Why not just make FIRs by hand?

<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 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 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 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

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)