Thought I’d update the thread with my ongoing Khozmo journey. I have recently upgraded all of my sources to balanced and also sold my original Khozmo to another SHF member so I could upgrade to a balanced Khozmo. The experience with Arek was just as good as my previous one and the quality of the new preamp is everything I expected it to be. I would comment on sound, but since it’s a passive preamp it adds nothing and therefore there is nothing to comment on. I will leave some top less pictures as I really like the clean interior layout of these preamps, and you can tell that some care goes into there design and construction.
I built a DIY preamp using a similar Khozmo balanced attenuator. The one I am using has an OLED display and a 6-1 input switcher built in. Mine is also built with Takman REX shunt resistors and Vishay Z-foil series resistors. I built an active preamp since my DAC has a fairly high output impedance and I am driving long cables (7M). But it easily bested my previous preamp (Parasound JC2-BP) with improved detail and dynamics. The Miflex caps are used for a second set of outputs to provide a low frequency roll-off to my main speakers since my subs cover the bottom couple of octaves. So I have both balanced and single ended DC coupled outputs and balanced high-pass outputs. I'm in the process of building another (considerably more sophisticated) preamp using the same attenuator, but this time I'm going to try it with Takman REY shunt resistors (based on Arek's recommendation) and AudioNote silver tantalum series resistors.
Excellent work Jay! I bought okc_craft's unbalanced Khozmo and am really liking it. This will get you closer to the original recording, and for some, that is the goal. If that is your goal and you can get the listening levels you desire from a passive, here you go, and reasonably priced as well. The unit is larger than I was expecting based on pics. Super nice piece of gear! I also have a Schiit Sys passive as well as an older Creek OBH-12 passive and both of those have potentiometers so the Khozmo is cleaner.
For McCormack geezers, here's my Micro Line Drive circa 1997 or so still going strong. It has both active and passive outputs. Doesn't need to be plugged in in passive. Has the funky dual mono volume pots tied together with a string! I sure wish this thing had a remote but otherwise no desire to swap it out. Anybody else remember the Micro series?
Thanks guys. I've found that a passive attenuator works well when the output impedance of the source device is on the order of 50 times lower than the input impedance of the amp and where the impedance of the attenuator is at least 10 times the source output impedance, and the cables are of moderate length. Since my Denafrips DAC feeds the outputs directly from the resistor ladder, the output impedance is on the high side and even the configuration I have is not ideal (inputs feed the 10K ohm attenuator directly which feeds an output buffer). In hind-sight, I should have used a higher impedance attenuator. The preamp I am working on has an input buffer with 500K ohm input impedance before a 5K ohm attenuator. The output of the attenuator feeds two different output stages- one is a fully-balanced discrete class A buffer with fairly high bias, the other is the same buffer I'm using in the preamp shown above (which has both balanced and single-ended outputs). The power supply is much more sophisticated with a separate chassis for the first stage containing the regulated digital supply to control the attenuator plus four separate +/- supplies for the analog section (400VA/100KuF). These connect to the main chassis with a 14 conductor cable to feed independent shunt-style class A regulated power supplies in the main chassis. I'm also building a much more robust chassis with 6mm top and bottom panels. I'll post some photos when it's done - hopefully in the next month.
I was recently facing a similar choice: Khozmo vs. Saga+. I wanted a passive preamp with a remote, as my 300B amp had only manual volume adjustment. I was all in favor of Khozmo and against the Saga+, save for one nagging detail: my Sparkler CD player somehow has a very low output level - way below the stated 2.1V, and sorely needs additional gain to sound good. Khozmo is purely passive, and the tube gain stage is another $1,300 or so. Whereas the Saga+ has an on/off active tube buffer providing the additional gain needed by the CDP. So, I can run the vinyl rig through passive mode, and engage the tube buffer for the CDP, when needed. In the end, the Saga+ just made more sense, so I ordered one. So, if you only plan to use the Khozmo in the passive mode - it certainly at least looks way cooler than the plain-vanilla Schiit pieces. But if you happen to need additional gain at least some of the time - give it another thought.
Had the Micro LD used in passive mode with a VTL 90/90. CD player was a tweaked Rotel RCD855 with a SimplyPhysics Isodrive clamp, and speakers were Spica TC50 with Harmonix tuning dots. How about that for ‘90s nostalgia? That system sounded so good, a friend upon listening wanted to trade me his Honda CRX lol. I refused, of course. (Sorry for the digression.)
I know the following defeats the purpose of trying to have as simple a system and thus an output as true to the original recording as possible, but I was not getting the loudness I desired with my B&W CDM-1SE and just the Khozmo so I used the "gain stage" of a Schiit headphone amp (which can also be used as stereo preamp, but for only one input and the Schiit HP amps also do not have remote control). A few years ago I ordered some Schiit HP amps (I dont own headphones) for this purpose to be used with https://www.amazon.com/TC-7240-Router-Switcher-Selector-Splitter/dp/B00KDQXITG, but I decided I could not live without remote volume control. A Khozmo solves the remote control problem but using a HP amp as a gain stage adds another piece of gear to ones stereo, so if one is a purist then I suppose this is a no no. But right now I am using a Class A Schiit Asgard 2 HP amp on the low 6dB gain setting with the Khozmo and can now hit the loudnessses I desire with the Khozmo, B&W, and a Denon POA-2800 (which is 200 W, the B&W are only rated for 120W, so I didnt think hitting desired SPL would be an issue, but it was). I suppose the pot of a Schiit HP amp could be bypassed thus turning the HP amp into a "fixed gain stage" (actually 2 since there is a choice of two gain settings) and making for a cleaner signal by bypassing the pot. So if one isnt getting the loudnesses they desire with just the Khozmo and an amp, using a Schitt (maybe other HP amps can be used as stereo pres as well?) HP amp can solve this problem. Also if one has an old integrated (or receiver) with pre out/main in jumpers but no remote, adding a Khozmo will give remote volume control. Could also use a Schiit Vali tube HP amp to add "tube flavor" to the Khozmo(granted this is probably not what someone buying a Khozmo wants to do, just saying). Just a heads up for someone who might desire more gain. I think? all of the Schiit HP amps have a choice of 2 gain settings. At one point I was looking for "fixed gain stages", but could not find any. Bypassing the Schiit HP volume pot would create a "fixed gain stage" (choice of 2 actually) that could be used with a Khozmo. Or just one without bypassing the volume pot, like I am now, works well!
That last sentence should read "or just use one without bypassing the volume pot, like I am now, works well!"
That's why I decided for Saga+: it has an active stage for the one (just like you) source I need, and the convenience of a remote control, in one box.
What’s your source? It looks like the Denon has a fairly low input impedance of 25k, and I happen to know you Khozmo uses a 22k resistor, so you may have a poor match to the amp, especially if your sources output impedance is on the high side.
Mr. Benzion I be confused (unfortunately a frequent condition of mine) Near as I can tell from the Schiit website, the Saga + is a passive device with a buffer when the tube is engaged. It offers no gain when the tube is engaged, all it does is match impedances better. Your statement implies that engaging the tube provides gain, Schiit says that is not the case. Please correct if I'm wrong.
Saga Specs: Hybrid Tube Buffer Stage: Frequency Response: 20Hz-20Khz, -0.2db, 3Hz-200KHz, -3dB THD: <0.001%, 20Hz-20KHz, at 1V RMS IMD: <0.001%, CCIR (active stage) SNR: >108db, A-weighted, referenced to 1V RMS Output Impedance: 180 ohms Maximum Output: >10V RMS Passive Stage: Output Impedance: varies, maximum 4.8 kohms Both Passive or Active Stage: Gain: Approximately 1 (0dB) through either passive or active stage Input Impedance: 10 kohms Crosstalk: >-75dB, 20Hz-20KHz
Source is a Schiit Bifrost 4490, I could not find its output impedence. I got higher SPLs on the B&W CDM-1SE with the Denon POA-2800 than with a Forte Model 3. But with the Khozmo maxed at volume level of 63, it was not loud enough for me at times with both amps and I could max the volume out at 63 on all albums I tried with no audible distortion or clipping. So the Denon (200W/350W) must have a higher gain stucture than the Forte(200W/400W). This is in a fairly large room (16x28) and I tend to listen on the loud side. I think >90% of audiophiles would be fine with the SPLs Im getting out of these speakers and just the Khozmo and an amp.
The one he's using has a 22K series resistor? That's pretty high for a shunt control, but it's always a compromise with shunt controls between the source and what comes after. So it's throwing away about half the output from the source at full volume when connected to the Denon?
When Arek built it for my I was running a Parasound with a 33k input and my McIntosh MC60s which has an input of .5 mega ohms. I am a little baffled as to why he is getting more output from the Denon, if memory serves his Forte has a much higher input impedance and would on paper be a better much. I did ask Arek about changing the shunt resistors before I ordered my first passive and it’s allegedly a fairly easy task for someone handy with a soldering iron.
It does sound a bit confusing to me too. The specs for the tube buffer say max output is 10 V - how do they achieve it w/o any gain then? I'm not too worried though - if it doesn't do the job, Schiit stuff is easily returned for full refund - they have people waiting in line to get one.
The only thing I can think off is 10V in - 10 V out although I'm not aware of any source that would produce such a high output. As luckybaer indicates by quoting Schiit's specs: Gain: Approximately 1 (0dB) through either passive or active stage.
The Forte is 47K input, but I don't know what the sensitivity is, the Denon probably has higher gain. Yes, that's what it means, and you can get over 10 volts from a phono preamp on a hot recording, provided it has enough juice (5mV cart into a 46dB gain phono pre on a record with a 20dB peak = 10V). Digital sources generally have a lower maximum output level since it is more formally defined.
I'm not sure if definitions are always supported by fact. My Sparkler CDP claims to output 2.1 V. In reality, the output from it sounds weaker and quieter than the output from my phono, which must be putting out about 598 mV (0.3 mV cart into 1:10 SUT into 46 dB of MM gain). I literally have to up the volume on my line preamp much higher for that CDP than for the phono, which is weird.
The loudness depends on the average recording level of the CD and the record, so the mastering determines how loud it plays. The CDP has a fixed maximum output of 2.1 V RMS, which is pretty standard, that corresponds to the maximum it can output, which is fixed with digital. It's a much different rating system, the "normal" output of the CDP is much less than that unless playing a modern highly compressed and maximized CD. On the other hand, there is really no maximum level on the phono, you are running a little hotter than a standard 5mV/ 40dB gain setup, but pretty close. Hard to guess which one will play loudest, so not too surprised at your findings.
