Audvance upgrades for your classic Revox

Audvance has designed new boards for your classic Revox B77 and PR99. These boards use modern high quality components and partly new circuits. The original seventies designs use inferior quality capacitors, resistors and integrated circuits. Although the original Revox boards are well designed and can sound quite good, many improvements can be made. Revox boards had to be swapped to change equalization between IEC and NAB during recording or playback. Basically Revox had three different boards for playback an recording. The Audvance boards offer all three versions on one board and switchable NAB/IEC equalization! You also get higher sound quality, extended bass and a lower noise floor.

Choose your machine below and find out what upgrades are available.


Revox B77/B77MKII 2-track
B77
Revox B77/B77MKII High Speed
B77
Revox B77/B77MKII 4-track
(no Dolby)

B77
Revox B77/B77MKII with Dolby
B77
Revox PR99
PR99MKI
Revox PR99MKII
PR99MKII
Revox PR99MKIII
PR99MKIII


All Audvance boards fit most B77/PR99 machines as you can see from the table below. This is why the boards will hold their value very well.



Audvance high-end modules

⚫ Dual headphone power amplifier modules HPA-1



These dual mono high-end headphone power amplifier modules are designed to drive headphones in balanced mode. Balanced mode delivers the highest fidelity possible. It is based on the PA-20 power amplifier and uses similar high speed, balanced, single ended MOSFET topology in Class A+ mode. There is no overall feedback applied with just a DC servo, the biasing is fully automatic and it will drive any headphone with ease. This amplifier can compete with any other headphone amplifier no matter its cost. The sound is simply breathtaking. Excellent stereo imaging with lots of speed and definition and rich saturated musical colors. The modules are mono amplifiers so you buy them in pairs. Each module has a single balanced input and a balanced output. Instructions for the built can be found here.

Many high quality headphones operate or can be modified to operate in balanced mode. The headphone cable has to carry four wires all the way to the plug to make this simple modification possible. My own Sennheiser HD800 is modified that way. I cut off the standard plug and soldered on a XLR4 plug. If the cord is detachable like on many you can also simply replace the cord. Many companies offer headphone cables for this purpose.

Specifications of the HPA-1:

• Power output (RMS at 1% THD): 700mW (8 Ω), 1W (16 Ω), 1.7W (32 Ω), 900mW (300 Ω), 450mW (600 Ω)
• Input impedance: 15 KΩ (to ground)
• Output impedance: <1.5 Ω
• Gain: 10dB
• Frequency response: 10Hz-600kHz (-3dB)
• Power consumption per channel: 32W (25VAC power transformer)
• Dimensions (each module) lxbxh: 275x90x66 mm

Price for a stereo pair: € 349

Add to cart

All things you need to build your stereo headphone power amplifier are:

• One pair of Audvance headphone modules
• A mains transformer
• Two XLR input connectors
• One XLR-4 output connector, or dual XLR3 output connectors
• Mains connector with fuse holder
• Power switch
• Cabling
• A cabinet

For your convenience I offer these parts here as well as you can see below.


⚫ Mains transformer and mains entry with twin fuses and power switch



Included in this package is a toroidal 2x25V/160VA mains transformer and a Delta 10C2 mains entry. This high safety entry includes twin fuses and a dual pole switch. More info on the switch can be found here. The transformer has a diameter of 105mm and a height of 47mm. It has dual primary windings to match both 115 and 230V mains voltages. Two fuses are included.

Price: € 69

Add to cart

⚫ Dual mains transformers and mains entry with twin fuses and power switch



This if you prefer a dual mono approach for the power supply as well. Included in this package are two toroidal 2x25V/80VA mains transformers and one Delta 10C2 mains entry. This high safety entry includes twin fuses and a dual pole switch. More info on the switch can be found here. The transformer has a diameter of 105mm and a height of 47mm. It has dual primary windings to match both 115 and 230V mains voltages. Two fuses are included.

Price: € 99

Add to cart

⚫ Two XLR3 input connectors and one XLR4 outout connector



All that is needed to connect to inputs and to a headphone when you want to use a single XLR4 connector on your headphone. Connectors are all high quality Neutrik ones with gold plated contacts. They need to be soldered to the wires. Inputs are type NC3FP-B-1 and output is type NC4FP-B-1.

Price: € 25

Add to cart

⚫ Two XLR3 input connectors and two XLR3 outout connectors



All that is needed to connect to inputs and to a headphone when you want to use a dual XLR3 connector on your headphone. Connectors are all high quality Neutrik ones with gold plated contacts. They need to be soldered to the wires. Inputs and outputs are all type NC3FP-B-1.

Price: € 25

Add to cart

⚫ Aluminium cabinet



Nice looking cabinet from MODU Italy. Front panel is 10mm thick. Two amplifier modules fit exactly with the transformer(s) sitting in the middle. The cabinet is type 1NSL02280B. I sell it including a better ventilated top panel type 3SLA0103280ASOLE.

Price: € 149

Add to cart

Audvance high-end equipment

PA-20MKII monoraul power amplifiers

The PA-20MKII wide bandwidth monoraul power amplifiers provide the most natural and uncoloured sound one can imagine. They do not impress with huge power numbers, but they do impress by presenting music the way it is recorded. These amplifiers are balanced, single ended and are way higher biased than regular Class A amplifiers are. It is named Class A+. While the PA-20MKII amplifiers supply 20 Watts RMS of very pure power into any practical load, they draw over 400 Watts of power from the mains each. The unusual high bias currents are used to create a very linear amplifier that requires no unwanted overall feedback and still has a low output impedance. This linearity results in very low levels of harmonic distortion and practical absence of any other forms of distortion. The PA-20MKII will drive your speakers to new heights. A DC-servo tightly controls the offset on the outputs.



PH-1 Phono Amplifier

The PH-1 wide bandwidth phono amplifier is a dual mono design with separate high voltage power supplies for both channels. It will give the best match with any cartridge. The signal path is built around discrete components only and the signal path is extremely short, resulting in amazing transparency. Overall feedback it not applied in this class-A design. The PH-1 has RCA inputs and outputs only.



CPA-1 Control and Power Amplifier

The CPA-1 amplifier is a combination of a wide bandwidth control amplifier and a power amplifier in one cabinet. It is a balanced design from input to output with a short signal path for the most transparent sound. No overall feedback is applied. It features two balanced inputs. The signals from the three RCA unbalanced inputs are converted in the first stage to balanced signals. All inputs are switched with relays, just like the advanced 24 steps volume control. The power amplifier produces 25 Watts RMS in pure class A per channel. A DC-servo tightly controls the offset on the outputs of the power amplifier. A standby switch is available to lower power consumption during interrupted listening. The amplifier is protected against elevated DC levels on the outputs, excessive output currents and overheating.

The control amplifier can be used standalone by turning the power amplifier in standby and using the preamplifier outputs rather than the loudspeaker outputs. Both balanced and RCA preamplifier outputs are available. As a control amplifier it pairs perfectly with the PA-20 mono power amplifiers or any other power amplifier of your choice.


A little history

Audio has always been in my blood since I was a 14-year old boy, building my first speakers with some help of my father who was a woodworker. At a very early age I knew that I wanted to study electrical engineering and so I did after I finished high school. I studied in Delft and did my master in analog electronics. Professionally I designed electronics for microchips but audio was my main area of interest. Over the years I designed many speaker systems, both for myself and for others. At a later stage I also designed and built various other items like turntables, amplifiers, tape recorder electronics and many other items. And of course the Audvance high-end components shown on this site. Below you can find pictures of a selection of these various projects ...


If you have inqueries please email me at info@audvance.com

About Me

Audvance amplifiers and boards are designed and handbuilt by Emile de Vlieger in The Netherlands. He is a specialist in analog electronic circuit design and started his career in 1990 at Philips Electronics, designing electronics for microchips. After 11 years with Philips he started his first audio company. In 2017 he started the brand Audvance Audio.

Links