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favourite midrange,treble tubes

pforeman

Member
2008-08-17 3:41 pm
I know many people don't like to recommend things like favourite tubes because there's so many paramaters that matter, but........
I'm not concerned about bass, thats being done by another amp a moscode driving a Hframe.
I have George's wonderfull tubelab simple se driving a open baffle driver
Currently using EH el34 sounds great!!
So great that I'd like to try some other tubes.
Because I'm really only interested in >200 Hz what tubes do you recommend for smooth sweet midrange and up and great imaging.
My moscode will provide for the for the rock so I don't think what kind of music you listen to is an appropriate question here, ( I listen to everything ((except for hip hop, rap and country)) ).
I've seen great things about el34 variants esp KT77.
Lots of nice things about lots of tubes but alot of you guys have a bass fetish, and with this amp, bass isn't much of a consideration.
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which tubes do you think I should buy (under $120/pair)
 
IMHO there are tubes that seem to do better, but to me the the biggest impact in mids and treble came from the iron. In the case of the Simple SE, the medium grade Edcors WAY outperformed the Bigger brothers. I am currently running some electraprint iron on an kt88 PP amp that was designed for bass. I doubt I will ever use the amps for bass alone. The mids and highs are too good to ignore. Just my $0.02

FYI my SSE also runs KT88's.

If you want sweetness, the 300B has a nice warm sound in the mids and uppers.
 
Hello Sy,

Microphonics may not be the only factor in good sound!

Who said it was?

But they are among the few that are extremely linear and have benign harmonic distortion.

That's something I see stated a lot. But is there data to back that up? Is there a DHT as linear as a 12AX7? Or D3a? Or 6SN7?
 
Hi!

Mechanical resonances, for one. This is especially true for directly heated (filament) tubes.


Well, yes DHTs are more prone to microphonics than other tubes. But that hardly explains why they sound better in many respects.

Steve Bench did an analysis about the variation of mu against signal level. In this test DHTs were superior to IDHTs and among DHTs those with thoriated tungsten filaments again measureed better (less variation of mu with higher signal levels). While this might not explain all the differences, it fits well to my own observation: I prefer DHTs over IDHT and thoriated tungsten filaments over oxide coated filaments.

But as has been mentioned the tube is only one contributor to overall sound. For example I'd rather listen to an all IDHT amp than one with thorieted tungsten filament DHTs but poorly implemented filament supplies.

Best regards

Thomas
 
The data is there, one only need search.

And while they may exist, I don't see many 12AX7 or 6SN7 power amp output stages.

Andy brought up the small signal tubes. But it's no different for power tubes, either- a 300B doesn't seem to be any more linear than a 7027. Put enough local feedback around the 7027 to equal the gain of a 300B and the comparison becomes ridiculous.

I've searched, and the data I've seen do not support the contention. People may LIKE the sound of DHTs (and clearly many people do), but that does not mean they're linear, it means that people like the colorations.
 

quikie22

Member
2009-09-24 1:53 pm
between tubes and SS, and DHT and IDHT, there must be a difference that we are not measuring but are able to hear. Based on just the factors of linearity, I would dare say that SS designs seem to be much more linear but actually may sound worse. DHT and IDHT, the difference may not be in the numbers or graphs that our limited knowledge can show... but for sure there is a difference.
 
Hi!

DHT and IDHT, the difference may not be in the numbers or graphs that our limited knowledge can show... but for sure there is a difference.

Hi!

As mentioned above, differences have been measured. Attached a graph which shows different tubes gain variation with output signal level. All normalized to peak gain.

I shows that IDHTs have a slight loss on gain with signal level, which could result in s slight compression effect. Oxide DHTs have the opposite behaviour, slight increase in gain with level, which could be translated to a slight expander effect. Thoriated DHTs seem to be the best according to these measurements.

Thomas
 

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I hesitate to walk into this one, but as someone said, what is there about valves which affects just one part of the audio range? Internal resonances is one answer: did I hear someone say "euphonic colouration"? In a badly designed circuit with huge grid stoppers (e.g. many guitar amps), anode-grid capacitance could be an issue: adjusting HF roll-off by "tube rolling" seems very poor engineering to me. Why not just add a trimmer cap?

Plain old-fashioned distortion would affect all frequencies equally, although perception might differ. Distortion seems to be a matter of taste, so asking what valve to use on this basis is a bit like asking someone else to tell you what your favourite food ought to be. Some people like their food, and their music, highly flavoured so they add lots of things to it (salt, pepper, spices, SE distortion). Others prefer to let the ingredients speak for themselves - I only discovered how sweet carrots are when I stopped adding salt.

PS very interesting graph in previous post - but does it show that some valves were used at the wrong bias point?
 
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bigwill

Member
2004-12-25 8:36 pm
UK
I pentode with local feedback can be pretty damn linear. As a beginner I was put off of pentodes because so called "gurus" always said they were unacceptable, but as I learned I realised there is nothing wrong at all with pentodes when used correctly, in fact they have huge benefits.
 
Hi!

PS very interesting graph in previous post - but does it show that some valves were used at the wrong bias point?

The graphs say nothing about bias points. I have not seen the setup or nmeasurements myself. As they have been doen by a very well espected and experienced persopn I assume bias points have been set up optimally for each of the tubes.

We can all speculate about reasons or assume that it must be colorations which make DHTs sound better to some people. But one person, S.Bench, actually took the task up and made some measurements. There are propably other things too which have not been looked at yet. I think just 'nice' sounding colorations cannot explain the quality and quantity of sound difference many experience from DHTs

Thomas
 
Change of gain with signal level indicates odd-order distortion. Something which is flat at first, then goes down (or up - but less likely) shows low amounts of odd-order distortion but perhaps at high orders (depends on the shape of the curve - the sharper the knee the higher the order). (see 801, 01A, 12B4 in graph)

Something which is rising or falling at first shows high amounts of odd-order distortion but perhaps at low orders (e.g. mainly third). If it then levels off this indicates higher orders coming in too. (see 864, 26)

The 6SL7 looks good at first, then suddenly hits a knee - start of clipping?

Accepting that the graph tells us nothing about even-order distortion, it may show why the 12B4 is so popular - it has low and smooth odd-order distortion.

DHTs look a mixed bunch - some very good, others quite bad.