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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
128x128Ag insider logo xs@2xfsmithjack
audioconnection
1,271 posts
 
(((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 
almarg's avatar
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almarg
9,670 posts
 
Fsmithjack, I’m not in a position to recommend a choice between the K-1xe and the ET3SE, and the recommendations you’ve received in favor of the Ayre come from members whose opinions and directly relevant experience certainly command great respect.

To add, though, to my earlier statement that:
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.
... I subsequently found the following statement in the manual for the ET3:
MAIN OUT:Connect to the input of your amplifier (or crossover in a bi-amplified system). We recommend the use of an amplifier with an input impedance of 20k ohms or higher. Since this preamplifier inverts phase, it may be necessary to invert the speaker leads to maintain correct absolute phase.
Also, given the reference in CJ’s description of the ET3SE to the use of Teflon capacitors it wouldn’t surprise me if similarly to the 17LS2 it uses two 2 uf output coupling capacitors in parallel, for each channel. That would probably result in an output impedance at 20 Hz of a little more than 2K, the exact value depending on the output impedance of the circuitry that lies ahead of the cap. That seems consistent with a 20K minimum load impedance recommendation, which appears to be satisfied by your amp, albeit just barely.

Good luck, however you decide to proceed. Regards,
-- Al

dlcockrum's avatar
dlcockrum
2,190 posts
 
Another great post, Al.

fsmithjack, the review below accurately articulates my long-term ownership experience with the K-1xe:

http://www.soundstage.com/revequip/ayre_k1xe_v1xe_followup.htm

Note the line: "You won’t mistake and K-1xe and V-1xe for tubes, but you won’t care either." Pretty much sums it up IMO. Also notice the reviewers emphasis on the K-1xe’s compatibility with a wide variety of amplifiers...

If you do get the K-1xe and plan to use it via its SE outputs vs balanced XLR, take heed to the manual re: that it inverts polarity via the SE outputs, so simply reverse the positive and negative speaker cables on both right and left amplifier outputs to correct.

Dave

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fsmithjack OP
712 posts
 
Thanks - this might be a dumb question but until funds get back up a little can I used rca single ended from M1 Dac into the Ayre then use balanced out to the amp? I know best but would it be ok for short term? Thanks  
almarg's avatar
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almarg
9,670 posts
 
Fsmithjack, re your question just above, that would be no problem.

BTW, I see that the K-1xe has a relatively low specified input impedance of 10K per phase, which means a balanced input impedance of 20K. And I suspect that it probably also means that the unbalanced input impedance is 10K, although that is not stated explicitly.

Your Bricasti DAC will have no trouble with either input impedance, but if you envision the possibility of ever adding a tube-based source component to your system chances are good it would have the same kind of impedance compatibility issue with the preamp that we’ve been discussing about the preamp-to-amp interface.

Regards,
-- Al

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