Difference 300B / KT88 ?

[Togil]

Just wondered what the difference from the designer's point of view was between these two valves, especially for SETs

I detect a slight preference for KT88 on this forum. The 300B is a genuine triode, the KT 88 was never meant to be ( so someone told me ! )

[Marco]

That's a good question, Hans, and one for Anthony or one of our other resident valve amplifier designers to answer properly. I like KT88s because to my ears, when implemented correctly, they just sound so 'alive', 'real', and 'un-valvey'. They produce the closest sound, in my opinion, to the best transistors but without their sonic pitfalls. SET fans (in general) hate them, but for anyone attempting the transition from solid-state to valves and seeking the smoothest ride, a KT-88 based amp is the one I would recommend.

Regarding the 300B, all I would say from my experience so far is that I rate it very highly as a valve, but much more so in push-pull mode than when used in an SET amp. For example, the World Designs 300B P/P which Greg uses is one of the best valve amps I've heard; conversely some of the low-powered SET amps I've heard using the same valve have been poor – therefore the conclusion? As always, it's all in the implementation!

Marco.

[anthonyTD]

That's a good question, Hans, and one for Anthony or one of our other resident valve amplifier designers to answer properly. I like KT88s because to my ears, when implemented correctly, they just sound so 'alive', 'real', and 'un-valvey'. They produce the closest sound, in my opinion, to the best transistors but without their sonic pitfalls. SET fans (in general) hate them, but for anyone attempting the transition from solid-state to valves and seeking the smoothest ride, a KT-88 based amp is the one I would recommend.

Regarding the 300B, all I would say from my experience so far is that I rate it very highly as a valve, but much more so in push-pull mode than when used in an SET amp. For example, the World Designs 300B P/P which Greg uses is one of the best valve amps I've heard; conversely some of the low-powered SET amps I've heard using the same valve have been poor – therefore the conclusion? As always, it's all in the implementation!

Marco.

hi hans,
the 300B is indeed a good valve when implemented properly, and in the right system, it can perform outstandingly well. it is a true triode. unfortunately some of the circuits its expected to work in leave a lot to be desired. the main reasons the KT88 valve in my opinion is so well used and loved by many audiophiles and musicians worldwide is because of its sonic qualities and also its power capabilities, for me this makes it a much more versatile valve than any triode, especially when used as it was intended as a TETRODE ! a lot of people make the mistake of using this valve as a triode, sure it will work, but its true potential is wasted in this configuration. KT66 is another story as when connected as a triode it can indeed be considered as a true triode!
most people on here will know that i am biased on this subject to a point, but my bias is not without merit, the reason the KT88 won my heart is simple, when implemented properly, its over-all performance is very difficult to better, sure there are valves that will do some things better, but when it comes down to consistency across the board on the things that matter, ie, linearity, distortion factors, and sheer power output, the KT88 is a hard act to follow.
regards,anthony,TD...

[Togil]

Thanks Anthony.
So do you use KT 88s in your Soul amplifiers in tetrode mode ?
And for the higher-powered ones in parallel configuration ?

[Marco]

the main reasons the KT88 valve in my opinion is so well used and loved by many audiophiles and musicians worldwide is because of its sonic qualities and also its power capabilities, for me this makes it a much more versatile valve than any triode, especially when used as it was intended as a TETRODE ! a lot of people make the mistake of using this valve as a triode, sure it will work, but its true potential is wasted in this configuration.

Most interesting, Anthony! That may explain why when I've heard it used as a triode the amp it's been used in has sounded soft and lifeless, lacking dynamics, and reproduces nothing like what I would describe as the sound of real music.

Marco.

[anthonyTD]

Thanks Anthony.
So do you use KT 88s in your Soul amplifiers in tetrode mode ?
And for the higher-powered ones in parallel configuration ?

hi hans,
yes, i use them in tetrode mode in the soul amps, and each valve has its own control circuitry, therefore each valve and its circuitry is classed as one module, and its parameters are locked and cannot deviate from its intended settings throughout the life of the valve. each valve module is contained on its own circuit board, therefore the 15 watt stereo versions have two power modules, one in each channel, the 30watt mono versions have two modules in parallel, and the 60 watt mono versions have four modules in parallel. the soul amplifiers are hybrids, single ended, and directly coupled throughout, so not really fair to put them in the same category as traditional valve amps, they also have multiple boards buried in the chassis where the rest of the power supply circuitry is contained, this was done to keep all the noisy stuff well away from the signal circuitry. they originally had a flat frequency range from 7hz to over 220k but later versions were restricted to around 120kz...
hope this helps.
anthony,TD...

[anthonyTD]

Most interesting, Anthony! That may explain why when I've heard it used as a triode the amp it's been used in has sounded soft and lifeless, lacking dynamics, and reproduces nothing like what I would describe as the sound of real music.

Marco.

quite possibly,
sadly one of the reasons a lot of amplifiers use tetrodes, and pentodes in triode mode is because the circuitry is so bad, and triode mode simply masks this somewhat, [ as you have already witnessed for yourself] and therefore presents an easier presentation on the year from an amp that might otherwise be in some cases un-listenable... but by doing this as you have clearly pointed out, the sonics in most cases have lost their definition, and the sound can be very tame, and lack lustre.
anyone reading this will by now assume that i am down on triodes, so lets clear that up, in fact the opposite is closer to the truth, an amp designed as a triode amp from ground up can, and will if designed properly give you all of the good properties that a good tetrode/pentode amp can, and in some case even more, so guys lets make this clear, its the circuit design i am condemning, and not the valve.
anthony,TD...

[SPS]

i would agree with anthony, i am in the Se camp, due to the speakers i use gives me that option.. and i prefer the what the extra simplicity can do the sound.. but its not that easy to get the sound right

some of the worst SE amps i have heard have used the 300b,
and some of the best ones i've heard have used it too
the implementation is important.. but choosing good valves is critical,
old stock valves give much improved sound and tighten the bass.. but because they are so popular. the prices reflect this, old stock kt88 are in comparison cheap..

so...
a good push pull kt88 is a good introduction into valves, when used with more 'normal' speakers,
but as marco has come to realise, there are further gains to be had with higher effeciency speakers that match well
its a slippery slope

steve

[Togil]

SE :
There are those ( cf the crazy but entertaining Goodsoundclub ) who say that SE only sounds good on horns, even if you have higher power

Anthony would you agree with that or do your Soul amplifiers work on low-efficiency speakers ( eg Quads ) ?

Certainly the Kronzilla ( which uses what I believe is essentially a large triple 300B type valve ) sounded terrible to me on the dynamic speakers in Munich this year.

Mr. Kang-Su Park's ( another genius like Anthony ) 300B Allnic amps sounded excellent in the various systems I heard them in in Korea this summer, but they were mainly horns.

[anthonyTD]

SE :
There are those ( cf the crazy but entertaining Goodsoundclub ) who say that SE only sounds good on horns, even if you have higher power

Anthony would you agree with that or do your Soul amplifiers work on low-efficiency speakers ( eg Quads ) ?

Certainly the Kronzilla ( which uses what I believe is essentially a large triple 300B type valve ) sounded terrible to me on the dynamic speakers in Munich this year.

Mr. Kang-Su Park's ( another genius like Anthony ) 300B Allnic amps sounded excellent in the various systems I heard them in in Korea this summer, but they were mainly horns.

hi hans,
good question, first of all many people that know me or have had experience of a product i have been associated with will almost definitely know that i only build products that work in what i describe as "the real world" that means any power amplifier i build or have built must be capable of working satisfactory with for eg, speakers from low eighties to well over a hundred db, i do however insist that valve amplifiers need as flat an impedance versus frequency range as possible, this i feel is much more important as far as valve amps are concerned.
i have customers who have used the soul series of amplifiers with great success on a wide range of speakers, ranging from tannoys through to quad 63's and on to wilson grand slams.
i hope this helps.
regards,anthony,TD...