How important is the preamplifier?

[Tom Bombadil]

I know many people believe that. But after more than 3 years of listening in my systems plus testing and including over a dozen other believers in cables in various tests, I came to the conclusion that as long as my cables were of good construction and not of dubious design, that they made no difference in my system. To me, spending big bucks on interconnects, digital cables, and power cords is a total waste of money. That is, I am not above spending $2000 to $3000 on a DAC, but would stop at around $30 for the digital cable to connect it to my transport and the same for interconnects to my preamp.

 

[E-Stat]

It wasn't such an "elaborate" test. Same DAC feeding two different preamps which then went into a high quality A/B switchbox and one output to the amp.

So, how did you split the signal?

At times I used the same brand and type interconnects to/from each preamp, at other times I varied them.

In which case the cable metrics of whatever you used would have been doubled.

The interconnects used made no discernible difference to me, or others who listened to the comparison.

When the metrics of both are combined, you are listening to "both" as compared to - well "both"!

Only measurements preformed were on volume from the speakers, where volume was level matched to within 0.1dB using test tones of different frequencies.

Which is in no way a control as to the contrived setup you used vs either by themselves.

Thanks for the response. Surely you understand this *test* has no basis in comparison as to simply comparing A to B.

 

[Tom Bombadil]

Didn't have to split the signal. The DAC had two pair of analog outputs. So it was DAC Output 1 to preamp A CD input to preamp A output 1 to switchbox to amp. And DAC Output 2 to preamp B CD input to preamp B output 1 to switchbox. To amp. All using the same interconnects. Volume levels were measured in the room at 3 different frequencies and volume controls on preamps were adjusted to achieve level matching to within 0.1dB on SPL meter.

Switchbox was custom made, using an Audio Reseach toggle switch, Cardas jacks, internally wired with Kimber silver wire and all connections soldered with silver solder.

I compared "both" this way and in a typical A/B comparison, several times, several days for each. There was no difference in the comparisons. When I could tell the preamps apart in the parallel A/B comparison, I could also tell them apart in a conventional A/B comparison. It was just that the parallel comparisons were much easier to conduct and bore out differences (if present) quicker.

And, btw, thank you for your response.

 

[E-Stat]

Switchbox was custom made, using an Audio Reseach toggle switch, Cardas jacks, internally wired with Kimber silver wire and all connections soldered with silver solder.

I have many of those ARC switches.

Switched hot side with common ground to prevent thumps?

 

[Tom Bombadil]

There were no thumps at all. I didn't do the build myself. Purchased it used for less than it would have cost me to build it.

I also tested for the switch effect by running one DAC output to the switch then to the Preamp and then the other DAC output directly to the preamp. Then would switch the preamp input selector to compare. I used the same interconnects on both sides.

I tried this with two different preamps and two different sets of interconnects. Had it setup this way for a week or two for both evaluations. So I could just casually switch it now and then. Never heard any differences. Decided that was good enough for me, since my goal was to find out what made differences in my system and where to spend my money on upgrades.

 

[E-Stat]

There were no thumps at all.

Good. There were common grounds.

So, you loaded down the DAC by paralleling the outputs to the two sources and doubled on the cable metrics as seen by either.

The common grounds to the preamps likewise combined electrical characteristics of the two preamps.

Electrically, you changed the environment with this arrangement as opposed to comparing one against the other sans the other stuff. The purpose of a control is to quantify the differences.

Assuming that none of these measurable changes had any audible effect makes for fun comparisons, but would never pass muster as a scientifically valid test.

 

[Tom Bombadil]

Like I said, my purpose was to compare gear to find what made an audible difference (and improvement) in my system, to my ears. The switch made no audible difference that I, and about 6 others, could hear. So that was good enough for me to move on to using it to compare interconnects, preamps, DACs, CD players, etc. Of course, it wasn't always present in all comparisons. I used other setups, such as running different interconnects from the two DAC outputs to a preamp, to compare interconnects. Or, many times, different DACs and CD players, to a preamp. I also used a high quality ALPS pot (just an input, the pot, and an output), when needed, inserted in-line to adjust for line level volume differences. That too was subjected to listening evaluations.

It was all great fun, informative, interesting when running comparisons with others (along the way 3 audio shop owners and 2 of their salesmen participated in various comparisons, along with 8 to 10 others). Some comparisons were shocking in that I, and others, could not discern any differences. In others, we identified differences which were verified under blind comparison conditions.

In the end, I am very satisfied with how these aided me in my purchases.

 

[E-Stat]

Like I said, my purpose was to compare gear to find what made an audible difference (and improvement) in my system, to my ears.

Objective quite clear.

The switch made no audible difference that I, and about 6 others, could hear.

Which completely misses the point. It's not the switch contacts that invalidate such a test. It is the combined electrical characteristics of the cables at the front end and that of the downstream DUT via the switch that are responsible.

There is a "cable comparison" test found on the Elliott website - click here. Its goal was to see if one could tell any differences between cables. Since the y-adapter employed likewise uses a common ground, what you ended up comparing was both cables to well, both cables! I set up the test myself and measured the results.

I'm sure your test is as well intentioned as that one.

 

[JP]

How, exactly, do common grounds combine the electrical characteristics of the preamps?

 

[Tom Bombadil]

Objective quite clear.


Which completely misses the point. It's not the switch contacts that invalidate such a test. It is the combined electrical characteristics of the cables at the front end and that of the downstream DUT via the switch that are responsible.

There is a "cable comparison" test found on the Elliott website - click here. Its goal was to see if one could tell any differences between cables. Since the y-adapter employed likewise uses a common ground, what you ended up comparing was both cables to well, both cables! I set up the test myself and measured the results.

I'm sure your test is as well intentioned as that one.

Most of my cable comparisons were conducted without the switch. Using the two DAC outputs into two inputs on my preamp (well, multiple different preamps) and comparing them. The switch was primarily used to compare preamps and other components. Also most of the preamp comparisons were conducted when using the same interconnects on both sides of the switch, done specifically to reduce any interconnect factor.

Oh, I've also done a few interconnect comparisons by running my DAC into a preamp and then used both outputs from it into a second preamp and would then switch the inputs on the 2nd preamp to compare. Setting the output from the first preamp to something less than 2V. Didn't do this very much.

 

[E-Stat]

Also most of the preamp comparisons were conducted when using the same interconnects on both sides of the switch, done specifically to reduce any interconnect factor.

In that case, you're only doubling the LCR metrics as seen by either end since they are summed.

 

[Mark B]

A cheap cure for digitalis and transistor glare :thmbsp:

Or you could buy quality components and not need to mask issues from sub-standard gear. :thmbsp:

Maybe I should sell the Lowthers and replace them with Infinity or trade the SET amps for a Yamaha.

Were you referring to your Lowthers and SET amps when you suggested a cheap cure for digitalis and transistor glare?

 

[Tom Bombadil]

In that case, you're only doubling the LCR metrics as seen by either end since they are summed.

Not worried about that from 0.5m cables.

 

[snip3r]

Hi guys, I'm currently using my dac directly to my poweramp which I can control the volume. I was thinking of adding a preamp. my dac is balanced so I was thinking of getting a full balanced system. What do you guys think? I will not be using long i/c or speaker cables as it's only in my study room. Beauty of using the balanced DAC is because of high db ( dynamics ).

Pls advise. Thanks.

 

[JoeESP9]

What makes you think that a balanced system will have better dynamics? The dynamics are determined by the source material not the connection/interface method.

 

[snip3r]

What makes you think that a balanced system will have better dynamics? The dynamics are determined by the source material not the connection/interface method.

For DAC, mostly single ended has lesser dynamics range ( sry left this out ) than balanced.

 

[JoeESP9]

In either case the dynamic range available from the gear is much higher than any source material. As I said, it's the source material that matters.