Sound Valves M60 Tube Monoblock Amplifier Pair

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Sound Valves is the name taken after Dynaco stopped selling DIY kits in the 1990s and set up shop in Columbus Ohio.

The M60 amplifier could be considered the next version of the Dynaco MKIII.

The parts used on these amps, aside from chassis and main board, follow the Dynaco design principal of being readily available – most parts are available from either Mouser or most tube suppliers.

There is great support out there for anything Dynaco and that includes these amps. Any place that repairs or mods Dynaco equipment can work on these amps.

The M60 audio circuit topology is a four stage, single channel power amplifier.

The front end consists of an all triode, Class A gain stage, phase splitter, and low impedance drivers.

The output stage uses 6550 tubes and operates in triode or ultra-linear mode selected by a switch between the output tubes and transformers. (NOTE: Manual states the switch can only be used when amp is off).

In triode / ultra-linear mode the first 17W / 30W are pure Class A, switching to Class AB1 for a maximum RMS output of 30W / 60W.

These units came to us from a collector that had dozens of amps so I suspect they got little to no use. They look new and the tubes look barely used.

We checked all tubes in our professional tester and they passed with flying colors. The capacitors were also checked for performance and leakage and also passed. It was driven to the full rated power without excessive noise or distortion.

They are like new and ready to make someone happy.

Below is the information from the manual:

ULTRALINEAR: 60 watts (into 2, 4, or 8 ohms). THDIIM (60 watts RMS, 20-20kHz): <0.5%; @1kHz: <0.1%. Frequency Response: 20-20kHz, +0/-.25dB. Full Power Bandwidth: 5-75kHz, +0/-3dB.

TRIODE: 30 watts (into 2, 4, or 8 ohms). THD+N (30W RMS, 20-20kHz): <0.8%; THD @1kHz: <0.2%. Frequency Response: 20Hz-20kHz, +0/-0.5dB. Full Power Bandwidth: 6-60kHz.

GENERAL: Input impedance: 300K ohms. Output impedance: <0.70. Max.power be¬ fore clipping: 70 watts. Dynamic headroom: 1.2dB. Signal-to-noise ratio (@60W): down better than 95dB. Input sensitivity: 1.2VRMS for 60W; (200mv for 1 watt; l.0V for 30 watts triode). Gain: +22.4dB (20 dB negative feedback). Polarity: non¬ inverting.

USA Tubes: 2-6550A, 1-12AT7/6201, 1-12AU7/5963.

Case Dimensions: 9-1/2"W x 7-1/2"Hx 11"D (12"D including binding posts). Net Weight: 32 lbs.

PROUDLY MADE IN THE USA.

Circuit Features:

• All-triode front end. Triode switchable output tubes.
• Massive custom-wound power/output transformers-exclusive custom designs by SV's Harry Klaus.
• Polypropelene signal caps. 1% metal film resistors. Hand-matched gain resistors. Mil-spec FR4 boards.. Shielded silver-Teflon wire between jack and board.
• Class AB1 operation-pure Class A to 30 watts (ultralinear); Class A to 17 watts (triode). Balancing trimmer on phase-splitter for ultralow distortion.
• Quality USA tubes: hand-matched, 48 hours burn-in. (May be internally reconfigured for EL34 or 6L6GC.)
• 2-ohm impedance load support for exotic speakers
• Visual bias adjust for each output tube. Instantly indicates tube status-shows when tube changes from Class A to AB, and eliminates need for matched pairs. LED indicator switch has center "off" position.
• "Soft Startup" for extended tube life. FET regulated power supply for front end tubes; regulated heaters.
• 2, 4, or 8 ohm selectable speaker impedance via four rear panel binding posts, "pyramid" configured for quick impedance changes via dual banana plugs.
• Ground lift switch for optimized signal-to-noise ratio plus IEC power socket with 14-guage power cord.
• Superb low volume level performance. Accurate musical colors, tonal timbres, and sound staging.

Cosmetic and Convenience Features:

• "Classic Chrome” plated steel chassis and bottom; additional internal supports for extra rigid platform.
• Stylized "Ultra-Vent ™" perforated cover-cage (included)
• Front panel tube bias LED status indicators
• Deluxe GOLD input signal jack and 30A 5-way binding posts