Audvance upgrades for your classic B77

In the diagram below you can see how the music signal flows through your machine. During playback the signal comes from the playback head and has to be amplified to a much higher level before it reaches the outputs. So to upgrade playback you can simply order a playback amp on this page. You will get lower noise, higher sound quality and both NAB and IEC/CCIR equalization as a bonus. So you can play any (non Dolby) 4-track tape from now on.

If you enjoy to listen to your recordings via headphones the new monitor amp is what you need. A high quality class A headphone amplifier is included on this board.

During recording the signal from your source will pass the input amp first. An upgrade for this input amp you can order on this page. Its circuit is has a much shorter signalpath resulting in higher sound quality. Next is the recording amp that drives the recording head. The upgraded recording amp can be ordered on this page as well. With this upgraded board you will enjoy higher sound quality and you can make recordings with both NAB or IEC/CCIR equalization.

Input amp for line input 1.177.223.00

• Optimized for line level only (microphone inputs not working)
• Superior sound quality with short signal path and high quality components
• JFET low noise input stage
• Extended bass down to 18Hz (-3dB)
• No calibrations needed
• Handbuilt in the Netherlands

This all new designed board supports only the line level inputs. Most use only the line inputs anyway, and this board is fully optimized for that purpose. The amplifier is a simple discrete design without overall feedback, resulting in a transparent sound, with lifelike staging and rich natural tones of instruments and voices. Elevate the sound quality of your Revox to a professional level! Just pull out the old board and plug in this new one. That is all. Switching to mono is not supported. Details about this board can be found here.

Price: € 169

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Record amp 1.177.234.00


Daniel from Hawai wrote:

"I received the circuit cards yesterday and am quite impressed with the quality of the work and components."


• Fully compatible with original Revox board
• Superior sound quality with optimized signal path and high quality components
• Record with NAB or IEC/CCIR equalization
• Extended bass down to 18Hz (-3dB)
• Board is pre-calibrated so you can use it out of the box
• Handbuilt in the Netherlands

This all new designed board features both NAB and IEC equalization modes. The power supply is extensively filtered. Expect sound quality that matches the best available. Just pull out the old board and plug in this new one. That is all.

On the board you can by means of included jumpers chose what equalization you want. Although this board is pre-calibrated when you receive it, you may wish to fine tune it for your machine. Instructions can be found here.

Price: € 329

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Playback amp 1.177.254.00


Tor from Sweden wrote:

"I received the board and installed it in my Revox B77 (very easy). The card sounds fantastic and I like the possibility to switch between NAB and CIRR. Background noise is very low and there is more headroom in dynamic passages. Even more information in the bass range. It's like listening to a new improved High End model of B77."


• Fully compatible with original Revox board
• Superior sound quality with short signal path and high quality components
• Switchable between NAB and IEC/CCIR, possible from the front of your B77
• Extended bass down to 18Hz (-3dB)
• 6dB less noise compared to original board
• Separate pots for low and high frequency levels, not speed dependent
• Board comes with pre-calibrated settings so you can use it out of the box
• Handbuilt in the Netherlands

This all new designed board features both NAB and IEC equalization modes. These can be selected on the board and you can even select one of these with an (optional) switch on the front of your recorder. The power supply is extensively filtered. Expect sound quality that matches the best open reel decks available. Just pull out the old board and plug in this new one. That is all.

On the board you can by means of included jumpers chose what equalization you want. Although this board is pre-calibrated when you receive it, you may wish to fine tune it for your machine. Instructions can be found here.

Price: € 329

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Monitor amp 1.177.900.00

• Class A discrete MOSFET headphone amplifier
• Superior sound quality with short signal path and high quality components
• High power to drive any headphone
• Output impedance <1 Ohms
• Extended bass down to 18Hz (-3dB)
• Pre-calibrated VU meter settings
• Handbuilt in the Netherlands

This all new designed board contains a high quality stereo headphone amplifier. This amplifier operates in Class A for highest sound quality. It is much more powerful than the original amplifier and able to drive any headphone. The extra power comes from a SMPS power supply on this board that has to be connected to the mains. A cable to connect it to the mains entry connector of your Revox is included (soldering is needed by a qualified technician). The amplifier is a simple discrete design without overall feedback, resulting in a transparent sound, with lifelike staging and rich natural tones of instruments and voices. Plug in your headphones and enjoy! This board also contains the electronics to control the VU-meters and peak level indicators. These will all be pre-calibrated but you may wish to fine tune it for your machine. Just pull out the old board and plug in this new one.

Details of this board and instructions can be found here.

Price: € 399

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Switch NAB/IEC

Optional switch between NAB and IEC equalization from the front of your B77. The most convenient option.
• This rotary switch fits (almost) in hole of chassis that is already there
• Including cables with connectors for two boards




Price: € 29

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