John Curl's Blowtorch preamplifier

[syn08]

Thanks, did you have a chance to evaluate OPA827?

Yes, I got a few engineering samples from TI. A truly amazing FET input opamp. Realistically, audio doesn't need anything better than this, as a low level gain block.

Bottom line, there's nothing wrong that I can measure with this opamp, in the audio range. About the "sound", I'll let others talk.

 

[john curl]

No, parts per 1000 in low frequency distortion.

 

[Steve Eddy]

No, parts per 1000 in low frequency distortion.

Eh?

se

 

[john curl]

As I recall, 1 part per 1000 is 0.1%. That is a common number on the Jensen transformer data sheet. Can I rub your nose in it even further?

 

[Steve Eddy]

As I recall, 1 part per 1000 is 0.1%. That is a common number on the Jensen transformer data sheet. Can I rub your nose in it even further?

0.1% at the lowest frequencies. Does it matter beyond numbers on a spec sheet?

se

 

[jam]

Newsflash!

John Curl Kinda likes transformers for low noise..............

Come on John is 0.1 % distortion at 20 hz relavent in this application?

What about distortion inheritant in the cartridge, cutter head, microphone, tape head...............speakers?

You might be wanting to guild the invisible lilly .......

Regards.

Jam

 

[Edmond Stuart]

Normally I count ppb's.

 

[john curl]

It is the amazing amount of warp signal that IM's the transformer. Jam, as usual, you are outside your level of understanding. I already explained the problem in an earlier post. Please read #6137.

 

[Steve Eddy]

It is the amazing amount of warp signal that IM's the transformer.

But because of the transformer's frequency selectiveness with regard to distortion, IM isn't the problem that it would be in an active circuit.

So again, does 0.1% at 20Hz really matter?

se

 

[jam]

Mr. Curl please read my updated post and explain to me what I am missing as I am outside my level of understanding...................seems to be a favorite line of yours.

Regards,

Jam

 

[SY]

It's easy to measure if the IM is a problem, instead of speculating about it, if anyone cares to and has the appropriate test record. The mechanism seems eminently plausible, now does experiment bear it out?

 

[jam]

SY,

I might be wrong but it seems to me that all the other forms of distortion in the playback system would swamp out any distortion inherent in the transformer.

This is not to say designing for lowest noise or distortion s not a noble goal but at some point we have to be realistic and choose the best compromise.

Jam

 

[john curl]

You think? Maybe prove? Put up, or get out of the way.

 

[hitsware]

I might be wrong but it seems to me that all the other forms of distortion in the playback system would swamp out any distortion inherent in the transformer.

Normally distortion is additive (aurally for sure).
I.E. One form does not swamp out another, but
adds to it, creating further audible degradation.

If that were not true, these discussions would
be moot, since loudspeakers would 'swamp out'
all but the grossest of distortions.

 

[jam]

Mr.Curl,

Get out of the way? Now, now...................you claim that you are here to teach...........so teach!

It sees to me that you are using this this forum as a vechicle to let the the rest of the membership know great you are, by your repeated chest pounding............pity.

Regards,

Jam

 

[jam]

hitsware,

Granted distortion is additive but 0.1% addeed to several %?

Something to ponder............Is distortion the most important issue in this context.........noise might be more important?

Jam

 

[PMA]

Distortions superimpose.

 

[jam]

PMA,

You are correct but my argument still holds..........

Jam

 

[john curl]

Hitsware, you are on track. I can't say that a single input transformer will completely change the sound quality of an audio chain, but I have spent the last 40 years and more, trying to provide an alternative.
By the way, Jam is mad at me, because I won't help him privately anymore. He must now rely on others. Goodbye Jam and good luck.

 

[jam]

Mr.Curl,

............being a trifle petty, are we? Why don't you explain what really happened.

So sad............a pity.

Jam