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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
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almarg's avatar
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almarg
8,673 posts
 
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

erik_squires
5,268 posts
 
Of course, the solution is to get another pair of 2uF teflon caps and wire them in parallel. :)
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almarg
8,673 posts
 
Further update: I see that in the latter part of Sam Tellig’s writeup it is stated that the 17LS2 design does in fact use two of the 2uf caps in parallel, on each channel. Which is fine in terms of impedance compatibility with a 20K load.

Regards,
-- Al

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jond
3,400 posts
 
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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