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.
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.
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And now the insides 
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.
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.Attachments
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
-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.
-Incredible Volume control ALPS HQPRO
-Drive output tube 12AX7 replaced by 12AU7 (for better drive)
-NOS 1957 Tubes
-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.
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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
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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.
I won't disclose all the exact schematics (copyright), but we can certainly discuss the topology.
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.
We can see there was a lot of listening and tweaking of this design, sound wise.
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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!!!$$$$) but ended up sending it back because of a sharpness in the treble. Went back to a lower powered valve amp and is much happier. Another friend with another atm2 doesn't have this issue at all.....
Great to see those pics Sylvain, plus a general description of the features of the amp. Can you tell are there dual HV windings?
Fran
Each one I've seen has really impressed my by its build quality though. I have a friend who bought an atm2 new (gulp!!!$$$$) 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?
Fran
I'll have to look at it first. It won't be before a few weeks at the soonest.
Leon08. Well, point to point wiring is always looking this way, like something we can do our self. I've done enough to know two things: It is more difficult to do that you can think, and to get a nice layout take time, practice and knowledge. Secondly even it is nice, it won't warranty performance, low noise level, etc. To get the right layout take a lot of try and test. Based on my experience, it is a very nice layout.
Leon08. Well, point to point wiring is always looking this way, like something we can do our self. I've done enough to know two things: It is more difficult to do that you can think, and to get a nice layout take time, practice and knowledge. Secondly even it is nice, it won't warranty performance, low noise level, etc. To get the right layout take a lot of try and test. Based on my experience, it is a very nice layout.
Nice pics, they certainly offer insight into a "high end" design/build.
What is the Alp HQPRO? Is that a discrete, stepped attenuator?
It never fails to amaze me that some of the best designs from the best designers, even those that post here, wind up with a cheap, noisy, opaque, mistracking, afterthought of a volume control such as the Alps Blue or other similar pot.
I'm guessing this unit was upgraded for the same reason?????
What is the Alp HQPRO? Is that a discrete, stepped attenuator?
It never fails to amaze me that some of the best designs from the best designers, even those that post here, wind up with a cheap, noisy, opaque, mistracking, afterthought of a volume control such as the Alps Blue or other similar pot.
I'm guessing this unit was upgraded for the same reason?????
This pot is an original AirTight upgrade option and cost 1K$ in itself...
It is refered as an ALSP RK50 type, search the net there is plenty and even here a discussion: http://www.diyaudio.com/forums/parts/43416-alps-rk50-best-volume-pot-world.html
As far as the upgrade goes, it was done by the original owner, I'm the third, so difficult to comment on its validity or not. I know that a good volume pot is a must in a good preamp preamp, and this is certainly a fine example. I got it almost for free for what I paid this preamp for. The rest is mainly film caps, are they better, I cannot say since I never heard a stock unit.
Sound pretty good to me as is
It is refered as an ALSP RK50 type, search the net there is plenty and even here a discussion: http://www.diyaudio.com/forums/parts/43416-alps-rk50-best-volume-pot-world.html
As far as the upgrade goes, it was done by the original owner, I'm the third, so difficult to comment on its validity or not. I know that a good volume pot is a must in a good preamp preamp, and this is certainly a fine example. I got it almost for free for what I paid this preamp for. The rest is mainly film caps, are they better, I cannot say since I never heard a stock unit.
Sound pretty good to me as is
Same unit for sale now on Canukaudio
I wonder if this is the same person/amp or have these photos been hi-jacked for a fraud.
Air Tight ATC-2 Tube Line Preamplifier, Dark Faceplate with upgrade ALPS RK-501 & internal caps For Sale - Canuck Audio Mart
Any info much appreciated as I was looking to purchase this unit until now.
Thanks
I wonder if this is the same person/amp or have these photos been hi-jacked for a fraud.
Air Tight ATC-2 Tube Line Preamplifier, Dark Faceplate with upgrade ALPS RK-501 & internal caps For Sale - Canuck Audio Mart
Any info much appreciated as I was looking to purchase this unit until now.
Thanks
Something fishy
In all the descriptions and photos of this unit there is no mention of who did the "upgrades" and yet somehow now it was found to have been done by none other than Roger Sheker of Audience.
" The preamp has several additional important upgrades, done by Roger Sheker of Audience in California. The one 12AX7 tube is replaced by a third 12 AU7 tube, in order to make the output impedance more manageable, and the 6X4 rectifier tube replaced by a 6CA4, for reliability and uniformity. Also, the original hardwired power cord has been replaced by an IEC socket so that any power cord can be used. The 5 inputs and two output jacks were replaced with Cardas jacks and the interior wiring with Audience wire. All power supply caps were replaced with new high quality caps (Vishay, Rubycon, etc...) All of this brings the ATC-2 to a new level of performance".
I think I will pass on this one.
In all the descriptions and photos of this unit there is no mention of who did the "upgrades" and yet somehow now it was found to have been done by none other than Roger Sheker of Audience.
" The preamp has several additional important upgrades, done by Roger Sheker of Audience in California. The one 12AX7 tube is replaced by a third 12 AU7 tube, in order to make the output impedance more manageable, and the 6X4 rectifier tube replaced by a 6CA4, for reliability and uniformity. Also, the original hardwired power cord has been replaced by an IEC socket so that any power cord can be used. The 5 inputs and two output jacks were replaced with Cardas jacks and the interior wiring with Audience wire. All power supply caps were replaced with new high quality caps (Vishay, Rubycon, etc...) All of this brings the ATC-2 to a new level of performance".
I think I will pass on this one.
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