On 24.08.2016 09:18, Tauno Voipio wrote:
> On 24.8.16 03:16, Steve Pope wrote:
>> <herrmannsfeldt@gmail.com> wrote:
>>
>>> On Tuesday, August 23, 2016 at 10:07:10 AM UTC-7, Steve Pope wrote:
>>
>>> (snip)
>>>>>> I don't recall that.  I think both sections were equivalent in the
>>>>>> 12AX7.
>>>
>>> (then I wrote)
>>>>> http://www.mif.pg.gda.pl/homepages/frank/sheets/137/1/12AX7.pdf
>>>
>>>>> Seems that some capacitance is slightly different, but I don't see
>>>>> anything else different.  The capacitance might be from electrode and
>>>>> pin position differences.
>>>
>>>> Thanks, I was mis-remembering then.
>>>
>>> There might be some that are different.
>>
>>> Otherwise, two matching halves are convenient for making a differential
>>> amplifier. Though they never warm up at exactly the same rate.
>>>
>>> http://tone-lizard.com/vtvms/
>>>
>>> reminds me that the 12AU7 is commonly used in VTVMs, but the examples
>>> shown are measuring a 12AX7.
>>
>> As a child, I built various tube amps and similar under the guidance
>> of my father, a radioman and ham from the old days.  I have a vague
>> memory of him advising me to use a 12AU7 in those circuits requiring
>> balanced behavior between the two triodes.  Looking back, this could
>> be just that it was lower gain and so balance is more readily achieved.
>> It certainly was used in voltmeters.
>>
>> Steve
>
>
> There were a set of double triodes: ECC81/12AT7, ECC82/12AU7 and
> ECC83/12AX7.
>
> 12AT7 was intended for RF work, 12AU7 for general purpose and 12AX7 for
> low-level audio.
>
> One tube with unequal halves was ECC88/6DJ8 and its successors (E88CC,
> ECC188), intended for RF cascode use.
>
... there was an ECC808, used in my 60s Hohner amp, with lower noise & 
pretty symmetric pinout (and quite expensive these days)

On 24.8.16 03:16, Steve Pope wrote:
> <herrmannsfeldt@gmail.com> wrote:
>
>> On Tuesday, August 23, 2016 at 10:07:10 AM UTC-7, Steve Pope wrote:
>
>> (snip)
>>>>> I don't recall that.  I think both sections were equivalent in the 12AX7.
>>
>> (then I wrote)
>>>> http://www.mif.pg.gda.pl/homepages/frank/sheets/137/1/12AX7.pdf
>>
>>>> Seems that some capacitance is slightly different, but I don't see
>>>> anything else different.  The capacitance might be from electrode and
>>>> pin position differences.
>>
>>> Thanks, I was mis-remembering then.
>>
>> There might be some that are different.
>
>> Otherwise, two matching halves are convenient for making a differential
>> amplifier. Though they never warm up at exactly the same rate.
>>
>> http://tone-lizard.com/vtvms/
>>
>> reminds me that the 12AU7 is commonly used in VTVMs, but the examples
>> shown are measuring a 12AX7.
>
> As a child, I built various tube amps and similar under the guidance
> of my father, a radioman and ham from the old days.  I have a vague
> memory of him advising me to use a 12AU7 in those circuits requiring
> balanced behavior between the two triodes.  Looking back, this could
> be just that it was lower gain and so balance is more readily achieved.
> It certainly was used in voltmeters.
>
> Steve


There were a set of double triodes: ECC81/12AT7, ECC82/12AU7 and 
ECC83/12AX7.

12AT7 was intended for RF work, 12AU7 for general purpose and 12AX7 for 
low-level audio.

One tube with unequal halves was ECC88/6DJ8 and its successors (E88CC, 
ECC188), intended for RF cascode use.

-- 

-TV

<herrmannsfeldt@gmail.com> wrote:

>On Tuesday, August 23, 2016 at 10:07:10 AM UTC-7, Steve Pope wrote:

>(snip)
>> >> I don't recall that.  I think both sections were equivalent in the 12AX7.
>
>(then I wrote)
>> >http://www.mif.pg.gda.pl/homepages/frank/sheets/137/1/12AX7.pdf
>
>> >Seems that some capacitance is slightly different, but I don't see
>> >anything else different.  The capacitance might be from electrode and
>> >pin position differences.
>
>> Thanks, I was mis-remembering then.
>
>There might be some that are different.

>Otherwise, two matching halves are convenient for making a differential
>amplifier. Though they never warm up at exactly the same rate. 
>
>http://tone-lizard.com/vtvms/
>
>reminds me that the 12AU7 is commonly used in VTVMs, but the examples
>shown are measuring a 12AX7.

As a child, I built various tube amps and similar under the guidance
of my father, a radioman and ham from the old days.  I have a vague
memory of him advising me to use a 12AU7 in those circuits requiring
balanced behavior between the two triodes.  Looking back, this could
be just that it was lower gain and so balance is more readily achieved.
It certainly was used in voltmeters.

Steve

On Tuesday, August 23, 2016 at 10:07:10 AM UTC-7, Steve Pope wrote:

(snip)
> >> I don't recall that.  I think both sections were equivalent in the 12AX7.

(then I wrote)
> >http://www.mif.pg.gda.pl/homepages/frank/sheets/137/1/12AX7.pdf

> >Seems that some capacitance is slightly different, but I don't see
> >anything else different.  The capacitance might be from electrode and
> >pin position differences.

> Thanks, I was mis-remembering then.

There might be some that are different.

Otherwise, two matching halves are convenient for making a differential amplifier. Though they never warm up at exactly the same rate. 

http://tone-lizard.com/vtvms/

reminds me that the 12AU7 is commonly used in VTVMs, but the examples
shown are measuring a 12AX7.

<herrmannsfeldt@gmail.com> wrote:

>On Tuesday, August 23, 2016 at 12:22:23 AM UTC-7, rickman wrote:
>> On 8/23/2016 2:38 AM, Steve Pope wrote:
>
>(snip)
>> > That may be, what I am recollecting is that the X7 had two
>> > different triodes, one with higher gain, whereas the U7
>> > had a balanced pair of triodes.  Much more _simpatico_ .
>
>> I don't recall that.  I think both sections were equivalent in the 12AX7.
>
>http://www.mif.pg.gda.pl/homepages/frank/sheets/137/1/12AX7.pdf
>
>Seems that some capacitance is slightly different, but I don't see
>anything else different.  The capacitance might be from electrode and
>pin position differences.

Thanks, I was mis-remembering then.

Steve

On Tuesday, August 23, 2016 at 12:22:23 AM UTC-7, rickman wrote:
> On 8/23/2016 2:38 AM, Steve Pope wrote:

(snip)
> > That may be, what I am recollecting is that the X7 had two
> > different triodes, one with higher gain, whereas the U7
> > had a balanced pair of triodes.  Much more _simpatico_ .

> I don't recall that.  I think both sections were equivalent in the 12AX7.

http://www.mif.pg.gda.pl/homepages/frank/sheets/137/1/12AX7.pdf

Seems that some capacitance is slightly different, but I don't see
anything else different.  The capacitance might be from electrode and
pin position differences.

On 8/23/2016 2:38 AM, Steve Pope wrote:
> robert bristow-johnson  <rbj@audioimagination.com> wrote:
>
>> On Monday, August 22, 2016 at 7:33:31 PM UTC-4, Steve Pope wrote:
>
>>> I think rickman  <gnuarm@gmail.com> wrote:
>>>
>>>> ones that use vacuum tubes as the tap elements (and making a CCD delay
>>>> line outa tubes) have a nice warm sound that is particularly well suited
>>>> for audio.  you might be able to do a nice convolutional reverb with,
>>>> maybe, 100,000 vacuum tube triodes (12AX7 has two triodes per tube).
>>>
>>> Heresy.  Use 12AU7's, otherwise the assymmetry might be audible.
>>>
>
>> when i was a kid, i had an old Knight-Kit breadboarding product that had
>> a 12AU7 in it.  don't remember the name of that product.  this was in
>> the 60s.  didn't need as high plate voltage that the 12AX7 needed.
>
> That may be, what I am recollecting is that the X7 had two
> different triodes, one with higher gain, whereas the U7
> had a balanced pair of triodes.  Much more _simpatico_ .

I don't recall that.  I think both sections were equivalent in the 12AX7.

-- 

Rick C

robert bristow-johnson  <rbj@audioimagination.com> wrote:

>On Monday, August 22, 2016 at 7:33:31 PM UTC-4, Steve Pope wrote:

>> I think rickman  <gnuarm@gmail.com> wrote:
>> 
>> > ones that use vacuum tubes as the tap elements (and making a CCD delay
>> > line outa tubes) have a nice warm sound that is particularly well suited
>> > for audio.  you might be able to do a nice convolutional reverb with,
>> > maybe, 100,000 vacuum tube triodes (12AX7 has two triodes per tube).
>> 
>> Heresy.  Use 12AU7's, otherwise the assymmetry might be audible.
>> 

>when i was a kid, i had an old Knight-Kit breadboarding product that had
>a 12AU7 in it.  don't remember the name of that product.  this was in
>the 60s.  didn't need as high plate voltage that the 12AX7 needed.

That may be, what I am recollecting is that the X7 had two
different triodes, one with higher gain, whereas the U7
had a balanced pair of triodes.  Much more _simpatico_ .

S.

On Monday, August 22, 2016 at 7:33:31 PM UTC-4, Steve Pope wrote:
> I think rickman  <gnuarm@gmail.com> wrote:
> 
> > ones that use vacuum tubes as the tap elements (and making a CCD delay
> > line outa tubes) have a nice warm sound that is particularly well suited
> > for audio.  you might be able to do a nice convolutional reverb with,
> > maybe, 100,000 vacuum tube triodes (12AX7 has two triodes per tube).
> 
> Heresy.  Use 12AU7's, otherwise the assymmetry might be audible.
> 

when i was a kid, i had an old Knight-Kit breadboarding product that had a 12AU7 in it.  don't remember the name of that product.  this was in the 60s.  didn't need as high plate voltage that the 12AX7 needed.