As posted in #52 by Gordy, here is Mr Wright's website:
Vacuum State - High End Hifi Equipment
Mr Wright, to clarify, we frown on advertising and product promotion in non-commercial threads. Explaining who you are and what you do is and always will be acceptable. It helps others to understand the the basis of the argument and or discussion.
Vacuum State - High End Hifi Equipment
Mr Wright, to clarify, we frown on advertising and product promotion in non-commercial threads. Explaining who you are and what you do is and always will be acceptable. It helps others to understand the the basis of the argument and or discussion.
Cal, that is a fair attitude, I just wish moderators in other forums held the same views.
Regards, Allen
And to amplify (sorry about the pun) on that point, since I have zero commercial interest in audio, I'll be happy to say that Allen's preamps are excellent, well thought out designs- and I do not withhold criticisms when people design things poorly. His Preamp Cookbook is certainly worth a purchase if you want to understand what he does; it is horribly in need of an editor and proofreader, but is chock full of excellent advice and interesting circuits.
OK, there's your plug.😀
OK, there's your plug.😀
This turns out to be one case where you really don't need any references, since it is so easy to prove. To do so you need a sine/square wave generator, an amplifier, a speaker and a VU meter.
Square waves are composed of odd orders.
So this test is simple: set the generator to sine, set the output level to 0 VU on the meter at the output of the amp, and get an idea of how loud that sounds. Then temporarily disconnect the meter, switch to square wave and set the volume to sound the same volume as the sine wave. Now connect the meter.
You will find that it is set about 20-25 db less.
I have used CD players over the years that were supposed to have pretty good outputs, i recently have had this discussion with others and they have found the same , their systems always sounded better with the addition of a pre.
There is no life in the music by comparison, when driven dorect or using Passive control, but i guess it could be better than using a bad pre!
CD"s players I have used to determine such over the years ...
Stax quarto
Wadia
Rega Jupiter
Sony XA777ES
My brother has a marantz CD player ( model unknown to me at the moment) he did use it direct for a number of years to drive his aragon amplifier, it 2 had stepped up with the addition of a pre ..
Hello John,
Yes i can see the load making a difference.
What i have really noticed over the years with any volume pot , there is always a sweet spot and this is not necessarily at the point where there is enuff gain. Somehow adding a pre always seems to add life to the system
Hmmm pretty interesting !
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Something that works well without a pre (all with all discrete "powerful" ouput stages):
Norma Revo CD (cdp)
Metric Halo ULN/LIO (dac)
Forssell DAC (dac)
The best way to determine what's the best is to buy or build both, Listen to music , Compare, Then decide.
My highest candidate for SS is the Pass B1 buffer, Easy to build and sounds way beyond expectation. I haven't tried tubes.
My highest candidate for SS is the Pass B1 buffer, Easy to build and sounds way beyond expectation. I haven't tried tubes.
So... nobody prepared to engage on the issue of efficiency?
Your perceived personal listening pleasure trumps any and every other consideration? Even when the audible difference by everybody's admission can only be trivially small?
Engineering is about ethics you know; ask a space shuttle designer. Preferably not one with an indelible blot on his conscience.
The drive for efficiency is part of aesthetics. This is something that, as designers and builders, should be in the forefront of our minds AS A GENERAL PRINCIPLE when we choose or build equipment. Science looks for elegance in solutions. An inefficient design is an UGLY design. Any engineer worth his salt has this engraved on his soul. Steam locomotives have a certain charm, but they are museum pieces. People who like to play at being engineers drive them at the weekends. Nobody is fooled though. I wish I thought the same of some of the participants here.
I can't say I'm surprised. I've seen other hobbies erode the sensibilities of the participants, change from a bunch of kids with a common interest playing together to a venue for name-dropping, technical one-upmanship, self-congratulation, commercial self-interest and obsession.
OK, I'll let it go at that, no point in working myself into a froth over something I can have very little impact on. I daresay that like the big-game hunters of the past there are tube preamp afficionados out there who got into it long before times changed and somebody suggested it might not be the best thing all round any more. You guys put me in mind of the people who go to a big-game farm to kill some poor hand-reared tiger, then you're gonna tell us your fee is preserving endangered species.
w
59 today.
Your perceived personal listening pleasure trumps any and every other consideration? Even when the audible difference by everybody's admission can only be trivially small?
Engineering is about ethics you know; ask a space shuttle designer. Preferably not one with an indelible blot on his conscience.
The drive for efficiency is part of aesthetics. This is something that, as designers and builders, should be in the forefront of our minds AS A GENERAL PRINCIPLE when we choose or build equipment. Science looks for elegance in solutions. An inefficient design is an UGLY design. Any engineer worth his salt has this engraved on his soul. Steam locomotives have a certain charm, but they are museum pieces. People who like to play at being engineers drive them at the weekends. Nobody is fooled though. I wish I thought the same of some of the participants here.
I can't say I'm surprised. I've seen other hobbies erode the sensibilities of the participants, change from a bunch of kids with a common interest playing together to a venue for name-dropping, technical one-upmanship, self-congratulation, commercial self-interest and obsession.
OK, I'll let it go at that, no point in working myself into a froth over something I can have very little impact on. I daresay that like the big-game hunters of the past there are tube preamp afficionados out there who got into it long before times changed and somebody suggested it might not be the best thing all round any more. You guys put me in mind of the people who go to a big-game farm to kill some poor hand-reared tiger, then you're gonna tell us your fee is preserving endangered species.
w
59 today.
Hello Telstar,
I suggest you give those a try with a good pre, the difference might be worth your while.....
😀
"Energy"?? What are the units on that? Do you really mean "impedance"?
I think your statement is to general. It may likely be the case that some CD players can't drive some amps. But mostly CD players have line level outputs and if your amp is got about a 20K input then it works fine.
What design for a preamp? Something simple? If you are building it yourself you don't need to be completely general purpose and you canbuilt to your exact needs. I've use an op-amp input buffer driving a volume control and then follow that with a unity gain driver stage. If you want tone controls or a balance knob it becomes much more complex. On the other hand if the amp has a volume control you don't need that on the preamp.
The first step is to carefully describe the problem to be solved. Then make a second pass where you describe the problem using numbers with prober units attached. For example you make say "Needs 6 dB of gain and ability to drive a 15K load" Next you decide what kind of technology you like. op-amps, discrete transistors or vacuum tubes. It some point you can make the build or buy decision.
Hello Chris ,
Thanks for the response , I see the topology you recommend , but which DIY kit has the topology you favor for a good pre ?
There is a difference between gain ( volume ) and energy. Live music is dynamic and has energy. I have had CD players with 6 volts output , plenty of drive , no energy. My system usually wake up with the addition of a pre-amp , i have never seen it otherwise, unless there was some kind of mis-match with the pre..
Thanks for the response , I see the topology you recommend , but which DIY kit has the topology you favor for a good pre ?
There is a difference between gain ( volume ) and energy. Live music is dynamic and has energy. I have had CD players with 6 volts output , plenty of drive , no energy. My system usually wake up with the addition of a pre-amp , i have never seen it otherwise, unless there was some kind of mis-match with the pre..
FWIW tube preamps are a lot more efficient than tube power amps. In fact denigrating tube preamps from an efficiency point of view is not going to win you any credibility, even with transistor designers, as the difference in power consumed is so slight. This is especially in light of the fact that you already are using tube amps for your guitars. Admittedly, you *need* tube amps for guitar to get them to sound right, but that admission is not helping your argument. I can use the same argument that tube preamps are needed to make my stereo sound right. So- I don't play guitar, is it OK for me to have my stereo sound right if your guitars sound right?
Of course there is a bigger picture and that is Peak Oil. I think it is wise to be concerned about energy consumption. I am saving to convert my home to solar power. I've been wanting to do it for decades. But in that solar-powered home, I still plan to run tubes. To keep power consumption down, I will use high efficiency speakers, and thus limit the power consumption at the point where it makes the most difference: the amplifiers.
There certainly is in the context of your usage of the words here. You use 'gain' in a technically correct objective way, however you use 'energy' in a descriptive (sentiment based) subjective way. As such you can not usefully compare one with the other.
Try again!!! 🙂
Fair enuff :
Gain ( volume) ring slightly above sea level !
Energy ! .........additional output above dynamic ring! (approx midway up)
Without the pre-amp , you lose the energy above the dynamic ring !...... 🙂
Gain ( volume) ring slightly above sea level !
Energy ! .........additional output above dynamic ring! (approx midway up)
Without the pre-amp , you lose the energy above the dynamic ring !...... 🙂
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Many preamp designers think that a preamp serves 3 functions. These are:
add any needed gain
provide for volume control
provide for input selection and signal processing.
In high end audio we keep the signal processing to a minimum- no tone controls is very common.
But there is a 4th function that is overlooked by 99% of all preamp designers. That is the requirement to control the interconnect cable. If this 4th requirement is met, you will not find the length of the interconnect nor its cost to have any bearing on the sound. IOW if you can hear a difference in interconnects between your amp and preamp, then your preamp does not control the cable.
This is why running a CD player direct will not always sound as good as using a line stage in between, as the line stage might be able to handle the cable better. Obviously this is the weak area for nearly all passives.
A line stage that is built right will buffer the volume control and prevent frequency response aberrations depending on its setting.
BTW many CDPs have digital controls, but I find them useless below about 85% of full output, due to loss of resolution. This is another reason why a good line stage can sound better- you run the CDP at 100% and use the hopefully superior control in the preamp instead.
To control the interconnect you need a low output impedance, one that remains low at low frequencies. Traditionally, this is the area where SS excels over tubes, due to tubes often using coupling caps that are responsible for LF output impedance increases.
Tubes can bypass this problem by using a transformer or direct-coupling. I prefer the latter method. IMO if driving balanced, the rule of thumb should be that a 600 ohm load at the input of the amp will not faze the preamp: no increase in distortion, no loss of bass. If single-ended, I think that impedance should be lower- around 50-100 ohms.
add any needed gain
provide for volume control
provide for input selection and signal processing.
In high end audio we keep the signal processing to a minimum- no tone controls is very common.
But there is a 4th function that is overlooked by 99% of all preamp designers. That is the requirement to control the interconnect cable. If this 4th requirement is met, you will not find the length of the interconnect nor its cost to have any bearing on the sound. IOW if you can hear a difference in interconnects between your amp and preamp, then your preamp does not control the cable.
This is why running a CD player direct will not always sound as good as using a line stage in between, as the line stage might be able to handle the cable better. Obviously this is the weak area for nearly all passives.
A line stage that is built right will buffer the volume control and prevent frequency response aberrations depending on its setting.
BTW many CDPs have digital controls, but I find them useless below about 85% of full output, due to loss of resolution. This is another reason why a good line stage can sound better- you run the CDP at 100% and use the hopefully superior control in the preamp instead.
To control the interconnect you need a low output impedance, one that remains low at low frequencies. Traditionally, this is the area where SS excels over tubes, due to tubes often using coupling caps that are responsible for LF output impedance increases.
Tubes can bypass this problem by using a transformer or direct-coupling. I prefer the latter method. IMO if driving balanced, the rule of thumb should be that a 600 ohm load at the input of the amp will not faze the preamp: no increase in distortion, no loss of bass. If single-ended, I think that impedance should be lower- around 50-100 ohms.
I believe it's a lot more complex than this. At least two further effects are at play but there is probably lots more to it.
1. Even wideband preamps serve as additional filters of digital noise. Probably not very effective below a MHz or so. May be the reason why analogue sounds fine to me even through a passive pre. In contradiction of this theory i use a transformer at the output of my dac and it still sounds better through an active stage 🙂
2. Solid state power amps seem to often employ input stages which sound better when driven from a very low source impedance. I think even distortion measurements show this.
The low source impedance also plays into cable control. A passive control at the output of a DAC puts you at the mercy of the interconnect cable- there is a three way interaction with the control, the cable and the input of the amplifier. So at full volume where the signal is straight-through is the only time the passives sound right- as you run the volume down from there the control comes into play so you loose bass and dynamic punch.
The trick is to build a line section that sounds better than that :/ To do so it has to have as few stages of gain as possible ('one' seems like a good place to start), very wide bandwidth, going down to at least 2 Hz and an output that is very low impedance. Its a tall order. I know tubes are up to it but I've not seen much in the way of transistor circuits that can do that without imparting a signature.
I know there are many who think tubes have a signature too, but as I mentioned before that is easy enough to deal with if you build a fully-differential circuit.
BTW I think a transformer at the output of a DAC can be a very elegant way of filtering digital noise.
The trick is to build a line section that sounds better than that :/ To do so it has to have as few stages of gain as possible ('one' seems like a good place to start), very wide bandwidth, going down to at least 2 Hz and an output that is very low impedance. Its a tall order. I know tubes are up to it but I've not seen much in the way of transistor circuits that can do that without imparting a signature.
I know there are many who think tubes have a signature too, but as I mentioned before that is easy enough to deal with if you build a fully-differential circuit.
BTW I think a transformer at the output of a DAC can be a very elegant way of filtering digital noise.
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