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    Building, troubleshooting and testing of these amplifiers should only be
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    the safety precautions around high voltages.

Need to find 300B tube amp use 6SN7 5U4G >25w/ch

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300B amplifier sound will very much depend on the quality of the output transformer and the rectifier valve. Then the actual 300B itself.
Chinese, so quality control is the big problem
You could get a gem, or one that bursts into flames like the 845 that I had!

To my ears every 300B amp has a character of being too rich in sound with a bloom over everything. But that is jut my opinion.
Mr. ColinA provide me an Idea of 300B Characteristic? If I buy only PCB then Quality control will be me. I will try to control the quality as much as I can. For Output transformer, I might buy from local shop with more reliable. Rectifier tube I will use Russian (I forgot 5Z3P maybe) that I have in my inventory.

For Mr. Merlinb, Is it better than KT88 in tighter bass, clear mid, silky high?
I like sound of my headphone "Vsonic VSD3S with stuff mod". Sound the best I have ever heard. Just mod with light thin "cotton". Sound is extremely good.

I want to here this sound in my house. I can listen to headphone for only 30 mins. I am afraid of loss of hearing and damage my ears.
Many people like the sound of 300B.
I do not, does that make it bad?...............No!
Everyone must judge with their own ears.
To compare a directly heated triode with tetrodes in one sentence, impossible.

Too many variations of components, design and how things are built.
Somewhere you must make a choice and see how things are to your ears.

For very many years my main amp has been a 2A3 SE with all vintage valves.
Recently I have built a Pass F6 which walks all over it for clarity, dynamics and bass.
Unless you can audition amps somewhere you just have to make a choice and see what happens.
Sorry if that's not too helpful but it's a lesson most of us go through.
Is 'clean' sound the same as 'clear' sound?

Putting into words what we hear as qualities of sound reproduction is one extremely imprecise business. I'm not an engineer or a scientist, but I've been grappling with hi-fi in one way or another for something like 40 years now. So I'll give it a go...

[Assuming flat frequency response]

In an amplifier driving a speaker, I think 'tight bass' equals high-ish damping factor. 'Loose bass,' 'woolly bass,' or 'rich, blooming bass' are most likely due to low damping factor, with subsequent looser control over the woofer causing rounded off transient response and increased output in the low frequencies.

'Rich bloom over everything' is probably a noticeable amount of 2nd harmonic distortion. That can be kind of fun to listen to, especially with certain kinds of audiophile-style 'girl with guitar' music. However, for complex music like large-scale orchestral works or large vocal choirs this type of reproduction can sound 'murky,' 'syrupy.' or 'muddy.' I'm pretty sure of this one.

'Dry, clinical sound' is likely fairly low distortion but with the remaining distortion harmonics skewed to the odd ones, like 3rd or 5th, with suppressed even order harmonics like 2nd or 4th -- as in a good push-pull amp. I'd describe this as 'clean' if the distortion is low, 'dry' if the distortion is a bit higher. That's a subjective call there. I'm less sure of this one.

'Hard, glassy but clean sound' is probably fairly low distortion but with some higher order harmonics present in low proportions, perhaps 5th and 7th order at low levels. It could also be due to IM distortion. This is where the solid state vs tube and SE vs PP wars start. Let's not go there.

'Clean sound' is so general a description that it's really hard to quantify. For me, it seems that the lower the distortion and noise, the more information and things going on ('detail'?) you can hear from within the recording.

Is there a way for a low distortion amplifier to reproduce sound that is subjectively 'unclear' or 'slow'? Why does my well-measuring Hafler class AB MOSFET amplifier not sound pleasing to me?

PS - Merlin, I'm enjoying your valve preamp book immensely. Fantastic job on that!
PPS - I find that once you're used to a certain kind of reproduction, let's say the sound from a good class AB solid state amp, the first time you hear an equally pleasing but completely different type of sound, like that from a good SE 300B amp, it's a kind of revelation, and one leaps to the conclusion that it's somehow 'better.' Beware the attractiveness of the new. It usually wears off.
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Is it better than KT88 in tighter bass, clear mid, silky high?

The 300b is a power triode and the KT88 is a kinkless tetrode, they are completely different devices.

Now if you apply some feedback you can make the KT88 have curves that look more like a triode. In fact the KT88 triode wired has lower plate resistance than a 300b and appears easier to drive. It doesn't look as linear as the 300b though.

Sound isn't so much the device but how it's implemented. :bullseye:
$4 triode wired sweep tube superimposed over a 300b plate characteristic graph.


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