There is no patent part in that circuit that’s not in the service manual. And that’s the problem with your understanding. You’re just making that jazz up. As Pass says, it "disappears". The active gain never shuts off or goes away. Of course the direct signal would become the dominant feature. Certainly not the only one.
How much do I need to spend to get a preamp that sounds better than no preamp?
Hello all.
I'm using an Audible Illusions L1 preamp and I think my system sounds better when I remove it from the signal path. Oppo BD105 directly to SMC Audio DNA1 Gold power amp. I have read that there is level of quality you need to hit before there will be an improvement in sound. I can't seem to find what that level is. Any ideas?
Thanks in advance,
Ben
I'm using an Audible Illusions L1 preamp and I think my system sounds better when I remove it from the signal path. Oppo BD105 directly to SMC Audio DNA1 Gold power amp. I have read that there is level of quality you need to hit before there will be an improvement in sound. I can't seem to find what that level is. Any ideas?
Thanks in advance,
Ben
Showing 50 responses by kosst_amojan
Looking at the schematic, I'm not sure it's not buffered by the gain stage to a degree. The entire length of the resistor ladder is fed by the MOSFET with the direct source line tapping into the ladder at RV6. It looks like the ladder just attenuates the MOSFET gain below the line level further down the ladder. |
I've looked at most of the schematics Pass has posted or published. Typically when he means to leave something out he posts a "simplified" schematic, such as you see currently for the F7. All the actual schematics in his owners and service manuals are sufficient to replicate the circuits it's describing, though not all the owner's manuals have full schematics. |
@georgehifi And the service Pass service manual for both revisions... https://www.google.com/url?sa=t&source=web&rct=j&url=http://forum.vegalab.ru/attachment.... As you can clearly see, the gain stage isn't on its own ladder. |
His wording on the thing makes it clear at 3:00 you're seeing unity gain at the output, and it's clearly a direct connection to the output, but given the other components in parallel with the input to ladder, there's got to be some small loss to be made up by a small amount of active gain. I'm not saying it doesn't behave just as he suggests, but it's obvious the gain stage shares the ladder all the way down. |
@georgehifi Give him a break? You're banging on as if this thing is audio divinity. Like so many things he's designed, it's a quirky component with a narrow appeal. Like the Zen amps. Like the F series. Like the SITs. Pretty much all of those products are ideal examples of something for someone, but their use must be carefully considered. The J2 might be a great amp. I'll never buy one because it would sound like garbage with my Focals. I don't think the Aleph L would be a particularly good pre-amp with my F5. .x% distortion would be an insane amount though that amp. |
@georgehifi You look at the schematic and draw conclusions that don't reflect the reality of the circuit you're looking at. And then you make stupendous claims about how magical it is. There's no way to avoid the fact that anywhere on that ladder you're getting a mix of direct signal and gain signal. I'm glad you like it. I'm sure it sounds awesome if you give it just the right home. The service manual clearly says .2% with .02% typical. I'm sure it's virtually all second harmonic because that's what single ended MOSFETs make, and I'll bet it's also negative phase distortion, too, which sounds really neat. That's still a lot of distortion and color and limits your amp options. I'm not sure why you keep bashing the 15dB of gain my amp has. I'd much rather make voltage gain in a pre-amp than a power amp. It's just a better place to do it for all kinds of reasons. |
@mrdecibel "First Watt exists because I wanted to explore a variety of amplifier designs in what I think of as neglected areas - amplifiers that might not fit into the mainstream and are probably not appropriate to my more commercial enterprise, Pass Labs. With oddball characteristics and output power ratings of 25 watts or less, First Watt is not for most people. If you have efficient loudspeakers, listen at reasonable levels and are obsessed about subjective performance, then you probably have come to the right place." You have no clue what you’re talking about. So far as I can tell, and by his own words, he's not groping at emulating tube sounds. His SIT amps kinda sound like triodes because of the gain character of the devices, but that's about it. Pass Labs gear is the broad appeal stuff. Amps and pre-amps that will drive anything. That's not what the FW stuff is. The most broadly appealing products from FW are the Aleph J and, you guessed it, the F5! All the others require special consideration. |
@georgehifi What your saying makes no sense. No matter how you try to reframe the man's words to fit your imagination of how it works, you can't avoid the fact that the active and passive lines are parallel and share the same ladder. The measurements say so! How else do you explain that much distortion in what you're claiming is basically a straight wire? The only explanation is that it's from the gain stage. .01 or .02 % typical distortion, the actual fact isn't important. The magnitude of it tells you something. It tells you at unity you're using some gain. |
@georgehifi Loosing you're cool there, huh? I'm sorry you can't just look at the schematic and see what it's doing. The numbers do make it obvious though. The "typical" distortion figure... The 20kR input impedance.... Straight wires don't do that. I couldn't care less about being able to use it or not. The B1 is a vastly better performer by the numbers. And who cares where you're getting your gain? If your power amp has 25 or 30 dB of gain, guess what? It's got 3 gain stages! The same number I'm using! I'd much rather have the most delicate gain stage isolated to it's own chassis, on its own power supply, in the most noise free environment. SE BAGS boards are $9 and I can put them anywhere I want. |
@georgehifi Please believe me when I say I'm not trying to be a weenie here, but the B1 doesn't use complementary parts. It uses same type N-channel parts in a common drain mode biased by a common source mode part. Your diagram looks a lot like the voltage gain stage for the complementary voltage gain stage in the BA-3 BAGS, F5, and F7. Are you varying the voltages across the transistors to gain attenuation? |
Correct me if I'm wrong, but isn't the connection between components somewhat similar in behavior to that of speakers to the amp? Is there anybody out there designing amps or preamps intended to be driven by sources in the thousands of ohms? I thought the whole point in there being massive impedance differences was so that the preceding component would see something as closely resembling a purely resistive load as possible. I'm sure 5kR would make no difference at all to my F5 with it's 100kR input, but lots of amps have 30-47kR input impedance. If you start showing those things 5, 10, or 15 kR sources, they're not going to behave well. Bottom line is that you pretty much have to build your system to play well with a passive volume. Throwing them willy-nilly at random systems isn't going to get good or consistent results. |
What forest? What trees? You just explained why active pre-amps should be as rare as hen's teeth, but you can't seem to explain why the exact opposite it true. If gain in a pre-amp is that obviously bad, and there's no technical justification at all to have it, why is it almost always there? That's all I want to know. This money scam jazz isn't reality. My guess is that if you're buffering with active devices to ensure the broadest, most uniform compatibility, you might as well throw a little gain in too since the penalty is below the noise floor. |
Hate to break it to ya, but... A) mine looks nothing like that B) I sourced my own parts from 7 different vendors. C) Mine drives more current and more voltage than Nelson's. D) mine has no current limiting like Nelson's does. Bottom line: I built a significantly more muscular F5 than Nelson did. Nobody is selling an F5 kit in a box. The only prefabbed parts you can get are the chassis and the boards. For everything else you're scouring DigiKey, Mouser, Antek, or whoever else has what you need because nobody even sells all the parts to build one. Go to DigiKey and tell me what are the best resistors for R9 through R12. I'm not at all saying I could design the thing by a long shot. In fact, as boxes of parts started showing up, I started wondering if I could do this. It took about $1000 to buy everything and I was really worried I'd reduce it to garbage at the flip of a switch. The opposite actually happened. The first time I flipped it on as a complete unit it did exactly nothing. Zero voltage or current at the outputs no matter how I turned the pots. It just sat there cold and dead with glowing LEDs. I was bummed. I gave up and slept on it. The next morning I realized my mistake. I forgot to recalculate the resistor values in the current limiting circuit. Mine we're too low for the higher rail voltage I'm running and the higher voltage at the BJTs bases was driving them to full conduction. It was a stupid mistake anybody with experience wouldn't have made. So I pulled the BJTs. Turned it on. Hooked up the DMM, and I got current! The F5 is not the easiest amp to build. The Zen Variations are. The F5 is odd in that he's taking advantage of using the transistors in different modes simultaneously. It's a much less straightforward design than the F4 or F6. There's a TON of stuff to learn about what every single resistor does. I really wish you'd just build something. Go through the process. Realize how much you don't know and learn it like I did. Go build an Aleph L. Get your fingers on the parts and really know what everything does. |
@mrdecibel Na... I'd much rather make friends than not. I kinda feel bad seeing George lose his mind because he doesn't know how a thing works. I'm not afraid to play with cables because I've made my own to see. I just don't indulge in snake oil. You, George, and few others seem to enjoy attacking me for learning, building, and restoring some stuff. Kinda sad really. Sounds like bullying to me. I'm not doing that to people. George and you are going ape for what? Because I'm waiting for Ralph to explain the Aleph L to George? That doesn't seem like a crazy over-reaction? And I'm hardly the only one who thinks the few harsh critics of the Kanta 2 are way off base. |
@georgehifi I'm sorry. I really am. I really feel bad you're this worked up. I think you've got an idea of how the thing works burned into your mind that doesn't reflect the circuit, the reality, or what the man has said. If I'm wrong I'd really like Ralph to set me straight. I've listened to Pass speak for hours and read gobs of his articles and writings. I'm imagining him saying what you've posted him saying with a big projection of that diagram on the wall behind him. I'm not getting the understanding you seem to. I really just want you to understand what you're looking at in that schematic, hear what the man is saying, and think it through on your own. You're missing the understanding of the circuit! If I had the money I'd pay you to build the thing just so you'd learn it! |
@georgehifi Just an FYI.... Any F5 can be made to yeild 25 dB of gain very easily. In fact, most who build the F5T do configure it for more gain. Mine is sort of a mix between the F5 and F5T V1. The F5T V1 schematic actually specifies the 22 dB gain configuration. It's a topology that can be scaled up to 500 watts given a big enough pile of MOSFETs and heatsink. People can and have done that so getting gain from an F5 isn't an issue. |
" It is a provisional patent, which has maybe been granted by now on this special circuit, he may not have given the secrete to how he bypasses the "active stage" in the the schematic so it runs totally passive, after all it is patented." Yeah, you DID completely reinterpret the man to suit your understanding. "Same goes for my Lightspeed Attenuator there is nothing active or any switch contacts in the signal path just a passive ldr, yet it is powered by the mains for the leds to function. Yet it is a passive preamp with no gain." https://ibb.co/choBZS That is NOT a passive circuit. Those are active devices the signal is going right through. They’re obviously powered, and they’re obviously providing current gain. You’re the one mischaracterizing things things left and right. You even falsely label the B1 Buffer in that schematic. Nelson Pass from the B1 Buffer article: " All of the transistors are N channel JFETs. The stock parts are 2SK170’s, LSK170’s or 2SK370’s, and you can use substitutes having Idss between than 5 and 10 milli-Amps and transconductance numbers from 5 to 30 milli- Siemens." What is wrong with you? |
@georgehifi I'm pretty sure you got taken to task on that jazz already. No matter how you cut the cake, a buffer is going to provide more ideal impedance matching. You seem to love banging on about Nelson Pass. Maybe you should go watch his BAF lectures where he demonstrates the differences between a 25 ohm source and a 600 ohm source. It's not an insignificant difference. And you're talking about putting upwords of a few thousand ohm on the amp's input. It makes a difference. That's why Nelson has never once produced a purely passive pre-amp. |
@georgehifi You're such a tool. You really are. All you can do is keep barfing up the same quotes to bolter the same poor understanding. I crunched the numbers the other night on the Aleph L. No matter how you figure, the gain stage contributes to the output signal and is NEVER fully attenuated. In fact, the "typical distortion" coorelates with the residual gain trickling all the way down the ladder. Again, and again, and again you keep trying to make Pass sound like some big believer in the virtues of purely passive attenuator. Yet the man has never once designed or sold one! If you're OPINION of how the Aleph L worked were the reality, the distortion would be below .001% in the passive region. Resistors don't make jack for distortion. 10 to 20 times that distortion tells you something is going on. Any fool can see that. Practically everything you claim is the case is refuted in the B1 article. And the B1 does it's job with a tiny fraction of the distortion the Aleph L does. At it's worst, pushing 2 volts out the outputs, it's still doing less than a quarter the distortion of the Aleph L. Don't sit there and tell me there's no audible different between between .003% distortion and .015%. The Aleph L is coloring the signal vastly more than the B1. |
@mrdecibel An active stage with gain is a good buffer by itself. Typically a pure buffer is just a gain stage giving you current gain, which translates directly into a lower output impedance. Benign, resistive loads like volume attenuators are very friendly to current sources. Because that arrangement is basically a follower, it tends to be very linear too. |
There's no technical reason to conclude getting gain in a pre-amp stage won't sound better. The reverse is true. The environment of a pre-amp is a very good place to gain some voltage because the power supply isn't subject to the demands of a huge power stage, it has less noise, and better filtering and regulation can be applied. |
@georgehifi Wrong yet again. That doesn't even make logical sense. Why would you amplify the signal to it's absolute maximum before attenuating it? It makes a lot more sense to feed the gain stage the least amount of signal to keep the distortion of the gain stage as low as possible instead of as high as possible. |
@georgehifi Yes, that's EXACTLY what you suggested! You said select a gain level and run it wide open! I'm not the only one who read that! Clearly you forgot your own words so I'll remind you" " I would have thought the least amount noise would come if the master is at or near full for loud listening, then the gain level if it is controlling the "tube gain" it’s then only increasing any noise to a minium level, as tube noise/distortion increases at the same rate as the gain will." As Atmasphere pointed out, small signal gain stages are very quiet in general so all you're really netting is the highest possible distortion from the gain stage. You're not even thinking about what you're saying. |
@georgehifi Yeah, which in a good line stage is basically insignificant. It doesn't hold a candle to the distortion generated by running a gain stage to it's limits. Getting better sound from more gain and less input signal makes perfect sense. It's really obviously, even to an unwashed rube like me. |
An active pre-amp certainly beats the hell out of a volume control that cannot avoid acting like a tone control, and that's exactly what they end up doing. George's argument is ludicrous. Over in the cable forum we've got folks arguing about cables that have tiny differences in impedance, capacitance, and inductance, and here we've got a few guys saying throwing a few thousand ohm into the signal path makes no difference, and WILDLY overstate the shortcomings of a modern gain stage. I have no clue what George is talking about when it comes to noise and hum. He says he's played with active devices before, but it's hard to believe. It's no problem at all to drive the noise and hum of a gain stage WAY below the noise of a vinyl record or even an analog mastered digital source. Sorry, but a volume control that acts like a tone control doesn't outperform buffers and gain stages that exhibit noise and what not you need to bury your ear in a cone or horn to hear. |
@georgehifi The following is copied directly from passdiy.com, projects section, B1 buffer preamp. AN ACTIVE PRE-AMP! Care to actually cite his published "stance on passive pre-amps"? What you're calling "his stance" is word for word what he wrote in his article for the B1 buffer. No doubt you cherry pick the article and mischaracterize the man's opinion because further down he refutes the case you try to make. So I say again... It's ridiculous to quote an article for an active pre-amp to bolster the rational for a passive. Project Categories ListAmplifiersPreamplifiersB1 Buffer Preamp Nelson Pass Introduction Side A So here we are in the New Millennium, and thanks to Tom Holman and THX we’ve got lots of gain in our electronics. More gain than some of us need or want. At least 10 db more. Think of it this way: If you are running your volume control down around 9 o’clock, you are actually throwing away signal level so that a subsequent gain stage can make it back up. Routinely DIYers opt to make themselves a “passive preamp” - just an input selector and a volume control. 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. And yet there are guys out there who don’t care for the result. “It sucks the life out of the music”, is a commonly heard refrain (really - I’m being serious here!). Maybe they are reacting psychologically to the need to turn the volume control up compared to an active preamp. I suppose if I had to floor the accelerator to drive 55 mph, maybe I’d think the life was being sucked out of my driving. Then again, maybe I like 55. Nice and safe, good gas mileage… Is impedance matching an issue? Passive volume controls do have to make a trade-off between input impedance and output impedance. If the input impedance is high, making the input to the volume control easy for the source to drive, then the output impedance is also high, possibly creating difficulty with the input impedance of the power amplifier. And vice versa: If your amplifier prefers low source impedance, then your signal source might have to look at low impedance in the volume control. This suggests the possibility of using a high quality buffer in conjunction with a volume control. A buffer is still an active circuit using tubes or transistors, but it has no voltage gain – it only interposes itself to make a low impedance into a high impedance, or vice versa. If you put a buffer in front of a volume control, the control’s low impedance looks like high impedance. If you put a buffer after a volume control, it makes the output impedance much lower. You can put buffers before and after a volume control if you want. The thing here is to try to make a buffer that is very neutral. Given the simple task, it’s pretty easy to construct simple buffers with very low distortion and noise and very wide bandwidth, all without negative feedback. There are lots of different possibilities for buffers, but we are going to pick my favorite: |