This phono preamp I made the circuit and PC board designs and was made from 1992 to 2001
It was called Sentec PP9.
I now present this original diagram, that never had been published before.
I do this as a discussion item and not for members to build it.
But members here are free to copy any part of it for their own use.
Also of interest for owners of PP9 to have a reference in the thread and diagram.
At the time don't supply the component list, but most components are visanle and seen on the photos.
It used 12 monolitic dual transistors where of 4pcs 2SK389, 4pcs 2SC3381 & 4pcs 2SA1349. These monolitics was required to achive the termal stability of the DC-coupled stages.
The first stage is a linear amp with the RIAA 75uS high frequency filter in the output. It feeds the next stage with active 500 & 50Hz poles.
It is all DC-coupled with a DC servo only around the output stage
The DC servo amp uses a Linear Technology LT1097/channel.
2 pairs of R-Ohm 2SB786 & 2SA737 in the additional MC step-up complementary transconductance amp.
Capacitor feed rectifiers to form 2 mirror image voltages from a singel 15VAC winding.
I think that the MC head amp is of much interest here, as I never seen this configuration in any other amp. This is an original design by me. It can deliver over 150mV clean RMS signal to the next stage. As it is a transconductance design, the amplification is only dependant of the load resistor.
Also the power supply's 2 full wave bridge rectifiers are feed by electrolytic capacitors (4x2200uF) to 2 floating dc voltages, that are series coupled and referenced to the signal ground. Any number of floating voltages can be obtained by this methode. The winding itself is losely referenced to ground by balancing 2 resistors.
The passive supply voltage filters with BD136/BD139 give magnitudes lower noise than the integrated types 317/337 stabilizers.
As I'm an busy old man in the 70's now, so I have limited time to answer questions, but will do so when possible.
For owners: Yes I still have some spare parts!
It was called Sentec PP9.
I now present this original diagram, that never had been published before.
I do this as a discussion item and not for members to build it.
But members here are free to copy any part of it for their own use.
Also of interest for owners of PP9 to have a reference in the thread and diagram.
At the time don't supply the component list, but most components are visanle and seen on the photos.
It used 12 monolitic dual transistors where of 4pcs 2SK389, 4pcs 2SC3381 & 4pcs 2SA1349. These monolitics was required to achive the termal stability of the DC-coupled stages.
The first stage is a linear amp with the RIAA 75uS high frequency filter in the output. It feeds the next stage with active 500 & 50Hz poles.
It is all DC-coupled with a DC servo only around the output stage
The DC servo amp uses a Linear Technology LT1097/channel.
2 pairs of R-Ohm 2SB786 & 2SA737 in the additional MC step-up complementary transconductance amp.
Capacitor feed rectifiers to form 2 mirror image voltages from a singel 15VAC winding.
I think that the MC head amp is of much interest here, as I never seen this configuration in any other amp. This is an original design by me. It can deliver over 150mV clean RMS signal to the next stage. As it is a transconductance design, the amplification is only dependant of the load resistor.
Also the power supply's 2 full wave bridge rectifiers are feed by electrolytic capacitors (4x2200uF) to 2 floating dc voltages, that are series coupled and referenced to the signal ground. Any number of floating voltages can be obtained by this methode. The winding itself is losely referenced to ground by balancing 2 resistors.
The passive supply voltage filters with BD136/BD139 give magnitudes lower noise than the integrated types 317/337 stabilizers.
As I'm an busy old man in the 70's now, so I have limited time to answer questions, but will do so when possible.
For owners: Yes I still have some spare parts!
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