50+ years of Sinclair Z-30 amplifier and 40+ years of my DIY mods
It was in 1969 when Sinclair Project 60 kit appeared on the market in UK and it contained Z-30 amplifier modules, advertised as 25W and 50W peak. It also advertised to be “the world's lowest distortion high fidelity amplifier”
and the news and kit description had soon, only few months later, appeared in our local hi-fi magazine Hudba a Zvuk.
I was building my first amplifiers (with Singleton input stage and awkward circuit topology) those days and I was excited! The differential input stage, CCS VAS load, it was something completely new in the DIY world. However, for us behind the iron curtain, an unobtainium. We had the only chance, to learn and to design and build the thing ourselves.
Several years passed and after I finished my university studies I was still an enthusiastic DIYer and I have returned to the idea to build Z-30. So I took an original schematics
made some small mods like modification to +/- DC power supply (to get rid off the output coupling capacitor) and also changed the transistors, as the originals were not available here. This was probably a good idea, as my power transistors were more robust. And this was the result, in 1980
I have chosen a modular concept, with a motherboard and modules that could have been changed to make different amp configurations. There was an RIAA phono module, linear preamp module, bass/treble equalizer module, two modified Z-30 modules and a power supply. All except for Z-30 were my designs. It took years to realize the project and this was the result in 1987
The amplifier was working well and had served me till 2001, the year when I returned to DIY hi-fi and realized to build something more advanced. The amp shown suffered from 2 major issues
Sinclair Z-30 rev2014 – my 45th anniversary project
In 2014, I got an idea to wipe dust from the Z-30 project and to make some modifications and make it a reliable amplifier with continuous maximum power capability, thermal stability and optimal bias of the output stage, to get rid off the crossover distortion. And I was curious
. So, this was the modified 2014 circuit
This was running pretty well, with power specified at 50W/4ohm, thermal stabilization of idle current and appropriate heatsink. Below please see the THD vs. frequency plot at 26W/6.8 ohm.
Z-30 2019, last mod 50 years after
And this is my last (as for now modification from 2019, 50 years after the original Z-30 was issued.
In BTL mode, it gives 100W/4ohm. And this is the THD vs. output amplitude plot
So this is my story of the Sinclair Z-30 amplifier. Even after 50 years, its basic topology is able to give good results. We have not moved much, since.
It was in 1969 when Sinclair Project 60 kit appeared on the market in UK and it contained Z-30 amplifier modules, advertised as 25W and 50W peak. It also advertised to be “the world's lowest distortion high fidelity amplifier”
and the news and kit description had soon, only few months later, appeared in our local hi-fi magazine Hudba a Zvuk.
I was building my first amplifiers (with Singleton input stage and awkward circuit topology) those days and I was excited! The differential input stage, CCS VAS load, it was something completely new in the DIY world. However, for us behind the iron curtain, an unobtainium. We had the only chance, to learn and to design and build the thing ourselves.
Several years passed and after I finished my university studies I was still an enthusiastic DIYer and I have returned to the idea to build Z-30. So I took an original schematics
made some small mods like modification to +/- DC power supply (to get rid off the output coupling capacitor) and also changed the transistors, as the originals were not available here. This was probably a good idea, as my power transistors were more robust. And this was the result, in 1980
I have chosen a modular concept, with a motherboard and modules that could have been changed to make different amp configurations. There was an RIAA phono module, linear preamp module, bass/treble equalizer module, two modified Z-30 modules and a power supply. All except for Z-30 were my designs. It took years to realize the project and this was the result in 1987
The amplifier was working well and had served me till 2001, the year when I returned to DIY hi-fi and realized to build something more advanced. The amp shown suffered from 2 major issues
- the heatsinks were too small and continuous available power was thus reduced (similarly as in nowadays miniature TPA3255 amplifiers)
- due to absence of Re resistors and poor idle current stabilization the idle current had to be kept very low, in order to prevent thermal runaway and destruction of power transistors. As a result, there was the crossover distortion. The same issues applied to original Sinclair modules.
Sinclair Z-30 rev2014 – my 45th anniversary project
In 2014, I got an idea to wipe dust from the Z-30 project and to make some modifications and make it a reliable amplifier with continuous maximum power capability, thermal stability and optimal bias of the output stage, to get rid off the crossover distortion. And I was curious
. So, this was the modified 2014 circuitThis was running pretty well, with power specified at 50W/4ohm, thermal stabilization of idle current and appropriate heatsink. Below please see the THD vs. frequency plot at 26W/6.8 ohm.
Z-30 2019, last mod 50 years after
And this is my last (as for now
modification from 2019, 50 years after the original Z-30 was issued.In BTL mode, it gives 100W/4ohm. And this is the THD vs. output amplitude plot
So this is my story of the Sinclair Z-30 amplifier. Even after 50 years, its basic topology is able to give good results. We have not moved much, since
.
