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Algar_emi 16th April 2012 04:45 PM

AirTight ATC-2 Preamp Pictures
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Hi. I'll post pictures of my new (used) AirTight ATC-2 reference tube preamp. It was highly modified and sound superb. The internal pictures may be of interest to us DIYer because of the great quality of the layout and assembly. Here the outside view.

Case is made of steel for rigidity and shielding, with good quality paint. Front panel is classy, knobs are all metal and controls feel solid and smooth. Volume control in particular, the upgrade ALPS HQPRO is silky smooth. Look at the bottom plate made of pure copper, nice foundation.

aptquark 16th April 2012 04:46 PM

thats one bad azz pre...I believe the version 3 came these are a good buy now

Algar_emi 16th April 2012 04:51 PM

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And now the insides :cool: This preamp is a real classic and it is built following the great school guidelines for a tube equipment. It is divided in two main internal sections. The top with tubes, transfo top and main caps. We can see also the few pcb used. The noise sensible controls (source selection, volume, etcc) are also located on the top portion. It is very clean and uncluttered. Bottom section contains the power wirings all point to point. Quality parts are used throughout the preamp as expected from such a statement product.

Algar_emi 16th April 2012 04:59 PM

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Extensive mods from the standard unit include (not my call, I bought it like this):
-Incredible Volume control ALPS HQPRO
-Drive output tube 12AX7 replaced by 12AU7 (for better drive)
-NOS 1957 Tubes :p
-HV Tube rectifier 6X4 replaced by 6CA4 for reliability.
-IEC socket for better power cord use.
-RCA jacks replaced with Cardas jacks (output and five Inputs)
-Interior wiring replaced by Audience wire.

Not bad, look at this all. No way I can build such a beast for I paid for it.

Algar_emi 16th April 2012 05:06 PM

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Now the details. There is mu-metal application to critical spots on top and bottom cover, nice. The source selection is on the back, near the connectors in its own shielded box. Complex Monitor switches selection (seldom seen these days, a classic...). Look at these monster coupling caps :eek:

woodturner-fran 16th April 2012 05:36 PM

In my experience, the build quality of airtight amps is second to none. The bigger amps use tamura transformers, very nice quality indeed.

There is very little information on the web about them - any chance of a schematic Sylvain?


Algar_emi 16th April 2012 06:19 PM

I'm planning in finding the schematic for me. But it is quite sophisticated and will take some time to follow all these wires around. Anyway it is no longer in production and some of these fancy parts cannot be buy anymore.

I won't disclose all the exact schematics (copyright), but we can certainly discuss the topology.

woodturner-fran 16th April 2012 06:32 PM

Grand - is it a standard design?

I had a close look at a jadis dpl recently - unusual design, but it sounded great. Better than a 6sn7 aikido....


Algar_emi 16th April 2012 09:55 PM

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At first look, I couldn't tell. I'll have to put it on paper first. Rapidly I can tell this: Custom power transformer with shielding. Regulated heater supply, one reg per tube, Electronic timer relay module for HV delay and mute. Dual mono HV supply with discrete reg (adjustable with pots), including CRC filter with Mills resistors. Film caps throughout for inter-stage coupling. Film caps bypass for the big electrolytic caps and transformer secondaries to prevent/reduce rigging. Four tubes complement, one HV rectifier, three 12AU7, probably one per side and one dual common tube for output or one common central tube and one tube per output, I'll have to check. I think the big yellow SideRealKaps film caps are upgrade too. Original Air Tight film caps seem to be with smaller with ones...Electrolytic are a mix of Rubicon and United Chemicon. Resistors are a mix of Dale, Carbon, Holco, Mills and some special very tight tolerance ones...

We can see there was a lot of listening and tweaking of this design, sound wise.

woodturner-fran 16th April 2012 10:17 PM

I've opened 2 airtight amps so far. One was just to have a look inside, the second (an atm2) had blown a cathode resistor. Both used single (mono) alps RK27 posts for audio, and I gotta say, in every case where I've used them, I've been underwhelmed by the RK27. Gigawork stepped pot from ebay beats it easy. Anyway, one of the things that would bug me a lot with these amps is the dual mono volume control.

Each one I've seen has really impressed my by its build quality though. I have a friend who bought an atm2 new (gulp!!!$$$$) but ended up sending it back because of a sharpness in the treble. Went back to a lower powered valve amp and is much happier. Another friend with another atm2 doesn't have this issue at all.....

Great to see those pics Sylvain, plus a general description of the features of the amp. Can you tell are there dual HV windings?


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