How much do I need to spend to get a preamp that sounds better than no preamp?

honashagen OP38 posts04-30-2018 8:02amLast night I think I talked myself into thinking my new pass preamp was sounding good. I was fooling myself. It still sounds too forward to me. I really want to like it.

Your Oppo has an output impedance of 100ohms, it will drive the 100kohm input of the DNA-1 in it's sleep, and just about anything else.
And the Oppo at 2.1v out for RCA and 4.2v out for XLR. It easily has enough v gain for your DNA-1 poweramp, which only needs 800mV (.8v) in to give it’s full output wattage!!!!. As you can see, you don’t need anymore gain from an active preamp. Just look at the maths?

Here is what Nelson Pass regards as his best sounding preamp, he says he can’t belive it didn’t make him filthy rich, and yes it’s totally passive untill the volume control hits 3 o’clock, then it becomes active for those that need the extra gain, "most likely because many of his poweramps are very low gain" but he also does say you take a hit in sound quality when 3 o’clock and over are used when it becomes active.

Yes your going to say, but he makes $$$$$$ preamps.

He’s not a fool he likes to make money, passives don’t make money because you can’t sell them for $$$$K I prove that.

" Nelson Pass:

The Aleph L is a single ended Class A audio preamplifier combining new design thought
applied to traditional topology and the experience of twenty five years of amplifier design.
This preamplifier flows from a commitment to create the best sounding product: a simple
circuit with the most natural characteristic. The Aleph L integrates discrete Mosfet gain
devices and single ended Class A operation in a simple active/passive topology in order to
deliver the most natural sound possible. The Aleph L absolutely minimizes the number of
components in the signal path, and uses these only when necessary.
Unique to this preamp, patent pending, is a volume level control which combines the best
qualities of a passive attenuator and active gain circuitry:
At the 3 o’clock volume control position, the Aleph L offers a direct path from input to output.
The only component in the signal path is wire and switch contacts.
At positions below 3 o’clock, the volume control functions as a precision passive attenuator
using discrete resistor ladders.
Above 3 o’clock, active gain is added to the output signal in 2 decibel increments, for a
maximum of 10 dB.
As a result, you suffer the effects of active circuitry only when additional gain is necessary.

Another quote from him

Nelson Pass,

"We’ve got lots of gain in our electronics. More gain than some of us need or want. At least 10 db more.

Think of it this way: If you are running your volume control down around 9 o’clock, you are actually throwing away signal level so that a subsequent gain stage can make it back up.

Routinely DIYers opt to make themselves a “passive preamp” - just an input selector and a volume control.

What could be better? Hardly any noise or distortion added by these simple passive parts. No feedback, no worrying about what type of capacitors – just musical perfection.

And yet there are guys out there who don’t care for the result. “It sucks the life out of the music”, is a commonly heard refrain (really - I’m being serious here!). Maybe they are reacting psychologically to the need to turn the volume control up compared to an active preamp."

Cheers George

Thanks George. I'll see what passive is like with the Axiom.

As George points out, suitable impedance matching and adequate voltage gain are critical to achieving good results with a passive.  Other considerations, depending on the type of passive, are the potential for changes in impedance with changes in volume, and the effect of cables on impedance and capacitance.  Passives seem to work best in situations where there are short cable runs after the passive.  You can read a lot about this in these forums.  Active buffering helps control impedance so that it stays low and consistent, and to help with consistent current delivery.
One thing you should consider is that while the stock DNA-1 has an input impedance of 100K ohms, if Steve's upgrade of your amplifier included adding transformers the resulting input impedance was likely changed to only 10K ohms, which would significantly affect your compatibility equation for use with a passive.  BTW, the amplifier I used for my passive comparison described below has input impedance of 100K ohms.

I’ve done a blind A/B with 30 of our audio club members using a 10kohm passive preamp. A source with 2.5v at 100ohms output impedance. We had a power amp with 1.5v input sensitivity for full output, the amp had a special switchable input impedance’s on the fly 10 x from 100kohm down to 10kohm

Nobody could tell the difference from 100kohm all the way down to 33kohm, when we got to 20kohm 5 of the 30 members though they heard something but weren’t sure, then it added up from there the lower we got.
During the whole time we made sure the level was spot on within 1 mV from the amps output using a 1khz sine wave.

Cheers George

Honashagen, some questions:

1)Are you using balanced or unbalanced connections between the Oppo and the Pass? I suspect balanced would be preferable, as I alluded to earlier.

2)Have you tried both the 4 db and 14 db gain settings of the Pass?

3)Are you setting the Oppo’s volume control at or near max when the Pass is being used, which I would expect to provide better results than having that control at a lower setting?

4)If you are using an unbalanced connection to inputs 1 or 2 of the Pass, is a shorting plug or jumper connected between pins 1 and 3 of the corresponding XLR connectors? (See the second from the last paragraph on page 3 of the manual).

Regards,
-- Al