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Old 31st August 2010, 12:58 PM   #31
Salas is online now Salas  Greece
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The sound of real instuments is totally dependant on the acoustic envoironment.
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I suspect that the musician and the instrument might be minor factors?
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Well said Sy; a skilful player can make any heap of junk sound good whereas an unskilful one with a great instrument is like a person surrounded by the highest quality ingredients but........ does not know how to cook. The parallels as far as this forum are concerned are obvious.
I had this friend who used to be regarded a young prodigy pianist but he would not look for a career in that later on. So we were out once and we passed a girl playing the violin in open air classical tunes basking. He told me, can you listen to the thin tone, that's a chamber violin, can't cut it in the open. He went on explaining to me that each acoustic instrument of the classic orchestra has been evolved in tandem with the usual space it was performing in. That thing he said lasted for centuries and it was a trial and error between requests of maestro's, musicians, and instrument makers. You probably think a Stradivari is so famous and mythically expensive because it must be the best hands down, he told me.
Well, no, he continued. Its the best loud violin for soloists in halls. If a Stradivari will play amongst Amatis in a chamber orchestra it will shadow 3 of them for volume, but it will sound positively gross also. The Amati is the delicate one. Each one to its own function he concluded. Don't know if this story ties here, but stories are nice.
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Old 31st August 2010, 01:34 PM   #32
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But its generally a small part of the main picture.
...

Just take everything stated off hand with a pinch of salt.
In other words, tube roll is not what it's typically praised to be by online reviews?
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Old 31st August 2010, 01:53 PM   #33
Salas is online now Salas  Greece
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I believe most reviews are in good will and honesty. The parameters just aren't fixed including the people. So the the reviews can be entertaining but they will never work as real guides. Just news and clues to check up on further in leisure.
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Old 31st August 2010, 01:58 PM   #34
TheGimp is offline TheGimp  United States
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Originally Posted by DF96 View Post
...snip....
When somebody says Valve A is better than Valve B, what he may really mean is that in one particular circuit at one particular bias point with particular items upstream and downstream that valve gives a sound which he prefers. ..snip....
How much can the variation in bias for a tube span from one vendor to another, and one time period to another?

What is the likelyhood that a lot of "Tube Rolling" results in tubes biased far enough off the sweet spot that it is noticable? If the tubes were individually biased for their own best point there wouldd there be near the difference if any at all?

Unfortunatly this would take a lot of effort to determine wheyther true or not.
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Old 31st August 2010, 02:00 PM   #35
Salas is online now Salas  Greece
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http://www.passdiy.com/pdf/sweet_spot.pdf
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Old 31st August 2010, 04:18 PM   #36
ChrisA is offline ChrisA  United States
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Originally Posted by piano3 View Post
Well said Sy; a skilful player can make any heap of junk sound good whereas an unskilful one with a great instrument is like a person surrounded by the highest quality ingredients but........ does not know how to cook. The parallels as far as this forum are concerned are obvious.
Just a comment, when people say the tube sounds "warm" it it generally means the sound has add 2nd and maybe 3rd order harmonic distortion. When they say "flat" and detailed they mostly main very low THD. Many people prefer "warm"

About the quote above....

What I tell people who want to do home recording is that what matters the most to the the end result is what is closest to the source of the sound. The #1 thing is the player and his instrument, then comes the space, this is the room acoustics and then the mic and where it is placed and then we get into mic preamps, A/D converters and software. For recording I'm sure that you are best to invest your money and your time in that which is closest to the source. If I'm recording my self I think adding practice time helps the most

For playback I think the opposite is true. The direction runs in reverse. That which is closest to the listener's ear matters the most. The room being the most important followed by the speakers and then the amp and finally the quality of the source. I think most agree, that speakers matter the most.

So if you look at the total system from musician to listener the amp is in the mid section of the chain when it is the ends of the chain that make the most difference.
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Old 31st August 2010, 04:29 PM   #37
kevinkr is offline kevinkr  United States
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Thanks for explaining

I messured 2,6V at that point so it's correct. And there is no cap to next stage

I think i leave it as it is

Regards //Daniel
The 125V that is supposed to be on the grids of the succeeding ECC99 driver stage is kind of important. It looks to me if the information you have provided is correct that a plate load resistance of 43K might be a better compromise for this particular circuit.

I have found that there are significant differences in the way that 6SN7 sound not necessarily based on less than ideal operating points for one brand vs another.. Some just do sound better IMLE than others regardless of operating point. My personal favorite is the Sylvania, more or less any version made prior to the late 1980s - with earlier ones being slightly preferred.

I have NOS Sylvania, US made cylindrical plate Tungsols (Not the New Sensor stuff), GE, RCA, Westinghouse and a whole lot others. I genuinely prefer the Sylvania to any of the others. I also like the Brimar version quite a lot, but they are rather costly these days, so consequently I currently have none.

I run 6SN7 at typically 8 - 10mA where they seem to provide the best linearity, and this has proven to be the case with any I have tried. Much above 10mA - 12mA you start to reach the point of diminishing returns and plate dissipation limits also have to be observed.
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Last edited by kevinkr; 31st August 2010 at 04:33 PM.
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Old 31st August 2010, 05:05 PM   #38
rongon is offline rongon  United States
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In a power amp with LTP driving push-pull triode-wired EL34's, I tried the old New Sensor "Sovtek" 6SN7 and found that they did sound a little different than my pile of 6SN7GT, 6SN7GTA and 6SN7GTB tubes. In that amp, the 6SN7 anode load resistors are 36k ohms, with 7.5mA current through each triode side. If I remember correctly, bias is about -5.5V, so that means anode voltage is probably about 185V.

In this particular amp, the standard Sovtek 6SN7's sound a little thin, less "powerful" than the USA 6SN7's. But the difference is very small. The USA-made 6SN7's all sound pretty close to each other. I found the Sylvania 'GTBs to sound very good, and GE 'GTBs also sound good (the GE might be my fave American version, but that's a personal taste thing, I think). My absolute favorite is a pair of rare, Soviet-era, metal-based 6SN7 equivalent (6N8S? I'm not home so can't double-check) that is by far the best of the bunch. Those are really a cut above, but they're expensive these days.

I think that with only 5.2mA going through the 6SN7 in your amp, you could be accentuating the differences between makes/types of 6SN7. Some are probably better suited to low-current, low-voltage operation. Some probably perform worse used under those conditions. If the circuit could be optimized so that there was more current going through the first stage 6SN7, then I have a hunch you'd notice less difference between the various makes/types of 6SN7, and that stage would begin to sound more full and less 'thin.'

Careful attention must be paid to the relationship between the anode voltage at the 6SN7 and the voltage at the joined ECC99 cathodes. The ECC99 cathodes will need to be a few (like 8 to 10?) volts higher than the 6SN7 anode. That creates the bias for the ECC99 triodes, since the two stages are DC-coupled.

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Old 1st September 2010, 01:15 PM   #39
Green77 is offline Green77  Sweden
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Hi!

I've tried to do some maths Have no idea if this is rights

But if it's right around the 6SN7 tube, what about the ECC99? Should something be changed? Like R12?

Click the image to open in full size.

Thanks //Daniel
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Old 1st September 2010, 01:45 PM   #40
TheGimp is offline TheGimp  United States
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13mA for the pair of ECC99 gives 6.5mA per tube.

top anode is at 440-(.0065*30000)=245V
A-K = 245-130 = 115V

Bottom anode is at 440-(0.0065*37170)=198.4
A-K = 198.4-130 = 68.39V

I believe the lower ECC99 will start saturating before you drive the KT88 fully and you will get high distortion.

I would lower the current through the pair by increasing R12, or change the anode resistor values to give less drop, or both. Depends on how the ECC99s are best operated.

I would have to look up the ECC99 and KT88 specs to give more detail.

I looked them up.

The KT88s are going to take around 110V p-p on the grids. so you need 55V peak before saturating or cutoff on the driver.

ECC99 I would not bias any colder.

I'd change the anode resistors. Maybe 20K total on the top and andjust the bottom accordingly, say 24.66K if you scale by your current selection.

You have 130V available in the cathode circuit. How about a current source instead of R12?

Last edited by TheGimp; 1st September 2010 at 01:57 PM.
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