"Liniac" by John LinsLey Hood esq.-

[bcarso]

Thanks Mark!

EDIT: Thanks Alex!

 

[Mark Burnley]

Great,

Thanks Alex!

I'll have to pull those links soon, my host can't handle them for much longer!!

Mark

 

[chrissugar]

Thanks for the article.

chrissugar

 

[strangeandbouncy]

Wow Wow Wow!

Mark you are a total star! i was all set for an afternoon in the British Library (did you know that the LEGALLY have to have a copy of EVERYTHING published in the UK?) thank you thank you thank you!

I have just got my lovely wife to pdf it all for me - looks like my dial-up leaves me miles behind you lot! Bah!

i am looking foreward to reading it and pretending that I understand. Perhaps it willl help my understanding.

You guys is da bestest!!!!!!! official.


All the best,

ANdyP

 

[strangeandbouncy]

finally,

3.2Mb .PDF file available here:-


http://homepage.mac.com/strangeandbouncy



Enjoy!



ANdyP

 

[strangeandbouncy]

Dear All,

So I am starting to understand a bit more having digested this article.

http://homepage.mac.com/strangeandbouncy

All very interesting! I am thinking about building something along these lines . . .

I notice that the 3 circuits fig 9 a.b + c on page 440 can all deliver 2V r.m.s. I have looked at the Sowter Decibels table, but I am confused, what level is this in dBu? do I multiply by 1.414 or 2.828? Also, any rough idea whether this circuit can deliver into 600 ohms? Ideally, i would like to deliver a fairly hefty level into 150 ohms and use a Profile or Sowter transformer to step up. I also have some ex-Audix step up output transformers that might do the job. Can I parallel the MPSA14, or is there a higher current Darlington i can use instead? Perhaps a SN3055 or BD139/140 pair could beef it up? If so, could anyone point me towards some suitable applications/schemos?

Please forgive my ignorance, but I have to start somewhere!


I have to thank everyone here on the forum. i would NEVER have had the confidence to try to make something like this a year ago! Cheers :thumb: :guinness: :thumb:


ANdyP

 

[daArry]

http://www.sengpielaudio.com/calculator-db-volt.htm

handy calc there ^

 

[strangeandbouncy]

Dan,


Hi! i emailed you my adress, did you recieve it?

Thanks for the link. Very helpful, ta!@


ANdyP

 

[daArry]

Andy, nothing on the email frontage nah...

 

[PRR]

> the 3 circuits fig 9 a.b + c on page 440 can all deliver 2V r.m.s.

They can deliver more if you raise the supply voltage; he stopped at 2V because that's all you'd ever need in Hi-Fi.

> what level is this in dBu?

About +8dBu.

BUT if you are talking dBu, you probably mean +4 nominal and +18 to +24 on peaks. Meaning you need 6 to 12 volts RMS (17 to 34V peak-peak).

> rough idea whether this circuit can deliver into 600 ohms?

In 9a, we have a 680 ohm DC load with 4.5V-1.1V- 3.4V across it. Pretending that 600=680, we can expect half that voltage on negative peaks, or about 1.7V peak. Doing the full math, 1.1V RMS when the output transistor taps cut-off. Even with all the feedback, distortion will soar by 1V RMS.

Another way: the DC load has 3.4V across it. 3.4V/680Ω= 5mA. We know (or can figure) that "Pro" outputs will pump 16mA-20mA on peaks with 600 ohm load. So it seems (and is) lightweight for such outputs.

> Ideally, i would like to deliver a fairly hefty level into 150 ohms

These plans are scaled for Hi-Fi levels in 5K and higher loads.

> Perhaps a SN3055 or BD139/140 pair could beef it up?

You get into the general insanity that comes from trying to push "Pro" levels out of a single-ended resistance-coupled stage. One gross spec is that you will need over 30V total supply voltage, and at least 30mA idle current for 600Ω loading, and really more than that.

Then you also have to un-match the load from the gain-stage's collector. There are several "Liniacs" proposed, with gain-stage current from 0.010mA to 3mA. To simplify: gain-stage Hie will be from 3K to 10Ω depending on current, most of these biases can be trimmed to give a gain of over 2,000, so the gain-stage collector node impedance must be 6Meg to 20K depending on bias. Throwing a dart at the geometric average we get 300K. The output buffer must have a higher input impedance if it is not to load the gain-stage. So 600Ω load, input impedance higher than ~300K, say 1Meg, 1,000,000/600= 1,700 required current gain. 2N3055 won't get over 150. TIP120 can exceed 5,000 at high current but sags at low current (due to internal resistors). You could find or build a Darlington to do this, but if you now ask 150Ω loads you need 4 times the Hfe. Or you could fiddle the gain-stage current higher and lessen the current gain needed in the output; in fact for most "Pro" audio chores I think you should. But that depresses the input impedance (which you have not specified).

I think you should build it. I don't think it is any kind of amazing amp, or no more than the HampTone. It is a simple circuit, and any "magic" has to come from ample over-building (so it will never embarrass itself) and then careful attention to details.

 

[strangeandbouncy]

Dear PRR,

Thank you so very much for your interest and input. I shall take time to work through all your points. I wish I knew more, but then I AM learning! I will build one, as much to try to understand what is happening as anything else. I am not expecting miracles from this, but I am sure I can find a use for it! It is the simplicity which attracted me. - less parts more understanding.


Thank you so much again, your reply is very much appreciated.


ANdyP

 

[mhelin]

Old thread but found an old article by Linsey Hood about low-noise cassette deck circuit. He used there a little bit different circuit consisting of three transistors , a PNP input followed by a darlington output with neg feedback, both feed up by a FET current source. Gain adjustment by a single resistor. This could make a nice mic pre, not much gain though (100x voltage gain but I guess you could get a little bit more). Here is the link to the article:
http://www.keith-snook.info/wireless-world-magazine/Wireless-World-1976/Low-noise%20low-cost%20cassette%20deck.pdf

 

[Rob Flinn]

One of my friends fatherused to have one of these cassette decks.    I remember adverts for the kits in electronics mags back in the day.

 

[ruffrecords]

The original article is now available on Doug Self's web site.

Cheers

Ian

 

[JohnRoberts]

Old thread but found an old article by Linsey Hood about low-noise cassette deck circuit. He used there a little bit different circuit consisting of three transistors , a PNP input followed by a darlington output with neg feedback, both feed up by a FET current source. Gain adjustment by a single resistor. This could make a nice mic pre, not much gain though (100x voltage gain but I guess you could get a little bit more). Here is the link to the article:
http://www.keith-snook.info/wireless-world-magazine/Wireless-World-1976/Low-noise%20low-cost%20cassette%20deck.pdf

This thread is only 11 years old.

A head amp with 680 ohm resistor in series with the input will not be low noise compared to modern mic preamp IC solutions (and the nominal 150-200 ohm mic's source impedance).

There have been many discussions here about low noise mic preamps in the last decade.

JR

 

[rock soderstrom]

The original article is now available on Doug Self's web site.

Cheers

Ian

Hi Ian, can you point me into the right direction, please. I can't find it.  Thanks! Cheers Thorsten

 

[ruffrecords]

Hi Ian, can you point me into the right direction, please. I can't find it.  Thanks! Cheers Thorsten

All Self's WW articles are here:

http://www.douglas-self.com/ampins/wwarchive/wwarchive.htm

but the Lindsey Hood article is not there. I stumbled across it the other day which is why I mentioned it.  It was here:

http://www.keith-snook.info/wireless-world-magazine/wireless-world-articles.html

and the actual article is here:

http://www.keith-snook.info/wireless-world-magazine/Wireless-World-1971/The%20Liniac%20by%20John%20L%20Linsley%20Hood.pdf

Cheers

Ian

 

[rock soderstrom]

Thanks a lot!

 

[pucho812]

Not sure if this got posted but I did find this link this morning...

http://www.keith-snook.info/wireless-world-magazine/Wireless-World-1971/The%20Liniac%20by%20John%20L%20Linsley%20Hood.pdf

 

[alexc]

Love reading these articles from John Linsley Hood and also (of course) Doug Self.

Thanks for the 'Liniac' article - I did not have that one!