Why do you need a preamp?

HT cOz · « **Reply #20 on:** 22 Apr 2011, 04:15 pm »

It sure seems like the pre is important. Also some have HT bypass and dual outputs. These are very useful to people whose systems are multi-tasking.

ajzepp · « **Reply #21 on:** 26 Apr 2011, 12:05 am »

Quote from: HT cOz on 22 Apr 2011, 04:15 pm

It sure seems like the pre is important. Also some have HT bypass and dual outputs. These are very useful to people whose systems are multi-tasking.

A tubed preamp with HT bypass is the most important addition of my 20 years in this hobby.

JLM · « **Reply #22 on:** 30 Apr 2011, 03:00 am »

So a pre-amp can...

Provide volume control (but so can stepped attentuators)
Can amplify the low level signal (but digital sources rarely need amplification)
Act as an impedance buffer to enhance system performance (may or may not be needed based on your particular components)
Typically connect multiple sources
Some offer phono pre-amplification
Can include tone controls (but DEQ offers much more control)
Some include various connectivity options (HT bypass, sub-woofer outputs, tape monitor loop)

roymail · « **Reply #23 on:** 29 May 2011, 10:12 pm »

Well, if you have only a single source, a CDP with 2 volt output for example, and your amp has a friendly input impedance (50K>), and your speaker's sensitivity isn't too low, mine are 92db, then using a passive stepped attenuator may be all you need.

I just described my little setup with my diy volume control using a Goldpoint/Elma stepped attenuator. Considering the weaker link theory, I doubt that an expensive preamp would sound much better.

I'd recommend plugging straight into your amp with some soft music to get an idea of what it would sound like. Best of luck.

Mike Nomad · « **Reply #24 on:** 29 May 2011, 11:30 pm »

+1 on plugging straight into the amp, if you can get away with it. I did that for years with my Parasound (had trim pots on the back). Some of the best sound I've ever gotten from a rig.

The only reason I moved away from that approach is because I needed more inputs (the perils of not living single). See Also: The long-running thread on Audiophiles & Being Happily Married...

JLM · « **Reply #25 on:** 30 May 2011, 12:23 pm »

Forgot to mention, most look for a pre-amp to add colorations, which can be very nice but I don't want everything to sound alike (have the same colorations). Analog, steak with extra spices/sauces.

So I'm with you Mike, my EE DAC is the closest thing I've had to a pre-amp and the only tube in my system. Now if I was a really brave audiophile I'd go straight into some high-end active studio monitors and hear what they do (or at least hope to) in the production booth.

geowak · « **Reply #26 on:** 30 May 2011, 01:38 pm »

I am running my amp directly to a Benchmark USB DAC1. It has a couple outputs and works just fine as a preamp. I also triples as a headphone amp.

DAC
PREAMP
HEADPHONE AMP

Sounds much better than any preamp I have used.

rollo · « **Reply #27 on:** 30 May 2011, 02:00 pm »

The Preamp is the heart of the system. The additional gain and weight is just not available with a passive or attenuator IMO.
Now the quality of the preamp and synergy is not an easy task. Saying that, is one better than the other ? No. Everything is system dependant.
You just have to try both and see what is liked by you. Your CDP needs a minumum of 2V output and the amp a sensitivity of less than 1 mv [ less even beter] for enough volume.
What you will get with a passive approach is clarity, less coloration and more detail with a leaner presentation. Where it gains in tranparancy it losses in weight and what I call Soul.
If you are of the analytical type a passive should be in your future. If you are meat and bones type go active. However try both ways ya never know.

charles

ctviggen · « **Reply #28 on:** 30 May 2011, 02:14 pm »

I have a modified Squeezebox that I tried to run directly into my amp. I could turn the volume all the way up and it wasn't loud enough. I had to add a preamp. I also like preamps because they allow you to add multiple sources. Currently, I'm using a Dodd tubed preamp, which I really like. I also like my Proceed AVP. Using receivers as preamps isn't as good (even in supposedly pass through mode). So, I'd recommend a nicer preamp.

doug s. · « **Reply #29 on:** 30 May 2011, 02:42 pm »

Quote from: JLM on 30 May 2011, 12:23 pm

Forgot to mention, most look for a pre-amp to add colorations, which can be very nice but I don't want everything to sound alike (have the same colorations).

i do not mind that my preamp adds colourations. i don't even mind that it makes everything sound alike. because, w/the right preamp, it is my experience that "alike" means closer to what real music sounds like, and less like electronics.

of course, it doesn't hurt that i can control the wolume remotely, that i can have my cd, winyl, dvd for movies, and two fm tunas connected. and, i also like being able to switch in-&-out my dbx 3bx for compressed source material.

ymmv,

doug s.

roymail · « **Reply #30 on:** 30 May 2011, 03:40 pm »

Charles commented... "What you will get with a passive approach is clarity, less coloration and more detail with a leaner presentation. Where it gains in tranparancy it losses in weight and what I call Soul."

Interesting observation and mostly true. My concern is that it would cost me lots of $$$ to get it all in one package. I'm sure it's possible but then I'd be forced to upgrade every other component.

I just can't afford that merry-go-round. Some of you can and that's fine. But, to my ears, my simple little system sounds better than what I've had before.

The fact that you can always move up the ladder to something that sounds better than what you have, is what keeps this hobby going. But for me, the music is what keeps me satisfied more than anything.

avahifi · « **Reply #31 on:** 30 May 2011, 04:29 pm »

A good preamplifier will have an active line stage with low output impedance and high drive current to properly charge and discharge the distributed capacitance of interconnect cables and amplifier input circuits. A passive line stage simply will not do the job because it has high output impedance and it interacts with your interconnect cables and your amplifier. You need a true high fidelity preamplifier to make your system work best.

Regards,

Frank Van Alstine

jimdgoulding · « **Reply #32 on:** 30 May 2011, 08:05 pm »

That's an ear opener for me, Frank, no pun intended. I've been using a tube line stage for quite some time with a SS phono pre. Does the phono pre do the work of an active line stage? I have a Counterpoint SA5 that's been boxed for a long time cause the separate tube power supply blew and there is some arcing going on where one corner of the main board and the frame meet. When I discussed this with Counterpoint, to look at it was as expensive as what replaced it let alone fix it so I bought my ARC LS-7 second hand. Got no complaints but if I could be missing something, I might re-visit my problem. Thanks.

JLM · « **Reply #33 on:** 30 May 2011, 09:48 pm »

Quote from: avahifi on 30 May 2011, 04:29 pm

A good preamplifier will have an active line stage with low output impedance and high drive current to properly charge and discharge the distributed capacitance of interconnect cables and amplifier input circuits. A passive line stage simply will not do the job because it has high output impedance and it interacts with your interconnect cables and your amplifier. You need a true high fidelity preamplifier to make your system work best.

Regards,

Frank Van Alstine

Thanks for speaking up Frank. We've heard that advance a million times (not a dizz), but I don't recall ever hearing what constitutes low output impedance or high drive current. If my DAC meets that criteria does that mean I can do without a preamp?

My DAC has an analog volume control, a tube stage output of 3 volts/22Kohm (not simply a buffer), and "adds a few pounds of flesh as good active preamps tend to."

Mark Korda · « **Reply #34 on:** 31 May 2011, 07:27 am »

You guys are great! I think I might have the missing link here..(The Ace Audio Zero Distortion Preamp)ala 1974.I brought out my High Fidelity(1975)and it's a passive preamp combined with a phono section for 82.50 as a kit.No tone controls or balance,just 2 cheap volume control sliders,that if lubed up will work perfect..I had to pry this away from my brothers (yuppie) home when he used it with the (Black Box) 400 Dyna,and the Dyna A-30-XL's,mind blowing!I got it back after I fixed his Dyna PAT-5 's frozen volume control.Some one told me to heat it up,alas,it was frozen,and when I did and a few turning twists,I got my Ace back.Before I hit the sack,this was the chosen preamp of the blind man that ran Cizek speakers,I wish someone would help me with the name of him,and of ever knowing this preamp.John Grauer was the man,maybe more famous for his sub-woofer crossovers,early days,cheap,and sub-sonic filters,pre cd...turntable stuff...I would love to hear from anyone about this subject.I went so far as building a transformer passive preamp I saw in AudioXpress..I got some pics if anyone is intrested...thanks for my bending your ears...Mark Korda

avahifi · « **Reply #35 on:** 31 May 2011, 09:03 pm »

Low output impedance and high drive current?

We would suggest that a low output impedance is in the under 1000 ohms range and that high drive current (for a preamp or line level source) is in the 100 mA range or higher.

In comparison, the typical op-amp used in the output section of a preamplifier, CD player or FM tuner probably will have less than 10 mA current capacity and an output impedance set by current limiting resistors to protect the active devices from failure. A small signal vacuum tube likely will be in the 5 mA current range or less, depending upon the circuit configuration.

The actual scientific way to deal with this issue is to first ask the question, "how much current does it take to charge and discharge the capacitive load represented by my cables and amplifier?" It is possible to measure the load and then do the math to answer this question. Then ask the second question, "how much output current capacity does the output stage of my CD player, tuner, or preamplifier actually have?' It is possible to measure this accurately too. Then, if you find out you do have adequate current reserves, relax, worry about some other issue. If the answer is "bung," then understand your system is not working properly from this aspect at least, and do something useful about it. Or much easier, get some better sounding cables and capacitors.

Regards,

Frank Van Alstine

HT cOz · « **Reply #36 on:** 31 May 2011, 11:47 pm »

Frank I'm a little confused by your two posts. At face value they seem to be written by two different people.

Thanks
Robert

mp9 · « **Reply #37 on:** 1 Jun 2011, 12:46 am »

I don't need a preamp, prefer to run my Fi 2A3 SET amp direct to source, a Sony CDP X707ES variable out.

I have a preamp for the rare occasion i spin vinyl (more a lifestyle choice), it's packed away in a closet along with the turntable, dvd player, various interconnects and other stuff i don't use.

JoshK · « **Reply #38 on:** 1 Jun 2011, 12:58 am »

I agree with Frank except that 100mA seems a bit steep. I guess it depends on the front end of your amp your driving (plus the capacitance of the cables). Typical tube gain stages don't seem to need that much current, unless your driving a pretty extreme miller capacitance. No idea when it comes to SS front ends, no design experience there.

roscoeiii · « **Reply #39 on:** 1 Jun 2011, 01:55 am »

Quote from: roymail on 30 May 2011, 03:40 pm

Charles commented... "What you will get with a passive approach is clarity, less coloration and more detail with a leaner presentation. Where it gains in tranparancy it losses in weight and what I call Soul."

Interesting observation and mostly true. My concern is that it would cost me lots of $$$ to get it all in one package.

I agree on both points in the quote above. Only when I moved to the substantially more expensive kW linestage did I find a preamp combining the benefits of passive and active pres. Those qualities and more (in ways that I don't think I can put into words).