Tube Line Stage Preamp to Drive Class D Amp
NCore amps work well with tube preamps at least the NC500 based ones do so the NC400 ones should be no different. There is a remote controlled Odyssey Candela for sale on Audio Circle for $950. Quality preamp for a good price. https://www.audiocircle.com/index.php?topic=159242.0 |
jbhiller The Nad M22 input impedance is a feeble 17kohms as are most Class-D's, be careful with tube preamps as most like much higher than that, tube preamps that have paralleled cathode follower output stages "maybe" low enough in output impedance to do the job, but many tube lovers don’t like the sound of them (to close to solid state is the complaint) but then muso’s do like them?? If you feel you need a bit of tube euphonics, to be safe stick with a solid state preamp that has tube colouration’s for a reputation. Or you could go with the Schiit Freya it has tube solid state or passive all switchable on the fly, the very best volume control and has multiple input outputs xlr and se. And it’s all remote controlled. Also you can send it back if not happy. the tube stage seems to be a paralleled cathode follower as it’s only 210ohm output impedance. http://www.schiit.com/products/freya Cheers George |
JB - fwiw I’m using a Schiit Freya pre with a Merrill Audio Class D power amp (Taranis). Very happy with the resulting sound. I use balanced ICs to the Taranis. Early on, I listened mostly to the Freya’s JFET buffer mode. More recently, I got some very nice sounding NOS 6SN7s and now listen in tube mode pretty much 100% of the time. Tubes seems to provide a deeper soundstage and (richer harmonics?) than either "passive" mode. George is right to caution about impedance matching. I followed a generally recognized rule of thumb that the load impedance of the amp should be at least 10x (some say 20x) the output impedance of the preamp. With the Freya, output impedances for... JFET (SE) mode = 75 ohms JFET (Bal) = 600 Tubes = 210 Comparing these values to the 17000 ohm input impedance that George cites for the NADM22, I think the Freya would be "compatible". I had been using 78wpc EL34 tube mono blocks and a different tube preamp before the Taranis. I don’t find myself missing tube amplification. I also have a Hegel H200 and a First Watt F7 that I switch off to periodically from the Taranis; so there is some on-going basis for comparison. They all have their virtues. The Taranis gives a good accounting of itself in that company. I am greatly enjoying music from the Taranis driving Totem Forest speakers. Hope this is of some use. |
Thank you!! George that’s a great idea! I could spend little, keep both summer and winter systems and still have tubes on the line stage with the muscle of the NAD. Ghostbouse, I really appreciate your anecdotal advice. I think this route is a reasonable way to go. And, I need a remote. Getting up to adjust volume is not ideal. Its good old to hear you like this combo with Totem Forests. I’m very familiar with them. It’s also good to hear you aren’t missing the tube power amps. I welcome ofger ideas too! |
You are welcome, JB. I've had the Freya going on 2 years now (p'chsd. Jan '17). No problems with it at all other than some noisy tubes when first received (Russian NOS) that Schiit promptly replaced. With well-screened tubes, it is very quiet (even with volume full up and nothing playing). In JFET & Passive modes, it is dead silent with volume all the way up and ear only inches from the speaker (I don't hold that position too long, however :-). If you expect to do a fair amount of tube rolling, get some socket savers (Parts Connexion has some that fit. Not all will). These will save the factory sockets and put the bottom of the tubes just about even with the top surface of the chassis. As supplied, the base of the tube is almost entirely inside the chassis. Socket savers make changing tubes easier and put more distance between the hot tube and internal electronics. If you get one, I hope it works out for you. You'll have 15 days to decide. I would recommend running signal to it 24/7 as it seemed to me to take some time to "open up". You can pull tubes and operate in JFET or passive mode during this time so as not to put hours on the tubes. That is one design aspect I would like to see changed: install a switch or circuitry such that tubes are not energized when using JFET or passive modes. Good luck whatever you decide. |
Ghosthouse, I ordered the Schitt to give it a run. If it's quiet and adds back tube flavor I may keep the Class D in winter operation too. I'm optimistic that it will sound great as folks seem to love it on forums. The engineering/design is strong. I really like the volume control and the active/passive function. If it ran 12au7s I'd be really happy as I have a pile of NOS in that compliment for my Primaluna. I also like saving a bit of energy and heat. I will follow back up with a report after I get it and put it in action! |
Like I said, hope it works out for you, JB. Quiet at the least, though wondering how "tubular" :-) it will be for you compared to your PrimaLuna. On the other hand, it might make a nice combination with the NAD (use those balanced inputs!). "Folks seem to love it on forums." I’m guessing one you could mean is HeadFi. There’s definitely a lot of Freya love over there on the Freya Impressions & Tube Rolling Thread. I hear you about the 12au7s. I have a shelf full of EL34s and 6CA7s with nothing to run them in right now. If I lost my mind and bought another tube amp, PrimaLuna would be at the top of my list. In fact, was looking that direction when I learned about First Watt and blew my $ on the F7 (it don’t take EL34s). Looking forward to your report. |
The 4P1L single ended Triode preamp. is about as pure as you can get and a very linear Tube . Look up Radu Tarta, a Great vacuum. Tube amp, preamp builder and a preamp like this under $2k Totally transformer based much much less expensive then anything equal commercially built . I recently purchased a Gato 400-S digital integrated amp . A fantastic match. he is building one for me actually my second from him . |
Thank you!!Glad to be of help, they are excellent value for money, as the chassis don't cost the earth, it's what's inside that counts. And it has the goods, if it were in a "glitzy" chassis people would buy it at $10k. And Mike Moffat's no slouch when it come to EE design, he made Theta what is was in it's heyday. Cheers George |
