chrissugar
Well-known member
Hi all
Unfortunately I have less and less time to log in the forum and contribute but as time permits I try to stay tuned to what all you felow DIYers do here.
In the last few month I did a lot of research into tape recording and reproduction in general and experimented lots of topologies and solutions.
I decided to build for my mastering needs an external tape rec/repro racks with direct connection to the heads of my two Studer A812s.
From the initial idea the whole thing went into two directions, a completely transparent capacitorless, jfet opamp based with DC servo circuit, and the second one a jfet/tube cascode circuit.
While experimenting with these two direction it came the idea to build as a challenge a self-contained battery powered tape repro electronics in the direction of the old Nagra and Stellavox portable recorders. The Stellavox portable machines were probably the most beautyful sounding recorders used in many audiophile classical recordings. Considering the small dimensions and the low voltage they were powered, their sound was a fantastic achievement.
So I had this idea to do it in a relatively small die cast box, 12Volt battery powered, class A, minimum number of capacitors in the direct signal path, IEC and NAB equalization and also manual tape EQ and head damping option with multiturn pots.
Slowly in some weeks the project evolved and managed to obtain some very good specs. Did a lot of tweaking and optimisation. Finally, with flux-loop measurement the freq response was linear from 100Hz to 150000Hz within 0.1dB, from 15000Hz to 20000Hz maximum deviation 0.2dB and between 25Hz and 100Hz 0.5dB. It is surprising that from 12V power I have a 10V peak-peak clean signal. Transistors were selected for minimum noise. Grounding and shielding done with great care considering the extreme gains necesary.
The final circuit has a very, very nice and clean sound (compared to the original A812 and the PR99).
Next time the no compromise external rack tape repro. I hope it will not take forever to finish it.
chrissugar
Unfortunately I have less and less time to log in the forum and contribute but as time permits I try to stay tuned to what all you felow DIYers do here.
In the last few month I did a lot of research into tape recording and reproduction in general and experimented lots of topologies and solutions.
I decided to build for my mastering needs an external tape rec/repro racks with direct connection to the heads of my two Studer A812s.
From the initial idea the whole thing went into two directions, a completely transparent capacitorless, jfet opamp based with DC servo circuit, and the second one a jfet/tube cascode circuit.
While experimenting with these two direction it came the idea to build as a challenge a self-contained battery powered tape repro electronics in the direction of the old Nagra and Stellavox portable recorders. The Stellavox portable machines were probably the most beautyful sounding recorders used in many audiophile classical recordings. Considering the small dimensions and the low voltage they were powered, their sound was a fantastic achievement.
So I had this idea to do it in a relatively small die cast box, 12Volt battery powered, class A, minimum number of capacitors in the direct signal path, IEC and NAB equalization and also manual tape EQ and head damping option with multiturn pots.
Slowly in some weeks the project evolved and managed to obtain some very good specs. Did a lot of tweaking and optimisation. Finally, with flux-loop measurement the freq response was linear from 100Hz to 150000Hz within 0.1dB, from 15000Hz to 20000Hz maximum deviation 0.2dB and between 25Hz and 100Hz 0.5dB. It is surprising that from 12V power I have a 10V peak-peak clean signal. Transistors were selected for minimum noise. Grounding and shielding done with great care considering the extreme gains necesary.
The final circuit has a very, very nice and clean sound (compared to the original A812 and the PR99).
Next time the no compromise external rack tape repro. I hope it will not take forever to finish it.
chrissugar
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