Will changing gain affect frequency response?

The preamp has two settings for gain, set internally, of 3 db and 12 db and came to me set at 3 db.

Back to my first post, which everyone overlooked, how is this reduction achieved? Is it via the feedback network??
If so, this can influence the tonal quality, of where these gain setting positions are used, and they have nothing to do with the vc knob being high or low physical position for the same given volume.

Cheers George

I second what rlawry says above about the non-linearity of the particular gain control, versus that of the volume control itself in particular.

Almost as an aside, Steve Deckert of Decware advocates introducing an extra gain stage control inserted after the source, in addition to the one at your amp (ZBOX). This allows you to do some "gain riding" as he calls it, letting you either turn up the gain going out of your source while also turning the gain down going into your amp....or vice versa. I haven’t tried it that way (yet), but he says that increasing the source output gain while lowering the amp input gain, definitely changes the overall character of the sound...in the right adjustment zone, he says the sound in that instance is much more dynamic. Presumably you can take this idea too far and it may begin to deteriorate the sound in some other regards the further your adjustments go, but his point is that you have a choice of what sounds best to you. If this arrangement produces that result, then perhaps it is not hard at all to accept that you are hearing, ghosthouse, a slight difference in tonal response in your set up (and that Al would be correct by way of what he has already pointed out, as usual, but I defer to Al and others on most matters ee).

Here is the ZBOX link which has a description and a link to the owner’s manual: www.decware.com/newsite/zbox.htm Steve makes mention of both impedance and frequency response.

Claims are a bit out there.
How can a tube buffer with 1000ohms output impedance, be a better impedance match than a 100ohms or even less output impedance source with it's own VC, into say the low 10kohm load  of one of the Pass Labs poweramps? 
And this 1000ohms output impedance will be even higher at lf as it's bound to be capacitor coupled!

Cheers George

You may well be right George. I have many unanswered questions about this unit and I'm certainly not here to vouch for it, as I've never seen one and don't intend to order one myself. When I go this route it will be with a simple, but good quality, distribution amp that I will be building myself since the Decware, nor any other unit that I could find, seemed to fit the bill for my particular setup. But, I wonder if any effect at all of the ZBOX will be at all evident with the distribution amp...even a small of it might be significant...not as any vindication at all of the ZBOX product (not at all recommending that ghosthouse go out and buy one), but simply pointing to the genuine impedance matching question, possibly.

George makes a good point that sonic consequences can particularly be expected if a gain change is implemented in a circuit via a change in the value of a resistor in a feedback loop.

Regarding Dentdog’s Zesto Leto, there doesn’t seem to be any indication at the website or in the manual as to how the gain change is implemented. (Although the manual states in bold-face type, in the paragraph dealing with the internal gain switch, that "due to high internal voltages there are no user adjustable switches, only authorized representatives can make these adjustments," and also states that the "warranty is void if the product has not been used in accordance with the instructions found in this owner’s manual.")

A schematic for the McIntosh MC60 can be found on the web and shows that its gain control is simply a resistive pot (potentiometer) used as a voltage divider and connected to the input through a capacitor.

As I see it the bottom line to Dentdog’s question, and to such questions generally, is that whatever sonic effects might result from changing how the overall gain is apportioned between components figures to be highly dependent on the specific designs that are involved. So in most cases the only way to find out is to try the various alternatives in the particular system, IMO.

Does trimming the gain on the amps give me less headroom when listening at higher volumes?

No, assuming that you don’t turn the gain controls on the amps so far down that you can’t drive them to full power (when and if that is required by the music and your volume preferences).

Regarding the ZBOX, it sounds like it uses the tube in a cathode follower configuration, and has an Alps pot at its input for gain control. It is described as using "large hi-end coupling caps," so perhaps the specified output impedance of "less than 1000 ohms" is conservative, even at 20 Hz. In any event, I would think that the key to its sonic effects, in addition to possibly allowing the gains of other components in the system to be optimized, is the mention that it "works by creating a starved voltage condition in the filament of the tube that in turn causes an increase in favorable harmonics and a decrease in objectionable distortion." Although I suppose the reduction in "objectionable distortion" may not really be a reduction, but rather a masking by the "favorable harmonics" that are introduced.

John ("Ivan"), thanks for the nice words.

Regards,

-- Al