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Dynaco's SCA-35 Integrated amplifier is the "sleeper" favorite of many audiophiles. Owners can't help expressing their enthusiasm with the sound of this amplifier. It is generally accepted that it's outstanding musicality to the output transformers and the use of the 6BQ5's in the power amplifier.

Like all Dynaco tube designs, the SCA35 designers combined outstanding transformers with cost targeted support components. The most serious offenders are the electrolytic capacitors (Quad Caps), pc board material and some hardware. These items do not age well - especially in the warm environment of the SCA35.

To meet these limitations, we have developed  several modules to address each of the weak points of this outstanding amplifier. They includes our System Capacitor Module, Power Amplifier Module & Input/Output Connector Module.

While each has been designed to address system reliability and longevity, it should be noted that our System Capacitor Module will also provide you with dramatic audible improvements.

SCA-35 Owners Manual (full)



Schematic Diagram

  • Completely New Power Supply Including Rectification, Filter Capacitors (bypassed) & Filter Resistors
  • Replaces Stock Output Stage Cathode Capacitors with TWO Independent Channels Each Polypropylene Bypassed
  • Replaces All Power Supply Electrolytic Capacitors with High Quality Radials Each Polypropylene Bypassed
  • Significant Improvement in in Dynamic Range and Resolution of Both Midrange and High Frequencies
  • Dramatic Improvement in Depth and Tightness of Bass Performance
  • Dramatic Improvement in System Reliability & Stability
  • Easy to Build & Install

Like many Dynaco amplifiers, the designers used outstanding transformers and then made their cost targets at the expense of other components. In particular, the electrolytic capacitors (Quad Capacitor) selected in all Dynaco designs are both electrically and physically poor designs.

These have very high ESR (effective series resistance) - this is like having a resistor in series  with the input terminal of each leg of the capacitor. The result is poor bass, compressed dynamic contrasts and soft and poorly defined highs. To make matters worse, their aging process is accelerated when exposed to the warm environment of the SCA35 (or any tube amp for that matter). This is why "exact" replacements cannot provide better audible performance and certainly will not provide any increase in system reliability.

In the Dynaco SCA-35, the designers not only used these caps in the power supply (like all other Dynaco amps) but worse, they used them in the cathode bypass circuit of the power amplifiers. The SCA-35, unlike the Stereo-70 and MK-2/3 does not use a fixed bias system but rather "self bias' which requires that  high value capacitor be placed in the cathode circuit of the output tubes. Quality is critical here since they are squarely in the signal path.

Consequently more than any other Dynaco amplifier, the SCA35 stands to yield the most dramatic performance and reliability improvement when these caps are replaced with modern technology caps.

Our solution is a complete system capacitor module. It houses all new high quality capacitors, associated filter resistors plus new rectification. Plus - we bypass every capacitor with high quality polypropylene film to ensure a musically clean signal path.

The result is a dramatic improvement in every aspect of the amplifier. All of the potential, hidden in the amplifier is realized when provide with the power to come through. The mids become more focused and refined and this extends into the highest frequencies. Bass is dramatically improved - you will be amazed at how much bass has been hidden in this amplifier.

The System Capacitor Module uses the high quality - high reliability radial capacitors that are rated conservatively both electrically and environmentally to provide you with years of service. is available as a blank PC Board, Kit (Board with parts) and Assembled (fully assembled and tested. The P/N and price for each is shown below along with a few optional items that you may require to complete your project.

Board assembly and installation are quite easy. The board is designed to drop into existing mounting holes and wire to existing connections inside your amplifier. You should be able to complete the project within a few hours depending upon your experience. You can download a copy of the Assembly & Installation Manual to review the project in its entirety.

·        Blank Board (P/N PWB-S35C) @ $65

·        Blank Board w/ parts (P/N KIT-S35C) @ $155

·        Assembled & Tested Board (P/N ASM-S35C) @ $195

Recommended Options

·        5 Pin Terminal Strip Teflon Rewire Kit (P/N TS-5) @ $8/ ea

·        Teflon Rewire Kit (4X 10ft Red, Black, Wht, Grn) (P/N TWK) @ $24/ set


PWB-S35-P10A Power Amplifier Module

Schematic Diagram

Coming 10-2017

copyright Curcio Audio 2017