Tube DIY Asylum

Output Coupling Caps updated for Marantz 7

45.64.242.182

Tube747

Rumour has it that upgrade the output coupling cap of Marantz 7 to larger size like 2uf to 3uf improved the sound dramatically.

Should I stick with small cap or go for 2uf?

Follow Ups:

RE: Output Coupling Caps updated for Marantz 7 - Chip647 07:03:12 01/30/25 (3)
You are referring to the 0.22uf output caps?

Running this into an amp with 50k input impedance will give your -3db point at 14hz. At 100k ohms you are down to 7hz. These are below the hearing threshold, but they can impact the bass phase response that you can hear.

Adding 2uf to 5uf here is fine and will eliminate the phase interactions. What you actually hear will be fairly subtle. A high quality 0.22 cap will sound better than an average 2uf cap. Of course, if this is a real historic Marantz 7 you will impact the value of it.
- RE: Output Coupling Caps updated for Marantz 7 - Tre' 07:24:37 01/30/25 (2)
  If you are 3db down at 14Hz then you are 1db down at 28Hz with phase shift all the way to 140Hz.
  
  If you want (and some people don't) 20Hz totally un-disturbed by the high pass filter, then the 3db down point of that filter needs to be 2Hz.
  
  Same is true at the other end. If you want 20kHz un-disturbed by a low pass filter, then the -3db point needs to be 200kHz.
  
  Tre'
  Have Fun and Enjoy the Music
  "Still Working the Problem"
  - RE: Output Coupling Caps updated for Marantz 7 - Tube747 04:56:50 02/03/25 (0)
    I found this web and the author actually put 4.7uf for output coupling, and increased the other coupling value to 1.2uf
    - Clone Marantz 7 (Open in New Window)
  - RE: Output Coupling Caps updated for Marantz 7 - Tube747 14:15:25 01/31/25 (0)
    I decided to use 0.22uf. Thanks all!
That will depend on the input impedance of what you are driving. - Tre' 06:39:40 01/30/25 (0)
According to this schematic the stock cap is .22uf
If your amp has a input impedance of 330k then the .22uf cap is large enough.
With an input impedance smaller than 330k it will not be.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
- https://www.thetubestore.com/lib/thetubestore/schematics/Mar (Open in New Window)
Edits: 01/30/25

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