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12AX7 and 12AU7 upgrade



 
 
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  #1  
Old October 14th 04, 10:07 PM
Lawrence
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Default 12AX7 and 12AU7 upgrade

Some people told me that a "good" and "no-so-good" 12AX7 and 12AU7 really
make a big difference to the pre-amp and power-amp.

I look at some Chinese 12AX7A which cost about US$12.00 a piece, and a
piece of Tesla ECC803S cost about US$50.00; similar goes to the 12AU7!

I wouldn't mind to pay for the difference, but I want to know if it is
worth paying that?

Can anyone ever tried that can be kind enough to share their experience?

Thanks in advance!

Lawrence
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  #2  
Old October 15th 04, 02:10 AM
Pooh Bear
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Lawrence wrote:

> Some people told me that a "good" and "no-so-good" 12AX7 and 12AU7 really
> make a big difference to the pre-amp and power-amp.
>
> I look at some Chinese 12AX7A which cost about US$12.00 a piece, and a
> piece of Tesla ECC803S cost about US$50.00; similar goes to the 12AU7!
>
> I wouldn't mind to pay for the difference, but I want to know if it is
> worth paying that?
>
> Can anyone ever tried that can be kind enough to share their experience?


I haven't tried it - but it would seem that you need some advice.

The ECC803S ( aka E83CC from some sources ) is a 'long life / high
reliability' type - quoted as 10,000 hrs operation. That's why it's more
expensive.

Any thermionic valve aka 'tube' has characteristic that are simply determined
by the structure of the electrodes ands the quality of the materials used.

Provided that the valve conforms to the correct electrode spacings etc - the
characteristics will be assured.

Clearly, the quality of materials used will affect usable life - hence the
premium price for your ECC803S.

In short - there is nothing about the operation of a valve that can make it's
characteristics *better* than it's *original* spec. A basic understanding of
electronic theory will help.

Don't expect brand X valve to 'sound better' than brand Y valve if they are
manufactured to original spec.


Graham

  #3  
Old October 15th 04, 03:19 AM
Patrick Turner
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Default



Lawrence wrote:

> Some people told me that a "good" and "no-so-good" 12AX7 and 12AU7 really
> make a big difference to the pre-amp and power-amp.
>
> I look at some Chinese 12AX7A which cost about US$12.00 a piece, and a
> piece of Tesla ECC803S cost about US$50.00; similar goes to the 12AU7!
>
> I wouldn't mind to pay for the difference, but I want to know if it is
> worth paying that?
>
> Can anyone ever tried that can be kind enough to share their experience?
>
> Thanks in advance!


Just buy some alternative tubes to try, plug them in,
and listen.

If you hear no changes, then you only wasted $100.

But if you hear better music, you have to decide if it was worth the $100.

But there are a heck of a lot of opinions out there about "tube rolling",
but only your own opinion matters.

Patrick Turner.

>
>
> Lawrence


  #4  
Old October 15th 04, 08:19 AM
Iain M Churches
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Default


> Lawrence wrote:
>
>> Some people told me that a "good" and "no-so-good" 12AX7 and 12AU7 really
>> make a big difference to the pre-amp and power-amp.
>>
>> I look at some Chinese 12AX7A which cost about US$12.00 a piece, and a
>> piece of Tesla ECC803S cost about US$50.00; similar goes to the 12AU7!
>>
>> I wouldn't mind to pay for the difference, but I want to know if it is
>> worth paying that?
>>
>> Can anyone ever tried that can be kind enough to share their experience?
>>
>> Thanks in advance!

>
> Just buy some alternative tubes to try, plug them in,
> and listen.
>
> If you hear no changes, then you only wasted $100.
>
> But if you hear better music, you have to decide if it was worth the $100.
>
> But there are a heck of a lot of opinions out there about "tube rolling",
> but only your own opinion matters.
>
> Patrick Turner.
>




There is also the matter of build quality. I have always used Telefunken
and Westingouse noval valves. I did however buy a matched quad of
Chinese KT88's. Two of these had internal structures leaning so badly that
one of them was nearly touching the envelope. I returned these unused
and the supplier made a refund. I have also been told about a Chinese
KT88 that was found to have a cigarette stub inside it.
The vacuum in the valve must have been good -
as the cigarette was no longer lit:-)

Iain



  #5  
Old October 15th 04, 12:45 PM
Andy Cowley
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Posts: n/a
Default

Pooh Bear wrote:

> Lawrence wrote:
>
>
>>Some people told me that a "good" and "no-so-good" 12AX7 and 12AU7 really
>>make a big difference to the pre-amp and power-amp.
>>
>>I look at some Chinese 12AX7A which cost about US$12.00 a piece, and a
>>piece of Tesla ECC803S cost about US$50.00; similar goes to the 12AU7!
>>
>>I wouldn't mind to pay for the difference, but I want to know if it is
>>worth paying that?
>>
>>Can anyone ever tried that can be kind enough to share their experience?

>
>
> I haven't tried it - but it would seem that you need some advice.
>
> The ECC803S ( aka E83CC from some sources ) is a 'long life / high
> reliability' type - quoted as 10,000 hrs operation. That's why it's more
> expensive.
>
> Any thermionic valve aka 'tube' has characteristic that are simply determined
> by the structure of the electrodes ands the quality of the materials used.
>
> Provided that the valve conforms to the correct electrode spacings etc - the
> characteristics will be assured.
>
> Clearly, the quality of materials used will affect usable life - hence the
> premium price for your ECC803S.
>
> In short - there is nothing about the operation of a valve that can make it's
> characteristics *better* than it's *original* spec. A basic understanding of
> electronic theory will help.
>
> Don't expect brand X valve to 'sound better' than brand Y valve if they are
> manufactured to original spec.
>


Either you are deaf or you haven't done any real comparisons. I can certainly
hear a difference between a NOS Mullard and a Chinese ECC83, even in a low-fi
guitar amp. Check out the curves from different manufacturers examples of a
specific valve. Notice that the non-linear bits at the extremes of the curves
are a little different? Try them on a distortion analyser and notice that the
relative amounts of harmonics are different. All the valves will be within spec.

The specifications given for valves are _very_ incomplete. Usually only plate
resistance, transconductance and hence mu at one or two operating points. I've
never seen a specification which even gave error limits for these three parameters
let alone anything which would pin down the linearity of the changes in these
parameters with changes in operating point.

So there very definitely is something about a valve that can make it sound
different from a differently manufactured example of the same type.

We live in a real analog world not an idealised one.

best

Andy
  #6  
Old October 15th 04, 02:30 PM
truegridtz
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Posts: n/a
Default


"Lawrence" > wrote in message
.42...
> Some people told me that a "good" and "no-so-good" 12AX7 and 12AU7 really
> make a big difference to the pre-amp and power-amp.
>
> I look at some Chinese 12AX7A which cost about US$12.00 a piece, and a
> piece of Tesla ECC803S cost about US$50.00; similar goes to the 12AU7!
>
> I wouldn't mind to pay for the difference, but I want to know if it is
> worth paying that?
>
> Can anyone ever tried that can be kind enough to share their experience?
>
> Thanks in advance!
>
> Lawrence


L: I clicked on an ebay link on the radio-phono NG about someone selling
silcion o-rings for tube dampers. Eventually I ended up on a website that
sells HALO tube dampers, looks like a good idea.

Anyhow, somewhere along the line I encountered an article about what you are
interested in. It may have been in the HALO site.

This guy gave an excellent explanation of why some tubes sound better than
others in a particular circuit. As I recall the bias is one factor. This
was an excellent article. If you can find it you will be glad you did.

He explains in a believable and logical way why there is no particular best
tube. Simply try them and use what you like in a particular circuit.

You can get Sovteks cheap from Parts Express, both WA and WB. They have the
one with the special low hum filament, too. They are supposed to have
different sounds. This would be an affordable place to start. I would be
cautious of anything from China.

I have also read that there are counterfeit tubes from foreign countries
that are marked to look like what they aren't.

I am not fortunate enough to own hi-fi tube audio, only vintage 50s record
players, so I don't know why people don't really like JAN (military) and the
similar 5xxx and 6xxx industrials. I have found that the manuf tolerances
in them are much more precise and their gain and gm is much better than
commercial grade.

The commercial grade will probably have a much wider tolerance range. Thus,
one may sound better than another due to better gain. This is a big factor
in RIAA equalizers. The 12ax7s must have full gain to really reproduce the
curve.

Someone gave me an old torn up muddy junker preamp awhile back. It had two
perfectly good Telefunken X7s in it. Old consoles are often full of good
USA 6BQ5s, and X7s. RCA sometimes used Amperex from Holland, as did
Magnavox. The late 50s is when they got good. Keep an eye out for junk.
Good Luck, Mark


  #7  
Old October 19th 04, 02:24 PM
WntrMute2
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Default

>Some people told me that a "good" and "no-so-good" 12AX7 and 12AU7 really
>make a big difference to the pre-amp and power-amp.


I recently replaced an assortment of Sovtek, J/J and Chinese tubes in my pre
and power amps with Sylvanias (12ax7) and RCA cleartops for the 12au7s. What a
difference. Overall warmer more liquid sound, highs which often were too harsh
smoothed out nicely. Just one opinion but I bought a few extras.
Dave
"Club Soda Not Seals"
 




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