new (to me) all-pass circuit

On 24/09/18 21:21, Phil Allison wrote:
> Clifford Heath wrote:
>> I'm sure you'll remember the ETI447 phaser,
>> <http://www.spontis.se/pdf/eti447.pdf>.
> ** I remember building one for a friend from a Dick Smith kit.
>     Half the supplied 741s did not work.

Gaak. I didn't know much then, but I knew to avoid 741's :)
I forget what I actually used, don't think it was LM324.

I must power it up again and see if it still works.

Clifford Heath

On a sunny day (Mon, 24 Sep 2018 22:49:12 +1000) it happened Clifford Heath
<no.spam@please.net> wrote in <f35qD.46045$xI1.19812@fx13.iad>:

>On 24/09/18 21:21, Phil Allison wrote:
>> Clifford Heath wrote:
>>> I'm sure you'll remember the ETI447 phaser,
>>> <http://www.spontis.se/pdf/eti447.pdf>.
>> ** I remember building one for a friend from a Dick Smith kit.
>>     Half the supplied 741s did not work.
>
>Gaak. I didn't know much then, but I knew to avoid 741's :)
>I forget what I actually used, don't think it was LM324.
>
>I must power it up again and see if it still works.
>
>Clifford Heath

There was nothing wrong with 741, I still have some.
Did an audio mixer with it.

On 09/24/2018 10:33 AM, 698839253X6D445TD@nospam.org wrote:
> On a sunny day (Mon, 24 Sep 2018 22:49:12 +1000) it happened Clifford Heath
> <no.spam@please.net> wrote in <f35qD.46045$xI1.19812@fx13.iad>:
> 
>> On 24/09/18 21:21, Phil Allison wrote:
>>> Clifford Heath wrote:
>>>> I'm sure you'll remember the ETI447 phaser,
>>>> <http://www.spontis.se/pdf/eti447.pdf>.
>>> ** I remember building one for a friend from a Dick Smith kit.
>>>      Half the supplied 741s did not work.
>>
>> Gaak. I didn't know much then, but I knew to avoid 741's :)
>> I forget what I actually used, don't think it was LM324.
>>
>> I must power it up again and see if it still works.
>>
>> Clifford Heath
> 
> There was nothing wrong with 741, I still have some.
> Did an audio mixer with it.
> 

Many mixing consoles from the 70s were full of them it's not like there 
weren't any good records recorded on e.g. SSL desks in the 70s. they 
don't have the slew rate to output a square wave at 1kHz at more than a 
couple 100s of mV that's fine most rock n roll and pop music doesn't 
consist of 1kHz square waves.

On 24/09/2018 16:23, bitrex wrote:
> On 09/24/2018 10:33 AM, 698839253X6D445TD@nospam.org wrote:
>> On a sunny day (Mon, 24 Sep 2018 22:49:12 +1000) it happened Clifford 
>> Heath
>> <no.spam@please.net> wrote in <f35qD.46045$xI1.19812@fx13.iad>:
>>
>>> On 24/09/18 21:21, Phil Allison wrote:
>>>> Clifford Heath wrote:
>>>>> I'm sure you'll remember the ETI447 phaser,
>>>>> <http://www.spontis.se/pdf/eti447.pdf>.
>>>> ** I remember building one for a friend from a Dick Smith kit.
>>>> &#4294967295;&#4294967295;&#4294967295;&#4294967295; Half the supplied 741s did not work.
>>>
>>> Gaak. I didn't know much then, but I knew to avoid 741's :)
>>> I forget what I actually used, don't think it was LM324.
>>>
>>> I must power it up again and see if it still works.
>>>
>>> Clifford Heath
>>
>> There was nothing wrong with 741, I still have some.
>> Did an audio mixer with it.
>>
> 
> Many mixing consoles from the 70s were full of them it's not like there 
> weren't any good records recorded on e.g. SSL desks in the 70s. they 
> don't have the slew rate to output a square wave at 1kHz at more than a 
> couple 100s of mV that's fine most rock n roll and pop music doesn't 
> consist of 1kHz square waves.

I recall avoiding the 741 dues to it's full power bandwidth. If all you 
wanted was a 2V p-p audio signal then they were fine on paper.

I used LM324s but these had sever crossover distortion. I got over that 
by biasing the output pin with a resistor to Vcc, making the output 
stage essentially class A.

-- 
Mike Perkins
Video Solutions Ltd
www.videosolutions.ltd.uk

On 09/24/2018 11:28 AM, Mike Perkins wrote:
> On 24/09/2018 16:23, bitrex wrote:
>> On 09/24/2018 10:33 AM, 698839253X6D445TD@nospam.org wrote:
>>> On a sunny day (Mon, 24 Sep 2018 22:49:12 +1000) it happened Clifford 
>>> Heath
>>> <no.spam@please.net> wrote in <f35qD.46045$xI1.19812@fx13.iad>:
>>>
>>>> On 24/09/18 21:21, Phil Allison wrote:
>>>>> Clifford Heath wrote:
>>>>>> I'm sure you'll remember the ETI447 phaser,
>>>>>> <http://www.spontis.se/pdf/eti447.pdf>.
>>>>> ** I remember building one for a friend from a Dick Smith kit.
>>>>> &#4294967295;&#4294967295;&#4294967295;&#4294967295; Half the supplied 741s did not work.
>>>>
>>>> Gaak. I didn't know much then, but I knew to avoid 741's :)
>>>> I forget what I actually used, don't think it was LM324.
>>>>
>>>> I must power it up again and see if it still works.
>>>>
>>>> Clifford Heath
>>>
>>> There was nothing wrong with 741, I still have some.
>>> Did an audio mixer with it.
>>>
>>
>> Many mixing consoles from the 70s were full of them it's not like 
>> there weren't any good records recorded on e.g. SSL desks in the 70s. 
>> they don't have the slew rate to output a square wave at 1kHz at more 
>> than a couple 100s of mV that's fine most rock n roll and pop music 
>> doesn't consist of 1kHz square waves.
> 
> I recall avoiding the 741 dues to it's full power bandwidth. If all you 
> wanted was a 2V p-p audio signal then they were fine on paper.
> 
> I used LM324s but these had sever crossover distortion. I got over that 
> by biasing the output pin with a resistor to Vcc, making the output 
> stage essentially class A.
> 

At some point it seems the audio gear industry settled on a few newer op 
amps which provided good price/performance and have more or less used 
them ever since, the JRC4558 for the "budget" market and the NE5532 if 
you were "high end", and JFET input amps like the TL072/TL082 for stuff 
not directly in the signal path like active rectifiers for meters, etc.

The NE5532 is a fine audio op amp with perfectly adequate specs for low 
distortion rail to rail sine waves out to 20kHz into a heavy load.

The JRC4558 seems to have a bad reputation among audiophools; I have a 
Behringer active solid state/tube hybrid mixer that's full of them 
sounds really nice to my ears just with mids cut about 2dB, bass and 
treble boosted around the same amount strapped in-between an iPod and a 
power amp, I'm too dumb to hear the badness I guess.

bitrex wrote
>On 09/24/2018 10:33 AM, 698839253X6D445TD@nospam.org wrote:
>> There was nothing wrong with 741, I still have some.
>> Did an audio mixer with it.
>> 
>
>Many mixing consoles from the 70s were full of them it's not like there 
>weren't any good records recorded on e.g. SSL desks in the 70s. they 
>don't have the slew rate to output a square wave at 1kHz at more than a 
>couple 100s of mV that's fine most rock n roll and pop music doesn't 
>consist of 1kHz square waves.

I know, but it was a lot more stable than the 709 IIRC,
Mine was used for music in an auditorium and speech, got compliments for the sound quality,
what more can anyone ask for.
'Square wave' is not the same to everybody, human hearing is usually way down above 15 kHz,
and few instruments are located above that at 100% amplitude.
Yes if you push your organ square waves through it... then it SHOULD have a low pass filter,
just to save the expensive tweeters :-)

 Mike Perkins wrote:

>

> >>
> >> There was nothing wrong with 741, I still have some.
> >> Did an audio mixer with it.
> >>
> > 
> > Many mixing consoles from the 70s were full of them it's not like there 
> > weren't any good records recorded on e.g. SSL desks in the 70s. they 
> > don't have the slew rate to output a square wave at 1kHz at more than a 
> > couple 100s of mV that's fine most rock n roll and pop music doesn't 
> > consist of 1kHz square waves.
> 
> I recall avoiding the 741 dues to it's full power bandwidth. If all you 
> wanted was a 2V p-p audio signal then they were fine on paper.
> 


** 741s work fine out to 80kHz at 2V p-p on sine waves.


> I used LM324s but these had sever crossover distortion.


** Plus the same Slew Rate as a 741.
 

> I got over that 
> by biasing the output pin with a resistor to Vcc, making the output 
> stage essentially class A.
> 

** Still results in way higher THD than a 741.


...  Phil 

On Tuesday, September 25, 2018 at 3:54:25 AM UTC+10, 69883925...@nospam.org wrote:
> bitrex wrote
> >On 09/24/2018 10:33 AM, 698839253X6D445TD@nospam.org wrote:
> >> There was nothing wrong with 741, I still have some.
> >> Did an audio mixer with it.
> >> 
> >
> >Many mixing consoles from the 70s were full of them it's not like there 
> >weren't any good records recorded on e.g. SSL desks in the 70s. they 
> >don't have the slew rate to output a square wave at 1kHz at more than a 
> >couple 100s of mV that's fine most rock n roll and pop music doesn't 
> >consist of 1kHz square waves.
> 
> I know, but it was a lot more stable than the 709 IIRC,

True, but the uA709 was Bob Widlar's, and his versions of the uA741 and uA748, the LM301 and the LM307, were appreciably better than the uA741 and the uA748.

IIRR the LM301 preceded the uA741, and was actually pretty popular for quite a while. National Semiconductor was a bit slow in putting the 30pF compensation capacitor onto the chip - it took up quite a lot of silicon, making the chip more expensive to make - and Fairchild managed to get the uA741 established in the market before National Semiconductor realised that there was a large market for a compensated op amp amongst designers who didn't want to think about what they were doing.
 
> Mine was used for music in an auditorium and speech, got compliments for the sound quality, what more can anyone ask for.
> 'Square wave' is not the same to everybody, human hearing is usually way down above 15 kHz, and few instruments are located above that at 100% amplitude.

When I was young (early twenties) I could hear the 15.625 kHz line scan noise from a regular (Australian - PAL) TV. That didn't last a long as cathode ray tube displays.

<snip> 

-- 
Bill Sloman, Sydney