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5 watt Akai Roberts conversion

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  • 5 watt Akai Roberts conversion

    A 5 watt tube rehearsal/studio guitar amp converted from a 1960s tape deck.
    This amp was designed and constructed using the basic foundation of a 1960s (Akai M8) Roberts 770X tube reel to reel tape recorder. The amplifier circuitry has been optimized to specifically serve as a guitar amp rather than as hi-fi equipment. Where practical the original vintage components, including the tubes, have been kept.

    There are 2 instruments inputs which share the common volume and tone controls. The 2 inputs however employ separate, and different, input stage tubes and therefore sound very different. The first input uses an EF86 (6267) tube. These tubes were used in 1960s vintage VOX amps, and are still used in some Dr. Z, Matchless, and other boutique amplifiers. The 2nd input uses a 12AX7 (12AD7) tube. 12AX7s are the most common preamp tubes used in guitar amplifiers such as Fender, Mesa Boogie, and Marshall. All of the tubes are the original vintage 1960s tubes. This amp is very quiet (background noise and hum) and breaks up nicely at reasonable volume levels.

    The tone circuit uses a modified passive Baxandall/James circuit (Bass and Treble controls) similar to the type of tone stacks used in the original Ampeg, Orange, and some Dr. Z amps. Additionally, a boost switch increases the gain and frequency response of the amp providing additional tonal flexibility.

    The output stage is a single-ended class A power amp. This amp uses an EL84 (6BQ5). Single-ended class A amps were used in many lower power 1950s-60s Fender Tweed and Blackface amps and in Vox's AC-4, which also used the EL84 tube. The amp uses a 6X4 tube rectifier. This amp works great for rehearsal, small venue use, and especially studio recording.
    Last edited by sll; 02-18-2021, 11:30 PM.

  • #2


    • #3
      Yes, I like those Akai/Roberts units. I built about 10 of them:

      I build and repair guitar amps


      • #4
        I just delivered my 10th and I have a backlog of 4 units now.they just sound so good and they're so quiet that they're perfect for recording and all of my friends want me to make them one.
        Last edited by 27613rdu; 02-26-2021, 01:49 PM.


        • #5
          Some cabinets my friend has been making for them. Working on a combo cabinet now.

          Dropbox is a free service that lets you bring your photos, docs, and videos anywhere and share them easily. Never email yourself a file again!
          Last edited by sll; 02-27-2021, 08:08 PM.


          • #6
            New demo, same player and amp.