Recommended Preamp for pairing an Adcom 555II Amp and Theil CS 3.5 speakers
My Bryston 0.5B preamp was inadvertently put down over the holidays by an incident now known as 'The Sippy Cup Mystery'. Regardless of the cause, I need a new preamp for my system. I am driving a pair of Thiel
3.5 (with the electronic bass equalizer) speakers with an Adcom GFA-555II amp. The majority of the eclectic music (classical, 80s, folk, funk) being played on the system is streamed from iTunes through my Audioengine B1 DAC. I have read a number of posts with various recommendations for the GFA-555II or the Thiel CS 3.5s but not for their paring. Short of winning the lottery this week, cost is a factor. Any suggestions or directions would be very much appreciated.
PLease join us over on the Thiel Owners thread since you own CS 3.5 speakers. Several of the guys also own this model as well. If you enjoy the Adcom 555 II amp, I would certainly consider an Adcom pre to match. At one time, I owned the 565 pre-amp / 555 power amp, then 5400 power amp combo on B&W 805 speakers.
You might want to be mindful of the Adcom’s low input sensitivity and input impedance numbers. The impedance might be a bit low for some tube pres output impedances and the high sensitivity could make the volume control on some tube pres (like some c-j’s) have rather restrictive range.
Stereophile's John Atkinson:. "
Jim Thiel has used some form of conjugate load system in his crossover designs to give such flat curves with frequency. (This is where elements are added to the crossover to compensate for phase and impedance changes to result in a simple resistive load.) I would suggest, therefore, the Thiel CS3.5 should be easy to drive, even given its 4-ohm rating."
I have had the older 555 paired with the 750 preamp for many years in my vinyl only system. I recently bought a full-tube preamp for another system and used it with the 555 for a few days and it really rounded out the rough edges, especially when played at higher volumes. There's another thread where someone is asking for tube preamp recommendations and should give you some good ideas. Lots of options out there, new or used.
I have used the GFA 555 with the GFP 565 and while the pair is very good sounding (and the 565 has a great phono section if your into vinyl). But, I will say that when I installed the Modwright SWL 9.0 SE ($1000 used) it really showed me how beautiful sounding the Adcom 555 can be. A tubed pre amp is what I highly recommend. Manley labs shrimp?? possibly. Doge 8 Clarity, Dehavilland Ultraverve III, these are all tube based and around your price range and are very special indeed. Also, all of these will have very low output impedance to drive the Adcom no problem.
iowanna33 Recommended Preamp for pairing an Adcom 555II Amp and Theil CS 3.5 speakers
Your Audio Engine B1 has Analog Output: 2V Max. Analog Output Impedance: 57 Ohms.
And your Adcom 555II as was pointed out has: 100kohm input impdance only needs 1.75v in for full 200w output
As you can see the 2v from your B1 is more than enough to run the 555 to full output, so you don’t need an active preamp with gain that you don't need. Also the output impedance of the B1 is 57ohms and this is a great match for a passive preamp, which will aslo match prefectly with the 555’s 100kohm input impedance.
Get one of these and save a fortune, you’ll have the most transparent/dynamic sound and save a fortune on not needing a fancy/expensive preamp that will colour the sound in comparison.
While george is right about the specs on paper, the actual outcome is a different story. I have tried the $49 Schiit Sys between my CD player and 555 and the sound quality was completely lifeless and flat as compared with my Adcom preamp and nowhere near the sound quality when I experimented with the tube preamp in there. The volume control on the Sys is also marginal at best. But it's definitely worth the $49 price when used as an input selector.
@kalali You beat me to it! I was going to respond to George much as you did above that my anecdotal understanding of passive units is that the PRAT as the Brits like to call it, is diminished. I'm not making a categorical statement here, just that anecdotally over many years reading lots of audiophiles' experiences, that the drive is diminished by passive gear.
I have tried the $49 Schiit Sys between my CD player and 555 and the sound quality was completely lifeless and flat as compared with my Adcom preamp and nowhere near the sound quality when I experimented with the tube preamp in there. The volume control on the Sys is also marginal at best. But it's definitely worth the $49 price when used as an input selector.
iowanna33 This all depends if you want the source to be transparent or you want to colour the sound, which a tube pre will do.
If you want to have it all, get the Freya and you have passive, solid state, and tube that you can change on the fly while listening, all with little or no gain, which in your case you don't need. Many here and on other forums that have bought it prefer the passive mode after they've lived with it for a while.
And in it you have the best volume control with the Freya which is 128 position switched relay volume control, better than any rotary volume pot, and it's all remote controlled, 3 x inputs, 2 x outputs all RCA or XLR. http://www.schiit.com/products/freya only $699 and you can send it back if not happy, win, win.
I have a pair of 555 Mk2's driving a pair of Kef 107's and I use a Cary SLP03 with them. I replaced an Adcom GTP760 with the Cary and there's just no going back. You can find this pre amp for around $1000.
Please explain to all here, what the difference is of the "drive" to the poweramp in electronic terms, whether it’s driven from a preamp output or from the sources output. when voltage output is sufficient enough for the poweramp to be clipped and impedance is a match is fine.
Nelson Pass: "Think of it this way: If you are running your volume control down around 9 o’clock, you are actually throwing away signal level so that a subsequent gain stage can make it back up.
Routinely DIYers opt to make themselves a “passive preamp” - just an input selector and a volume control.
What could be better? Hardly any noise or distortion added by these simple passive parts. No feedback, no worrying about what type of capacitors – just musical perfection.
And yet there are guys out there who don’t care for the result. “It sucks the life out of the music”, is a commonly heard refrain (really - I’m being serious here!). Maybe they are reacting psychologically to the need to turn the volume control up compared to an active preamp."
When considering a pre that will be used with Thiel 3.5's I would suggest that one consider those pres that either have an extra analog tape loop and/or preferably have most of their design parameters based around single ended output, unless one either has two Thiel 3.5 eq's modified to mono balanced operation or one can find a better stereo balanced eq with at least 12 dB of boost (and good luck with that). Otherwise the extra money and effort spent on balanced operation will be for naught.