1. Home
  2. amps-preamps
  3. 196394-82901

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
pindac's avatar
pindac
4,052 posts
 

Being an individual reintroduced to 300B Amp design in both PP and SE over the past two years and hearing designs with Interstage Tranx's and Coupling Cap's, the experiences had changed a long term dislike I harboured towards such a Valve Amp.  

I was left with an impression which resulted in my purchasing a 300B SE Amp'.

Off Topic:

With the now available options for myself to have experiences of different 300B Valves. There is now known a substantial difference is able to be produced within an End Sound when different Valve Brands are being used in a 300B Amp'. 

I am confident in the suggestion a lot can be achieved towards betterment of the End Sound when Valve Brands are also being considered.

I am confident in the suggestion a lot can be achieved towards betterment of the End Sound when the Amplifier is mounted on pneumatic footers, and even more betterment is on offer if a Resin Impregnated Densified Wood Board is used as a  Sub-Plinth for the Amp'.

rauliruegas
13,390 posts
 

Dear @salectric  :

 

x-over.jpg (800×533)

 

You can see in this crossover speaker at least 5 different capacitor models and that crossover goes insida 250+K speakers.

Yes all those different caps in the same speaker could says that the designer used the caps as " tone /eq/ passive devices looking for a higher quality that maybe the speakers has not and certainly all those caps are only spreading full colorations/distortions.

 

16092016c.jpg (800×533)

 

TID9142-13.jpg (1920×751)

Well for a gentleman with the knowledge levels you have all those is self explained and confirm what I posted. Of course that I can be wrong but I'm only sharing first hand experiences.

 

R.

rubjel OP
16 posts
 

@salectric I read an older post on audioasylum where you seemed to be quite disappointed with the Duelund Cast tinned copper cap. Would you mind sharing your thoughts about this capacitor, why did it disappoint you? 

Also I would love to hear your impressions of the Audio Note copper foil that you recommended :)

rubjel OP
16 posts
 

Also, I would be grateful if anyone has compared Vcap CuTf and ODAM and would share their impressions.

salectric
784 posts
 

@rubjel It’s been 5 or 6 years since I last compared Duelund CAST to Copper V-Caps, too long for me to recall details accurately.  But I was definitely disappointed by the Duelunds, in both electronics and speaker crossovers.  However, people have different tastes and what sounds good to one person may not to another.  That’s why I try to avoid posting about such topics these days.  I know what I like and what I don’t like, but that may not translate to other people who do not share the same priorities.  My only advice is to try different caps and reach your own conclusions.  It takes time and can get expensive but that’s the only way.  Getting into circular discussions like some posts in this thread (not yours) is rather pointless.  

More to discover