[Doublej]

I am running the following setup for desktop listening:

Hsu HB-1 (92dB efficiency)
Assemblage L-1 Preamp
B&K EX4420 (200 watts into 8 ohms I think)

Listening distance is 18-24 inches from the speakers. The issue I have is that I sometimes listen at very low volume levels but my preamp has a problem with minimum volume in the left channel.

In other words if I set the volume as desired only the right channel has output. As this is only a couple of degrees rotation from minimum on the volume control, I don't know if there is a problem with the preamp itself, an issue of needing a lower powered amplifier, an issue of needing a preamp with less gain, or something else.

What are my options for addressing this issue?

[mcgsxr]

Not my area of expertise but - could you use one of those inline attenuators (Rothwell 10db as an example)?

Assuming that you would still have enough volume on the top end of the volume twist - do you go past 12pm on the volume often when listening louder?

[wilsynet]

The preamplifier is at fault if it can't maintain a fairly equal gain or attenuation of signal across both channels.  This may be an inherent design flaw of a component as opposed to a faulty component that can be easily fixed.  A number of lower cost volume pots out there do not track channel balance well at low levels.  The Assemblage L-1 may have just such a volume pot.

Do you know the gain of your preamp and the gain of your amplifier?

Also, what are you using as source components?

[wilsynet]

Oh, here we go.

EX4420

Input sensitivity: 1.65V
Gain: 28 dB
Input impedance: 33 K ohm

Do you have specs for your preamp?  I couldn't find them.

With 92dB efficient speakers and 1.65V input sensitivity, I would guess that you really don't need a preamp with gain at all.  Although buffering may be important and we'd have to see what the output impedance of your sources are too.

[roscoeiii]

wilysnet is dead on here. I will only mention that while the lower end of an attenuator is where there are usually the most difficulties with channel balance (you can see this in the measurements sections of Stereophile reviews of preamps and integrated amps), if you aren't getting any sound from one channel, then I think that the pre would likely need a repair. Channel imbalance is one thing. Only getting sound from one channel is another.

Passive pres or in-line attenuators could be solutions. But be sure you look into the drawbacks and think about your listening preferences. Passive pres are great on detail, but don't give the utmost in dynamics and drive ("oomph" factor if you will). And some are better than others. I have had best luck with passives that are of the buffer variety, particularly the Dodd Buffer (sorry again wilysnet for taking so long getting that one to you. Still ashamed of that). But I eventually decided to stay with my active pre (which is also much pricier than the Dodd). That said, for the type of listening you do, at low levels, a passive may work very well. If you go that way, be sure to also look into the component matching requirements of a passive as well.

[Speedskater]

This is typical of logarithmic (audio slope) potentiometers as they approach the low end of travel. An attenuator pad at the input of the amplifier is a quick cheap solution.

[Doublej]

Assemblage  L-1 specs:

Gain: 20dB
Input Impedance: 47K
Output Impedance: 525 Ohm
Rated Output: 1 VRMS
Maximum Output Voltage: 40 VRMS

Source is an iMac. Either an internet stream or unripped CD. iMac volume set to max. I can't go past 10 o'clock on the volume control as it becomes too loud for me.

Question - At extremely low volume will there be much of a difference in sound quality between inserting an attenuator and simply reducing the output volume from the Mac?

[mcgsxr]

I am not familiar with how the iMac trims volume (ie does it drop digital bits to reduce volume at low levels), so it might sound worse to change the output from the iMac.

[wilsynet]

sorry again wilysnet for taking so long getting that one to you. Still ashamed of that

Water under the bridge, long forgotten, I don't think of it.  We're all good. =)

[wilsynet]

Source is an iMac?  The headphone output, or are you using USB or TOSLINK to an outboard DAC?

If you are playing via iTunes, the newest releases of iTunes have a 24-bit dithered volume control, that while likely not as good as PureMusic or Audirvana, will probably do the trick for you.  And if you are listening to streaming music, you're starting with pretty substantially compromised source material anyway, so who cares if there's some small loss of ultimate resolution.

I would ratchet the iMac down to 3/4 volume (don't go below 50%) and see if the preamp volume control now works for you.

Having said all that, it may be worthwhile to get a repair tech to check out the preamp and see if (for example) the volume pot needs replacing.

[Doublej]

I am using the headphone out. I dialed down the volume on iTunes to 3/4 and turned up the preamp volume control. That takes care of the channel imbalance and while I haven't done at low volume critical listening it sounds fine for me.

On my preamp the left channel kicks in approximately 2 degrees of rotation after the right channel so I wonder if it's not simply within the tolerance of the pot. At low volume and higher (as opposed to very low volume levels) both channels work fine.