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Understanding Gain in the ARC Ref Phono 2 SE


On my ARC Ref Phono 2 SE, it has a high gain and low gain setting. I am having
to use the high gain setting for adequate volume output. The low gain is just
too quiet, even when I turn up my Rowland Synergy IIi volume all the way. Now, this was different on my Rowland Cadence where I could use the low gain settings on it and the volume would be just fine. Although the high gain setting in the ARC Ref Phono 2 SE is fine, I would like to use the low gain setting if at all possible as it optimizes the lowest electrical noisefloor.

So here is some info/technical data on my system:

Cart:

Dyna XV-1s:
Output 0.3 mV; resistive loading recommended > 30 ohms

Here was the typical settings I would have on the Rowland Cadence:

Low gain: 64 dB (high would be 74dB). Cart loading ranges from 30-400 ohms


Here is the ARC Ref Phono 2 SE: (I run SE from tonearm to phono pre, balanced out of phono pre)

Gain: 51 dB low gain, 74 dB high gain (BAL) ; 45dB low gain, 68 dB high gain
(SE)

Cart loading: 50-200 ohms

Output impedance: 400 ohm balanced out (recommended load 50K-100K ohm)

I'm guessing my volume in low gain on the ARC is due to running BAL (51dB)
compared to BAL on the Rowland Cadence at 64 dB. On to
something there?

Then I wonder despite the above if the pre amp specs may still play a role:

Rowland Synergy IIi

Input Impedance: BAL at 36K ohms or 600 ohms. This is switchable and default
is 36K ohms. Never tried the other lower ohm setting.

Output Impedance: Balanced at 80 ohms

Eventually if I purchased an ARC REf 5SE preamp, here are the ARC Ref 5SE preamp specs:

Input Impedance: 120K ohms balanced

Output Impedance: 600 ohms balanced; 20K ohm resistive load

So I'm guessing again its the difference in output in the BAL configuration low gain settings from the Cadence (64 dB) to the ARC low gain BAL (51dB). Any way to use the low gain setting in the ARC through my Rowland Synergy IIi to get adequate volume output without turning up the volume to maximum settings? Changing the input impedance of the Synergy to the lower ohm setting? Eventually would a new ARC Ref 5SE preamp help this?

Any input or advice would be appreciated as I would like to use the low gain setting in the ARC as I did in the Cadence.

philb7777
jjrenman
279 posts
 
Thanks for the extensive info, always appreciated when trying to get to the bottom of an issue.

Have you listened to the noise floor in both low and high gain on the ARC? I checked the spec's and if I understand them they actually show less noise in the high gain mode. Probably because the design uses very low noise fet's on the high gain input.
actusreus
733 posts
 
The Cadence is a MC-only phono preamp, while it appears that the ARC can accommodate both MM and MC cartridges. So the low settings on each of the preamps are meant to be used with different types of cartridges. The low setting of 64 dB on the Cadence is meant to be used with higher output MC carts, while the high setting of 74 dB is meant for low output MC carts. The ARC's low setting of 45/51 dB is too low to provide enough gain for an MC cartridge (at least the ones I'm familiar with), but would certainly easily accommodate any MM cartridge out there. Your MC Dyna cartridge needs approximately 61 dB of gain so while the 64 dB with the Cadence was just about perfect, 45/51 dB with the ARC's low setting is not nearly enough, and that's why you have to use the high setting.

Members who are more knowledgeable than I are free to correct me, but input and output impedance do not really factor in as far as the volume level and gain are concerned.

Btw, congratulations on this candy piece of equipment as well as the cartridge.
almarg's avatar
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almarg
9,670 posts
 
Excellent points by the others.
I'm guessing my volume in low gain on the ARC is due to running BAL (51dB) compared to BAL on the Rowland Cadence at 64 dB. On to something there?
Yes. As ActusReus indicated, 51 db of phono stage gain is too little for use with a 0.3 mv cartridge, at least in most systems.

I see that your Synergy IIi provides adjustability of its overall gain for each of its inputs over a very wide +/- 20 db range, in 0.5 db increments. Have you experimented with different settings? If not, that is where I would start. Perhaps reducing it for the high gain setting of the phono stage, and increasing it for the low gain setting, and comparing both sonics and noise levels for various settings.

I would NOT suggest that you change the preamp's input impedance setting to 600 ohms. That is much too low a value for the phono stage to drive properly.

Regarding possible upgrade to a Ref 5se line stage, I have no particular knowledge of that preamp but my guess is that it would not help. Its maximum gain is 12 db balanced/6 db single-ended, which I doubt is enough for use with the low gain setting of your phono stage; its noise performance may not be any better or even as good as that of the Synergy; and the limiting factor with respect to system noise performance when a phono source is being used will generally tend to be noise that is generated or picked up where signal levels are lowest, i.e., in the phono stage and/or the phono cable.

Regards,
-- Al
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