Stellar GCD - Phono stage input sensitivity


#1

Hi, new here.
I have a Stellar GCD and I’m having problems using a Phono stage with it.
I have tried several balanced Phono stages connected to the Balanced analogue input, but they all sound poor, flat and lifeless. They need a doubling at least of the volume control over my digital sources.
My LOMC cartridge (AT33PTG II) has an output of 0.3mV which is in the middle ground for LOMC.
I have a Project Phono Box RS in at present, which has a 66dB Gain using balanced, its the best so far but not great. My Aqvox 2Ci II used in Current amplifier mode, with balanced in/out, sounds very poor and has to have the Stellar’s volume wound up into the Thirties, but still sounds flat. This is a good Phono stage and normally sounds very dynamic.
Anyone else have problems matching a phono stage?
Any suggestions for a known good match?


#2

Hi Qwin,

Welcome to the forum! Mind if I ask you a few questions?

What resistance are you loading your AT33 at?
Whats the gain setting of the Aqvox preamp?
Have you tried another line preamplifier other than the GCD in this exact setup?
Could you elaborate a little more about what you define as flat sounding? We audiophiles tend to have words that can mean different things to different people :slight_smile:

-Darren


#3

Hi Darren
I was using the Aqvox Phono stage in Current Mode, with balanced in/out so no loading is used.
It has variable gain pots for each channel 55dB to 76dB. Usually sounds best around the middle of the range.
I also tried it in Voltage Mode using RCA out and fixed loading positions of 100 and 1k ohm tried and in high gain (+20dB) it still didn’t seem to have enough gain.

I tried the Project Phono Box RS with on the fly infinitely adjustable loading between 10 to 1200 ohm and 66dB gain using balanced.
Yes I tried a different line Pre, the Project Pre Box RS, solid state with a valve output stage. This worked better, but it has a special input for phono stages with 12dB Gain, its other inputs are 6dB Gain this is also balanced.

The sound with the Aqvox has no dynamics it sounds dull and lifeless no punch (Yamaha NS-1000M speakers). When you turn up the volume on the Stellar GCD it needs a lot of movement to get an increase. There just seems to be a lack of gain in the chain somewhere. Digital sources I am playing at 14/16 for moderate levels, I need the high 30’s for the same level with the Phono stage. Mid twenties with the Pro-Ject Phono.

I am presuming, from the spec sheet, the Stellar GCD needs 1V, to get this from the AT33 (0.3mV) would need 70.5dB of gain from the phono stage, if I am calculating correctly.
Maybe it would be better to use a cartridge outputting 0.5mV that would require 66dB gain to achieve 1V?

I am going away for a few days, but borrowing a valve phono stage (single ended) with a Gain around 75dB, which I will be bringing back with me. I will see how that works out.

The sound with my digital sources is fantastic by the way, very pleased with that.

Ken


#4

Well, I tried the Valve Pre with its built in hybrid mosfet/valve phono stage that I borrowed and it was a big improvement. Bit too valvey for my taste, slightly soft in the bass and a considerably higher noise floor. This was a single ended device with RCA outputs.

I decided to retry the Aqvox, which gets very good reviews and is very quite for a MC phono stage.
I went back to basics and read what the manufacturer recommended for optimum performance on their website.

The short answer is that the AQVOX 2 Ci II now works extremely well with the Stellar GCD.

I kept the Isokinetik “Isotone” tone arm wires on my linear tracking arm. This is a single strand of pure silver, wrapped in Silk. These terminate in a 5 pin DIN tonearm socket at the back of the arm.

AQVOX recommended using balanced, current mode and not to use shielded cable between the TT and Phono stage, but to use a twisted pair for each channel. Also to run a loose separate wire alongside each twisted pair, as a kind of antenna to pick up interference. These extra wires are connected to pin 1 of the XLR plugs at the phono end and left unconnected at the 5 pin DIN, TT end. A separate Ground lead was used from the arm base to Phono Stage. This is similar construction to AQVOX’s own cables.
I used Amtrans single strand (dia 0.4mm) OFC Gold plated Copper (HFC in UK supplied). This wire is resin coated and sold as a twisted pair without screen or jacket. I put each twisted pair and its “Antenna” wire into an ABS plastic woven jacket, keeping left and right channels in separate sleeves.

The result is very impressive, I can’t say enough good things about this twisted pair cable for Phono use. It’s only got a couple of hours on it and continues to improve with use. My Turntable performance is now equal to my digital sources, maybe better. :smile: