In exclusive partnership with top-tier modification house Modwright, Underwood HiFi is proud to offer the following carefully tested, factory-authorized performance enhancement package for the Monolithic Sound phono stage.


By virtue of selling consumer-direct, we can offer these super-charged, brand-new models for a better price than the same modifications would cost retro-fitted - though we offer that, too.

Owner Feedback

Hi Walter,
Greetings from Texas.
Thought I'd send along some musings on my MMF-7 and DW modded PS1/HC1B w/ Revelation PCs. The modded PS1 takes at least several hundred hours to burn in (a painful experience I might add – but finally it takes on a completely different character): Dead-quiet background - spooky, really; detail retreival that really does rival my expensive PCM CDP - but without the "digititus"; very open and extended upper range (air abounds); lower frequencies are tuneful and natural overall, quite extraordinary for the $$$.
Monolithic Sound PS-1 Signature Mod $588 ($250 retrofit)

Our Signature mod installs:
  • replacement of all rectifier bridges with Harris Fred rectifiers.
  • key internal power supply decoupling caps replaced with larger value Elna electrolytic capacitors
  • replacement of two stock op-amps with Burr Brown's best OPA-627 op-amps.
  • four critical signal path resistors replaced with Vishay VSH metal film resistors.
  • two key decoupling capacitors replaced with Black Gate STD series capacitors.

Sonic benefits of our Signature mod:

  • Signal-to-noise ratio: The noise floor is greatly lowered, allowing higher resolution of low-level ambient and spacial details as wall as micro dynamics.
  • Smoothness coupled to more detail - you're hearing more of the music that previously remained hidden in the grooves.
  • There is an improvement in presence and overall 3-dimensionality of the soundstage. The music has more weight and substance.
  • Both bass and treble extension are improved, providing greater pinpoint imaging detail and resolution as well as deeper and better-defined bass.

The 12-month Monolithic Sound factory warranty is honored unconditionally on this modified unit. Click here for stock specs. Click here for reviews

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