300B Heresy

[toms wait]

So.. pink, quite tiny, easy to dust, only one knob to turn on and off.....

Apart from pink, those other criteria aren't actually that bad.
I once had a 7 box amplifier that even I struggled to turn on in the right order.

 

[nak]

No he doesn't have one and I'm not carting this up stairs at Scott Towers. Not sure where that leaves us. I think it will be a fresh start, with my Mrs ears!

Looking forward to the write up after your visit.

 

[toms wait]

Looking forward to the write up after your visit.

Oh dear I had better make notes.

 

[JamieMcC]

I was having a read up of the Emission Labs 300B Mesh plate earlier today on their website and noticed they in fact also have a 5-year warranty for the first owner when the purchase is registered on the Emission Labs website. So Western Electric don't have a monopoly on offering a five year warranty.

 

[THOMO]

It is not just 300B SETs that can sound too slow,laid back and boomy.It i s the general character of SETs.Especially those using no negative feedback. That is because they have high output impedance/low damping factor so can't control [or damp] the bass drivers properly .
All SETs should have variable negative feedback control so you can better match them to your speakers.I owned an Almarro 318B with that modification and it really helped to get the best out of different speakers.The stock factory setting actually had too much negative feedback for some speakers but I never liked its sound with zero negative feedback.
The worst sounding amp I have tried was an Audio Note 300B.One of the better ones was an Elekit 300B.Same valves but very different sound and configuration.The Elekit sounded far more neutral and accurate.

 

[pmcuk]

All SETs should have variable negative feedback control so you can better match them to your speakers.

You won't get universal agreement on this. Many like tube amps exactly because they don't have feedback loops. Yes, it may tighten the sound but at the expense of other side effects. In fact, designers like Nelson Pass have tried to reduce feedback in solid state Class A amps as much as possible, since it can sound more natural.

 

[Ady]

My amp is a 300b push pull with three different feedback settings. I prefer the zero feedback setting as to me it gives an open wider soundstage.
Cheers Ady

 

[rabski]

Negative feedback in push-pull amplifiers can be useful to reduce distortion primarily and to stabilise gain, but is a blunt instrument and needs a lot of care to avoid varying phase shift.

Negative feedback really doesn't sit well with single ended in my experience. If your SET valve amp sounds slow, laid back and boomy, then it's more likely that the amp and speaker combination is less than ideal. There are good reasons to match SETs with high-efficiency speakers, and those reasons aren't just to get enough volume.

 

[Jazid]

Cathode degeneration of the driver valve is about the only SET feedback I have found generally beneficial, but high output impedance and flabby bass is a scourge of SET topography, sad to say.

 

[THOMO]

My amp is a 300b push pull with three different feedback settings. I prefer the zero feedback setting as to me it gives an open wider soundstage.
Cheers Ady

Yes with push pull that could make sense.I prefer SS amps that have no global negative feedback-Dartzeel and Bakoon for example.
Not so much SETs.

 

[steve 57]

Cathode degeneration of the driver valve is about the only SET feedback I have found generally beneficial, but high output impedance and flabby bass is a scourge of SET topography, sad to say.

I've had a few friends bring their se 300b amps around to mine with a variety of valves, that flabby bass, was obvious (even with my 100db speakers) in varying degrees with just about all modern production valves.
( although some of the more expensive new valves where much better)

On every occasion my pair of 1940s 4300a valves totally cured this, and improved the sound tremendously across the board.
Work on the powersupply can improve the low end flabby-ness performance substantially, but does not make modern valves sound like the genuine original 300bs

I'm pretty sure the plate impedance drops tremendously in some valves at the bottom end, causing extra stress that some power supplies cant handle.
On top of this many cheaper output transformers can thicken (distort) the bass and exaggerate the problem.

 

[Tarzan]

Yes, I'd agree with that in general.

I had a Viva 300B amp and it absolutely excelled with a friend's Snell A1 speakers - a match made in heaven. It was nowhere near so good on my own speakers. The friend bought the amp!

Pretty.

That is not an amplifier that is an engine block...

 

[THOMO]

A typical frequency response of a 300B SET using zero negative feedback.The green line is for a simulated 8 ohm speaker load .This was a Mastersound 300B.
A very long way from a flat response.

 

[JANDL100]

A typical frequency response of a 300B SET using zero negative feedback.The green line is for a simulated 8 ohm speaker load .This was a Mastersound 300B.
A very long way from a flat response.

+/-3db 40hz - 30khz.
Show me a speaker that can do better than that.

 

[THOMO]

Yes but it is not a speaker.Those deviations from flat can compound between the speaker and the amplifier producing more like + or - 6db.Which will be very audible.
If you add in room gain which very often coincides with the bass hump at around 60 -100hz you will get the boomy bass for which SETs are known.

 

[toms wait]

Boomy bass wasn't my problem with the Triode 300B. It was the levels of strident detail, mostly from compressed music choices as it turned out from dem with a really well specified 300B amp.

 

[rabski]

As before, there are other factors. A loudspeaker is a reactive load, not a pure passive resistance. With any single-ended amplifier, regardless of the valve type, the electrical circuit is a coil driving a coil, which is far from a straightforward relationship.

Overall, I agree that single-ended triode amplifiers tend to have 'looser' bass than push-pull alternatives. Nevertheless, not every combination of single-ended and speaker is the same. Not every push-pull design is the same either, nor is every solid-state one.

 

[JANDL100]

I mentioned before the Magic of pairing my 300B valve amp with Snell A speakers.
You've got to get the speaker synergy right with 300B tubes and then magic can happen.
I suspect that it's just that much rarer with 300B than many other valves. It can be well worth persevering imo.

 

[toms wait]

I mentioned before the Magic of pairing my 300B valve amp with Snell A speakers.
You've got to get the speaker synergy right with 300B tubes and then magic can happen.
I suspect that it's just that much rarer with 300B than many other valves. It can be well worth persevering imo.

300B's worked beautifully with Kevin's new R80 speakers at Scott towers.
Less so with home brew Scanspeak/Vifa Impulse H6!
Although to be fair to my speakers, programme choice was crucial.

Mine where compressed pop, Kevin's where well recorded music of a more grown up persuasion.
Blue Aeroplanes and Talking Heads vs Mari Samuelson and Arvo Part and St Germain!

 

[savvypaul]

Please send your unwanted 300Bs to me. I will carry your burden.