300B or 6L6 ??

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Niteshade

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300B or 6L6 ??
« on: 27 Sep 2008, 11:09 am »
What do you think of both tube types? Which do you like better?
« Last Edit: 27 Sep 2008, 06:50 pm by Niteshade »

jrebman

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Re: 300B vs 6L6
« Reply #1 on: 27 Sep 2008, 03:45 pm »
Depends on the implementation -- I've heard superb and horrible examples of each.

A well executed 300B -- preferrably a 3-stage design with a pentode for voltage gain, direct and/or transformer coupled, and with good iron and PSU, to my ears will leave pretty much everything else in the dust.  Unfortunately, there aren't a whole lot of these, and they don't come cheap.  That said, most 300Bs are too mushy and syrupy in the bottom end, and too rolled off in the highs for me to really enjoy them long term, and double hard if they happen to use the WE 300Bs.

-- Jim

doug s.

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Re: 300B or 6L6 ??
« Reply #2 on: 27 Sep 2008, 08:05 pm »
300b tubes are yust too expensive to be in the running for any amps i'd be interested in buying.  from what i have heard, and from what i have read, i'd take el84, 6c33c, 6l6, el34, 805, el519...

ymmv,

doug s.

hmen

Re: 300B or 6L6 ??
« Reply #3 on: 27 Sep 2008, 10:26 pm »
In a certain part of the sound spectrum, mid to mid-hi, the 300b is the best. Unfortunately that slice of the spectrum is too small. Also, a lot of people say the best implementation of the 300b is directly heated, which leads us to humpots.   

NagysAudio

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Re: 300B or 6L6 ??
« Reply #4 on: 29 Sep 2008, 01:05 am »
300B sounds so much better than 6L6 there is no comparison! There shouldn't even be a discussion if we're talking about sonics.

Niteshade

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Re: 300B or 6L6 ??
« Reply #5 on: 29 Sep 2008, 02:07 pm »
Sometimes it can be difficult to separate the sonics of the components from the circuit, which is responsible for tying it all together. It was mentioned that the 300B can sound so-so to excellent, but this opinion has to do with the circuit and its underlying components as well as the tube. The same quality circuit and components can be applied to any power tube. What do you folks think is special regarding the 300B tube in and of itself? As I said, please try to separate tube qualities from circuit qualities.

Another way to think about it: What tube based amplifiers have you listened to that remind you of a 300B amplifier, either single ended or push pull?

NagysAudio: Were you referring to the tube itself or specific implamentations of the tube?

Scott F.

Re: 300B or 6L6 ??
« Reply #6 on: 29 Sep 2008, 07:00 pm »
Strange, I don't seem to have the same experience as some that have posted.

A given tube can sound both good and bad depending on what associated equipment and more so what speakers are connected to it. I've had a little better than a half dozen 300bs (SETs and push pulls) through here over the years and haven't found any of them to be syrupy sounding or lacking decent bass. Granted, install a veiled sounding coupling cap or employ some weird derivation of a proven circuit and you'll likely experience issues but stick to what works and you shouldn't have problems. More than anything, watch what speakers you try to mate to SET (or even low wattage PP) amps. Go to Gizmo's (Triode Guild) website and read Heart of Speaker Darkness. It is a good primer for the proper mating tube amps to speakers.
http://coneyislanddreams.com/Tri/june/Darkness.html

I agree regarding the WE 300b and the new production tubes aiming to sound like the WE. To my ears, and in my systems, these tubes are so midbass and midrange forward that it seems that the treble is rolled off (the bass isn't that great either). I personally don't like that sound but I can see where some might find it seductive. Myself, I run the Sophia 300b Meshplates in the Wellborne DRDs. For those  unaware, the DRDs have one resistor in the signal path, thats it.... no caps, no chokes, just two tubes, a resistor and then the output iron. The DRD is the cleanest amp I've heard and totally absent of veiling or or ill-defined bass.

Regarding the 6L6, I've only heard them as a PP design. Much like any other tube amp around, mate them with quality coupling caps, resistors, decent iron and you can make a fine sounding amp. If memory serves, the 6L6 in PP does about 25-30 watts. If my memory is correct and it were my money (or design), I'd use the EL84. You get almost as much wattage, the tubes are less expensive, there are more NOS available (if you go for that sort of thing) and the EL84 has a 'tone' that really lends itself to music. Its my personal favorite tube, but thats just my opinion, YMMV.

NagysAudio

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Re: 300B or 6L6 ??
« Reply #7 on: 30 Sep 2008, 12:19 am »
There are not that many circuit variations out there, a 300B amp is very straightforward. I've built their amp www.angela.com and can personally say that it sounds fantastic.

It's important to understand what parts to use and where to get the best sonics and not buy into the hype of audiophile parts.

300B tubes, I like JJ Tesla. (Stay away from China and Russia)

Philips NOS drivers tubes.

For rectifier I would use a silver plated mil spec bridge.

Power caps, LCR, Philips, Chemicon.

Coupling/bypass caps, Vishay MKT1822, Philips metalized polyester.

Resistors, metal film Vishay, Mills, Dale.

Output transformers, Hammond.

Potentiometer, Alps, Noble.

Hum pots, Clarostat, or anything sealed mil spec.

Ceramic tube sockets.

But to answer your question, in similar circuits with similar parts, the 300B tube sounds superior to the 6L6, no comparison! The clarity and liquidity of midrange/treble is unrivaled.

To put a twist on this whole conversation, MOSFET transistors operate and sound just like tubes! An extremely high quality MOSFET amp, with a mil spec dual jfet input stage will always outperform any tube amp sonically.

Building/designing solid state amplifiers is thousands of times harder than building tube amps. And in this case, circuit topology can significantly change the sound.

Some of the very best amplifiers in the world were built by Goldmund in the late 80's early 90's, with their Mimesis 3 amplifier being the king of the world. I have schematics of the Goldmund (including the schematics for their top secret A1 input modules) that I might post here if anyone is interested. It's a fairly unstable and complex circuit, which sounds absolutely amazing!

Niteshade

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Re: 300B or 6L6 ??
« Reply #8 on: 4 Oct 2008, 01:19 am »
NagysAudio,

Thanks for all that information!

I can see that SS amps are more difficult and want to design one myself sometime soon.

What FET amplifier do you recommend? I have an Ashly FET 500 but didn't believe it sounded anything like a tube amp.

ZLS

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Re: 300B or 6L6 ??
« Reply #9 on: 4 Oct 2008, 03:19 am »
Strange, I don't seem to have the same experience as some that have posted.

A given tube can sound both good and bad depending on what associated equipment and more so what speakers are connected to it. I've had a little better than a half dozen 300bs (SETs and push pulls) through here over the years and haven't found any of them to be syrupy sounding or lacking decent bass. Granted, install a veiled sounding coupling cap or employ some weird derivation of a proven circuit and you'll likely experience issues but stick to what works and you shouldn't have problems. More than anything, watch what speakers you try to mate to SET (or even low wattage PP) amps. Go to Gizmo's (Triode Guild) website and read Heart of Speaker Darkness. It is a good primer for the proper mating tube amps to speakers.
http://coneyislanddreams.com/Tri/june/Darkness.html

I agree regarding the WE 300b and the new production tubes aiming to sound like the WE. To my ears, and in my systems, these tubes are so midbass and midrange forward that it seems that the treble is rolled off (the bass isn't that great either). I personally don't like that sound but I can see where some might find it seductive. Myself, I run the Sophia 300b Meshplates in the Wellborne DRDs. For those  unaware, the DRDs have one resistor in the signal path, thats it.... no caps, no chokes, just two tubes, a resistor and then the output iron. The DRD is the cleanest amp I've heard and totally absent of veiling or or ill-defined bass.

Regarding the 6L6, I've only heard them as a PP design. Much like any other tube amp around, mate them with quality coupling caps, resistors, decent iron and you can make a fine sounding amp. If memory serves, the 6L6 in PP does about 25-30 watts. If my memory is correct and it were my money (or design), I'd use the EL84. You get almost as much wattage, the tubes are less expensive, there are more NOS available (if you go for that sort of thing) and the EL84 has a 'tone' that really lends itself to music. Its my personal favorite tube, but thats just my opinion, YMMV.


    What he Said; prefer an EL84 in PP configuration. 

NagysAudio

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Re: 300B or 6L6 ??
« Reply #10 on: 5 Oct 2008, 09:54 pm »
Niteshade, if this is your first time building a SS amplifier, I would recommend building any of the Nelson Pass amps, you can find schematics online. They are some of the easiest mosfet amps to build.

jon_010101

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Re: 300B or 6L6 ??
« Reply #11 on: 5 Oct 2008, 11:36 pm »
300B sounds so much better than 6L6 there is no comparison! There shouldn't even be a discussion if we're talking about sonics.

I generally disagree, and would say that this varies much by implementation.  A 6L6GC in triode gives up a little power compared to a 300B - but the real magic will happen when used as a proper beam pentode.  A KT66 or 6L6 in a unity-coupled configuration, a la McIntosh, requires slightly more voltage drive than a 300B, but offers comparable damping and lower distortion, and much greater efficiency.  The tubes cost an order of magnitude less than WE300Bs, too.  I am working with a friend on an amp design using this approach, and it measurably outperforms any 300B push-pull amp that I am aware of, even without global feedback (0.02% THD at 1 watt, ~5-100kHz bandwidth, using a $70 output transformer).  The driver is perfectly capable of driving a 300B into oblivion, so we may eventually invest in a set plus OPT for comparison - however, I fully expect the unity-coupled 6L6 to be equal or superior at a fraction of the cost :thumb:

IMHO, beam power tubes are tremendously underrated for no good reason.

Niteshade

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Re: 300B or 6L6 ??
« Reply #12 on: 7 Oct 2008, 12:16 am »
"IMHO, beam power tubes are tremendously underrated for no good reason."

If I were to make an educated guess, it would be that 6L6's and similar tubes are/were being used with poor circuits. There are good circuits out there, but people remember the poor ones. I have listened to several unremarkable amps made over a wide time spectrum.

It's a shame that stereotypes lead people to, "blame the tube", rather than the circuit. Providing the iron within an amplifier is good quality, the amp's signature/voice will be primarily dictated by the circuit.


kbuzz3

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Re: 300B or 6L6 ??
« Reply #13 on: 7 Oct 2008, 01:15 am »
300B sounds so much better than 6L6 there is no comparison! There shouldn't even be a discussion if we're talking about sonics.

I generally disagree, and would say that this varies much by implementation.  A 6L6GC in triode gives up a little power compared to a 300B - but the real magic will happen when used as a proper beam pentode.  A KT66 or 6L6 in a unity-coupled configuration, a la McIntosh, requires slightly more voltage drive than a 300B, but offers comparable damping and lower distortion, and much greater efficiency.  The tubes cost an order of magnitude less than WE300Bs, too.  I am working with a friend on an amp design using this approach, and it measurably outperforms any 300B push-pull amp that I am aware of, even without global feedback (0.02% THD at 1 watt, ~5-100kHz bandwidth, using a $70 output transformer).  The driver is perfectly capable of driving a 300B into oblivion, so we may eventually invest in a set plus OPT for comparison - however, I fully expect the unity-coupled 6L6 to be equal or superior at a fraction of the cost :thumb:

IMHO, beam power tubes are tremendously underrated for no good reason.

For those of us without much technical knowlege and for education only, how would this approach differ from say the Sid Smith, Craftsman/williamson approach which also used the kt 66.

jon_010101

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Re: 300B or 6L6 ??
« Reply #14 on: 7 Oct 2008, 02:22 am »
For those of us without much technical knowlege and for education only, how would this approach differ from say the Sid Smith, Craftsman/williamson approach which also used the kt 66.

I have a pair of Craftsmen 500as, and they sound bloody-fantastic - possibly my favorite amps :thumb:  The Craftsmen Williamson approach is to wire the KT66/6L6s as triodes (screen grid connected to plate).  You get about 15 watts with very low distortion, fantastic load tolerance, and good damping.  It is a nearly faultless design, but somewhat "inefficient"... 

... the alternate approach is that of McIntosh (i.e., MC30) - which is closer to what we are doing in the project amp.  With the McIntosh amplifier, the KT66/6L6 is wired as a pentode (screen grid at fixed voltage), but the transformer load is split equally across the cathodes and the plates (called Unity Coupling, or a "distributed load" configuration).  This makes a pentode look a bit more like a triode (in terms of distortion and damping), but with full efficiency.  It also makes it harder to drive - hence the 4 tubes vs. 2 in the driver stage.  The MC30 is easily capable of 30W+, and the project amp does about 1% THD at 30W - About twice as much power as a Craftsmen 500a.  While I've never even listened to my MC30, I am betting that the Williamson sounds better at reasonable power levels.  The project amp might fit somewhere in the middle (although we would like it to be better than both), but is not fair to compare since it uses some solid state parts.  :wink:

rajacat

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Re: 300B or 6L6 ??
« Reply #15 on: 7 Oct 2008, 02:44 am »
My Heathkit W5m's were just totally rebuilt with upgraded modern parts and some mods . I believe this amp uses a Williamson cicuit.  I've been using KT66's but 6L6's can be used, in fact I have a selection of 6l6's that I'm going to roll.
The amp is still breaking in so it'll  be awhile before I can run through all these tubes. So far the amp is sounding better and better all the time which is saying a lot. I can vouch that KT66's can produce a sweet, detailed and dynamic sound. aa

--Roy

jon_010101

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Re: 300B or 6L6 ??
« Reply #16 on: 7 Oct 2008, 04:14 am »
"IMHO, beam power tubes are tremendously underrated for no good reason."

If I were to make an educated guess, it would be that 6L6's and similar tubes are/were being used with poor circuits. There are good circuits out there, but people remember the poor ones. I have listened to several unremarkable amps made over a wide time spectrum.

I agree, and think a big problem is that many try to stick them in a Dynaco ST70, which really doesn't have the driver balls necessary for the tube.  The output transformers also do not provide an optimal impedance match, where the tube would prefer a 6K6 load for a UL configuration.  With a more serious driver, and a proper OPT, the 6L6 should be more at home.  :)

Roy, the W5s are awesome - a great example of a 6L6/KT66 amp  :thumb: