The rule of thumb is the input impedance of the amp should at least be 10x the output impedance of the preamp. You can do the math and you will see if you think it is a good match?
PLEASE match Advice Pass Labs X350.5 (20k) to Hovland HP-100 (2500ohms) Miss-match ???
GUYS / GALS NEED YOUR HELP PLEASE!
A friend said this preamp is outstanding and will sound great with Pass Labs amps and to not get caught up in the specs but the measurements say different.
Pass Labs X350.5 amplifier with input Impedance 30k ohms Balanced or 20k ohms Single ended*
(*source Pass Labs Manual)
Hovland HP-100 source impedance 2500ohms*
(*source Stereophile)
Guys / Gals, can I used my Pass Labs X350.5 amp with Hovland HP-100 preamp? Has anyone used Pass amps with Hovland pre's. I will be using Magico S5 Speakers and Bricasti M1SE DAC but want it to sound the best it can. Should I just stick with the Aesthetix Calypso pre I was leaning toward before my gut said to go for the Hovland HP-100
Hovland HP-100 Preamplifier: * Output impedance: approximately 2500 ohms or according to Atkinson, Hovland HP-100 (2500ohms) its source impedance was high at 2.4k ohms, rising to 4.3k ohms at 20Hz. The partnering power amplifier would best have an input impedance of at least 47k ohms if the bass is not to sound lean*. The Pass Labs doesn't meet the x10 requirement it is supposed to but it is sort of close when looking at it. What do you guys think? I am not sure what to do but you guys will know what to do?
Stereophile: Its input impedance was a usefully high 100k ohms in the midrange and bass, with just a small reduction to a still-high 86k ohms at 20kHz. Despite the claim that the HP-100 uses a cathode follower output stage, its source impedance was high at 2.4k ohms, rising to 4.3k ohms at 20Hz. The partnering power amplifier would best have an input impedance of at least 47k ohms if the bass is not to sound lean.
Read more at https://www.stereophile.com/content/hovland-hp-100-preamplifier-measurements#YZXZfGLbbL2COkLR.99 https://www.stereophile.com/content/hovland-hp-100-preamplifier-measurements#YZXZfGLbbL2COkLR.99
A friend said this preamp is outstanding and will sound great with Pass Labs amps and to not get caught up in the specs but the measurements say different.
Pass Labs X350.5 amplifier with input Impedance 30k ohms Balanced or 20k ohms Single ended*
(*source Pass Labs Manual)
Hovland HP-100 source impedance 2500ohms*
(*source Stereophile)
Guys / Gals, can I used my Pass Labs X350.5 amp with Hovland HP-100 preamp? Has anyone used Pass amps with Hovland pre's. I will be using Magico S5 Speakers and Bricasti M1SE DAC but want it to sound the best it can. Should I just stick with the Aesthetix Calypso pre I was leaning toward before my gut said to go for the Hovland HP-100
Hovland HP-100 Preamplifier: * Output impedance: approximately 2500 ohms or according to Atkinson, Hovland HP-100 (2500ohms) its source impedance was high at 2.4k ohms, rising to 4.3k ohms at 20Hz. The partnering power amplifier would best have an input impedance of at least 47k ohms if the bass is not to sound lean*. The Pass Labs doesn't meet the x10 requirement it is supposed to but it is sort of close when looking at it. What do you guys think? I am not sure what to do but you guys will know what to do?
Stereophile: Its input impedance was a usefully high 100k ohms in the midrange and bass, with just a small reduction to a still-high 86k ohms at 20kHz. Despite the claim that the HP-100 uses a cathode follower output stage, its source impedance was high at 2.4k ohms, rising to 4.3k ohms at 20Hz. The partnering power amplifier would best have an input impedance of at least 47k ohms if the bass is not to sound lean.
Read more at https://www.stereophile.com/content/hovland-hp-100-preamplifier-measurements#YZXZfGLbbL2COkLR.99 https://www.stereophile.com/content/hovland-hp-100-preamplifier-measurements#YZXZfGLbbL2COkLR.99
111 responses Add your response
I have a bit more info from Stereophile: They say someone with solid state amps with input impedance of under 10k ohms this will not be a good match (see below) but my Pass Labs X350.5 has a 20k ohm impedance. So it is double what they say I should avoid so this makes me think I am ok but just not sure. I am hoping someone much smarter than I with much more experience and knowledge can chime in and help me. I thought this info helpful and wanted to share. I know I can be safe and stay away but its a local sale and a decent deal so I wanted to turn to you guys/gals! Thanks Stereophile: This graph was taken into the kind 100k ohms load. Reducing the load to 10k ohms, a typical input impedance for many solid-state power amplifiers (fig.5), increased the second harmonic almost tenfold, to -60dB (0.1%), and added some third harmonic. Dropping the load to the admittedly punishing 600 ohms raised the second harmonic to -44dB (0.6%, not shown). It is probably inadvisable to use the Hovland with those few power amplifiers that have input impedances below 10k ohms. Read more at https://www.stereophile.com/content/hovland-hp-100-preamplifier-measurements-part-2#fmWMvbWLqXD0mMfO... |
Yes, definitely a bad match. You have the answer in your post. "The partnering power amplifier would best have an input impedance of at least 47k ohms if the bass is not to sound lean*." I had experience with a bad matching pre/power. In addition to lean bass, it also sound lifeless, no dynamics. When I changed amps to a proper match and 1/3 less power, the bass was there and it was more dynamic with less power. Also, the first amp sound great with a correct matching preamp. |
As much as I like the Aesthetix Calypso I tried using it with a Pass Labs 250.5 and it was not a good match. It seemed like something was missing from the music and I could not listen for long. I ended up trying an Audio Research Ref and that was a much better match. In the end I sold the Pass and bought an Aesthetix Atlas and kept the Calypso. The best preamp I ever heard with the Pass was a Pass preamp. It’s been a while and I can’t remember which preamp it was but they go extremely well together as you would expect. This is is just my opinion and YMMV. Good Luck! |
If you want a tube preamp you should check out Conrad-Johnson. They have a low output impedance of 100 ohms and will work fine with your Pass amp. http://conradjohnson.com/current-products/ |
Guys, I should point out that though the rule of thumb isn't bad, it's also not precise, and cannot account for personal taste. Yes, it seems like the amp's input impedance is a little low.... but the combination may work out spectacularly. Personally I think the best Pass amps are those matched with other pre's. Best, E |
If the design of the Calypso hasn’t changed significantly since Stereophile measured it in 2005, especially with respect to the value of its output coupling capacitor, neither it nor the Hovland is an ideal match for the Pass X350.5. Not so much because of distortion concerns, but primarily because of the deep bass rolloff and other sonic issues that are likely to result from the output impedance rise of both preamps to high values at 20 Hz. As Tony (Tls49) correctly emphasized. It is of course always possible that a non-ideal match might be subjectively preferable in a given situation, depending on listener preference, and especially if the non-ideality works in the direction of compensating for an issue elsewhere in the system or the room. But why take a chance by introducing a known and predictable issue into the system? It’s usually best to address the root cause of any issues that may be present, rather than trying to compensate for them. Regards, -- Al |
To add to my previous post: What can often be more significant than the ratio of the two impedances, as defined at the worst case frequency (which is usually 20 Hz for preamps having capacitively coupled outputs, which means most tube preamps as well as at least a few solid state preamps), is how much **variation** there is in the preamp’s output impedance over the frequency range. And in that respect what is by far the worst case situation among the two preamps that are being considered occurs at the balanced output of the Calypso, where "the balanced output impedance was 112 ohms at 1kHz and above, this increasing to 3900 ohms at 20Hz due to the finite physical size of the output coupling capacitors." Differences in how preamp output impedance **varies** over the frequency range are IMO probably the main reason that some people report good results when the 10x guideline is compromised, and others do not. The less variation the better, if the 10x guideline is not met at 20 Hz or any other audible frequency. Regards, -- Al |
Thanks guys - this is great stuff... I knew I would get great feedback from you guys. Excellent - thank you !!! Al, you are right, both of these are poor matches for sure. I like being able to look at the specs and get feedback from people that understand this better than I. I know enough about it to ask for help and feedback. Both these pres seem to be poor specs matches even though I know they may sound great. The only reason I don't want go to a Pass preamp is because I really want to try and get tubes into the chain. I am getting new to me speakers delivered on Monday. Magico S5's and many of the folks tell me their sealed box design can really benefit from warming a little warming up of the lower midbass being one not used to the speed and type of bass these offer. Little tube richness in there plus I love tubes but know to properly drive Magico's would cost a fortune with tubes. Heck the Pass X350.5 is pretty close to a tube amp so a tube pre with this amp should make a tube lover happy - I hope :) My buddy told wanting tubes try and find a tube amp that can both get the desired output impedance and preferably one without a cathode follower. Those tend to cause different impedance swings verse a pre uses tubes in paralell to lower impedance. In my price range what do you think of a BAT VK50SE. It is in my mid $2k price range and people speak high of them. Some say they can be a bit dark but people that combo with Magico speaker might be a nice match. There is a 51SE but its a $1,400 more and out of what I want to spend. What do you guys think? Thanks so much! |
Pass Labs X350.5 amplifier with input Impedance 30k ohms Balanced or 20k ohms Single ended* I believe that you have those two numbers reversed. The way I read it on the Pass Labs website: Input Impedance (SE & BAL Kohms) 30/20. The way that reads to me is that the Input impedance is 30Kohms for SE, and 20Kohms for BAL. Still, the fact that the Hovland output impedance rises to 4.3 Kohms at 20 Hz would make it a poor choice for even an amp with a 30K input impedance. I would think a 50Kohm amp would be the minimum for the Hovland. |
The BAT VK50SE has an output impedance of 200 ohms. That would be fine with the PASS amp! Here are the specs! https://www.stereophile.com/content/balanced-audio-technology-vk-50se-line-preamplifier-specificatio... |
Thanks guys Darn I was all set with the BAT until I read this: The BAT's input impedance measured a high 220k ohms, and its output impedance at 1kHz was 414 ohms from both sets of output jacks. This figure rose slightly to 422 ohms at 20kHz, which is a negligible change. At 20Hz, however, the source impedance was a very high 4.6k ohms, which suggests undersized output coupling capacitors, even with the Six-Pak option, which I assume was fitted to the review sample. Care should be taken when mating the VK-500SE with power amplifiers that have an input impedance of less than 10k ohms. The voltage-divider action of its high source impedance at low frequencies and the power amp's input impedance will roll off the low bass. Read more at https://www.stereophile.com/content/balanced-audio-technology-vk-50se-line-preamplifier-measurements... One of the guys above smartly stated he thinks the Pass is 30k input impedance - so that is better but still everyone says must be careful with tube preamps and the input impedance specs are great unil 20k. i just don't want the BAT's bass to roll off. I mean 20k is low so I don't want to go crazy over the numbers but i also want to be smart and set it up properly. Do you think the BAT could be ok? |
I prob should have shared a bit more of the article. Into the Linn Klimax 500, for example, which has a low load impedance of 7.7k ohms, the BAT's response at 20Hz will be down 1.8dB compared with the level at 1kHz. That Jonathan still found the combination to sound fine is presumably due to this being outweighed by other, positive aspects of the BAT's sound. This rolloff at low frequencies can be seen in fig.1, where the lower pair of traces was made into a 600 ohm load, which is typical of some professional amplifiers and is a switchable option on the Jeff Rowland designs. Into a more typical 100k load (top traces), the LF response is flat down to the 10Hz lower limit of the graph. At the other end of the audio band, the output is -0.3dB at 20kHz, with slightly more audio-band rolloff into the low load. Channel separation was better than 80dB below the mid-treble, but with a rise in crosstalk to -67dB (L-R) and -76dB (R-L), due to capacitive coupling between channels. This will be subjectively inconsequential. Read more at https://www.stereophile.com/content/balanced-audio-technology-vk-50se-line-preamplifier-measurements... |
Jmcgrogan2 10-8-2017John, I’ve noticed that apparent anomaly in the specs of the Pass .5 amps in the past, and I’m pretty certain it is a mistake in the specs, and what was intended was 20K single-ended/30K balanced. All of the Pass .5 amps are spec’d the way you stated, but John Atkinson measured the input impedance of the XA30.5 as 20K single-ended/29K balanced. Also, the fact that the .5 amps require a jumper between pins 1 and 3 of the XLR connector when the RCA input is used would seem to indicate that the same input stage is being used for both inputs, with one of its two "legs" being grounded when the RCA input is used, and the balanced input impedance (representing the sum of the impedances between each leg and ground) should therefore be higher than the unbalanced input impedance. Best regards, -- Al |
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Fsmithjack, re the BAT VK-50SE (the reference in JA’s measurement writeup to VK-500SE appears to be an error), given my previous comment you would have a balanced output impedance of 4.6K at 20 Hz driving a balanced input impedance of 30K (or perhaps 29K), which is a ratio of a bit more than 6. You would also have a very wide variation in output impedance over the frequency range (from 414 ohms to 4.6K). Not ideal, and personally I wouldn’t risk introducing a compromise like that. The Atma-Sphere preamp that was suggested would certainly be fine in terms of impedance compatibility (Ralph’s designs do not have capacitively coupled outputs), but I don’t know if it would provide the warmish sonic character you appear to be looking for. Regards, -- Al |
OP, Reading through this thread it seems that you are reading reviews, listening to advice from others, and looking at specs for components. My suggestion is that you call Reno HiFi. They have new, used and demo product from Pass. They allow you to demo, and return if not satisfied. Get a Pass preamp and try it in your system. I don't own any Pass (I have an Aesthetix preamp and amp), but you already have the Pass amp, so I would recommend trying a Pass preamp. Good luck with your search. Jim Perry |
OK - so I am committed to make the BAT work if you guys think it will. I emailed Nelson also. That said: I can get a Pass Labs XP-10 for similar price but with my Magico S5 Speakers everyone says the lean sounding lower midbass can really be helped with the tubes. Not that Magico S5 bass is lean but the sealed cabinet is an adjustment for folks like me used to warmer ported sounds. Plus I love tubes and thinking best to keep some tubes in there I think that will be more toward my liking but I have never heard the Pass XP-10 and if it will be that much better match wise maybe I just go for that? Wish I could try it out in my system but buying used so not possible. Thanks Al Kali - buying used and really just looking at used pre's that are available today via the Agon, the Marts and the bay and are under $3k is how I have come up with the ones I am thinking about. Trying to not make a mistake and give my speakers the chance to sound their best. I will try my Bricasti direct also but I have always found I love preamps. Maybe it is mental but the Bricasti is also known to be at its best when volume is wide open and a pre does the attenuation chores imo ymmr. I will update everyone with what Nelson thinks but would love what you guys think - also maybe there is another pre i am overlooking or something. You guys are the best of the best. This is the best place for audio anywhere. |
... so I am committed to make the BAT work if you guys think it will.It will certainly work in a fairly reasonable manner, but as I said it would be introducing a known compromise, that IMO represents a significant risk that you would ultimately be disappointed. I’ll add that in addition to the relatively small but likely perceivable amount of roll-off of the deep bass that would result, undesirable phase shifts could very possibly occur to an audibly significant degree in the bottom octave or two, that would vary as a function of frequency. In any event, good luck however you decide to proceed. And thanks for the nice words. Regards, -- Al |
So if you are just looking at used preamps here this caught my eye. https://www.audiogon.com/listings/tube-just-factory-serviced-perfect-2017-09-25-preamplifiers No affiliations and a max output impedance of 1200 ohms would seem to work on paper, I'm not much of a measurements guy. It's also well constructed with a very stiff outboard power supply. I've never heard any Canary stuff personally but its always looked intriguing to me and this fits your price range. |
Almarg - You are the man! Thank you Jim Perry - very good idea and certainly makes sense - but I'm buying used because new and demos are so much more money and my recent speaker purchase has the old audio fund barrel down to scraping status - I was hoping to spend $2k and also get a used XLR IC - for balanced as I have one already but thought to get a better pre now and get a cable later after saving a bit - the high $2k range seems to open the used pre world to so much more better options - the Pass XP-10 I have found is about a $1000 less then Reno's so that scraps that but thanks the is a good idea. jond - wow that thing looks like a beast and right at my price range - I never noticed it - thanks - anyone know if this is a good one? I love the 6SN7 tube. I actually have a mint pair of NOS bad boys and Gray glass RCA tubes already? yogiboy So here is what I have - all right about $3k and a just bit more than my target price but its doable. What do you guys think of these? CJ CT-5 CJ ET3SE CJ 17LS2 so bat vk-50se or the canary or these CJ's?? I am buying one today - thanks !!! |
The title of the ad for the Canary preamp refers to it as a CA-800, which is a one-chassis design (having a specified output impedance of 650 ohms), but the photo and the text indicate that it is a C800, which is a two-chassis design (having a specified output impedance of 1200 ohms). Also, I’m pretty certain that the word "maximum" which appears after the reference to a 1200 ohm output impedance applies to the subsequent spec on gain (meaning the gain that is provided when the volume control is at max), not to the output impedance spec. So I would be wary of the possibility that the output impedance could be considerably higher than 1200 ohms at deep bass frequencies. The CJ CT-5 is ok in terms of impedance compatibility, based on JA’s measurements. The 17LS is as well, so I suppose the 17LS2 and the ET3SE are likely to be also. CJ preamps tend to have high gains, which in some systems can limit the usable range of the volume control to undesirably low settings, but in combination with the moderate gain of the Pass amp and the not particularly high sensitivity of the Magico S5 I suspect you’ll be ok in that respect. So given also your desire for a warmish sonic character I would vote for one of the CJs. Good luck! Regards, -- Al |
Hmm, after looking a little further I see in "Sam Tellig’s" comments about the 17LS2 that one of the differences between it and the 17LS involved the introduction into the design of ten 2uf Teflon capacitors. **If** one of those is used as the output coupling capacitor for each channel (rather than two of them in parallel on each channel, or something else altogether being used as the output coupling capacitor), that would translate to an output impedance upwards of 4K at 20 Hz, too high to be optimal with a 20K load. So I’m uncertain about the suitability of the 17LS2. Regards, -- Al |
So Al is right the word maximum is a bad cut n paste from the gain spec. It is a C-800 Mk2 so that impedance spec is right but no idea how it varies at different frequencies. Whichever way you go good luck I know its hard taking a blind leap of faith but at least buying used you can often resell for minimal loss. |
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See if you can find a used Manley Jumbo Shrimp, it has a real low output impedance! https://www.upscaleaudio.com/collections/manley-laboratories/products/manley-jumbo-shrimp |
John, I’ve noticed that apparent anomaly in the specs of the Pass .5 amps in the past, and I’m pretty certain it is a mistake in the specs, and what was intended was 20K single-ended/30K balanced. Al, thanks for your input. I might have to contact Pass directly to get the true numbers. I just assumed that the 30K SE/ 20K BAL was correct because of Threshold history. Many old Threshold amps had a SE input impedance of 50Kohm while the Balanced inputs were rated at 600 ohms input impedance. https://www.stereophile.com/content/threshold-stasis-sa12e-power-amplifier-specifications Also, Coda amps, which were designed by 3 ex-Threshold engineers, always had very low balanced input impedances as well. The spec sheet on the Model 15/15.5 shows an SE input impedance of 50K with a Balanced input impedance of 1K ohms. http://coda.cc/product/index.php So I just assumed it was something in this family design that always had the balanced input impedance lower than the unbalanced input impedance. It does look like Nelson has addressed this flaw with the .8 series. Cheers, John PS: I see in Stereophile's measurements of the XA60.5 amps they measured a 17K input impedance in both SE and BAL. Who knows which figure is right? https://www.stereophile.com/content/pass-labs-xa605-monoblock-power-amplifier-measurements |
If I go SS pre for max matching I have these 2 options for exact same very good price. The matching brand via same company obviously would be best matchm but have heard more than a couple times it can be kind of sterile which I hate and the Ayre. No one ever calls them sterile. Same money Pass Labs XP-10 Ayre K-5xeMP For $800 more and money matters CJ ET3SE or add another $300 ARC LS27 These tube amps have low enough source impedance to work as they use JFETs to solve the problem. I'm leaning towards Ayre or CJ I think although part of me still wants the BAT - what do you guys think? Thx |
Oops guys just got back me. Ayre K-1xe for $150 more than the ARC - i head these are great - long in the tooth but great - really want the one out of these that is the best but also match impeidamce wise and will match my Pass amp best and work with Magico S5's - so I can swing any these price wise? |
With your decision-making, perhaps take into account tube-rolling. I have a tube preamp (Musica Bella) & tube dac (CJ). Neither of which presents the old-style soft, bloated, tubey sound. Quite the contrary, the music is crystal clear. With tube-rolling, the sonic signature of each component can be significantly altered. Different tubes will offer different presentations. |
I know I love tubes but want the best matching pre but also the very best pre for the money. I just had a nice fellow offer me a nice deal on a Ayre K-1xe but at a better price. Quite a bit less than the tube amps and only $300 more than these Pass Labs XP-10 Ayre K-5xeMP Looks like Ayre K-1xe will be my pre of choice to go with Pass Labs X350.5. Really wanted to get some tubes in there but from and this is an older pre but from what i have heard it is an excellent and very non solid state sounding from a clinical or flat standpoint. What do you guys think. That's funny it started with either a Hovland or Aesthetix or BAT but evolved toward a Ayre K-1xe. |
You will love the K1 The first time i heard it was magic. I never knew Cowboy Junkies Trinity Sessions Margo Timmons was also singing with the support of her brother softly but so vividly in the background.Luka Blooms 12 string had life that was kind of magic Let it run in for a bit after about four days or so and you should get what I heard. Best JohnnyR |
The Ayre and the Pass Labs are both great SS preamps. They will both work great with the proper surrounding components. That said, I find it odd that you have heard that the Pass Labs unit can be sterile, while no one finds the Ayre to sound that way. This does not mimic my impressions, but c'est la vie. Personally, I have no desire to ever return to a SS preamp. However, if forced to pick a SS preamp, my clear preference would be a 7 series unit from Klyne Audio Arts. |
Thanks audioconnection - i love that album - ill listen for it. jimcgrogan - those statements about pass xp10 being sterile i should have been explained a bit more and have to be taken in context though - as they relate to tube amps. They can also be more dynamic and precise so never knocking pass pre - I love pass products but to be fair the xp10 is the entry level pass product vs a reference cost no object preamp. If I could had got a xp20 but those are 3 times the money . |
OK guys - went to bed - done deal - buying the Ayre K-1xe but woke thinking man I am going to want some tubes -awwwe... Opinions guys - I am deciding soon - if you had to choose what do you think - they are only a $200 apart price wise. CJ ET3SE - full warranty with about 20 hours on it Ayre K-1xe - upgraded to xe in 2010 If you had to choose one right now what one? other gear recap Magico S5 Speakers - (being delivered today - so excited :) Pass Labs X350.5 amp Bricasti M1SE DAC microRendu w/Uptone Audio ISO Regen, Amber Regen, (2) LPS-1, JS2 HiDiamond Full Loom and matching conditioner (3) Verastarr Grand Illusion Signature II AC cables (dac,pre,amp) (2) Sumiko S.9 Subwoofers (hopefully not needed w/Magico's) Just need to decide is CJ ET3SE or Ayre K-1xe will match the best with my gear above Room 15 x 24 w/cathedral ceilings set up on the long wall Music - typical mix but no hard heavy metal or large scale orchestra but most everything else. |
(((Pass Labs X350.5 amplifier with input Impedance 30k ohms Balanced or 20k ohms Single ended*))) I love tube preamps don't get me wrong. in your unique situation with regard to the lowish input impedance, the only reason to install tubes would be the well-intended committee peer pressure agreement choice. Most of the folks offering advice are not running tube preamps into lowest impedance amps or suffered the bleak lifeless consequences. so, in reality, they believe in their bias. its a choice of optimization of course if your not totally blown away w K1 you can easily sell it for close to the deal you picked it up for and have this experience under your belt and revisit with the expectation of differnt results. My ten buck says you'll be way too busy enjoynig music JohnnyR |