help me to understand the gain

We have an amp that has only 23 db of gain. It works really well with ZU speakers too.

The problem you are having is classic- a DAC with too much output. I don't understand why DAC manufacturers do this- to me it seems like a fundamental misunderstanding of how power amplifiers work. There is not a power amp out there that needs more than 3 volts input, so why do you need 5 or 6V?

With that kind of output you have to attenuate the signal, either by passive control, digital volume control or something like the Rothwell attenuators. *All* of them rob the signal of musicality! With digital and passive controls, the higher you can run the control the better they sound (although for different reasons). So why force the user to turn things down so much??

Enough of my diatribe- you have gotten good advice from other posts here...

Sell the Zu speakers and get another speaker with lower, say mid-80s, efficiency. You'll get more of you're money back selling the Zus, they are a hot item compared to the McCormack amp. There are plenty of fine speakers out there that like an amp with power and current.

Gte357,
I`m a huge avocate for SET amplifiers(particularly with your speaker`s 101db sensitivity) however power and gain are`nt the same. you can have a low wattage amp with very high gain and a high powered amp can have normal or low gain. You must also factor in the amp`s sensitivity, for example 300mv is very sensitive and 2v would be far less sensitive. Your current system simply does`nt need the gain of the active preamp. Thus direct source to amp or a passive preamp. If you want to keep your preamp you`ll need an amp with much less gain than your DNA1.

It seems the gain of the amp is not a published specification. I can only see it inside the Stereophile review under measurement section.

As a rough approximation, you can calculate the gain by using the input sensitivity and output power numbers, and then adding a few db to the resulting number:

First, convert the 8 ohm power rating into volts, based on

P = (Esquared)/R,

where P is power in watts;
E is the voltage corresponding to rated continuous power into 8 ohms;
R is 8 ohms.

In this case, P is 150; R is 8. Therefore E = square root (150 x 8), or 34.6 volts.

Using the 1.5 volt sensitivity rating that was provided above by Dave, the voltage gain is 34.6/1.5 = 23.1.

Next, convert that gain to db by taking 20 times the logarithm of the voltage ratio:

20 x log(23.1) = 27.3db.

As I indicated, the actual gain will be somewhat larger than that number (in this case by 5db), because the continuous power rating will be lower than short-term power capability, and because of margin that is provided in the specs.

I would like to try the SET amp.... Does the requirement to have input impedance > 100k Ohm still apply?

Yes. That is a consequence of the preamp's output impedance characteristics. As for specific amp recommendations, you might want to research past threads to see what amps people have used with the particular Zu model, and/or start a separate thread on that question.

I can lower my DAC input so I can make the volume know of the preamp within a usable range. This is similar to if I lower the volume in iTunes. My question is, how would this affect the sound? Will I run into the bass roll off problem like using attenuator?

IMO reducing the setting of that volume control is a reasonable thing to try. The bass rolloff effect I described has no relevance to that. As Ralph (Atmasphere) indicated, the sonic effects of reducing the setting will depend on the specific design, and only you can make that judgment.

Regards,
-- Al

oNHWY61,
The problem is`nt the Zu`s high efficiency(often a big plus). Again it`s not too much power or current, excess gain is a entirely different matter.Elizabeth uses very inefficient (84db) speakers and has the same issue. It`s gain folks.