V.S.P.S: Listening Test

Rushed home from work today as I can’t wait to listen to my V.S.P.S…..

My current tube phono stage has to give up its place for the V.S.P.S for the time being. The V.S.P.S weights only a fraction as compared to the tube phono stage. The main transformer of the tube phono stage is already heavier than the entire unit of the V.S.P.S.

I have chosen a few LPs for this initial listening test which are shown below.

1st LP(The Fame): After sampling a few well know tracks, I found the mid-range to high frequencies sounded pretty decent. For low frequencies, it is a bit disappointing.

2nd LP (We Sing,We Dance, We steal things) : Jason Mraz vocals sounded good and once the drums kicks in, it exposed the bass “deficiency”.

3rd LP (Appetite Destruction): Sounded a bit harsh on the upper frequencies and confirm the lack of bass.

Since the components are yet to be run-in, the initial listening test gave me the impression that this phono stage is pretty decent. The mids and high are better than the built-in phono stage inside my integrated amp. However, the low frequencies are a bit disappointing. Hope there is an improvement after some hours of running in. Overall, this V.S.P.S could not beat my tube phone stage as the later is more dynamic and lively.

V.S.P.S: First Power Up

Yesterday activities on the V.S.P.S was purely soldering and mechanical work. The power supply module was yet to be tested and there are doubts on the Tamura transformer as I could not find any datasheet for it as it is already an obsolete part. The wiring of the transformer is based on PURE guessing based on the coil resistances.

Before powering up, I have ensured that there are no short circuits on both the power supply and main board. I have also disconnected the power supply wires from the power supply board and main board in order to not to fry the main board if I have screwed up on the voltage rails.

Plugged in the power cord and switched on the AC switch and no smoking of components. That was a good sign. Next the voltage measurement at the connector on the board reads close to +/- 15V. Perfect!

Next action was to connect back the power supply wires between the 2 boards and measured the regulated power supply rails for the opamp on the main board. The opamp was not inserted during this test as I wanted to measure the no load conditions of the supply rails. Upon powering up, both the positive and negative voltage was close the 12V.

The last measurement was the most critical one as quite a number of V.S.P.S builders have complained about noisy or humming at the outputs. I was a bit anxious when I was about to land the oscilloscope probe on the first test point which is the+12V supply. Hmmm…. the noise margin was lesser than 10mV which is very close to the ground noise.  Similar result was observed for the -12V supply 🙂

The final set of measurement will be on the output of the phono stage. This will need the opamp to be inserted into the IC socket. The reference part for the V.S.P.S is the NE5532 which many have commented that it sounded a bit “boring”. For this reason, I bought 2 different opamp to pair up with my V.S.P.S. The first is Burr Brown OPA2134 and the next is National LM4562.

The OPA2134 will be used for now and the LM4562 will be the “upgrade” part at a later date.

When I probed both the output RCA connectors, I was really delighted as I did not see any oscillations and the noise margin is similar to the power rails. The measurements gave me a boost of confidence prior to the listening  test. By the time I finished the measurement, it was already past 10pm and I do not wish to wake up my fishes and also do not want my neighbours to knock on my front door. 🙂 Therefore I gotta wait another day for the listening test.

That’s all for a weekday night…..

V.S.P.S: Construction Phase

Found a decent chassis for the V.S.P.S  yesterday. Simple and elegant chassis that matches the design of my Moving Coil Step Up Transformer.

Spent the entire day building the power suppl, populating the V.S.P .S board and mounting everything into the chassis.

For the power supply module, the Tamura transformer was mounted directly onto the bare board. Ultra Fast Recovery diodes (UF4007) were used for the rectifier, which are followed by a CLC filtering.

Populating of the V.S.P.S main board was pretty easily except for the 2 output coupling capacitor which are too big to fit nicely onto the board.

The chassis that I bought is made of aluminum which make the drilling and opening of holes much easier than steel chassis.  The power supply board was placed far from the input and output signal paths and the best position will be at the front of the chassis. This placement will allows the hook up wires of the input and output signal connections between the V.S.P.S board and RCA sockets to be as short as possible.

The back plate will hold all the connectors and the power switch so that the front plate will only used for aesthetic purposes.

Next step will be the “firing up” of the phono stage and doing some electrical measurements……