^^ You are correct about that. Redbook has most DACs too much voltage for most amps made.
Have Passive Preamps Finally Come of Age?
Back in the late 90s (eons ago) I tried a variety of passive preamps (PPs). The most musical was an autoformer, but back then my system was not balanced. For the last decade I have been using active preamps, both tube and solid state, but finding a quality balanced preamp under $4K is damn near impossible. Enter the Parasound P5 (2.1), which in addition to having balanced I/Os, it has a separate bass management circuit (MSRP $1095), and I was hoping it would provide better control over the built in class D plates incorporated into my 2 SVS powered subs, whose volume controls are STUPIDLY sensitive: when barely cracked from zero they overwhelm. Alas, no bueno.
Recently i watched a PS Audio YT video that was emphatic about NOT connecting powered subs with interconnects; instead he recommends speaker cables piggybacked off the main systems amp/s. I had a spare set of DIY flat copper cables, and was shocked how much better they sounded, but doing so did not change the volume control problem and unfortunately this id not bypass the SVS amps whose class D chips are now ancient. Thinking there could be an impedance problem led me to revisit PPs.
I sold my P5 and was using the XLR outs from my Oppo 105 (upgraded power supply and IEC/wiring to the power supply) direct to my Emerald Physics 100.2SEs (class D). The noise floor dropped tremendously, allowing me a much better view into the music. My Core Power Technologies 1800 PLC had more than a little to do with this, but...
Days of PP research later, I came across LDRs, which seem like the ultimate PP option, but XLR versions are ~ $2K and up, with the Tortuga coming in at $2700, seems like a true SOTA bargain, just not in my current budget. Scouring the' for sale' sites I came across a Hattor XLR (MSRP $995) which was in my price range. Hattor's www had links to 2 reviews both were extremely positive: one used it in combination with a class D amp. Bingo! I snapped it up.
It arrived late yesterday, although Hattor's www pictures look awesome, they do not compare to seeing and touching it. The metal carrying case was an indication of the designer's dedication. This is an etremely well made piece of kit, but how does it sound? Alas it came with no manual and Hattor's site does not have a PDF. How hard can it be to hook up? Well, after a couple scary minutes, I discovered that it would not light up until I connected the 105.
Stone cold, the first thing that shocked me was a further reduction in noise floor and an incredibly wide and deep sound stage, but as can be expected, it was dry. Fingers crossed, in about a half hour I began to be rewarded with texture as well. Tis only got better as the night wore on
I hope somebody chimes in with their Tortuga experience, or any other high quality PP information.that goes under the reporting radar.
Recently i watched a PS Audio YT video that was emphatic about NOT connecting powered subs with interconnects; instead he recommends speaker cables piggybacked off the main systems amp/s. I had a spare set of DIY flat copper cables, and was shocked how much better they sounded, but doing so did not change the volume control problem and unfortunately this id not bypass the SVS amps whose class D chips are now ancient. Thinking there could be an impedance problem led me to revisit PPs.
I sold my P5 and was using the XLR outs from my Oppo 105 (upgraded power supply and IEC/wiring to the power supply) direct to my Emerald Physics 100.2SEs (class D). The noise floor dropped tremendously, allowing me a much better view into the music. My Core Power Technologies 1800 PLC had more than a little to do with this, but...
Days of PP research later, I came across LDRs, which seem like the ultimate PP option, but XLR versions are ~ $2K and up, with the Tortuga coming in at $2700, seems like a true SOTA bargain, just not in my current budget. Scouring the' for sale' sites I came across a Hattor XLR (MSRP $995) which was in my price range. Hattor's www had links to 2 reviews both were extremely positive: one used it in combination with a class D amp. Bingo! I snapped it up.
It arrived late yesterday, although Hattor's www pictures look awesome, they do not compare to seeing and touching it. The metal carrying case was an indication of the designer's dedication. This is an etremely well made piece of kit, but how does it sound? Alas it came with no manual and Hattor's site does not have a PDF. How hard can it be to hook up? Well, after a couple scary minutes, I discovered that it would not light up until I connected the 105.
Stone cold, the first thing that shocked me was a further reduction in noise floor and an incredibly wide and deep sound stage, but as can be expected, it was dry. Fingers crossed, in about a half hour I began to be rewarded with texture as well. Tis only got better as the night wore on
I hope somebody chimes in with their Tortuga experience, or any other high quality PP information.that goes under the reporting radar.
238 responses Add your response
This was posted on Audio Advisors site during a review of their 5 best selling Dacs under $500. I believe I am disagreeing with them on two counts. 1st : the Dacs they yested do not put out the standart 2 volts, so to make a comment like that is not really true. 2nd : Talking about the gain controls on the two recommended Parasound amps would not give you higher output. This was in a thank you response to customers who bought and rated these Dacs they bought from AA, and I feel the person who wrote this in not very knowledgeable. " Audio Advisor05/14/18Thank you for your comments. All the DAC/Preamps on the market have limited output gain and therefore cannot drive most power amps as well as a stand-alone preamp. A great choice to mate with this Pre Box S2 Digital would be one of the Parasound amps - I’m thinking of either the Z-Amp3 or the Classic 275. These have a gain adjust on the rear panel that will give you higher output from the S2 or any other pre-level source ". Enjoy ! MrD. |
Just wanted to add an update. I revamped my setup quite a bit since I posted to this thread. Changed out 3 power cords and got some shorter RCA interconnects at the same time. I took out the Yaquin tube buffer and reconnected the Tortuga Audio passive using short .5 meter interconnects. One short IC goes from the phono stage to the Tortuga`s Input and the other short .5 meter IC goes from the Tortuga out to my main amp and then a 1 meter IC goes from the passive to my subwoofer amp. Sounds nice and there`s a lot of volume on tap ! I start listening at a lowish level to warm things up including my ears so that`s a 30 on the volume display. As things progress I bring it a few notches at a time and usually end up around 40-45 with the highest so far being 50 and it`s plenty loud for me. The Tortuga tops out at 70 btw ! I couldn`t imagine what that would do :0 Anyway...no need for me to use a buffer at all. |
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Practically nobody is running an impedance converting amplifier like the F4. It is, for all intents and purposes, a gigantic buffer that allows high impedance sources to drive low impedance loads. It's designed on the premise that the best place to get voltage gain is in the line stage/pre-amp where noise, heat, and power are much better controlled. I'm pretty sure I pointed that out when somebody suggested that the only place worthy of applying gain was in the power amp. Go ahead now... Flag away. I'm sure the mods are waiting for you to make my point. |
celander My Teo Audio Liquid Pre passiveA very good passive, and from what my sources tell me, it’s a 23 position "shunt" type passive volume control, 1 fixed series resistor, and 1 variable shunt resistor (48 total), not the best way of doing a passive volume control, the "ladder" is best, "series" being the worst. https://www.stereo.net.au/forums/uploads/monthly_2018_06/Capture.JPG.93bbd2ce49060300b06abfd1a62ce8f... This is a 23 step stereo "ladder" using Dale resistors, total of 92 resistors total, signal still only goes through 1 series (variable) and 1 shunt resistor (variable), this give more stable output impedance compared to "shunt" http://www.analogmetric.com/images/200812/1229844904628152861.jpg Cheers George |
My Teo Audio Liquid Pre passive is in line with an Oppo DVD player and ATC SCM20-2 active monitors, all connected via Teo Audio liquid metal conductor-based IC’s. I’ve never experienced a more authentic, transparent, three-dimensional musical reproduction experience, including reproduction from my previous audio systems having what I now know to possess perfectly-matched impedances throughout. |
mrdecibel This is also why some get their nickers in a knot big time about passives, as they have amps that are very left field with next to zero gain, and they can’t use passives or even in some cases a 0 gain buffer, like this one of Nelson Pass’s below unless their source put out voltage big time, which I've never seen. "The F4 needs a preamp that has voltage gain - a passive preamp or buffer will not drive an F4. This amp has no voltage gain so works best when paired with an active preamp that has reasonable gain." Cheers George |
mrdecibel You hit the nail on the head MrD with that proof. The others above are just in product protection mode. RK I suggest you don’t align yourself with the your new yes man, it won’t be healthy for you in the long run. mrdecibelYes it’s true, those impedance issues hardly raise their heads these days, that’s why passive are the way to go, buffers are the next choice if there’s impedance issues. tweak1Yes they have, and it’s more to do with what’s the sources are doing now that make them the preferred volume control choice, because today sources are low output impedance, have higher output voltage, are mostly dc coupled, and their output stages are as good if not better that many active preamps especially tube ones The only way of getting better sound than a passive this is to go direct from source to poweramp if the source has it’s own digital domain volume control that can be use in it’s top 25% so it doesn’t "bit strip". Cheers George |
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I have run 3 different dacs, 4 different tuners, a Samsung cable box, and a laptop from it’s headphone jack, through the passive, all with excellent results. I have also used 4 of my power amps, again, all with excellent results. If I am listening to distortions, so be it. It betters the preamps in detail, transparency, and neutrality. Enjoy ! MrD. |
Well, it seems to me the gain issue ( voltage ) has just be proven by kosst's last post, taken from Nelson Pass himself. Take care of the impedance issue, using buffers ( 0 gain ) and the source can drive most power amps quite well. Enjoy ! MrD.This is certainly true- if your only source is digital. If other sources are involved (such as a tuner, tape or phono) then it won't be the case. We've built buffer-only preamps for some of our customers that are digital only, but at least one of those shipped his preamp back after about 5 years and had us install the active gain circuitry as well, despite all his sources being digital. If you have more than one source, occasionally you run into the issue that not all digital sources actually conform to RedBook output standards. These sources will need additional gain. The thing is, if you do your design homework, the distortion and bandwidth limits of the active line stage can be much better than those of the source itself and if you do your engineering homework, its possible to insure that the kinds of distortion it does make are of the type to which the ear isn't particularly sensitive. |
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it may explain why good active line stages can easily outperform passive devices in some cases."In some cases" Very few. With 10k passives only if output to input impedance matching is below 1:10 ratio, which in most cases it’s not, unless the amp is 25k or lower. Some preamps are designed to have very large s/n ratios and very large voltage swing range capacity. This results in a far higher level of signal quality on the output, with regard to preserving micro differentials in the signalAn active preamps gain stage after the volume control cannot give micro detail a "leg up" compared to the original, as the gain stage amplifies everything up, so it remains the same. But it does include it’s own noise and distortions on top of the original, which may give the illusion of detail. Nelson Pass on passives pres: "What could be better? Hardly any noise or distortion added by these simple passive parts. No feedback, no worrying about what type of capacitors – just musical perfection." "Just musical perfection" Which means "true to the source" nothing added or taken away. Cheers George |
Your right MrD, they can’t. Some preamps are designed to have very large s/n ratios and very large voltage swing range capacity. And then the designer of the circuit puts sort of passive volume pot implementation -in front of the high gain preamp. This results in a far higher level of signal quality on the output, with regard to preserving micro differentials in the signal, which is where the music works for the human ear. Some tube preamps are more likely to be designed this way. Or, some preamps are designed so the volume pot is part of the gain of the circuit itself. I believe that Charles Hansen made a version of such topology in one of his SS preamp designs with Ayre. A switched resistor circuit where each step was optimized to provide best low distortion and highest fidelity. Not just individually gain stepped but individually tweaked on each of those steps. (IIRC, that is, source: interview with Charles at Stereophile) The one you take note of, which is the most common way to do it for reasons of a ’safe’ output section, is also the lowest fidelity way to set up a preamp circuit topology. The variable loading does indeed change the transient distortion of the circuit, and it also makes the output sensitive to the cables and input it is hooked up to, in a way that is non linear as one scales through the volume settings. eg, the one with the hardset gain with the input being varied via a potentiometer at the start, that one... is more linear and constant in it’s coloring of the sound signature, as one scales through volume level changes. Most (IIRC) of the Bruce Moore tube circuits were set up this way. There is a danger aspect as a potential problem, though, as the full gain is always applied to the amplifier inputs, via the preamp circuit. So, one can accept the cheaper and easier to implement most common design method (volume pot just before preamp output) and have mediocre warmed over sound quality ...or.... play in the danger zone and have a notably greater fidelity in ways that matter to the human ear. (volume pot at front of full gain output) I made that trade off over 30 years ago, and the cost of problems that have happened, over the years, was less than the cost of one single item upgrade. Less safeties on the system (DC or full scale output issues, etc) and more care needs to be taken, but....the pay off was over 30 years long, on a key point in fidelity. And that was priceless. Priceless. Essentially, it’s too bad more people don’t understand how fidelity in audio works. It’s not all that simple... After trying every active topology known to humanity, I gave up at the max grade preamp level of a customized three chassis MFA ’Venusian’ preamp (capable of over 165Vp-p into a standard load!), and went to passive circuits, but only when done via the liquid metal design we have on offer. IMO and IME, active is too complex and too colored. All of them. 100% of them. Even simple buffer circuits, even though they generally exhibit the least harm... In my personal experience a liquid metal passive preamp defeats all passive contenders and all active contenders at any price. At the $10k level, at the $50k level, no matter. Additionally, the consensus on that, within the group of people who have actually heard such an arrangement of gear with the given specific passive preamp... is rather high. With zero caveats. How? the liquid metal does not behave like wire, on the fundamental scale of what impedance in dynamic living terms --actually is. high correlation on it being best? let me clarify: Hundreds of people, and maybe three or five disagree. But this as a pronouncement, depends upon the rest of the system, all the individual components, of source, cables, speakers, etc.....and most importantly...the wiring of the mind and ears of the listener....all being up to snuff, in being at the center of the maelstrom of what each is required to do with regard to projecting and exhibiting (and hearing/realizing) the maximum fidelity of signal. |
And Al, a source that gives out 2v is always going to give it out, even if you shunt half of it to ground because you don’t need it, because you have more gain to make it back up in the active preamp.Not all volume controls shunt signal to ground. The traditional volume control does not shunt any at all. But there are shunt-style controls and they have been around for a while. They rely on a resistor (usually of significant value) to be always in series with the source (meaning that the resistor affects the sound if not carefully chosen), so that when the volume control is shunting the resulting output, the source will not distort or be bandwidth limited (IOW not significantly loaded). Now if the shunting element is the same value as the series element, the signal loss will be 6db, as the the output voltage will be cut in half (at full volume). With most passive systems this sort of loss is unacceptable- so the shunt portion of the circuit (the actual control) is often much higher than the series element; as much as 10 times higher. The question then is - what is the value of the composite control? For example George has stated quite often that his controls are "10K" (10,000 ohms). If its a shunt-style system as one might infer from the above quote (since many controls don’t shunt the signal at all), then is he stating that the series element is 10K? That would allow for the minimum value that the source (DAC or CDP) would be 10K. This would imply then that the *actual* control is considerably higher. At any rate, the statement in the quote above is problematic. The designer of a passive control I would **assume** would not want to give an active preamp an edge over his product by loading the source in such a way as to increase its distortion! If this point is ignored by some passive designers, it may explain why good active line stages can easily outperform passive devices in some cases. FWIW, no *active* preamp loads a source in the way George describes; the volume control (if at the input of the preamp, which is a good place to put it) is chosen to be a value such that no source of any type will be challenged by it!! Again, this is just common sense engineering (much like the built-in headroom that all competent preamps and sources have), and I hope that this is obvious to anyone reading these words. |
All prior comments were when using my Oppo 105 either direct for SACD/DVD-As, or as a transport, after getting the Audio Alchemy DDP-1 DAC/PRE A couple days ago I decided to dust off my Pioneer PD 65 CD player (inverted platter) Stage 3,modified over a decade ago by Musical Concepts; with outboard power supply: it is a CD player with optical output After a brief warmup, the music is so much richer, adding texture to the entire musical spectrum My Hattor does not provide for toslink, so it was a good thing I bought the AA DDP-1, or I would have never known what I was missing with the Oppo Hattor definitely going up for sale now |
@tweak1 Agreed regarding impedance matching. My ATC active monitors have built-in amps having an input impedance of 10-kOhms. While this is typical for pro amp gear, it’s on the low side for consumer gear. And the adage of sticking with gear from the same manufacturer is wise advice with regard to ATC. Their preamps have output impedances set at 10-Ohms. (Typical pro preamps have output impedances of 600-Ohm or less, so I gather.) |
The reason behind my question had to do with better design and higher quality parts making for a better end product than in ages gone by In my case, the missing ingredient was not understanding the importance of impedance matching in order for them to get along with the amplifier/s. This tidbit alluded me then and now, as electronics is foreign to me |
Ugh.... This is from Wiki: “In a home audio system, the term ’preamplifier’ may sometimes be used to describe equipment which merely switches between different line level sources and applies volume control and possibly tone control circuits. Such equipment prepares the signal before amplification but, in fact, no actual amplification circuitry may be involved.” In professional lore, this definition is usually used, as no phono stage is included in a professional mixing console. The term “line stage” was created to alert the home audiophile of the absence of a phono stage in the box. But the converse isn’t necessarily true in the case of a preamp. |
@rwwear why not? “Preamp” literally means a control device upstream of amplifierActually a preamp has a phono stage. The correct term is "Line Stage" if there is no phono preamplification and equalization. And a passive line stage does not pre-amplify anything. |
Mr Db. My comment is borrowed from data analysis fields and applies with equal force here. Whatever distortions are passed to a control device will be passed on to the next device downstream. In other words, I agree explicitly with George and implicitly by inference to your query. This is principle applies equally to passives and actives alike. |
I am really disgusted at this point, with the bickering going on here. I found Passive to be wonderful, so I know it works. I am judging this based on my 50 years of listening, and, my " current " system. Yes, there are instances when passive will not work, and we all understand this. But come on guys. Audio Research has an integrated amp that does not have a preamp ( gain stage, others too ), so, what does this tell you. If we cannot be civil, it is no longer my worth and time to be here, sharing my knowledge, and learning from others what I do not know. I have gotten this same crap with horns, cables, and some other audio related issues. It is bullshit ! Enjoy ! MrD. |
If sources with 2 V output go into some kind of distortion mode ( running out of steam, if you will ), how can a preamp help the distortion ? Enjoy ! MrD.Your right MrD, they can't. By reducing that 2v source with the volume control of an active pre, just shunts part of the 2v to ground. The other part being used (just as "distorted") goes to the preamps volume control then the gain stage, "yes" to be boosted back up again along with it's own distortion and noise also. Cheers George |
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almarg And Al, a source that gives out 2v is always going to give it out, even if you shunt half of it to ground because you don’t need it, because you have more gain to make it back up in the active preamp. So the distortion from the source "whatever it is remains the same", it does not change because you’ve decided not to use half of it and shunted the other half to ground. If anything shunting more of it to ground "could" make it distort more. Cheers George |
migueca91 posts08-04-2018 7:30amTisbury Audio passive preamplifier. Very nicely thought out for the price, with -10db and -20db gain dip switch ability for high gain systems, and output dip switch for configuration. Just click on the photos. And they picked the right value to go with 10kohm, which suits most systems. http://www.tisburyaudio.co.uk/mini-passive-preamplifier Cheers George |
Jay23 8-3-2018Sorry I misunderstood. Upon re-reading that page of the thread I believe you are referring to statements by Ralph such as: Atmasphere 7-27-2018and by George such as: Georgehifi 7-27-2018On that particular point I agree with Ralph 100%. And in fact a very common means of assuring that "any source that has been designed to give out 2v has been done so to be done to do so in it’s most linear state" [quoting George] is to design in exactly the manner Ralph described, providing a good deal more voltage swing capability than will actually be necessary. Also, consistent with that, a few posts prior to their exchange on that issue I had commented as follows: Almarg 7-27-2018 Regards, -- Al |
My conclusion is that someone else designed the Lightspeed for you.You really need to look before you leap, this statement really shows your real worth. I don't even know why you bother posting on a "passive preamps" thread when you don't make them or don't believe in them. All I can think you're only here to denigrate them as best you can, because your trying "product protect" your own commercial stuff, because they are making a big dent in your sales. |
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celander You shouting!!! never joke about having a beer to an Aussie, mate, he'll be on to you like a rat up a drain pipe. Sorry Tweak again with the off topics. |
Just looked at it tweak1 OP they missed the mark as nowhere does it say you can switch out the J-Fet buffer, that's a bummer. Nelson Pass kindly made a buffer for the Lightspeed Attenuator 10 years ago so his customers could drive a couple of models of his low impedance amps with the Lightspeed. I built one up and yes it sounded good and you needed it for those low impedance amps, but still, no buffer sounded better if it wasn’t needed. That’s why I say they missed the mark by not making it switchable. Here it is https://ibb.co/im8ZrK Cheers George |
atmasphere Really, you need a history lesson back to the 1970’s, your not worth the effort after that statement, you’ve really shown your ignorance now. tweak1 OPSomeone had to do buffered one, it’s been nagging at me to do it since Class-D came about with their very low input impedance, 10k many of them. But it really needs to be able to be switch out when not necessary into amps with high input impedance, as the best buffer is no buffer, just like the best coupling cap is no cap Cheers George |
@mitch2 "I mostly agree. For example, what does "finally come of age" mean?" I think this phrase mostly relates to Tweak1 having discovered a nice balanced stage passive preamp for use in his system having (at the time) a class D amplifier. He wanted to extend his discovery to a discussion about other passive preamps to this group. @tweak1 Thanks for posting this thread query. It's been a bit chippy at times (and continues to be--Lol), but I learned a lot from the contributors herein. |
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I auditioned their tubed buffer when it was on "tour" and thought it sounded pretty good for the price when in line with two different passives I have here (both resistor based). I am a little surprised they are not offering both tubed and JFET buffer sections in the active preamp since they already have the tubed buffer designed. I suspect the preamp will represent a relatively high value for a modest price. |
