but some of it dates to the 60's.
--------------------
N11GPS Fastar//TOA-130S//MK66 Std//AT6RC//Vintage C5//Megrez II 80mm APO//SolarMax 40
NJP Temma II//Sirius EQ-G
Too Many Astro-Cameras//Mallincam Color Hyper Plus
Two not-spoiled Golden Retrievers - Casey and Nelson
Lot 19 Deerlick Astronomy Village (Canis Major)
Sometimes I think we're alone in the universe, and sometimes I think we're not. In either case the idea is quite staggering. - Arthur C. Clarke
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Anonymous
Unregistered
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Hmm.... nobody seems to keep their old tube stuff. You're lucky that some of the solid-state stuff still works.... impurities and migration has tended to kill transistors within about 20 years. And they told us transistors would far outlast tubes..... Heck, some of the tubes I'm using now were made in the late 50's!
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BluewaterObserva
Postmaster
Reged: 05/18/04
Posts: 5748
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Well, $3000 for 14 channels of tube amplification is to rich for me, to improve my system. Even $1500 is a good jump considering the performance I get right now.
I do love the sound of the not so respected Denon power amps though. But, there is no sound like bi-amp'd sound.
So on your tube amp(s), you just attenuate for the pre-amp soruce. Full bias all the time on the amp? That would be a pretty easy design.
I would need some attenuation, to balance out the gain staging in my particular current need. I have always found input signal auttenuation, tricky with tubes circuits.
Just currious as to your impressions on this?
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Anonymous
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If you already have something decent for home theater, I don't consider it worthwhile to spend alot of money on many tube amp channels. It's more worthwhile for stereo if you enjoy acoustical music and want a livelier sound (tho' it was also interesting on british rock). I have also noticed that tube amps are little unforgiving of less than ideal speakers; they don't like speakers whose impedance varies much! The response changes. So there are pitfalls.
I am learning to pick tubes in such a way that I get the right amount of gain. There is a volume control on the input of my amp, but the gain still needs to be in a reasonable range. Guitar amps have alot more gain, too much for stereo. Different tubes have different gain, and there's a huge range there. Half the design seems to be in tube selection and type of circuit.
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BluewaterObserva
Postmaster
Reged: 05/18/04
Posts: 5748
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Yes, the impeadence thing.. I remember that one all to well... This reminds me, of why tubes aren't always best driving the bass drivers where impeadance can change drastically in an extremely dynamic manner.
My trip to the snotty dooty audio store is set for Sat. morning.
More to ponder on... Even the Pentode suggestion, got me thinking about tube selection some. While these are great for guitar and probably even some pro audio applications, I don't think they would be a very good choice at all for home audio applications. So your tube selection opinion is right on from my experiences.
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Anonymous
Unregistered
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Well, hi to all audiophiles on the forum, my very first appearance here.
I own SET custom made integrated amp ( 6SN7 driver, 83 rectifier, 300B EH output, 10W )Very nice iron, point to point inter, bla, bla ... Have heard a number of PPs : 6F6, 6F6, EL34, KT88, Kt90, simply now match for my SE ( ss gear even worse, incl. some very expensive beasts )Details, stage, timbre, you name it. Paid only 1.000 Euros here in Belgrade, Serbia ( yes, one thousand )Stop searching, call it euphonic, warm, but say frankly who is A1.
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Anonymous
Unregistered
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Nice choice of tubes there, unsung! If you're going to go SET, it does seem best to go for the best tubes and iron you can find, and big enough tubes to get reasonable power. Of course, the other tubes you mention are pentodes, and certainly cannot compete with a good triode, regardless of circuit configuration.
My own experimenting seems to indicate that the choice of tube, followed by the choice of transformers, is most important. Single-ended versus push-pull is also significant, but both can be good (though different).
I think a very good SET will always beat anything else for natural effect and depth of image. But for less than ideal conditions and with smaller, lower cost components, my triode PP has significant advantages over my little triode SE. But I certainly would not compare any of my triodes with the 300B (which also cost 20 times more than my 6S4A's)! But I am having great fun AND getting better sound without spending more money than I want to!
Hope things are going well in Serbia,
Kent
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