Stereo 120 "enhanced" Power Amplifier - Pre Order Details

  • Fully rebuilt and customized, upgraded. 
  • Incredible stereo fidelity and "enhanced" for performance, it sounds Amazing  
  • A really special piece of modernized vintage audio equipment. 
  • Painstakingly rebuilt, improved, burned in and tested 24 hours. 
This is one well built amp that will deliver an exceptional music experience for many years to come. 
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Ask yourself this, would anyone spend so much time, apply such great detail, invest so much money into building an amplifier like this and have it not sound spectacular? No, the answer is definitely no. That is the foundation principal of these builds; the sound, without that you have done nothing. This configuration is proven, I build these on a regular basis and they sound incredible. These rebuilds are so far ahead of a stock 120 that there is really no fair comparison. This amp will crush a stock 120 and leave the ST-70 out in the cold shivering. These are simply on a different level altogether.
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So inside the performance “enhanced” amplifier are (6) 3300 uF capacitor arrays arranged in two "Dynamite Triple" capacitor configurations which yields 9900 uF per channel for the coupling duties. You may also select to have (2) large single 10,000uF caps instead of the "triple array, same price, same sound.
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  • (2) 3,900uF Nichicon and (4) 3,300uF Cornell Dubilier caps at provide the filtering and power supply duties.
  • The replacement circuit boards are very heavy duty and populated with all new components from Panasonic, Murata, WIMA, Nichicon, Vishay, TE Connectivity / Holsworthy, Yaego, Xicon, and Dale.
  • The (4) power transistors will be brand new. 
  • Modern film capacitors in the signal path make this amp fantastic sounding.
  • All metal film 1% resistors provide accurate function and reliable current for the precise and proper operation of the circuit design. 
PERFORMANCE:  
In factory stock trim the Stereo 120 has a damping factor of 40 vs. only 10 for the Stereo 70, this is where even the stock Stereo 120 will easily run away with the show. Adding to this advantage is the large increase of capacitance in this particular 120. This amp now provides tight, clean, and sustained bass, surpassing the capability of a stock 120 and well beyond that of the Dynaco model 70. This 120 has a power supply capacitance now rated at 20,400uf. In stock form it was a meager 3,300uf, this enhancement is nearly a 7 fold increase! The output capacitance was originally 3,300uf per channel, it is now right at 10,000uF per channel. The increased capacitance not only delivers much better response it greatly reduces low frequency distortion. The new high performance power supply board was needed to provide the clean steady power requirements for these capacitance increases and it works wonderfully. Higher output wattage from the Stereo 120 increases the overall performance distance between the Stereo 120 and ST-70 amps. But there’s more, a stock ST-70 has a Frequency response of 10Hz to 40kHz. An ST-120 has a wider rated Frequency response of 5Hz to 100kHz. The 120 has a lower distortion rating of 0.5% vs the 1% rating of the 70. The 120 is 60 watts per channel vs. 35 watts for the model 70.

The Dynaco Stereo 120 "enhanced" Power Amplifier 

  • The specifics: 

NOTE: If you choose the volume control option, this limits the two big capacitors out in the middle with colored wire wrapped around them. There is only adequate space for the volume control by using the "triple" capacitor array. the large single Supertech capacitors cannot be installed with a volume control, not enough space.

The original stock value of capacitor C12 was just 3,300 uF, not quite enough to get the maximum amount of low frequency power out of a Stereo 120. The new C12 capacitor configuration consists of (3) 6,800 uF 80 Volt Cornell Dubilier electrolytic capacitors. These are wired in a paralleled triple configuration to safely produce an impressive capacitance value of 20,400 uF.
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The original speaker coupling caps (C7) were also a bit on the small side, at 3300 uF each. This amp now uses (2) 9,900 uF "Dynamite Triple" electrolytic capacitors or (2) 10,000uF Supertech caps. These produce better bass by providing more power, and lower distortion. These capacitance increases made necessary the upgrading of the related components (like the power supply) and some other capacitors to make this all work properly, maintain long life and produce higher performance.  
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The original Dynaco Stereo 120's power supply performance depended upon unpredictable parameters in the transistors. As such, it has a reputation of being somewhat unreliable and is difficult to repair. This modernized amplifier includes a new fully redesigned regulated power supply. This new PSU discreetly replaces the old PC-15 regulator board and the Q9 pass transistor. It re-uses the original heat sink and is coupled to the new upgraded capacitors at C9 and C12 with their values also being increased from 1,000uF each to 3,900uF each. This improved design and more reliable power supply also provides a soft start, has predictable current limiting, short circuit protection, accurate output voltage, super low output impedance, and low noise. 
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  • This amp is simply better (and much safer) now than when it was new! 
  • Original Dynaco transformer tested right on the money, superb quality USA manufacturing.
  • Original aluminum heat sinks reinstalled with fresh AAVID thermal paste to provide excellent heat dissipation. 
  • 4 brand new feet with steel bushings are installed and the bottom of the chassis 
  • The original power switch was cleaned and serviced, the old orange neon bulb can be replaced with a nice Blue LED for the illumination or a new Orange Neon type.
  • Original power cord is reused if it is in excellent condition, a new one is used if needed.
  • Input RCA jacks are replaced with brand new high quality jacks. Chrome silver finish, much nicer looking than the originals were.  
  • The speaker terminals are cleaned up thoroughly and will be in great shape or replaced as necessary, these will accommodate either bare wire or banana plugs.  
  • The chassis will be nice and straight. The entire chassis is hand polished to a decent shine, as you can see. The are always a few bad spots that remain, they're cosmetic only and very light. Some scarring and stains from previous use and neglect will always remain and must simply be accepted, consider it as "character". After all, these are nearly 50+ year old chassis! As you can see, it is now very presentable.  
  • The cover is goin to be straight, no dents, dings or warpage. 
  • Runs nice and cool, a great amp from the "golden age" of audio.
This amp will be fully reconditioned into a fine state of appearance with super fantastic performance. Idles and operates dead quiet, no hum or hiss. If you've never heard one of these in this type of condition you are in for a real treat. It has all the elements of a tube amp but the punch of solid state, it is amazing! 
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  • Amazing output quality and has excellent low end punch. Incredible sonics! 
  • A discreet and compact design, both clever and convenient, allows the amp to be placed where space is limited. 
  • Everything inside is in the same location as was originally and uses the original brackets and mounting locations. 
  • Run any speakers rated from 4Ω up to 16Ω (Ohms), simply hook them up.  
  • Rated at 100K ohms (100,000 ohms) of input resistance, be sure your preamp impedance is appropriate for use with this solid state slugger. (under 10K ohms) 

  • Description:  (from original Dynaco literature referring to a stock unit)  
"The Dynaco Stereo 120 is an all silicon transistor basic power amplifier for use with separate preamplifiers which have their own volume controls. The unit contains two 60 watt amplifiers on one chassis with a common power supply. Although the Stereo 120 is a solid state device, containing transistors and similar semiconductors, it has been designed to be used under normal conditions without special safety precautions, just as if it were a high grade tube amplifier. Thus it can be connected to source and speaker components and used with confidence in all conventional arrangements. There are no circuit breakers, speaker fuses, or other resettable devices to impede the use of the Stereo 120 under any reasonable conditions of use or abuse. This is achieved by using novel circuits (on which patents are pending) which automatically and instantly protect the amplifier. 
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  • Specifications (from original Dynaco literature referring to a stock unit) 
Power output: 60 watts per channel into 8Ω (stereo)
Frequency response: 5Hz to 100kHz 
Total harmonic distortion: 0.5% 
Damping factor: 40 
Input sensitivity: 1.5V 
Signal to noise ratio: 95dB 
Speaker load impedance: 4Ω to 16Ω 
Semiconductors: 15 x transistors, 15 x diodes 
Dimensions: 13 x 10.5 x 4 inches 
Weight: 20lbs 
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