Lowrider57, Yes, if nothing else is stated, then the output impedance is specified at 1KHz. |
Chad-
both the ARC & C-J gear are sonic matches for your Bryston power amp. |
I've only seen preamp output impedance's listed either by itself or at 1kHz. |
to Atmasphere...
Very important point regarding Output Impedance at the lower frequencies. But the preamp spec sheets I've seen never state how their output impedance was measured.
Should we assume that it's at 1000Hz unless otherwise indicated? |
Interesting thread, I will keep close view of this one. |
A friend of mine has an Act 2 and it is very quiet. His system has speakers that are 105 db/w efficient, so they reveal the smallest amount of noise in the amplification chain and he has no noise issues with this linestage. |
Chad2635, My pleasure.
The ART and ACT 2.2 are very quiet. They are line stage only so I can't speak for CJ's phono stages. I do run an outboard phono stage thru the ART and it sounds great (and quiet).
In my previous post I meant to type that I use "15" foot rca interconnects. Somehow a "1" became an exclamation mark. Hate when that happens. :-) |
Onemug, how quiet is the cj gear? Thanks for the feedback by the way! |
Chad2635,
I've had a CJ pre/Pass amp combo for several years now. It is one of the best combos I've ever put together. They seem to be made for each other. Hope you get a chance to try it yourself.
I wouldn't worry about the volume control, it's a very good one and they are important. It's not push, push, push. You just hold the remote or preamp button down and a motor moves it until you get where you want. There is the "clicking" but I got used to it immediately. As far as longevity, it should last a long time.
I've also found that the 3 CJ preamps I use, two ARTs (6922 based) and one ACT 2.2 (6h30 based), have been very compatible with other amps I have used...SET's, PP tubes and a couple Tripath based chip amps. !5' rca interconnects were no problem with my CJ's 500 ohm "average" output impedance.
Good luck with your choice. |
Interesting. Thanks, Ralph. |
If you want a tube preamp to drive a solid state amplifier, the thing to look at is the output impedance at 20Hz. What it is at 1000Hz is really not that important- most any tube preamp will have an acceptable output impedance at that frequency. Its how the preamp behaves in the bass that is important.
This is because most tube preamps have an output coupling capacitor that is part of the equation of output impedance. At 1KHz, its no big deal but at 20Hz that coupling cap becomes a major influence on the numbers and can cause a loss of bass impact.
To counter this issue, some tube preamps have a large coupling cap so they can drive solid state. The problem is, the bigger you make that capacitor, the more it can color the sound, even if its Teflon. The reason has to do with the inductance that the cap has which is something independent of the insulator in the cap. The bigger the cap, the more inductance (due to the fact that the cap is wound). This creates a tension in the design where the cap is chosen to color the sound the least, while at the same time not affecting the bass. It is at best a compromise.
A very small number of tube preamps have a direct-coupled output, which sidesteps the issue. |
Not sure about your price-range but VAC is a thought. I run a Phi Beta pre-amp into Bryston 28B-SST2 amps and the combo works beautifully together. This VAC model, like the Signature 2a, is based on the 8416 tube, an Amperex 12v version of the 6DJ8/6922/7308 family. But it has a switch enabling the use of the latter, so you can tube-role to your heart's content. I prefer the 8416, personally.
The 28B input impedance is 16.5K, single-ended, with 23db of gain on its low setting, which I use. Not sure but I'd think the 4B-SST2 would be the same. VAC claims the Phi Beta will easily drive loads down to 200 ohms, so no issues there; and it outputs 12db of gain. VAC pre-amps other than the Phi Beta and Sig 2a are much higher gain--more than 20db, I believe--so be sure to check with VAC about compatibility if you're thinking about trying one. They're helpful folks. |
Check out Quicksilver, has low output impedance(100 ohms).Give Mike a call and I am sure he will take a return if you do not like! |
I would check out the Nagra PL-L. |
Lloydelee21, I am very curious to see how the et3se would sound with my pass labs...in fact I have read in other forums that it is a good match, however I just don't think I'd like the push button volume control. Yeah there is a remote but same thing there. My experience (not with the cj gear) is that push buttons wear out. I'd rather turn a dial then push, push, push... a button. On the flip side it must work and be reliable because everything from the et3 on up has this type of volume control. |
Zd542,
I didn't take any offense at all, I was just attempting to clarify my viewpoint. |
Charles1dad,
I wasn't finding fault with you in any way. Sometimes I can be a bit direct in how I word things. I kind of know what I'm doing now, but it was a long and expensive journey to get here. I've made just about every mistake an audiophile can make (several times in many cases). That's why I'm so direct. I'm really good at hearing the train coming off in the distance. |
I totally agree....what looks good on paper might on the other hand be the worst combination that could be put together (sonically)...at least for a given system. I spend countless hours reading and researching (I enjoy this by the way) but in the end it's all guess work. I think my overall problem is that I don't know what I'm after in sound quality. Yeah it needs to sound good but what does that really mean. I could have a half a dozen preamps both SS and tube with each one having their own characteristics that rise above the others. Maybe that's why we audiophiles tend to keep searching for more...do we ever achieve "the one preamp" or is it just perception based on what we make ourselves believe is the one. |
I've had many many tube pre and SS amp and agree with Kyomi_audio that output impedance is an important aspect to consider in a tube preamp.
You definitely have more tube rolling options with 6sn7 and 6922/e88cc but not all 6h30 situations sound like SS. My only 6h30 experience is with MW Transporter. I found the Reflektor NOS 6h30-dr was the best sounding 9 pin signal tube in the Transporter. It had the best of SS and tube properties.
One of the beauty of a tube pre is tube rolling so personally I prefer a 6922/e88cc or 6sn7 pre but try to demo with your SS amp if possible before purchase. |
From my own experience, it is an absolute requirement that the specific tube linestage be tried with the specific solid state amplifier. Even with supposedly compatible impdedances and short cable runs, etc., the result of going from tube into solid state is quite unpredictable (most often in a bad way), than any other combination; I would be much more confident predicting the result of solid state feeding tube than the other way around. I am certainly NOT saying that tube feeding solid state doesn't work well, but, the combination must be tried first.
From a practical standpoint, you should also look for a tube linestage that can be completely muted while it is warming up or one that does not emit ANY noise when turned on and warming up, or the solid state amp must have a mute circuit. I have found that solid state amps sound their best when left on all the time or at least warmed up for a very substantial amount of time. Tube gear, on the other hand, warms up faster and really should not be left on all the time. That means that the tube linestage has to be turned on AFTER the amp--any startup noise could be nasty and potentially harmful to the speakers.
For what personal preferences are worth, I generally like linestages with 6SN7 tubes. There is a HUGE variety of these tubes so it is possible to tailor the sound of a linestage by choice of specific brand/vintage/model of tube. I haven't heard a 6H30 linestage I really liked (sounds lean and brittle to me). On the exotic side, I like linestages that use 310 tube -- warm, great midrange presence, but a little rolled off on top. |
Zd542,
You make some valid points, I made it clear to chad my description of the
various tube characteristics were "general" . Of course the
option to hear a component in your system is by far the preferred way to
proceed, this isn't possible in many cases. Gathering information from
those with some actual experience does help establish a data base and is
useful.
I have four components in my system that were purchased without any
prior listening. I used reviews and perhaps even more importantly (to me)
input from owners on this site and other forums, results exceeded my high
expectations I'm happy to say.
There simply wasn't a way for me to hear these components in my system
without buying them, that was the reality. I know I'm not the only one who
has had to do it this way either. You have to begin the quest somewhere.
Charles, |
Chad, I am no techie, but I think CJ make quite a big deal of their volume attenuator, indicating they use a discrete resistor for each volume increment to attenuate the volume (in 0.7db increments all the way through)...somehow preserving the integrity of the signal by having just the one resistor at that increment? AT least that what I could make out of it...sorry for not reading it properly if I got this wrong. Its on their website. Perhaps there are better ways to attenuate, but as people like to say, its often about the implementation than the theory anyway. Hope you get a chance to hear the CJ ET3SE...if it sounds as close the GAT as people say, then it should be quite a special preamp. |
You're probably right. It's tough being an audio enthusiast and reading about new makes and models with everybody trying to outdo everybody else but in reality who actually has access to audition even a fraction of what's out there. Even the hifi shops can't afford to stock all models....I know because I've called and more times than not if they don't have what you want they make you special order it and will only exchange it. I guess what I need to do is pick a shop that carries at least 2 brands I'm interested in to better my chances of finding a match. |
"12-25-13: Chad2635
Thanks for all the feedback. Based on all the research I've done I'm leaning towards 6SN7 or the 6922. I have had my eye on the cj et3se however I'm not sold on the volume control that it uses (push button/remote) and I'm not sure the entry level classic 2se (both use a single 6922) is enough of a preamp (ie performance not features). Herron audio has a 6922 based pre that I may investigate. There is a used VTSP-1a/166 here on audiogon and a NOS VTSP-2."
That's not a good way to go about this. You can have 2 preamps that use the exact same tubes and they will both sound very different. In a case like this, demo's aren't optional. You have to do it. If your only demo option is ARC, I recommend you try to put something together with them, as opposed to just guessing. When you buy equipment without listening to it first, be prepared to fail. (Understand that I'm not trying to be negative or mean. I'm just very direct in how I communicate.) |
Thanks for all the feedback. Based on all the research I've done I'm leaning towards 6SN7 or the 6922. I have had my eye on the cj et3se however I'm not sold on the volume control that it uses (push button/remote) and I'm not sure the entry level classic 2se (both use a single 6922) is enough of a preamp (ie performance not features). Herron audio has a 6922 based pre that I may investigate. There is a used VTSP-1a/166 here on audiogon and a NOS VTSP-2. |
Just to clarify, the input impedance of the amp should be at least 10x the output impedance of the preamp.
Tube preamps can have fairly high output impedances, e.g. 1.5 kohms. 10x this output impedance would require an input impedance of at least 15 kohms for your amp. That's a pretty low input impedance for an amp, but they are out there, Pass Labs for example.
Many SS amps have an input impedance of 47 kohms or higher and you should have no problem pairing a tube preamp with one of these amps.
Try to find a review with measurements of the tube preamp you are interested in because manufacturers give a nominal output impedance with their specs. The preamp may hit a significantly higher output impedance at certain frequencies.
This question comes up often and there are a number of threads on this subject you can browse for that will give you recommendations for specific combinations. |
+1 for Charles1dad, we're on the same page. |
Depending on your budget you may want to consider the Atma-Sphere preamps, which btw include (I believe optionally) what is by all accounts that I have seen an excellent built-in high gain phono stage. My understanding is that they would have no problem driving any amplifier in existence. They are also fully differential, which would be complementary to your Pass amp. They use 6SN7 and 12AT7 tubes, and also 12AU7's in one model.
Regards,
-- Al |
Hi Chad,
You ask good questions that are tough to answer. As you noted there are
many variables to consider with all things in audio. I'll give an admittedly
general impression based on personal listening encounters.
The 6H30 tube tends toward a leaner tone and body character. Some would
say neutral and accurate sound ( and call it "solid state like") . It
doesn't appeal to me as the sound is flatten and clinical, it isn't organic and
loses emotional communication.
If built -implemented to a high quality standard I'd rather have a 6sn7
based preamplifier, better sound, fuller and more realistic tonal color,
weigh and vibrancy. Just comes closer to my experience with live sound
compared to the 6H30 examples I've heard (which obviously isn't
everything out there).
I've also heard good sound with 12x7, 6922 based preamps as well.
My top choice is a preamp that uses DHT(directly heated triode) type tubes,
but that's just me.
Charles, |
Rogue Audio has preamps which offer low output impedances, low enough to mate with SS amps.
The Athena has an output impedance of 220 Ohms,
the Hera II output is 120 Ohms. Gain is 12dB single ended, and 15dB Balanced. |
I recently swapped to a cary slp-05 from a classe dr6 in my rig. It feeds a sanders sound esl-300 ss amp and a pair of Maggie 3.7's.I should have made the swap to a tube pre a long time ago.... it is the best upgrade in sound quality I have had from one piece of gear. Since it only uses 6sn7's there is a huge number of brands and types of tubes to roll both NOS and new production you can find the exact sound you want easily. |
The most important aspect to consider is the output impedance of a tube preamp. The lower it is , the better it is going to drive SS amps. One of the very few preamps that can drive ANY SS amp is CAT. It has the same 100ohm output impedance as the hybrid GAT LLoydelee21 mentioned. However, CAT is all tube with an outboard power supply.
Dealer disclosure. |
My first tube preamp was a CJ 16ls 2 that I ran into a Mark Levinson 336 amp. It replaced a Krell SS KRC preamp and I was very happy with the sound - much smoother and more detailed.
The 16LS 2 is a great choice if you can find one used, although it is picky on interconnects and my understanding is it does not do well with long runs.
I ended up selling the Levinson and going to lower power Cary Tube amp which the CJ also did very well with.
I used 1 meter Synergistic Designer Reference (top of the line from early 2000s) RCA cables and was very happy with this setup for many years.
I most recently upgraded to a CJ GAT, which surprisingly, was not a quantum improvement over the 16LS 2.
|
Hi Chad,
Always a challenge...good luck. I can only share my own experience. the newer CJ (ET3SE and GAT) have SS-like output impedances which can work extremely well with SS amps and Tube amps. GAT is 100ohm and the general rule I am told is 10x this figure for the input impedance of your amp. Personally, I owned the ACT 2 (6H30)...and now the CJ GAT...6922... and I think there is no comparison. Jeff Day, Myles Astor have said so in print, and I know Myles (who owned ART 3 for 12 year)...never went for the ACT 2 but DID go for the GAT in the end, finding it superior. Jeff concurs, and so does Turntable who is also here, and had the ART and now CJ GAT. My two cents. Good luck. BTW, CJET3SE has similar output impedance and thus should also be fine with SS amps. |
I know of audiophiles who have mated ARC tube preamps with vintage Threshold amps so the ARC Pass Labs combo might work for you. I say audition the ARC stuff first as it isn't too long of a drive before you start buying and trying. |
