Matching tube preamp to ss amp

rule of thumb is 10x - so you shd be fine

u can do better than a nad though...

@oldgzzrr

oldgzzrr Prima Luna Evo 100 with an output of 2800 ohms

Looking at this, https://ibb.co/MndcmrB the Prima Luna Evo 100 uses 0.47uF output coupling caps. With the Nad’s 25k input this equates to -3db at 14hz, -1.5db at 28hz and - 0.75db at 56 hz. So that output impedance of 2800ohm of the PL, gets even higher than 2800ohm as the frequency goes below 100hz

The output coupling cap really should be a min 1uF preferably 2uF

And if it were used with amps with 10kohm input impedance, which are becoming more common now, especially with Class-D, the those bass roll off figures double to -3db at 28hz, -1.5db at 56hz and -.75db at 112hz.

If you can solder, it looks an easy 1/2hr job to do from the top as it’s plate through pcb. Just heat pull out old and cut to length and solder the bigger ones in place. Something like these.
https://www.partsconnexion.com/MUNDORF-70328.html
https://www.partsconnexion.com/SOLEN-51541_ss43777.html
https://www.partsconnexion.com/SOLEN-51541_ss43745.html
https://www.partsconnexion.com/product49152.html


Cheers George

According to my research, yes 25 KOhm, the Nad would be used until funds available for a better amp.

Thanks George, Unfortunately that would be something beyond my abilities. Are you saying as is, these two would not be a good match? the Nad would be used until funds were available for a better amp.
Jeff

Are you saying as is, these two would not be a good match?

Yes as they are they’re already borderline 1 : 10 (output to input) ratio. And with the coupling caps raising that 2800ohm output impedance even higher at low frequencies the bass quality "could" and probably will suffer. It would be far better if those Prima Luna output coupling caps were 2uf instead of .47uf.

Do get me wrong, it's safe to use it though.

Cheers George

I agree with George, it’s borderline. Under normal conditions it shouldn’t be a problem, but during peaks and transients, there might be noticeably weak bass.

Don't play the 1812 Overture.

There are plenty of tube preamps that have less than  2800 ohms output impedance.

pmm is correct

conrad johnson tube pre's for instance, have for years made their low output impedance an important selling point

cj premier 16ls2 is <700 ohms
cj et5 is 100 ohms

It is not be the best match, as others have said,  it is borderline. How low in the bass region do your speakers go? How do the pair sound to you? While saving for another amp. look into ones having input impedance of 50ohms or greater. 

I have not purchased the pre yet, it's about at the top of my budget right noa at $2K. Speakers are Qacoustics Concept 40 that are rated to go down to 53 hz 90 db sensitivity

There are a number of tube preamps  within your budget that have a lower output impedance. Jolida, Aric Audio, Quicksilver, Atma-Sphere, Van Alstine, Rogue, and others. 

Otherwise look for an amp with higher input impedance. Either way when changing amplification, I would improve on the impedance ratio.

Giving your speakers are not attempting the lower octave you may not be hearing a problem with your current matchup.

+1 @mesch .
For a modern preamp 2800 ohms is high. 

Actually 2800 ohms isn't bad- what's important is the output impedance at 20Hz; the 2800 ohm figure was probably at 1000Hz. If the output impedance at 20Hz is greater than the 1000Hz value (which is common unless the preamp does not employ an output coupling capacitor), you will experience less bass impact with the NAD.


This is one of the reasons tubes get docked for bass relative to solid state. But its more a matter of properly matching components than whether tubes can play bass right or not!