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PostPosted: Tue Feb 07, 2017 1:18 am 
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Muriel
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Hi,

alexandre wrote:
T, sounds lovely indeed, but not all of us can!


Why not? What's stopping you? Fairly affordable 1:20 Microphone transformers with permalloy core exist.

alexandre wrote:
In your opinion, does a small cheap E-I with dual primaries work well as a 1:1 coupling trafo?


At 50/60Hz and if low distortion is no concern, of course. For audio, maybe less so...

Ciao T

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PostPosted: Tue Feb 07, 2017 1:33 am 
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Benjamin

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Now, if you want common-base stages, with transformers.....................well, this is my kind of circuit:

http://www.thegleam.com/ke5fx/norton/lankford.pdf

(Has absolutely nothing to do with audio, and their idea of what a transformer is........................)

BTW, anyone know who KE5FZ is, and what he invented?

Some of you have seen results of its use, but have no idea................................

(I am broadening your education.)


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PostPosted: Tue Feb 07, 2017 1:48 am 
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Muriel
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Hi,

Jocko Homo wrote:
If you like tirodes. I think folks who are building a common-base I/V (which is what the thread was about) probably are not into things that glow and put off a lot of heat.


You could of course use common base/gate/grid I/U conversion and then use a Tube buffer. But J-Fet Buffers (especially the kind where a J-Fet forms a Szikali with a PNP BJT) can also be used, or even Op-Amp's. Many buffers are possible.

Jocko Homo wrote:
And run on much higher rail voltages.


Not absolutely. Many "high perveance" tubes can be useful with 48V rails.

Jocko Homo wrote:
And some of us aren't into picking "magic caps". I can think of more useful things to do than listen to a bunch of caps, to decide which one I like.


I see septics still don't get irony...

But honestly, someone is modding one of my budget DAC. The main change other than fancy "heavy metal" RCA's which I avoided on purpose - is to convert a perfectly decent direct coupled design to one where the line outs are coupled through some "magic caps". He charges about twice the retail of the original DAC for his "mods". Most shockingly, he has customers.

Jocko Homo wrote:
Quote:
BTW, after a lot of work on current conveyors, I ended up not using them. YMMV.


You call it a "current convertor". RF engineers call it a common-base stage. With cascodes. Which is what we are used to dealing with.


I call it "current conveyor", as it is in both structure and intention somewhat different to a plain grounded base/gate/grid stage.

https://en.wikipedia.org/wiki/Current_conveyor

Something like this:

Attachment:
2nd Generation Current Conveyor.gif


Also tried really plain common base BTW.

Jocko Homo wrote:
Anything else you would like to lecture us on about why we should all use triodes, transformers with silver windings, and "magic caps"?
I'll pass. Thanks, but no thanks.


Well, I could tell you WHY what I suggest would be a good idea, but hey, we can not all agree all the time...

You should like Transformers and Followers as there is no feedback involved and the resulting SNR and Linearity can be spectacular.

If I were to build this for an existing DAC/CDP, I'd just use some good quality permalloy cored microphone transformers, which are fairly small and affordable and available off the page (and yes, I DO have them in my junk box - many pairs from ancient pulls to very recent samples) and a J-Fet Sziklai Buffer, DC coupled and servoed by adjusting the current sink.

Hey wait, I DID do that not so long ago. For a modern DAC with very high output current. Sounded decent (for the DAC Chip used) and measured peachy, > 126dB SNR and triple zero THD & N, pretty much 20Hz to 100kHz. Plus, what THD was there was all H2 and from the follower unless the DAC started to loose it above around -3dBFS. As a bonus, it galvanically isolated the DAC and all the circuitry on that side, from the audio output side.

Anyway, there are viable and simple alternatives to common base / current conveyor structures that are, for DIY at least quite interesting.

Ciao T


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PostPosted: Tue Feb 07, 2017 1:53 am 
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Muriel
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Jocko,

Jocko Homo wrote:
Now, if you want common-base stages, with transformers.....................well, this is my kind of circuit:

http://www.thegleam.com/ke5fx/norton/lankford.pdf

(Has absolutely nothing to do with audio, and their idea of what a transformer is........................)


I think turning the BJT into a suitable triode or pentode will improve the circuit.

Seriously, I build Radio's with Tubes (and transistors and IC's) in my youth down to winding the filter circuits.

Jocko Homo wrote:
BTW, anyone know who KE5FZ is, and what he invented?


Given it's a HAM it's gotta be an oscillator (unlike us audio guys they always seem to want to make everything oscillate, whereas we in Audio do NOT want things to oscillate).

Ciao T

(PS, I know it's Pierce's call-sign)

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PostPosted: Tue Feb 07, 2017 2:01 am 
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Muriel
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PS,

Jocko Homo wrote:
I think folks who are building a common-base I/V (which is what the thread was about) probably are not into things that glow and put off a lot of heat.


Well, think again...

http://yanasoft.jp/yana/iv221.html

Image

Attachment:
common base tube I-U converter.png


Ciao T


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PostPosted: Tue Feb 07, 2017 3:30 pm 
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Benjamin

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Kuei Yang Wang wrote:
I see septics still don't get irony...

But honestly, someone is modding one of my budget DAC. The main change other than fancy "heavy metal" RCA's which I avoided on purpose - is to convert a perfectly decent direct coupled design to one where the line outs are coupled through some "magic caps". He charges about twice the retail of the original DAC for his "mods". Most shockingly, he has customers.



Well, we don't know that, do we now?

Yes, shocking. Yet typical.

Quote:
I call it "current conveyor", as it is in both structure and intention somewhat different to a plain grounded base/gate/grid stage.

https://en.wikipedia.org/wiki/Current_conveyor

Something like this:

Attachment:
2nd Generation Current Conveyor.gif


I see the sketpics still don't get the irony. (Where did I see this before?)

Structure and intention aside, it is still a common-base input.

Just like some of us call a diff amp an "emitter follower driving a common-base".

"If all that you have is a hammer, then the whole world looks like a nail."

Quote:
Anyway, there are viable and simple alternatives to common base / current conveyor structures that are, for DIY at least quite interesting.

Ciao T


Never said there isn't, and aren't. This was about common-base, not what you think an interesting alternative is.

That deserves its own thread: not this one.

The irony still evades some....................


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PostPosted: Tue Feb 07, 2017 3:41 pm 
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Benjamin

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Kuei Yang Wang wrote:
Jocko,

Jocko Homo wrote:
Now, if you want common-base stages, with transformers.....................well, this is my kind of circuit:

http://www.thegleam.com/ke5fx/norton/lankford.pdf

(Has absolutely nothing to do with audio, and their idea of what a transformer is........................)


I think turning the BJT into a suitable triode or pentode will improve the circuit.

Seriously, I build Radio's with Tubes (and transistors and IC's) in my youth down to winding the filter circuits.

Jocko Homo wrote:
BTW, anyone know who KE5FZ is, and what he invented?


Given it's a HAM it's gotta be an oscillator (unlike us audio guys they always seem to want to make everything oscillate, whereas we in Audio do NOT want things to oscillate).

Ciao T

(PS, I know it's Pierce's call-sign)


OK, I just realized that I typed the wrong call sign. The right one is in the link, just ol' fat fingers blind-as-a-bat done screwed up.

OK..............KE5FX.

BTW, in my youth, I did a lot more than just wind the filter circuits. None of which used a stinking triode. Or pentode.

Or anything else that couldn't run off of a 12 V car battery. (There was a reason for that, and it had nothing to do with poverty, or lack of anything else.) (Yes, there were gizmos that could take 12 V, and make it into a much higher voltage. Wasn't my goal.)

Not that I didn't wind many a power transformer, salvaged from an old TV.

But, those were for power amp supplies. Which had nothing to do with ham radio.

(I stopped doing ham radio, when everyone and their brother had a 2 m handie-talkie.) (Made by J. A. Pan, Inc. Somehow, that took all the fun out of it, and kinda sorta missed the whole point of doing ham radio crap.)


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PostPosted: Tue Feb 07, 2017 3:49 pm 
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Benjamin

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Kuei Yang Wang wrote:
PS,

Jocko Homo wrote:
I think folks who are building a common-base I/V (which is what the thread was about) probably are not into things that glow and put off a lot of heat.


Well, think again...


Oh, good grief....................putting transistors, with foil over them, to assure thermal coupling, right next to something putting off heat.....................

I can see he never designed a low phase noise oscillator.* I'll leave it at that, and not comment further.

Or reply, so save your breath.

(* = or possibly phono stage.)

(OK, might be able to get away with it in that circuit. Still, not a good idea. Last comment, period.)


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PostPosted: Tue Feb 07, 2017 11:26 pm 
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Cow

Joined: Mon Nov 28, 2005 1:10 pm
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I was not as fortunate as you guys... The first two kits I built as a child already used ICs. The amp worked and the FM tuner didn´t.

BTW, thanks for the oshpark.com link over at the disaster area!


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PostPosted: Tue Mar 21, 2017 10:55 pm 
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Sheep

Joined: Wed Jun 18, 2008 4:54 am
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Jocko Homo wrote:
Now, if you want common-base stages, with transformers.....................well, this is my kind of circuit:

http://www.thegleam.com/ke5fx/norton/lankford.pdf

(Has absolutely nothing to do with audio, and their idea of what a transformer is........................)

BTW, anyone know who KE5FZ is, and what he invented?

Some of you have seen results of its use, but have no idea................................

(I am broadening your education.)

You'll find more about KE5FX following the 'About me' link at the end of the page http://www.thegleam.com/
His most notable contribution to the old HP/Tek test equipment community is the free GPIB tool kit including an HP 7470A plotter emulator for screen capture, a phase noise measurement tool using spectrum analyzers and a VNA utility.
He is also the mastermind behind some modern phase noise/jitter measurement gear. http://www.miles.io will redirect you to the product page.


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PostPosted: Wed Mar 22, 2017 3:56 pm 
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Benjamin

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I know who has the first one he made. Even though he protested it was not ready for release.

Draw your own conclusion.


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