Great future as they do make a difference, more so then the power amps. This is especially true if you are into vinyl, as they contribute much more then any combined unit. I have a knock off of the HK Citation 1 (VAS) and it is a joy for vinyl listening. The design of this unit is almost fifty years old, so when you marry it with current SOTA parts, like VAS did, it comes close to blowing away many Audio Research units. I think, aside from the DAC technology, pre amps will around along as there is vinyl.
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Personally, I don't see preamps disappearing from this hobby anymore than I see tubes and vinyl disappearing.
IMHO, the preamp is the heart and soul of the system. In my experiences, finding the *right* preamp has always been the most difficult task in assembling a system that draws me into the music.
Since I ventured into computer-based (source-)audio I've passed on hardware preamps. I guess luck, or perhaps even taste has seen to it that none of the poweramp/source-direct constellations that have gone through my setups have turned out less than favorable - i.e. where impedance/gain matching have tilted the sonics towards the anemic or body-less, something that is quite often reported to occur when named matching goes wrong. My current, and by all accounts future volume control option is 24-bit (preferably 32-bit in the near future) dithered digital attenuation via JRiver MC19; it works and sounds excellent. From what I'm able to assess it's not digital volume controls like the one I'm using right now that inflicts any character on the sound of the sort an analog volume ditto and associated component of the hardware preamp with cables as a whole would create, so whatever character arises with the use of a software-based digital volume control, insofar the poweramp/DAC-direct combo is an electrically suitable match, is more likely to be an "effect" created, and to be corrected elsewhere. This, at least, is my stance as is.
The future use of hardware preamps may maintain a certain level due to the continuing bloom of turntable/LP use. I'm likely never to return to analog, so the hardware preamp won't either.
A preamp has four functions:
1) control gain
2) provide any needed gain
3) provide input switching
4) control the interconnect cable
Of these functions, most digital sources provide one, which is to control gain. Unfortunately, Redbook specs call for the digital device to put out 4 volts, which is far too much for any power amplifier, so right away the signal has to get knocked down (and on the way, degraded) in order to be useful.
The problem is that many volume controls degrade the sound, and if they are not buffered (as in passive controls) the math often works against you, causing loss of bass if the control is anything less than full on, and often a lack of dynamic punch. This is caused by the resulting output impedance of the control in series with the source being so high that the interconnect becomes of sort of tone control that is interjected.
Now you could throw a lot of money at that problem by looking for just the right cable and many audiophiles do. But the simple fact is that the passive control is a big compromise, not based on the quality of the control so much as the approach: the control and interconnect effectively interact with the source impedance to behave as a filter.
One way around this is to have a PVC with a lower resistance value overall, but this can be hard for some sources to drive.
A buffered volume control does not have this problem. You will find that most preamps are far less susceptible to the cable than passive controls are as a result.
FWIW, the industry would be better off if the output of digital devices was limited to about 2 volts. One really does have to wonder what the authors of the Redbook were thinking!
Due to the variability of competence in line sections of preamps, you will find that the issue of passive (and TVC) volume controls VS active line stages will be an on-going debate. There are line stages that can so completely control the interconnect cable that you can no longer hear the differences between them. IMO/IME this is when you really start getting to transparency, as the filter I mentioned earlier is removed.
12-10-13: UnsoundI haven't ever had occasion to look at the redbook specification document, but the de facto norm seems to be "full scale" (i.e., maximum) amplitudes of 2 volts unbalanced and 4 volts balanced. That would be based on the usual convention of defining balanced amplitudes as corresponding to the instantaneous difference between the voltages of the two signals in a balanced signal pair, the 4 volt number therefore reflecting each of the two signals being 2 volts.
Ralph's designs are balanced, of course, although they often provide both balanced and unbalanced inputs. I suspect that is why he mentioned 4 volts.
Based on my experience the preamp is the heart and soul of a system. Sure one can argue I don't need fine food or Parma ham to survive, but these foods are simply more enjoyable than bread and water. Ya, I can survive without them. Yes, my system works without my tube preamp, but it does not taste as good:-) Pretty simple stuff.
@ Atmasphere, Hi, Who told you that 4 volts was to much for an amplifier?,, LOL!, Nearly all pre-amps output to an amp is way more than 4-volts, an example of what I am saying is, My krell 700cx amplifier min sensativity is 3.5 volts input, in other words, if you do not have atleast the 3.5 volts, the amp is not being driven correctly, the krell 700 cx amp input max is 18 volts!, then you have every krell pre-amp ever made that puts out 8 to 12 volts to to the amps, I have personally talked to krell about this issue, they ex-plained the input specs of my amp, because I was under the impression that the 3.5 volts was max, turns out to be the minimum!, most digital cd-players and dacs do not have enough volts out-put to drive amps to their potential, and then you have bit stripping of the sound quality if you have a pure digital volume control at low volumes, on the bright side, a digital componet running direct to amp with a analog volume control, or a transformer based volume control yeilds way more transparency than most pre-amps could ever do in alot of systems, your signal does not have to go thru another chip board, there is some pre-amps out there that can give you all that you want for sound, very few can surpass running direct to amp, the pre-amps that can are very exspensive!, cheers.
One way or another, there has to be sufficient gain to go from line level, or phono cartridge level, to eventually be able to drive loudspeakers, such that any stages prior to the final power amp gain stage should be considered as preamp. So, in my logic, preamps will always be required as long as we are driving louspeakers.
Audiolab, what Atmasphere said about voltage levels is essentially correct (given my subsequent clarification), although his comment is most probably not applicable to the proprietary CAST interface that is provided on your amplifier.
For conventional (non-CAST) preamp outputs, the max output spec that for most high-end preamps is much greater than 4 volts represents the maximum output voltage they are CAPABLE of providing. That number SHOULD be much greater than the maximum output voltage they will ever be called upon to provide under reasonable input voltage conditions, in order to provide margin and assure good distortion performance.
For the non-CAST balanced input of your amp, the 3.58 volt sensitivity spec represents the approximate amount of input voltage that would cause the amp to put out its maximum rated output power (700/1400/2800 watts in this case(!), into 8/4/2 ohms respectively), assuming that spec is defined in the same manner that nearly all other amp manufacturers define it.
Most amps will be driven to their maximum rated power by inputs in the range of about 0.5 to 2.5 volts for unbalanced inputs, or around twice those numbers for balanced inputs. If you research the specs for amps from various manufacturers you will see that.
I have no knowledge of the voltage levels that the current-mode CAST interface operates at; perhaps the 18 volt figure you mentioned relates to that.
Hi Al, take a look at this link on DIYaudio:
Scroll down a little and you will see something very similar. I rather doubt that such a setup would see much in the way of voltage swing- current mode suggests that the current of the driver is being drawn through the interconnect cable from the receiver.
I agree that phonostages are here to stay. But it seems to me that digital sources with volume control, and various types of all-in-one products (including integrated amps) could marginalize the role of the preamp. The loss of transparency introduced by the preamp needs to be counterbalanced by other sonic benefits. Otherwise, the preamp is little more than a fancy switchbox.
The loss of transparency introduced by the preamp needs to be counterbalanced by other sonic benefits.
Actually if the preamp is working right, most people experience an increase in transparency, not a loss. I have already mentioned one reason why; an additional one is that many digital controls don't work that well. So the digital device works better if run at full volume, run through an active line section and the preamp's volume control is used instead.
Ralph (Atmasphere), thanks for the link and the comment about CAST. I see what you mean, and I agree. So I have no idea what the 18 volt figure mentioned by Audiolabyrinth would pertain to. That figure does not appear anywhere in the manual, btw, which includes a fairly comprehensive set of specs.
Perhaps it was a miscommunication he had. I would expect that 18 volts into that amp would stand an excellent chance of destroying the speakers, the amp, and the eardrums of anyone nearby, if a fuse didn't blow first :-)
They'll evolve and stick around for a good while but I would not invest in analog ones. Various forms of digital pre-amps have a healthy future in store still I suppose in various forms only a small % of which will remotely resemble what most of us would recognize as a traditional hifi analog pre-amp.
@ Almarg, Hi, I am sorry, I did not mention my source of info was from krell, when we were dicussing the input sensativity of the krell 700cx, the 18 volts is max, that is never used!, the amp gets 6 to 8 volts,pending what model krell pre-amp being used, that has nothing to do with cast, thats balanced!, then I was saying a source componet with a real analog or transformer based volume control running direct to amp has the performance I mentioned above, not the digital volume control that likly will do bit stripping of the signal!, and if you actually have a very high quality pre-amp that has the transparency of a direct to amp source componet has?, thats likly due to the gain that pre-amps have, you hear more information, more sound, sometimes, more dynamics, pending on the pre-amp used, not really more transparency!,
"Might be controlled from ones phone."
I can control my Squeezebox Touch device (which includes
digital volume) wirelessly from any mobile device including
phone or tablet on my home wifi network today.
The technology exists to control anything from a phone
today. All that is needed is a market.
I use a pre-amp mainly because I have analog source (phono
and tape) in addition to digital. It may sound better this
way as well. Never tried it without the (tube) pre-amp), so
Even if direct does not sound sound as good as with pre-amp
in my case, I see no reason why a separate pre-amp is
required for better sound. It may or may not be better
case by case it seems to me.
Wadia is still very much around. Owned by the same company that owns ARC. They are a good example of why an analog preamp is handy- their volume control is an example of what I was talking about earlier.
Audiolabyrinth, I can tell you with great confidence that you have your numbers wrong. Krell amps can be driven to full output by any preamp made, so they have at least 30 db of gain. That means that they need less than 2 volts. I bet though that their *preamps* can make 18 volts (we can make 32 volts with ours) before clipping; this is done to keep the preamp totally unstressed while doing its job.
Mapman, the reason not to own a digital preamp is simply that you will have to sell the unit to upgrade. So far all digital products have had a short shelf life as digital continues to evolve. Analog is a bit more stable design-wise.
"So far all digital products have had a short shelf life as digital continues to evolve. Analog is a bit more stable design-wise."
I always wait as long as I can even to buy my next home computer because I know the longer I wait the more I will get for my investment. I don't see that changing anytime soon.
@ Atmasphere, Hi, what are you talking about?, I am talking about the voltage out-put of a pre-amp of the signal to the amp, There is no way that 2 volts will drive my Krell 700cx correctly, the input sensativity is 3.58 volts min!!, all the krell pre-amps ever made put out more volts than that!, call Krell, I can tell you that with confidence!, the 18 volts was a given spec before clipping with the krell 700cx amp.,,BTw, I have used over a period of time, a source componet with analog 2.5 volts out-put direct to amp!, Thats funny!, the amp sounded like it was at half volume compaired to useing a pre-amp by anybody!, that BTw, do more than 2 volts out-put, I also understand the gain a pre-amp can give as well, LOL!
@ Atmasphere, Hi, I do apoligize for my post, However, I am correct with the pre-amps of krell, I am only saying what they told me on phone, on their site, it only gives out put over load specs of all the current pre-amps of 8 to 16 volts out-put, regarless, because of the gain a pre-amp gives, I believe I need a pre-amp to drive my Krell 700cx to full capacity!, I enjoy your post, and appreciate your input here,I run balanced, so the 16 volts out-put is over load, thats why krell told me pending on an older pre-amp or newer, 6 to 8 volts out-put is the norm for a krell pre-amp balanced out put, thankyou.
Audiolabyrinth, Krell states that the gain of their amps is only about 25db. FWIW that is quite unusual (I had assumed their gain to be a more typical 30db), so in a high power amplifier you would indeed need more than 4 volts to full output. The spec on your amp is 3.58 volts for full output, so your amp probably makes right around 500 watts, assuming a similar gain structure.
The industry standard is 1 volt FWIW; that standard is really eroded at this point. However, most audiophiles do not push their amps to full output all the time- you still have to knock down the signal from a digital source if you want to use it. So a preamp is still useful.
The specs indicated in the manual for the Krell 700cx are 3.58 volt sensitivity (for its balanced input), 26.4 db gain, 700/1400/2800 watts into 8/4/2 ohms respectively.
26.4 db is a voltage gain of 20.89, based on db = 20log(Vout/Vin).
20.89 x 3.58 = 74.79 volts.
(74.79 squared)/8 = 699 watts into 8 ohms, corresponding almost exactly to the 700 watt rating.
Double that into 4 ohms (= 1398 watts), and double it again into 2 ohms (= 2796 watts). The results again correspond almost exactly to the rated power capabilities.
Ralph, I think you were right in the first place!
Concerning Keith's reference to "3.58 volts min," that is probably the result of a miscommunication. Sensitivity specs are usually neither min nor max, they are simply the (approximate) input voltage required to drive an amp to its rated maximum output power. And based on these calculations, that certainly appears to be the case here.
An additional point: The 700cx is spec'd as being capable of putting out a maximum output voltage of 84 volts RMS.
Based on the amp's voltage gain of 20.89x (see my previous post), that output voltage would be produced by an input voltage of:
84/20.89 = 4.02 volts.
Therefore if someone indicated to Keith that the amp can handle an input of 18 volts without clipping either what that person said was misunderstood, or that person misunderstood the question, or that person didn't know what he was talking about.
Keith- Meet Al, our resident technical analyst and voice of reason on all things electrical/quantitative. He's not a manufacturer or designer. He's kind of like our Spock but with a love of music ,a keen dispassionate "eye" for techno-babble, and a willingness to help all of use non-EE types understand some of the basic science, math, and engineering behind things audio.
Keith- I hope you were not offended. I know how foolish I once felt when I tried to explain to a client how difficult and expensive it would be to build a certain type solution to a coastal erosion problem he was facing, only to find out later that:
1. the guy was one of the most experienced and competent architect/builders on the northeast and
2. he had more $ than god!
3. he was too much a gentleman to tell me either.
@ Atmasphere, Hi good to meet you, I took a peek at your products, impressive to say the least!, for some crazy reason my friend here, jmcgrogan2 believes I am in over my head, I suppose he does not know me enough to make that call, as far as the 3.58 volts min to input of my krell 700cx, I will again call krell and talk to Ray Munchler, the service manager to confirm if that spec is min or max input spec, I have had this conversation with him more than once, so I hope he does not think I have a bad memory! anybody can make a mistake, this is why I will ask for the third or fourth time, as I said, Ray said, the spec of 3.58 is what it takes to drive the amp, and it can take max of 18 volts to over load the input, I assumed the 3.58 was max spec too!, Thats when Ray munchler corrected me! another situation is that I cannot use typical tube pre-amps or sources direct to amp, or I would have to activate the coupling capacitors that are not active inside the amp to protect is from tube unstableness!, Its a direct coupled amp, a real one!, this is in my owners manual that I have, and Ray confirmed that as well, He also stated not to activate the coupling caps, they will degrade the performance of my amp, so he said make damn certain if you use a tube product, make sure it is designed to be able to work with the amp, he said they are out their, an example of what he says is this, a tube source with the tube buffers before transformer or transformers, in other words, the signal comes thru the transformers before out-put, now thats if I am useing a tube source with volume control direct to amp, not useing a pre-amp, I will post my findings from Ray here by tuesday, I do enjoy tube sound, so my question to you was, will any of your tube pre-amps work with this extrodinary amp?, Thankyou so much, Its a privelege to talk with you and an honor!
@ Almarg, Hi, I enjoy your input and post that I have read numerous times, I appreciate that you posted the krell 700cx specs, and explained them, kinda bailed me out here!I agree with what you are saying about the 700cx input spec, you said, sensitivity specs are usually niether min or max, they are simply the approximate input voltage required to drive the amp to its rated maximum output power. the miscommunication is here, when Krell said that 3.58 is min spec for input of the krell 700cx, that is the same as max input to be able to drive the amp to potential full power, however, the amp will take more voltage input into the amp that most pre-amps do for their out-put into the amp, and the 18 volts is the over load point to this amp to clip.,, Almarg, Can you look into this for me, the spec of 18 volts input to clip, this is the max input told to me over the phone by krell, you can do more of the math and engineering calcalating for me to find a explanation for me?, LOL!, I will never use over 10 volts to input anyway!, just currious to know my amp,, when I said that the 3.58 is the min that krell told me, they said that because all of their pre-amps put out around 6 to 8 volts for balanced operation, and this will not do nothing harmful to the krell 700cx, its the normal that I am told by krell if useing a krell pre-amp, regardless of the voltage input to drive the krell 700cx, I will not realize the power of this amp with out the speced gain you provided of the krell 700cx that a source direct to amp does not have, atleast I have not found a source with the gain I need to drive the krell 700cx, I enjoy the clarity a source direct to amp provides, but this is why I have said that the krell 700cx sounds to be half the volume its suppose to be, its still loud enough without the gain, LOL!, I just believe the amp will sound better with the appropriate db gain, do you believe that?, can you imagine the cost of a pre-amp that can do the clarity and realism a direct to amp source does with the gain I need?, thats a thought I do not like to entertain!, this is why I said, a pre-amp that would be to my liking would be very costly and you would have to provide more interconnects, in my case, very, very, exspensive, I use Taralabs zero gold, retail $14,500.00 new, around $5,000.00 to $8,000.00 used a meter balanced, yes, I bought My zero gold used, I am not that crazy to buy new, I do not agree with esoteric cabling pricing!, however, the I/C is worth what I paid used to me!, to keep the performance to my standards, I would want to buy another zero gold i/c for use with a pre-amp, there you have it, this entire conversation on this thread is a big deal to me$,, I have to be sure and carefull at the same time, this is why your input is most welcome to me, thankyou.
@ swampwalker, LOL!, I can see Almarg being an asset to us all, and called mr. spock!, we all need a mr.spock in this hobby!, thankyou for the introduction between us,I am not offended, there seemed to be a mis understanding here with what I was saying,I enjoy learning, no one knows it all, so far, I have not been corrected, misinterpreted, yes!, however, If I am wrong and corrected, I embrace it and enjoy being corrected, this is how I add to my exsperience, It would be quite foolish to do other wise!, I have never talked to you, good to meet you as well, I do require all of us to be gentleman, I do not believe someone is not a gentleman if they correct me or help me, and I hope all here does not believe if they do, they are not a gentleman, that is not the case for me, cheers.
@audiolabyrinth- Pleased to meet you as well. I just wanted to make sure it didn't come across as snarky; I'm glad it didn't. I'm gonna risk it again, however, and ask you to do us all a couple of favors:
1. get a new computer that actually has a "period" key. You know, the one in between the "," and the "/" ;-) You may have just set the record for the longest sentence ever posted on Audiogon:
Almarg, Can you look into this for me, the spec of 18 volts input to clip, this is the max input told to me over the phone by krell, you can do more of the math and engineering calcalating for me to find a explanation for me?, LOL!, I will never use over 10 volts to input anyway!, just currious to know my amp,, when I said that the 3.58 is the min that krell told me, they said that because all of their pre-amps put out around 6 to 8 volts for balanced operation, and this will not do nothing harmful to the krell 700cx, its the normal that I am told by krell if useing a krell pre-amp, regardless of the voltage input to drive the krell 700cx, I will not realize the power of this amp with out the speced gain you provided of the krell 700cx that a source direct to amp does not have, atleast I have not found a source with the gain I need to drive the krell 700cx, I enjoy the clarity a source direct to amp provides, but this is why I have said that the krell 700cx sounds to be half the volume its suppose to be, its still loud enough without the gain, LOL!, I just believe the amp will sound better with the appropriate db gain, do you believe that?, can you imagine the cost of a pre-amp that can do the clarity and realism a direct to amp source does with the gain I need?, thats a thought I do not like to entertain!, this is why I said, a pre-amp that would be to my liking would be very costly and you would have to provide more interconnects, in my case, very, very, exspensive, I use Taralabs zero gold, retail $14,500.00 new, around $5,000.00 to $8,000.00 used a meter balanced, yes, I bought My zero gold used, I am not that crazy to buy new, I do not agree with esoteric cabling pricing!, however, the I/C is worth what I paid used to me!, to keep the performance to my standards, I would want to buy another zero gold i/c for use with a pre-amp, there you have it, this entire conversation on this thread is a big deal to me$,, I have to be sure and carefull at the same time, this is why your input is most welcome to me, thankyou.
2. Seriously consider switching to decaf! My blood pressure went up to 249/135 just reading your post!!! If decaf doesn't float your boat, maybe some 'ludes???
All said w tongue firmly planted in check, I hope you understand.