Vintage HiFi Audio Forum
Audio Discussion => General Discussion => Topic started by: Reverend on January 27, 2015, 11:38:19 AM
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Is anyone using or have used a passive preamplifier? I bought a little Schiit passive and I'm running it with my baby carver tube amp and love the sound. No coloration, gain, etc. I'm mulling over trying this in my main system and would like your input. I've read/heard repeatedly about having to use short interconnects/etc. As a test I ran 1m cables from the source > pre > amp vs. 2m cables. I couldn't tell any difference and really, I don't have any interconnects over 1.5m so it's not a concern. I'd love to hear your opinions.
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If you do set that up, let me know, I'd be interested to hear it. I'm not surprised that it sounds good, being that I've heard two Schiit pieces, and they're awesome. I will be surprised if you end up liking this more than the Melos though, primarily because of price point (it just doesn't seem like the Schiit was designed to be as good as or even compete with something high end), but if any company would prove that whole thing wrong, it would not surprise me if it was Schiit.
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Oh boy....from capacitors to passive preamps. We are stirring the pot hard this week >:D >:D >:D
(Please note the devil smiley)
Rev...I love passive preamps. Using a DIY version now. Zero noise floor. Properly implemented completely
transparent. Excellent macro/micro dynamics. It all comes down to two variables (IMO).
The volume control and switching method.
POTs: I've used carbon, cermet, vintage ,new, ALPS, Noble, generic
And the very best sound pot ever (again, to me) is a Spectrol 10 turn wirewound pot. Transparent all the way.
Forget about carbon, sprayed conductive plastic, etc. They all pale in comparison.
Best switching circuits is two dpdt center off switches...gives you four inputs and very easy to wire up.
And I suspect much better surface area/contact force over a rotary switch.
I have an ElectraPrint PVA passive in the works now. Have all the parts but need to assemble it.
From my breadboard testing its superb as an inexpensive passive. Certainly a worthy contender until I find
A tube preamp I like. You're going to find most folks will slam a passive. They just don't have mass appeal.
Use your own ears and you decide. I've used them on/off for decades. Out of all the versions I've built I've only had issues with one transformer based unit and tuners. Several mid fi tuners just wouldn't work with input impedence of the transformers used at that time. CD players have all been extremely successful. Never an issue there. They must have more robust output circuits.
Again..passive aren't popular. Many hate them w/o ever hearing one. Some just can't get past the idea of turning the volume control beyond 12 o'clock...like its some mental barrier. Trust your own ears and keep an open mind/ear.
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I've been switching back and forth between my two main preamps for a month now, one of which is the Schiit SYS. I haven't had any issues with sound degradation due to cable length, even with the 2m cable I run from the SYS out to monoblocks on separate sides of the room. No issues from the sources I've used either, my DAC, turntable and CDP.
I do think the passive sounds a bit better than the active,as ataudio states a move towards better transparency and dynamics, but lean towards using active of late. I run the SYS wide open and use an iPod for volume control, but the convenience of the active -between the remote, more inputs(and outputs), etc- seems to win out.
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Thanks for your input guys. Yeah the Schiit SYS is what I've been playing around with. I just really liked the non-colorized tone with the mini carver. I will try the little SYS in the main system and see what happens. Unlike some others on the forum, I feel like I can hear differences in anything and price point is not something i really take into account even though I like to bust OBG balls about it. Mainly because he's a cheap bastard. :laugh:
I'm looking at a "high-end" passive right now that I might be able to pick up on the cheap. I don't have any immediate intentions to get rid of my Melos, it's still one of the best pre's I've heard in combination with my setup. Tube dual mono pre w/ giant external power supply vs. a Passive. You can't get two more different pieces of equipment then that. Should be fun experiment.
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This is the passive pre I want to try:
http://www.amazon.com/Emotiva-Control-Freak-Unbalanced-Passive/dp/B00JRHUGDI/ref=sr_1_1?ie=UTF8&qid=1422387172&sr=8-1&keywords=emotiva+volume+control&pebp=1422387174245&peasin=B00JRHUGDI (http://www.amazon.com/Emotiva-Control-Freak-Unbalanced-Passive/dp/B00JRHUGDI/ref=sr_1_1?ie=UTF8&qid=1422387172&sr=8-1&keywords=emotiva+volume+control&pebp=1422387174245&peasin=B00JRHUGDI)
8)
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Definitely keep us posted. Would love to hear which passive you get and its pros/cons.
I hope to get a TVC passive someday. Good luck...let us know.
And if you decide to sell the passive give us first shot ;)
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Definitely keep us posted. Would love to hear which passive you get and its pros/cons.
I hope to get a TVC passive someday. Good luck...let us know.
And if you decide to sell the passive give us first shot ;)
Too bad, I saw a 'standard' Prometheus at a shop in Portland, but didn't realize how what a good deal it was.
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I've been using a Creek OBH-12 passive pre with a Belles One amp for years, with a number of speakers, in a number of locations. Right now it's in my woodshop. I have always enjoyed the sound - it seems to be a great match for the Belles and, as a bonus, has a remote.
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I've never heard a passive pre. The lack of a tape out has kept me from seriously exploring it. Sorry I can not be any help.
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I've never heard a passive pre. The lack of a tape out has kept me from seriously exploring it. Sorry I can not be any help.
My Creek OBH-12 has a tape loop:
http://img.ukaudiomart.com/uploads/large/119422-creek_obh12.jpg (http://img.ukaudiomart.com/uploads/large/119422-creek_obh12.jpg)
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My Creek OBH-12 has a tape loop:
http://img.ukaudiomart.com/uploads/large/119422-creek_obh12.jpg (http://img.ukaudiomart.com/uploads/large/119422-creek_obh12.jpg)
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What does the power supply do for a passive pre?
This is the passive pre I want to try:
http://www.amazon.com/Emotiva-Control-Freak-Unbalanced-Passive/dp/B00JRHUGDI/ref=sr_1_1?ie=UTF8&qid=1422387172&sr=8-1&keywords=emotiva+volume+control&pebp=1422387174245&peasin=B00JRHUGDI (http://www.amazon.com/Emotiva-Control-Freak-Unbalanced-Passive/dp/B00JRHUGDI/ref=sr_1_1?ie=UTF8&qid=1422387172&sr=8-1&keywords=emotiva+volume+control&pebp=1422387174245&peasin=B00JRHUGDI)8)
Too bad it doesn't have a ganged volume control to allow balance adjustments.
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My Creek OBH-12 has a tape loop:
http://img.ukaudiomart.com/uploads/large/119422-creek_obh12.jpg (http://img.ukaudiomart.com/uploads/large/119422-creek_obh12.jpg)
What does the power supply do for a passive pre?
It is only for the motor for the remote controlled volume pot. It works manually without being plugged in.
This is the passive pre I want to try:
http://www.amazon.com/Emotiva-Control-Freak-Unbalanced-Passive/dp/B00JRHUGDI/ref=sr_1_1?ie=UTF8&qid=1422387172&sr=8-1&keywords=emotiva+volume+control&pebp=1422387174245&peasin=B00JRHUGDI (http://www.amazon.com/Emotiva-Control-Freak-Unbalanced-Passive/dp/B00JRHUGDI/ref=sr_1_1?ie=UTF8&qid=1422387172&sr=8-1&keywords=emotiva+volume+control&pebp=1422387174245&peasin=B00JRHUGDI)8)
Too bad it doesn't have a ganged volume control to allow balance adjustments.
[/quote]
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Of course, thanks.
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Last night for Schiits and giggles I put the SYS into the main system. I connected my mac mini > DAC to the pre. I sat down thinking, there's no way this little $50 box is going to sound any good. I was wrong, I played one song and was amazed at how much the noise floor dropped. The harshness of the ribbons was completely gone but the imaging was still just as good if not better with a wider presence.
Pepe swung over a little later and I had him sit in the listening chair. After awhile I asked him if it sounded better not telling him what I had done. He could tell right away that something had changed and that the ribbon harshness, my system has an issue with, was gone.
Pros: Smooth sound, much lower noise floor, a more natural imaging, greater dynamics and it really let the source and amps shine.
Cons: This really has to do with the Schiit SYS; it's a good little box but you could tell some mid dynamics were missing. This should easily be fixed by either purchasing a higher end passive pre or building a DIY one with better connections/pot/wiring.
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Thanks for the review.
Having just last weekend to the same Mini > DAC set up, versus streamed from an Airport, I should try this out in short order. The optical straight from the Mini was already a giant improvement in sound quality, in dynamics, detail and signal strength, but I haven't tried the SYS quite yet.
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Dropped by Rev's listening room last night, sat down and listened, observed "it sounds clearer, especially at higher volumes, what did you change?" The only change was that the Melos pre was out of the loop and he had a tiny inexpensive ($50!!) passive pre hooked up in the back. Impressive. Less can be more.
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Somehow Schiit figured out how to make components in the USA that are high quality but priced very reasonably. BJ and his wife bought me their Valhalla tube headphone amp for my 60th birthday back in May and it's awesome. Last month for Chanukah they bought me the Modi 2 DAC and though admittedly I have no other experience with DACs I'm very pleased with it and I know the cost was reasonable. The build quality is top notch. Only complaint about the Valhalla is that the power switch is inconveniently located on the back.
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I decided that I'm going to make one for now. Pepe is donating a killer pot, I have some toggle switches and litz wiring. I'll post more as I go along.
(http://i803.photobucket.com/albums/yy313/RevAmish/IMG_0137_zps0de7beb0.jpg)
(http://i803.photobucket.com/albums/yy313/RevAmish/IMG_0138_zps581b2dc1.jpg)
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So Pepe is donating killer pot huh. Remember puff, puff, pass...
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Mexicans. ;D
(http://i803.photobucket.com/albums/yy313/RevAmish/408608D2-76E6-4B56-AEAA-983EA7EC7998_zpsuyjlvxn9.jpg)
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Cool. Please do keep us informed about how it turns out!
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I'm still looking for a volume knob but for now a knob from Pepe's favorite reel to reel works fine.
(http://i803.photobucket.com/albums/yy313/RevAmish/985EA8FF-6E21-4641-9BDA-9259BD43E699_zpsqwz478iw.jpg)
(http://i803.photobucket.com/albums/yy313/RevAmish/9C60B259-D51B-44FC-B22B-D32712E687F5_zpsoe1r7uqb.jpg)
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Given the shape of the switch plates, a chrome chicken head or maybe one of the rectangular knobs that Yamaha used would look great.
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Here, I even did the leg work for you...
http://www.mojotone.com/guitar-parts/Metal-Guitar-Knobs/Aluminum-Flat-Topped-Chicken-Head-Knob (http://www.mojotone.com/guitar-parts/Metal-Guitar-Knobs/Aluminum-Flat-Topped-Chicken-Head-Knob)
(http://www.mojotone.com/core/media/media.nl?id=91020&c=923962&h=cc1644c97f4ede1c382d)
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That one is sold out, try this...
http://www.ebay.com/itm/TOG-CHICKEN-HEAD-KNOB-CHROME-SET-SCREW-BRASS-INSERT-/360442118815 (http://www.ebay.com/itm/TOG-CHICKEN-HEAD-KNOB-CHROME-SET-SCREW-BRASS-INSERT-/360442118815)
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Going with this knob. It's 4" in diameter so it should take up most of the front of the pre. It needs cleaned up a bit but it should look killer.
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Nice... it has a bit of a kitchen appliance feel to it!
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Rev
Nice! You may want to shield the inside with copper foil.
Ron
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I thought of copper shielding as well as some inline resisters for the ground but I've had it connected to 3 different systems so far and no noise. I'll leave it be for now. The knob is off of some old 60's piece of test equipment, I just liked the look.
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the volume pot looks bad ass
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What do you think about your DIY passive, Rev? Does it surpass the Schiit? Mid range dynamics any better?
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Yes, it had more balance than the SYS but that little Schiit is pretty damn impressive for $50. I used quality RCA's, a really nice pot donated by OBG, industrial gold plated toggle switches and 16 gauge litz copper wiring. If any of you have ever messed with litz you'll know it is a pain in the ass but worth it. Each strand is individually coated. You have to torch off the coating then sand the ends to solder correctly. 16 gauge was overkill but I happened to have a small roll of it in-house.
The mid end does seem more prominent now and the imagining has also improved. The dynamics are through the roof. I haven't been able to spend more than an hour in my system so I still have some sit down time before I can comment further. I did end up taking it to Tom's last week and we hooked it up to one of his carver baby tube amps, my ipad, and the large advents in the basement work area. It sounded really damn good. The imaging was crazy good. Even Tom was surprised.
(http://i803.photobucket.com/albums/yy313/RevAmish/IMG_0151_zps4db10d70.jpg)
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I'm glad to hear of your positive results. As mentioned earlier I've used them for many years. They don't seem
to garner the respect they deserve. Perhaps others had other issues that just complicated the use of a passive.
I've breadboarded my inexpensive ElectraPrint PVA and am extremely impressed. Bass is tighter, faster. Mids/highs
are extremely smooth and just damn good. And..a bonus...it has GAIN. Its a STEPUP transformer based passive.
Check out Jack' website for more details. Its a very worthwhile upgrade to an already good passive.
Just be aware of the input impedence. Its on the low side...(mine is 150 ohms) which any decent CD, DAC can handle
with zero issues. Haven't tested my tuner yet which gave me greif on an earlier tranny based passive.
You can pick the input Z And he winds the tranny to your specs.
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OBG or Rev-what kind of pot is that and where did you get it?
This looks like a relatively simple project even I can do. and, I suspect my amps have more than enough gain to work. I'll need two sets of outputs; will splitting the volume out adversely affect the signal (other than maybe reducing it)?
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Heard the passive pre last night.... what a big upgrade over the Melos! Sound is fantastic. Not many times will a single component change make that big of a difference. Super job Rev.
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OBG or Rev-what kind of pot is that and where did you get it?
This looks like a relatively simple project even I can do. and, I suspect my amps have more than enough gain to work. I'll need two sets of outputs; will splitting the volume out adversely affect the signal (other than maybe reducing it)?
I find myself inspired as well. I've has the SYS back in over the last week and thought it sounded great, though it is decidedly less user friendly. As MacGeek stated, I think this is a project I could do fairly easily assuming I can narrow it down to a good pot and find other quality parts.
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Klaus, adding a second output shouldn't be an issue. Not including the chassis and/or knobs, it can be made for less than $100. I recommend a wooden chassis as you're less likely to develop a ground hum of some kind but this can be gotten around with copper shielding, inline resisters in the ground path or even an external ground.
Here is the link to the pot that i'm using: http://www.analogmetric.com/goods.php?id=1000 (http://www.analogmetric.com/goods.php?id=1000) I went with the 100k Ohm version.
Wire that I used: http://www.ebay.com/itm/50ft-New-England-Wire-Technologies-100-Strand-Type-2-Litz-wire-AWG15-5x20x38-/191165549170?pt=LH_DefaultDomain_0&hash=item2c825aca72 (http://www.ebay.com/itm/50ft-New-England-Wire-Technologies-100-Strand-Type-2-Litz-wire-AWG15-5x20x38-/191165549170?pt=LH_DefaultDomain_0&hash=item2c825aca72) I believe for the ground path I used 20 or 22 gauge solid copper wire.
Toggle switches: http://www.ebay.com/itm/2-Carling-80-000-Series-E60272-LR39145-2GK54-73-DPST-ON-NONE-OFF-Toggle-Switches-/191121798969?pt=LH_DefaultDomain_0&hash=item2c7fbf3739 (http://www.ebay.com/itm/2-Carling-80-000-Series-E60272-LR39145-2GK54-73-DPST-ON-NONE-OFF-Toggle-Switches-/191121798969?pt=LH_DefaultDomain_0&hash=item2c7fbf3739) I bought mine from Graingers and they were slightly better quality but the same brand.
RCA Jacks: http://www.ebay.com/itm/10-pairs-Female-Amplifier-RCA-Jack-Chassis-Sockets-TOP-QUALITY-USA-SHIPPING-/141560208817? (http://www.ebay.com/itm/10-pairs-Female-Amplifier-RCA-Jack-Chassis-Sockets-TOP-QUALITY-USA-SHIPPING-/141560208817?) Great seller, have used him for years.
From the photo I posted previously it should be pretty simple to use that as your guide. I can answer any questions you have. I used DPST switches but a rotary switch would work just as well. I took the design from a modguy who used toggle switches for each input. In his case he went even further overboard and had a dual mono design with 3 inputs = 6 switches. The one thing that's hard to see, and I did slightly harder then it had to be, was the toggle switches. DPST means double pole single toggle (if you didn't already know). This means that there are two channels/sides or left/right for a single switch. The easiest thing to do is wire the positive of both left and right from the input to the bottom two terminals. That leaves the top terminals open and easy to work with. You then connect all 3 top left terminals together (if it's a 3 input design) and do the same thing with the right side. The volume pot will then be connected to the top left and right terminals you daisy chained together.
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Thanks for the info, seems like there might be a number of these rolling around in short order!
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Made it even easier for you guys.
(http://i803.photobucket.com/albums/yy313/RevAmish/PassivePre_zpsd9bd370b.jpg)
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Fantastic! Good visuals are always helpful for a neophyte like myself.
Do you think the Litz wire is critical component? I might well buy a spool, you just made it sound difficult to work with.
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Excellent components lead to excellent results as Rev has shown.
Another critical component are the interconnects. High quality interconnects
quickly come into play with passives. Everyone on this forum knows this but the key point
here is to avoid high capacitance cables....you'll lose all your high frequencies and then complain that your
passive sounds dull, lifeless, no dynamics, etc.
Dispite their controversial design I'm going to build a DIY version of the "anti cable" interconnects using
magnet wire and clear packing tape. Very low capacitance cable.
Litz wire....that does sound like a shit load of work per connection. Maybe someday.
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Thanks for the parts list and schematic, Rev. I have some shielded, tinned wire (used in the boat) I am going to try. An old cigar box may serve as a cabinet. I think have an old parts rotary switch I may use in place of the toggles; however, the toggles may provide better isolation.
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I bought this amp from Kegger on AK. He built it from scratch using an HP Oscillator cabinet. Have always wished the large knob on front actually was a volume knob, instead of just to look at now.
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I would not recommend using tinned wire in any audio application.... I've never heard good results when using it in interconnects nor as speaker wire. The risk reward is just not there for the few cents in cost savings.... even low oxy copper with real silver coating has its own unique audio sound.
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There are many variations of litz wiring, the stuff I used was a bit of an overkill. You really don't need that thick of wire (I used 16 gauge, 20 or 22 would be fine) but I really recommend using it or silver. You can get a 6' piece of silver wire for around $25, that might be another option.
I got the knob I ordered in but it's a little big. I kind of like it but will look at smaller ones. (sorry for the crappy pic).
(http://i803.photobucket.com/albums/yy313/RevAmish/IMG_0169_zpse5814c80.jpg)
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I dunno, Ryan, that looks pretty cool.. kinda in the same ballpark as the amp bmw posted.
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I just ordered this one, it's about .75" smaller in diameter. I dig that amp, very cool design.
(http://i803.photobucket.com/albums/yy313/RevAmish/knob_zpsd0c8ab6f.jpg)
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I hear good feedback on Rev's passive and look forward to listening to it first hand.
For anyone considering cooking their own as well: the pot that Rev used is 100 Kohms, not 10 Ks (Rev - maybe update the diagram to include that spec?)
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Rev, you've got a great looking knob! >:D
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That pot Pepe gave you looks excellent! I was surprised that it was only around $35. My buddy replaced his volume pot on a Krell preamp. It was crazy how many steps it had, cost around $150 or so if I recall.
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I was able to audition Rev's passive preamp this weekend. It is possibly the best pre I have listened to so far. The cleanliness of the sound, tight imaging, soundstage - etc. [I know all those sound like cliche terms - but in this case they actually apply without reservation] are vastly improved.
This almost makes the case for having a passive pre [like this one] in the path to the power amps after your "regular" pre. As Rev & I discussed - you can almost leave the volume pot out and just have a switch box wired w Litz to switch in the right output (probably your DAC) to the power amps, since most software control volume digitally anyway. Rev has the Melos going into the passive as an input to use the phono pre, so in a way he is doing that.
The sound was great - I could have listened to that setup for several hours. This also speaks to the potential of the Carver ribbon paired with a decent woofer in a cabinet, and the cleanliness of the ECS-U holography processor, assuming that it was online while auditioning.
Pepe
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I was able to audition Rev's passive preamp this weekend. It is possibly the best pre I have listened to so far. The cleanliness of the sound, tight imaging, soundstage - etc. [I know all those sound like cliche terms - but in this case they actually apply without reservation] are vastly improved.
Agreed; it really brought the sound to life. It's cool because with an invisible pre, you can get a feel for how the amps actually sound, uncolored by anything after the source before the amps. The sound stage was so much bigger than it was with the melos; I didn't feel like I needed to sit in the "sweet spot" in order to get a feel for the sound. i am kind of compelled to make a passive pre, but it isn't feasible in my current setup, so that'll maintain being on the backburner for a while.
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Passive preamps don't work well if you have long interconnects.
The capacitance of the interconnects rolls off the highs.
Thats why I use a tube preamp with a cathode follower output which lowers impedance so it can drive the long wire without rolloff.
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Passive "preamp" is kind of a misnomer. It actually is not a preamp but an input selector with an attenuator. There is no amplification.
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Hehe...."Pre"amp......as in "before" the amp. ;D
But I certainly understand the conventional nomenclature and what people
expect when someone says preamp. But it is surprising how good they can perform
for such a small investment. Everyone should try one at least once. Properly executed
they excel in openess , zero floor noise, etc. Short of pushing long interconnects they easily
beat most mid-fi preamps. IMO anyway.
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You're right.....my bad
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When my last preamp crapped out on me, I temporarily connected my CD player, which has a volume control, directly to the power amps while I shopped and waited for a replacement. That's when I realized what a pre-amp can do to or for the signal path (this comparison convinced me I should be happy with the replacement pre, by the way)
Why not simply connect source components with an output level control (my R2R, cassette deck, tuner and CD player have variable outs) directly to a switch box to eliminate the attenuator and achieve the same, or even better result?
A Niles TSB3 used as a switcher adds tape loop functionality. Some DATs have a variable out. I imagine finding a phono pre with a variable out may be a challenge, but a standard preamp with phono can serve the purpose for LP playback.
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Ron was pawned on this one ;D.
I would have never imagined the difference to be that great between a regular pre and a passive. but take note - the passive requires a bad ass power amp. Ryan has the Carver 305s - that gives him enough power to be fine with the lack of gain in the pre. You cannot get away with that with lesser amps. And still he does not get crazy volumes - at 90% throttle he is getting decent but not crazy volume levels. Your results may vary depending on the efficiency of the speakers.
Still, what volume he is getting is pretty dang good sound.
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OBG-good point. The ability to max the power amp will depend on the source voltage. I find, however, that I seldom get above unity gain (0db) when adjusting the pre amp volume, and I do occasionally like to play it loud.
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That's certainly true OBG. I get around this by using a transformer (not a true TVC though) unit that has gain.
I suspect it will drive just about any amp to clipping if turned up all the way....at least on the few amps that I have
on hand. Compared to my "straight passive" (like Rev's) that I have it plays noticibly louder.
Fun topic. I really enjoyed it.