AudioCircle

Audio/Video Gear and Systems => The Starting Block / Introductions => Topic started by: Rclark on 21 Apr 2011, 02:32 am

Title: Why do you need a preamp?
Post by: Rclark on 21 Apr 2011, 02:32 am

 Why do you need a whole seperate box to "step up low level signals"? Why can't an amplifier step those signals up on its own?

  To me it's like feeding pre-chewed grass to a cow.
Title: Re: Why do you need a preamp?
Post by: cujobob on 21 Apr 2011, 02:41 am
Some do, but amplifiers are not just for two channel listening.  There are also sonic advantages to separating pre-amps from power amps.

You can buy power amps with volume controls and also buy integrated amps.
Title: Re: Why do you need a preamp?
Post by: Rclark on 21 Apr 2011, 02:48 am
It just seems like such a simple, mundane function to have a seperate box for, like having a separate volume control box for the seperate step-up-low-level-signals box.
Title: Re: Why do you need a preamp?
Post by: stereocilia on 21 Apr 2011, 03:13 am
For digital sources, the preamp usually ends up decreasing the gain which makes the idea of a line stage preamplifier even weirder.  It's more like an active attenuation box.  Correct me if I'm wrong, but I think the preamp just gives the source an easier load to drive.  For whatever  reason, an active linestage sounds better to me than just putting a volume control between the source and the amp.  You'll find many who say otherwise.   

For vinyl, for multiple sources with tape loops, tone and balance controls and what not the need for a preamp is more obvious.
Title: Re: Why do you need a preamp?
Post by: Rclark on 21 Apr 2011, 04:20 am
okay, that makes sense.
Title: Re: Why do you need a preamp?
Post by: Sonny on 21 Apr 2011, 06:28 am
Also, you're using it to switch sources...A volume control on the amp is great if you only have one source.  The EVS Ultimate Attenuators are nice..plugs into any amp!
T
Title: Re: Why do you need a preamp?
Post by: jtsnead on 21 Apr 2011, 10:33 am
I have had multiple preamps, but I feel this is the best option with battery power supply:

http://doddaudio.com/BatteryPoweredTubeBufferPreamp.aspx (http://doddaudio.com/BatteryPoweredTubeBufferPreamp.aspx)


(http://www.audiocircle.com/image.php?id=45845)

remote control with three inputs
Title: Re: Why do you need a preamp?
Post by: JohnR on 21 Apr 2011, 10:48 am
Another factor that hasn't been mentioned is flexibility. If you have an active preamp, you can use different amps or types of amps (tube, SS, class D, monoblocks, etc). Finding a preamp that you like is the hard part, however... in the end, certain functions need to be performed and whatever way you find best to do those is all you need :thumb:
Title: Re: Why do you need a preamp?
Post by: bhobba on 21 Apr 2011, 11:20 am
Why do you need a whole seperate box to "step up low level signals"? Why can't an amplifier step those signals up on its own? To me it's like feeding pre-chewed grass to a cow.

The answer is you don't.  There are some mighty fine integrated's out there such as my Leben CS300XS.  In fact I tend to prefer them these days.

However if you go the separate pre-amp route then IMHO, and you will probably get people who definitely do not agree with me, its function is to switch inputs and impedance match - not amplify.  Most DAC's produce something like 2.5V and amps have something like 500mv sensitivity for full output.  Amplification is simply not required - unless you have some ham fisted recording engineer who records at some insanely low level - which occurs only extremely rarely (I have only one recording like that - a best of Aretha Franklin) - although of course it should never happen.  But even omn those recordings I still find I can get adequate volume without any gain.

Thanks
Bill
Title: Re: Why do you need a preamp?
Post by: fsimms on 21 Apr 2011, 11:41 am
Ideally you don’t.  However, I like a solid state amp and a tube preamp.  I don’t know of any integrated amp that has both a solid state amp and a tube preamp section near as good as what I have.  Maybe the designs are different enough that it would be impossible to find an expert in both areas.

Bob
Title: Re: Why do you need a preamp?
Post by: doug s. on 21 Apr 2011, 11:11 pm
i need a pre for several reasons.  two (or 3) tuners, computer for movies, cd, turntable, dbx 3bx expander in tape loop...  and, a good (tubed) pre will make everything sound better than no pre at all.

ymmv,

doug s.
Title: Re: Why do you need a preamp?
Post by: Elizabeth on 21 Apr 2011, 11:33 pm
many years ago a preamp had a LOT of features.
Preamps universally had a phono section. They had tone controls, and a balance control. Many had tape loops.
ALL input devices, tuners, tape machines etc had aa electrical input voltage of 1/4 volt. maybe high end stuff got up to 1/2 volt.

Then a strange thing happened CD.

CDs had an output (for mysterious reasons to do with sales tactics only) a HUGE output of 2 volts. and even the gain of a preamp was neutered, and preamps became mere attenuators.

So gradually the line stage appeared. most phono preamps died off and line stages took over, with separate phono boxes. Then the tone controls vaporized. Defeatable or not out they went.

 Bad for audiophiles, and no respectable audiophile was allowed to own a preamp with tone controls. It was like having head lice. (The proper audiophile was supposed to buy $10,000 tone control interconnects instead, and did)

So now we have a nearly useless box with nothing to do.
I own three nice, nearly useless preamps;
Bryston BP-26
Audio Research Sp-15
VAC Standard.
All three have separate power supplies.
Title: Re: Why do you need a preamp?
Post by: FullRangeMan on 21 Apr 2011, 11:40 pm
> Why do you need a preamp?

Good question. I can no see why I would buy a preamp, even an inexpensive one, as there is many power amps with a volume control, some even had a remote.

Many digital recordings are mastered with low price DACs or even expensive that use a cheap ''clock'' and this create a lot of ultrasonic digital noise in the disc, that cause auditory fatigue after some short time of listening.
So a good tube pre-amp may filter this digital noise, but a power amp also can do it if it had tube circuits.
Two cents.

> Never go to a psychiatrist, adopt a cat or dog from the street. On the streets pets live only two years average.
Title: Re: Why do you need a preamp?
Post by: stereocilia on 22 Apr 2011, 12:08 am
With my Jeff Rowland Consonance I can switch the absolute phase on the fly, go from unbalanced inputs to a balanced output, switch from stereo to mono, store volume levels in memory for comparing two sources that have different output levels and switch instantly between them, connect more than one amplifier, or a pair of subwoofers.  I can instantly cut the right or left channel, mute, adjust the balance, and record from any of six inputs while monitoring the output.  I can connect to any amplifier or amplifiers I want with just about any length interconnect I need.  I can put the remote control sensor anywhere I want if I have a long enough DIN cable.   I can use either inverted phase or normal phase output jacks. 

So, are line stages useless if they don't have a phono stage or tone controls?  Mine isn't.  By the way, I compared this to an FT Audio LW-1 passive, and I had a hard time telling the difference, but I like the sound slightly better with the Rowland.  Same result with a Benchmark DAC-1.  I'm not absolutely sure I could tell the difference in sound with the preamp in or out, but I sure do prefer remote control.
Title: Re: Why do you need a preamp?
Post by: ramante on 22 Apr 2011, 12:42 am
To me, functionality is the only valid argument.  Just a switcher, attenuator and a phono section if needed.  If you don't need this, then you don't need a preamp.  If you think you do, then your system is not well matched.  It's just an expensive tone control.

I've owned Audio Research, Aesthetix, Shindo and others and none have sounded as good as nothing.

Just my 2 cents. :)
Title: Re: Why do you need a preamp?
Post by: FullRangeMan on 22 Apr 2011, 01:19 am
> ...and none have sounded as good as nothing.  :thumb:
Title: Re: Why do you need a preamp?
Post by: Rclark on 22 Apr 2011, 05:42 am
Loving this guys, and learning a lot.  :thumb: :thumb:
Title: Re: Why do you need a preamp?
Post by: jimdgoulding on 22 Apr 2011, 06:53 am
Gotta go with Fullrangeman.  Running an old Sony CDP into my active speaks was a revelation to what a preamp, least ways the one I had at the time, could do to add something to the sound.  It was clear, exactly, as a freshly wiped plate of glass, maybe none at all.  But, there was a deficiency in dynamic range.  My preamp fugues that exactitude up but in an acceptable way, I gots more illumination and warmth.  However, I would recommend trying it if you can.  I would if I still could.  My pre is more romantic, too, like me.
Title: Re: Why do you need a preamp?
Post by: Mark Korda on 22 Apr 2011, 07:30 am
Hi R.Clark,this is the best question ever,great post....Elizabeth told the reasoning before me,man...she hit it right on the nail head,describing simply the true facts as I see in my mind,wow!I have been working on building switch boxes with the best attenuators,gold connections,silver wire,since what you questioned today.When cd players came out,Stereophile had a drawing of a simple passive preamp,and I've tried to build my own.I have some pictures I would like to show you,but I'm still working onto attachment pictures using Vista?R. and Elizabeth,my favorite preamp,one I will take to the grave,is the Ace Audio Zero Distortion preamp from ACE Audio.I have not heard of anyone on here that remembers this.The year was 1974,company owned by John Grauer.It was bare bones and cheap,but was the favored preamp by a blind speaker manufactorer Cizak.Sorry I'm rambling,but you two spark my audio intrest,if you have e-mails I might have the mental ability to send you the pre amp pictures,but I still have trouble attaching them to this post....I always need easy instructive help...thanks Mark Korda
Title: Re: Why do you need a preamp?
Post by: doug s. on 22 Apr 2011, 11:21 am
To me, functionality is the only valid argument.  Just a switcher, attenuator and a phono section if needed.  If you don't need this, then you don't need a preamp.  If you think you do, then your system is not well matched.  It's just an expensive tone control.

I've owned Audio Research, Aesthetix, Shindo and others and none have sounded as good as nothing.

Just my 2 cents. :)
i must respectfully disagree.  my system is well matched, but even if i didn't need the functionality, i have found that a good preamp will be able to increase dynamics and soundstaging w/o any masking of detail or degradation of timbre...

of course, for me, as i described earlier, it is a moot point, as i am always running at least two tuners, a cd player, a dvd player, a turntable, and a dbx thru a tape loop, so it's only in the signal path for compressed recordings.  and, remote control of wolume is nice, too.

ymmv,

doug s.
Title: Re: Why do you need a preamp?
Post by: 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.
Title: Re: Why do you need a preamp?
Post by: ajzepp on 26 Apr 2011, 12:05 am
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.  :thumb:
Title: Re: Why do you need a preamp?
Post by: JLM 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)
Title: Re: Why do you need a preamp?
Post by: roymail 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.
Title: Re: Why do you need a preamp?
Post by: Mike Nomad 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...
Title: Re: Why do you need a preamp?
Post by: 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).  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.
Title: Re: Why do you need a preamp?
Post by: geowak 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.
Title: Re: Why do you need a preamp?
Post by: rollo 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
Title: Re: Why do you need a preamp?
Post by: ctviggen 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.
Title: Re: Why do you need a preamp?
Post by: doug s. on 30 May 2011, 02:42 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.   8)

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.
Title: Re: Why do you need a preamp?
Post by: 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'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.
Title: Re: Why do you need a preamp?
Post by: 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
Title: Re: Why do you need a preamp?
Post by: jimdgoulding 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.
Title: Re: Why do you need a preamp?
Post by: JLM on 30 May 2011, 09:48 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."
Title: Re: Why do you need a preamp?
Post by: Mark Korda 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
Title: Re: Why do you need a preamp?
Post by: avahifi 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
Title: Re: Why do you need a preamp?
Post by: HT cOz 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
Title: Re: Why do you need a preamp?
Post by: mp9 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.
Title: Re: Why do you need a preamp?
Post by: JoshK 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.
Title: Re: Why do you need a preamp?
Post by: roscoeiii on 1 Jun 2011, 01:55 am
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).
Title: Re: Why do you need a preamp?
Post by: Steve on 5 Jun 2011, 04:46 pm
The stereo world has been without direction for a very long time.
Let's take an in depth look at each component and see the state of affairs. I won't list every type, but in general.

1) CD players have an output of approximately 2 volts, largely due to
an analog stage with a gain of approximately 2, or 6db. A whole stage with only a gain of two. There are several types.

 A. Op amps with huge amounts of negative feedback, and cheap parts, about $1.99, if that. That is not kidding.

 B. Discrete parts, feedback or not, about $2.99, if that. Again not kidding.

 C. Tube analog stages. Probably better than options 1, 2 but not nearly enough physical room to design a great accurate, natural analog stage.

 D. Many use electrolytic capacitors for coupling capacitors.

The thing is the analog output of the digital to analog output chip (DAC chip) is already 1 volt. So why add an extra cheap stage, a bottleneck, to one's system?
And why spend 10 grand on the rest of the system with a $3.00  bottleneck in the CD player?

2) Preamplifiers, like any other stage varies in quality. However, the one advantage a separate has is that it has its own power supply. This basically prevents frequency sensitive musical feedback from stage to stage through the power supply or through any common wires to two stages.

For those skeptical, use a 6 inch piece of 20 gauge wire as common ground between two component's inputs, say player and tuner. The tuner will "bleed" into the other input. Decoupling filter capacitors are much worse than a 6" piece of wire, and are frequency sensitive.
Think of the delicate harmonic structures being degraded.

3) Integrated amplifier. Sure one gets rid of an IC. However, the problems associated with a common power supply, feedback, imperfect grounds (bleeding) etc, see previous points, cause some real problems.

Speakers are all over the place, with a seemingly infinite varieties of frequency responses, powers, dispersion characteristics etc.

The solutions are, eliminate unnecessary stages. Use only necessary well designed stages.

Isolate each stage as fully as possible. This means separate power supplies (including transformers), minimizing the length of all common grounds and parts between multiple stages.

The above points are not easily, or cheaply accomplished, but necessary if optimum, natural sound is to be achieved.
I believe some standards should also be changed, such as using 1 volt analog output rather than two volts output, as this will eliminate the cheaply designed analog gainstage mentioned above.

One more point. DAC chips are usually if not all class B pushpull output. Make the chip a little larger and run class A single ended. This would eliminate the push pull and the phase splitter stage.

The audio scene could be cleaned up for better sound.

Cheers.

Title: Re: Why do you need a preamp?
Post by: roymail on 5 Jun 2011, 06:56 pm
All I know is what I have experienced.  My nicely modded cd player > Goldpoint/Elma stepped attenuator > amplifier > 92db sens speakers... sounds better than using any average priced preamp.  I still have one but I don't use it.

Perhaps high end, expensive preamps will likely sound better.  However, for me in my situation, I'd rather upgrade either my source, amplifier or speakers instead.
Title: Re: Why do you need a preamp?
Post by: Steve on 6 Jun 2011, 04:51 am

Perhaps high end, expensive preamps will likely sound better.  However, for me in my situation, I'd rather upgrade either my source, amplifier or speakers instead.

Of course, completely understandable; didn't mean any offense. Practical considerations are prominent.

I think it is beneficial to explore the pros and cons. The more knowledge, the more power one has.

Cheers.
Title: Re: Why do you need a preamp?
Post by: doug s. on 6 Jun 2011, 07:18 am
All I know is what I have experienced.  My nicely modded cd player > Goldpoint/Elma stepped attenuator > amplifier > 92db sens speakers... sounds better than using any average priced preamp.  I still have one but I don't use it.

Perhaps high end, expensive preamps will likely sound better.  However, for me in my situation, I'd rather upgrade either my source, amplifier or speakers instead.

Of course, completely understandable; didn't mean any offense. Practical considerations are prominent.

I think it is beneficial to explore the pros and cons. The more knowledge, the more power one has.

Cheers.
yes, practical considerations are prominent.  but roy, i am not sure what you mean by average priced preamp vs expensive high-end preamp.  i guess it depends on your budget.  but, ime, you could spend as little as $500, if you are willing to consider used equipment, and have a preamp that will make a significant improvement to your system.  one that will make an appreciable improvement to any other source/amp/speaker upgrades you may then make.  up the price to $1k if you are wanting more features/inputs/etc...

doug s.
Title: Re: Why do you need a preamp?
Post by: roymail on 8 Jun 2011, 02:27 am
I don't take issue with anything here since I don't have nearly as much $$$ invested in audio gear as most of you.  As I said before, there is always something that sounds better than what we have.  For now, I'm listening more to the music and paying less attention to my gear.

However, if I hear something that knocks my socks off and can afford it, things may change.  A man's got to keep his options open... right?
Title: Re: Why do you need a preamp?
Post by: JoshK on 8 Jun 2011, 02:45 am
My $.02....tifwiw and all that...

I think most preamps have too much gain, any more than 6db (12db is pushing it) and I think you have too much unless your speakers are <85db or you listen room is a stadium.   I think the real benefit of a preamp is in current delivery and impedance matching.  Hence a good buffer with switch and volume should suit most folks.

Title: Re: Why do you need a preamp?
Post by: Steve on 8 Jun 2011, 05:30 pm
May I again suggest ridding of the gainstage in the CD player. Afterall it is the cheap bottleneck and only 6db of gain, which is basically worthless.

Are you referring to a buffer with no gain, or one with gain yet low impedance? Anyway.

I would prefer a setup with minimal analog stages. For a true example, a CD player (minus the cheap analog gainstage), preamplifier and amplifier with a grand total of three analog stages. Of course one or two high gain stages is needed, in preamplifier or amplifier or both makes no difference.

I don't think one wants the volume control at 9am, nor at 2pm (with lowest high frequency response).

Output Z of CD player is a few hundred ohms (with impedance and voltage protection), output Z of the preamplifier 3k ohms ok, so no need of low output impedance cathode follower.

If some think 3k ohms output Z is high, with 50pf IC the high frequency response drops by approximately .045db at 100khz and   .0015db at 20khz.

With 200pf IC, the high frequency response drops by approximately  .6db at 100khz, and approximately .03db at 20khz. However, I don't wish to go higher than 3k ohms.

Cheers.

Title: Re: Why do you need a preamp?
Post by: JoshK on 8 Jun 2011, 07:30 pm
My particular DAC has a current output DAC, not the typical delta-sigma voltage output.  Thus it takes a transconductance stage, which is all discrete.  So my case is not necessarily everyone else's.  I do concede your point about generic CD players.  I am not sure that fits most of folks cases these days.  DACs seem to be more popular nowadays, but many still have opamps I am sure.

Quote
Are you referring to a buffer with no gain, or one with gain yet low impedance? Anyway.

I was suggesting one doesn't typically need gain, so buffers work fine in many cases.
Title: Re: Why do you need a preamp?
Post by: Steve on 8 Jun 2011, 08:41 pm
My particular DAC has a current output DAC, not the typical delta-sigma voltage output.  Thus it takes a transconductance stage, which is all discrete.  So my case is not necessarily everyone else's.  I do concede your point about generic CD players.  I am not sure that fits most of folks cases these days.  DACs seem to be more popular nowadays, but many still have opamps I am sure.

I was suggesting one doesn't typically need gain, so buffers work fine in many cases.

Yes, you make a good point, DACs are often used and your design would not allow such. I would also bypass the analog stages in Delta type DACs, even when built with discrete parts, since the gain is only two (6db), and the DAC chip has an output Z of less than 10 ohms. (Of course I can see the need if the particular circuit design needs one to work properly.) I have found the current is plenty to drive ICs into a preamplifier/amplifier input.

I can understand adding a buffer stage when using transistors and if the output Z of the tubes is very high, such as with 6CG7, 6SN7, 12AU7, 12AT7, 12AX7 etc type of tubes (Check Rp of a particular tube type, then add cathode resistor times the Mu to Rp (if the cathode resistor is not bypassed)).

However, although adding a buffer stage increases high frequency performance, the buffer still deteriorates the sonics in and of itself (there are lots of parameters to deal with and no stage is perfect by any means), such as allowing frequency sensitive musical feedback to occur through the power supply itself.

Cheers.

Title: Re: Why do you need a preamp?
Post by: roymail on 9 Jun 2011, 02:22 am
Steve, what would be your preference for a single source cdp setup with volume control?
Title: Re: Why do you need a preamp?
Post by: Steve on 9 Jun 2011, 02:38 am
Steve, what would be your preference for a single source cdp setup with volume control?

I have none.

Cheers.
Title: Re: Why do you need a preamp?
Post by: FullRangeMan on 9 Jun 2011, 02:50 am
I have none.

Cheers.
One time I see a repair tech using a CD player direct on the tube power amp and driving a low sensitive Avalon speaker, there was no volume control.

You run something like this??  or use a integrated ?
Title: Re: Why do you need a preamp?
Post by: Steve on 9 Jun 2011, 03:03 am
One time I see a repair tech using a CD player direct on the tube power amp and driving a low sensitive Avalon speaker, there was no volume control.

You run something like this??  or use a integrated ?

Hi Gustavo,

Interesting comments/questions. I have been designing for some 40 years (50 years total). Also worked in RF, consulted professors over a portion of that time, and never ran into a scenario you have described. By not using a preamplifier, or necessary gainstage, the tech's system lacked the necessary gain.

My CD player output is 1 vrms. My preamplifier has approximately 21db of gain. The first stage of my two stage amplifier has approximately 15db of gain and drives my output stage. Speakers are Phast Jr. with sensitivity of approximately 89-90db. My volume controls are usually set around 10-11 o'clock.

Total of three gainstages, no buffers.

I hope I have answered your question satisfactorily.

Cheers.
Title: Re: Why do you need a preamp?
Post by: FullRangeMan on 9 Jun 2011, 03:28 am
Thanks Steve for your detailed reply. This image are the system I refer, from Mr.Richard Kern, at an PFO test, a VT100 + Avalon Arcus.
Regards, Gustavo
(http://www.audiocircle.com/image.php?id=47669)
> Never go to a psychiatrist, adopt a cat or dog from the street. On the streets pets live only two years average.