Bruce from the USA has completed his second follow up to his original OddWatt tube amplifier project (a EL84/6BQ5 Push-Pull Tube Amplifier) with the Odd Blocks. The Odd Blocks are a pair of KT88 Push-Pull Mono Block Tube Amplifiers. Like the Oddwatt 225 (a KT77 SIPP (Push-Pull) Tube Amplifier), the Odd Blocks are also scalable and will work with a number of octal tubes such as KT77, EL34, 6CA7, 6L6GC, KT88, 6550 and KT90. A photograph of the finished mono block tube amplifiers is shown below.
Like the previous OddWatt tube amp projects, the topology of the driver stage is an SRPP this time using 12SL7 tubes. This feeds a self-inverting push-pull (SIPP) output stage operating in Class A Ultra-Linear (UL) mode. The output tubes are Gold Lion KT88. LM317HV regulators are used to form the constant current source (CCS) on the output tubes. An underside view of the amplifier is shown below.
Like the precursors to this project, the KT88 provides very good performance. The SRPP and SIPP output stage combine to produce a very low noise floor. The design can be scaled for use with other tubes by simply adjusting B+ voltage and cathode current.
For complete information about this project, see the Odd Blocks project page - KT88 Push-Pull Mono Block Tube Amplifiers.
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