Audio Research LS22 DIY

[terfyo]

Hi all,

For the new year of 2013, I would like to state my new year resolution; I am going to build an Audio Research LS22 pre-amp from scratch.

Schematics can be found on the Audio Research unofficial database.

Any words of advice for a beginner?

Regards,
Terfyo

 

[theduker]

I bought 2 of them, personally, I would go for easier.

 

[analog_sa]

Gee, what made you pick that particular circuit? I can only scratch my head in wonder looking at it: equivalent performance can be achieved by half the tube count. Marketing considerations took over?

 

[theduker]

I have to agree, this is such a difficult circuit for a new person. Start small, keep it reasonable... Maybe a curcio daniel? maybe a bottlehead kit? Like I said, I own two of these, they're fairly complex...

 

[terfyo]

Well, it may seem difficult. I have soldering skills and experience.

My only concern is with the availability of the components used to build the unit.

I am afraid that when I start building one, the availability of components is a hindrance.

Possibility?

 

[theduker]

There's nothing in them that would be difficult to find.

 

[terfyo]

Hi all,

I'm sorry to have disappeared for a year. Well, since the time I had decided to build the LS22, I bought a LS8 instead. Really, go for the easy.

Any positives on the LS8?

Cheers.

 

[directdriver]

The LS22 is too complicated for its own good when they could use half of the tubes, as "analog_sa" pointed out, to get the same result and less parts in the signal path and possibly better sound.

An externally hosted image should be here but it was not working when we last tested it.

A more simplified circuit can be achieved:

What's curious is that in the later more expensive model LS25, they did exactly that. If you have to copy their circuit, the LS25 is a better choice. After the LS25, ARC decided to go hybrid from that point on, so it's their last all tube line stage in the LS series, besides the Reference series.

An externally hosted image should be here but it was not working when we last tested it.

 

[Ketje]

Unless you use a delayed power-up ,there is +180V on the grids of tube2 at the start(tube is cold then).
Not a good idea.The two diodes prevent it.Ones the tube conducts the diode is blocked as if it isn't there.
Mona

 

[directdriver]

Unless you use a delayed power-up ,there is +180V on the grids of tube2 at the start(tube is cold then). Not a good idea.The two diodes prevent it.Ones the tube conducts the diode is blocked as if it isn't there.

Yes, understood. I was reusing the ARC schematic and modified from it and indeed they use timer power supply in the stock circuit.

Original ARC LS-22 schematics:

<schematic of signal circuit>

<schematic of mute & switching>

<schematic of power supply>

 

[sb****33]

Hi guys

I'm trying too to build this preamp.
Directdriver and Ketje posts are very interesting.
I'm not very skilled at electronics and I get a problem with two power supply components : Q8 and Q9.
I found 2N6761 for Q8 (I'm not 100% sure) but but nothing for Q9.

Any ideas ?

Regards.