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AirTight ATM-300 - new Coupling Caps

So I want to replace the coupling caps in my Airtight 300B amp. The original ones are $5 Sprague orange drops. 0,1uF interstage caps between input tube (12AU7) and driver tube (12BH7A) and 0,47uF between driver tube and 300B.

I love the amplifier, it is very resolving and airy with great soundstage separation. However I miss some body and fullness, and tighter bass, hope new coupling caps can help with this. I like a natural sound with lots of body and texture, good detail and a tight and deep low end.

I have read alot of forum posts and narrowed my choices down to these 3;

Duelund CAST cu sn tinned copper

Jupiter copper foil paper and wax

V-cap ODAM

I have read that some capacitors are best used in lower voltage applications and others are better in higher voltage applications, so I am open to using different brands in interstage/300B coupling. 

Please share your experiences, impressions and recommendations. Not necessarily with the Airtight, but preferably used as a coupling cap.

rubjel
salectric
783 posts
 

@rubjel 

I am not aware of anyone claiming copper V-Caps sound thin.  That might possibly apply to the original TFTF series but not the CuTF V-Caps.  The Copper V-Caps are warm and rich in the bass and have body for sure.  I have compared CuTF caps to Duelund CAST and TFTF many times and each time I preferred the CuTF.  I have not tried ODAM so I can’t how they compare.  ODAM might be a viable candidate where CuTF is too expensive, but that’s just speculation.  Another factor is long term reliability.  V-Caps have an excellent reputation for reliability as high-voltage coupling caps.  Having experienced failures of Jupiter and Vitamin caps, I put a high priority on reliability.

One final point.  When I built my current amps, I used Sprague coupling caps initially since I wasn’t sure how things would work out.  The Spragues were an inexpensive way to test the design.  After a few weeks I replaced them with CuTF couplers so I have an idea what you would hear with your Air Tights if you make the same swap.  The V-Caps sounded better in all respects and were a very worthwhile improvement.

logistics
63 posts
 

@rauliruegas Yes, I noticed this sort of trend tends to apply to other items, such as power conditioners.  I was gifted what someone thought was a non-working UPS, but when I opened it later I realized was a hefty conditioner.  Turned out to be an Ametek PowerVar, which had large transformers and capacitors inside.  It immediately made my sound cleaner on my headphone listening rig.  Admittedly, my entire apartment runs on a single, 20 amp breaker running on old, cloth-covered hook and loop wiring in a 1940's house.  But its a beast compared to those 1U Furman units i see changing hands constantly, and they use them in hospitals and industry, rather than marketed towards audiophiles.

kennyc
2,834 posts
 

Interesting.  I know amp caps wear and eventually need replacement, but didn’t think much about voicing and keeping the voicing consistent for possible resale value.  

gareents
80 posts
 

OP,

I replaced the coupling capacitors on my Airtight ATM-300 with MultiCap film and foil polystyrene and polypropylene caps. Even bigger, more detailed sound with great tone. A bit more neutral.

   -GAR

devinplombier
1,637 posts
 

@kennyc 

It depends.

On the one hand, a recapped 70s Kenwood receiver will probably command a premium.

On the other hand, an amp that largely derives its value from the careful voicing imparted upon it by a respected designer will surely lose a significant chunk of cash as a result of being modded by a random owner. If the mod were designed and executed by the designer itself or a known marque expert, it might be different.

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