Tube stories

[JBLRaiser]

If anyone is interested, I would like to hear from those out there using tubes in your audio setup. Do you bi/triamp on the high end or run all your drivers from one amp. Is it push/pull, single ended, triode,pentode,etc? I would like to here about the different tubes you have used. Whether in preamp/amp configs, amp or just preamp use. What kind, why you chose what you did and what tube makes and models you consider the best. And last, but not least, what are you willing to pay for a tube? Please respond to any or all of these questions and add what you want.

[DaveV]

Hey ya'll from up here in Aiken, SC. What tube equipment are you referring to? Vintage, new or both?

[Chas]

Tri-amp 4345/Sub1500

High pass power amps:

Monoblock's, four winged "C" KT88's per channel with Plitron specialist series O/P transformer/cathode coupled feedback usually operated in "Super Triode" mode - similar to UL , but with cathode coupling.

O/P tubes are driven by four 5692's per channel in a balanced-differential configuration. Amps are balanced throughout. No global feedback.

Powered by four independant all-tube regulators. Bias is regulated as well and fully adjustable to run class A if desired...(If I can stand the heat build up)

These amps are overkill, they were originally done to drive a pair of Magnepans. I have parts to build another pair using only two KT88's with half the output, but I just don't have any time.


Preamp:

Four 5691, four 6DN7, two 12AT7, 5651 with a tube regulated supply. Single ended in, balanced out. No global feedback.

Band pass and low pass power amps, crossovers and phono preamps are all SS.

[Steve Schell]

The group of solder sniffers I hang out with are into directly heated triodes, transformer coupling and single ended amplifier circuits. My mainstay homebrew amp for several years now is a battery biased, transformer coupled 26/45/45 design.

The wild frontier DIY builders are increasingly using big, hairy transmitting triode outputs in the search for more power in an SE DHT design. Here are a couple of links to some cutting edge builders who build to order:

http://www.experiencemusic.net/

http://www.electronluv.com/index.html

Ron Welborne makes some very good sounding, reliable and highly affordable 45 and 300B SE amps, available as kits or fully assembled. My business partner and I have partnered with Ron at several shows to demonstrate our horn speakers.

http://www.welbornelabs.com/

Most often at home I run my two way horn systems from single amp channels and passive crossovers. At times (and often at shows) we run the DEQX unit and drive the high frequency horns with Ron's Star Chief 45 amps and the low frequency horns with his Terraplane 300B amps. If we use a sub it is self powered or run from a separate amp.

There are several tube oriented discussion forums over on the Audio Asylum. There are experienced builders there who are usually happy to answer questions, and searching the archives there will answer many questions.

http://www.audioasylum.com/index.html

[SUPERBEE]

My main system is 2 Mcintosh MC75s running thru a Mcintosh MX110. The 75s are outfitted with Genalex Gold Lion KT88s. All this runs thru a set of JBL Olympus and I LOVE IT! Nothing fancy. Just a straight stereo set-up.

I have heard 6550s and various other KT88s and prefer the Genalex Gold Lions.

I am curious if anyone here has used "Tube Dampers" and what they thought about them?

[JBLRaiser]

Hey ya'll from up here in Aiken, SC. What tube equipment are you referring to? Vintage, new or both?

Anything with a tube

[JBLRaiser]

My main system is 2 Mcintosh MC75s running thru a Mcintosh MX110. The 75s are outfitted with Genalex Gold Lion KT88s. All this runs thru a set of JBL Olympus and I LOVE IT! Nothing fancy. Just a straight stereo set-up.

I have heard 6550s and various other KT88s and prefer the Genalex Gold Lions.

I am curious if anyone here has used "Tube Dampers" and what they thought about them?

what are your options when it fails? Do you have more? Would you buy on the open market?

[SUPERBEE]

I would also be curious if anyone has tried these yet? I would love to hear a report card on them.

[JBLRaiser]

Tri-amp 4345/Sub1500

High pass power amps:

Monoblock's, four winged C KT88's per channel with Plitron specialist series O/P transformer/cathode coupled feedback usually operated in "Super Triode" mode - similar to UL , but with cathode coupling.

O/P tubes are driven by four 5692's per channel in a balanced-differential configuration. Amps are balanced throughout. No global feedback.

Powered by four independant all-tube regulators. Bias is regulated as well and fully adjustable to run class A if desired...(If I can stand the heat build up)

These amps are overkill, they were originally done to drive a pair of Magnepans. I have parts to build another pair using only two KT88's with half the output, but I just don't have any time.


Preamp:

Four 5691, four 6DN7, two 12AT7, 5651 with a tube regulated supply. Single ended in, balanced out. No global feedback.

Band pass and low pass power amps, crossovers and phono preamps are all SS.

if so, how did you go about choosing a topology to follow? What was your reasoning behind choosing the 5691/6sl7 vs. the 5692/6sn7 in your preamp? Any sonic difference. By the way, I visit Aurora, Ont. from time to time. My wife is from there. Would love to hear your system someday. I'll be in Collingwood for Christmas, but not long enough for a trip to Toronto. Thanks for your input.

[SUPERBEE]

what are your options when it fails? Do you have more? Would you buy on the open market?

I have gone thru 2 KT 88s so far. I will keep finding them thru friends or Ebay if I have too.

I love my main system too much to not keep it running. I am recording and listening to some great British mid 60s Psych right now.

[DaveV]

I like what is now called "vintage" equipment probably for the general look and the comfort level of having old friends that I couldn't afford when they were new because I wanted to try them all.
I've heard some new tube stuff and didn't care for it so that was enough and I'm not into boutique parts and snake oil. Just the great sound that can be had without them.
During the "golden Years" of Hi Fi that I consider to be from about 1954 to about 1968 SET was just a memory and it wasn't mentioned much to my recollection. I'm curious what all the hubbub is about but not enough to venture into it.
I've had a long line of tube equipment and what I settled on through trial and error is a Mac C-22 preamp and 225 power amp.
If hard pressed for a second choice that had to be different it might be Fisher 80C preamps and MC30's. Kind of hard to say now because I have different speakers since I've heard most of that stuff.
I seem to like 7591 or 7868 based amps with SS rectification like the Fisher 400, Scott 299C & D, Scott 340B and of course the Mac 225. I don't however like the Fisher 500C so it must be something other than the outputs in that piece that makes it sound so lifeless to me.
The Scott 299 with 7189's and some others with 6BQ5's like the Dyna SCA35 and Scott 222C are very detailed and sweet sounding integrated amps too.
I have heard amps with 6L6's and EL34's that sound good and bad to me so I can't say I have a favorite output tube.
But it might be the 7591 sound plus the extra kick of SS rectification that really floats my boat but I can enjoy the MC30's at times along with an EL34 Scott integrated I have.
I prefer NOS American 7591,6L6 and maybe the 6CA7 more than EL34.
In my Dyna MKlll's I preferred GE 6550's over Gold Lion KT88's of 1980 vintage.
I have no problem with 12AX7's for phono and I use Telefunkens as a general rule because I have a good stash of older ones and they last forever.
I do like cleartop RCA 12AU7's over a Mullard 12AU7 in the 225 and RCA 12BH7's over some other brands I tried.
I'm not a big tube roller but now and then I do. There's so many other things you can do to change the sonics besides tube roll but that is one of the easiest ways although expensive.
A coupling cap change could be a subtle or huge change in sonics but most people seem to like to tube roll more than try different caps.
What would I spend for a tube? I can't answer that one because I stocked up on tubes i'd need before the prices went crazy so I don't need any for the rest of my life.

[Chas]

if so, how did you go about choosing a topology to follow? What was your reasoning behind choosing the 5691/6sl7 vs. the 5692/6sn7 in your preamp? Any sonic difference. By the way, I visit Aurora, Ont. from time to time. My wife is from there. Would love to hear your system someday. I'll be in Collingwood for Christmas, but not long enough for a trip to Toronto. Thanks for your input.

Hi, the topology was derived via trial and error, I suppose. It has lead me to the point where I am a big advocate of fully balanced tube power amps. Among other benefits of this topology - I think that phase inversion should occur in the line stage or at least somewhere where levels are in the order of less than a few volts. I have found that this provides the best linearity of symmetry vs. doing it within the power amp.

5691's in the preamp were chosen for two applications, cathode followers with the two sections in parallel and as voltage amps/phase inverters, since PI is usually best achieved with high mu tubes.

BTW: I shamelessly copied Bruce Moore's 6DN7 cathode folower output from his famous preamp, since it's really hard to beat.

I find the 569X versions of these tubes to have generally the lowest noise and microphonics.

You're more than welcome to stop by for a cold one and have a listen, PM me in advance of your trip. Good luck in Collingwood this year - assumimg you are planning to ski, we have been experiencing a heat wave this December!

[Ducatista47]

From the key tapping of Steve Schell:

The group of solder sniffers I hang out with...

This is for me the best phrase I have seen since I joined this site.

...are into directly heated triodes, transformer coupling and single ended amplifier circuits. My mainstay homebrew amp for several years now is a battery biased, transformer coupled 26/45/45 design.

In audiophile circles why does transformer coupling have a bad name? Iron core inductors of any kind outside of power supplies, in other words in the signal path, seem to elicit sneers. Some here want to banish them from crossovers for the rest of humanity's time on the Earth. The voltage adapter box for my Stax electrostatic headphones is supposed to be an inferior piece because it employs transformers. Sorry in advance for my ignorance. I seem to remember transformer coupling being used extensively in the classic high-fi era of tube amplification.

Ron Welborne makes some very good sounding, reliable and highly affordable 45 and 300B SE amps, available as kits or fully assembled. My business partner and I have partnered with Ron at several shows to demonstrate our horn speakers.

Highly affordable 300B amps must be relative. In my low budget world they might be until you have to buy the 300B's! And buy extra, because I have heard tell the grids break when they read a newspaper account of a bump.

Personally, it seems to me EL34's would make GREAT triodes. I know it has been done, but I have not heard them yet. I think building a power amp with them is in my future. They are the only pentode without internal grid shorting that I am aware of, and the characteristics look outstanding. They are not directly heated, I admit. They are not currently price inflated, either. I can tell you EL84's make fine triodes, too. That is what I listen to.

I'll add that as a first tube in a voltage gain stage in a preamp, the 6N1P-EV absolutely kills. From Russia with love, Mr. Bond.

Great post, Steve. As usual!


Clark

[Ducatista47]

Do you bi/triamp on the high end or run all your drivers from one amp.

I biamp my 4345's, using tubes for the top for now. Probably tubes for the woofer in the future, unless I can afford to build a Nelson Pass design (MOS-FET). I may mess around with my JoLida 502B and try it there too.

Is it push/pull, single ended, triode,pentode,etc? I would like to here about the different tubes you have used. Whether in preamp/amp configs, amp or just preamp use.

Single ended all the way. Integrated amp with inverted line out available. It is a triode-pentode voltage gain stage coupled to a switchable pentode or triode output. A store-bought amp, which I HIGHLY RECOMMEND. Grommes PHI-26. $995. We don't understand, but it seems to drive anything we have tried it on. Six watts pentode, 1.8 watts triode. If DIY is your thing, you can figure out how to design the heart and soul of this utterly superior design by reading this paper: http://www7.taosnet.com/f10/mustage.html
Bear in mind Grommes uses really superior transformers custom built for the exact design of each of their amps. I can also tell you it is probably not possible to build this amp for less than you can buy it for. The Chinese looked at Grommes amps and could not figure out how to do it for what Grommes charges the customer, never mind less.

What kind, why you chose what you did and what tube makes and models you consider the best.

I'm no genius at this stuff, but I did talk with the brilliant designer of this amp and I rolled a tube he recommended, the 6P14P-EV, to replace the EL84's. This was after replacing the stock JJ's with Electro-harmonix types, EL84-EH's. The 6P14P-EV's blew the others away by a wide margin.

And last, but not least, what are you willing to pay for a tube?

What I think I can afford. Not much in my case, but there are bargains out there unless you are looking for 300B's and such. I am becoming a firm believer in Soviet era NIB military spec tubes. You may find this thread interesting:http://audioheritage.org/vbulletin/s...ad.php?t=12955
Despite being started by yours truely, there are some nice contributions to the thread. I got my 6P14P-EV's from France for about $52 per matched quad. That beat local prices for E-H tubes.

Doing a search for posts by Steve Schell is a great way to find about about the higher end of tube design. I don't mean expensive boutique crap, I mean great DIY stuff. Look at his replies on this thread if you like:http://audioheritage.org/vbulletin/s...ad.php?t=12274
Be patient and talk will turn from drivers to tubes. His links in his above post tell the what but these posts tell the why.

Anyone into tubes is alright with me.

Clark in Peoria

[Steve Schell]

DaveV, I sense a bit of scepticism in your regard for Single Ended Triode amps. I think this is great, as there is a lot of snake oil in modern hi fi, and a lot of illegitimate concepts are foisted upon the gullible.

I began experimenting with SE and OTL (Output Taransformer-Less) amp designs in the mid 1980s with a buddy, after reading of some of the things those "crazy" Japanese experimenters were up to. I found a 1960s Eric integrated amp in the trash, one that used 6BQ5 output in a single ended ultralinear configuration. That amp possessed a naturalness that we could not duplicate with any of our push pull amps.

The SET movement really got started in the U.S. with the debut of Sound Practices magazine in 1992. The publisher Joe Roberts wrote an article in the first issue that detailed the building of a modern version of the Western Electric 91A SE 300B theatre amp. Many more articles followed, and the movement was off and rolling. Dennis Had of Cary Audio began selling his small, inexpensive kit amp that could use either 2A3 or 300B in the output. Eventually there were numerous commercial builders and the products became more and more popular at trade shows. At first the mainstream press ignored the phenomenon, then grudgingly began to write reviews that mostly trashed the products based on measurements. Nowdays SET amps are seen everywhere at the shows and their future seems secure.

The funny thing is that SE amps were never regarded as high fidelity, even in the 1930s, but were a budget choice when a low power application didn't require a push pull output stage, i.e. a table radio.
My impression of SE circuits, and those using directly heated triodes in particular, is that they sound very natural and pass a tremendous amount of fine detail that places the listener in the recording space. Most of these amps do not employ a global feedback loop, the prevailing philosophy is that the sound is more clear without it despite the higher measured distortion. Actually triodes have very little inherent distortion compared to tetrodes or pentodes, and the distortion sans feedback is not a problem unless an amp is run too hard, as was often done in the magazine reviews.

The SET circuits have a fairly high output impedance (low damping factor), which helps in achieving critical damping with highly efficient speakers. We have been fed the mantra of high damping factor in the press for several decades now, but this can make speakers with strong magnetic damping sound choked and rolled off on the low end. Jim Lansing used to advocate amplifiers with an output impedance of 12 ohms or so.

Clark, I'm reminded of a description in an issue of Sound Practices, where an amp builder is described as toiling away in a basement, subsisting on a diet of cold coffee and solder fumes. Sounds about right.

In the 1920s and into the 1930s audio transformers had poor frequency response and tons of phase shift. John Hilliard wrote about the dire situation with the Western Electric recording electronics in the movie studios in the early 1930s, where the circuits would have thousands of degrees of phase shift. Ercell Harrison of Lansing Manufacturing Company (yes, that Lansing!) was given the task of improving matters. Harrison studied the situation and wound transformers that greatly reduced the phase shift, improving the fidelity of the recording chain. He is also famous for designing some of the finest audio trannies of the 1940s and 1950s, the Peerless 20/20 and 20/20 Plus series.

Transformer coupling worked okay in the early days in low-fi applications, where the humpty dumpty response curves were not a detriment or were even desired. By the time of the 1950s hi fi craze, RC coupling had taken over. These days, interstage transformers are wound with wide, flat bandwidth and have proven to provide an ideal load and efficient coupling for the low mu triode circuits. They allow the elimination of capacitors from the circuit (except power supply filters) and sound ultra fast and clean. The only real downside is that they are a lot more expensive than a resistor and capacitor.

I haven't spent much time with sure 'nuff W.E. 300Bs, since they have always been so expensive. I am currently running the TJ mesh plate 300Bs, which sound better to me (less flabby bass, mostly) than others I have compared them to. We have hauled them to shows and they don't seem to be delicate.

Most guys have built triode connected pentode amps before breaking on through to DHTs. Don't really know why, but there is something special in those filamentary cathodes. For the most adventurous only thoriated tungsten filaments will do, i.e. the transmitting triodes. Filament current may have something to do with it; higher current filaments have always sounded better to me. I never tried EL34s, though. Give it a go Clark, and report back!