if your speakers were updated and with new panels, I would buy VTL TT 25 monos and let the world roll......
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They don't really need 30. I use to use a Dynaco Stereo 35 power amp which had 17.5 watts a channel and my friend, who has a pair I sold him in the mid 70s, uses a rebuilt Heathkit with 8 watts. The Marantz 8B in triode, which was 12-15 watts [ I think, it has been a while], was also very good. Stability is the main thing as the impedance curve is extreme [ under one ohm in the top end]. The original Quad tube amps are being produced again but are not cheap. I never found the 57s very sensitive to differences in amps and I used them from 1964 to the time the 63 replaced them.
I share your enthusiasm for these speakers.
I have tried different SS / Tube amps with mine.
The original 303 amps they came with were good for 28 wpc at 16 ohms and 45 at 8 ohms.
I have a 405 amp.
Quad recommends resistors be put in the 405 100 wpc amp to limit its output with them.
Does anyone know what power this limits the 405 amp to - I am assuming about 50% ? This would answer the question as well.
I agree with Stanwal that they need very little power to sound "full".
And I am surprised at how good they sound with the 33 pre and 405 amp. These vintage Quad gear are readily available.
The original 57 was designed to be used with 15 to 20 watt amp, because the early production did not have protection circuitry and people fried the speakers. Later versions, came with protection circuitry. There are new protection boards you can buy. With them installed, I've heard people using 150 to 200 watt amps without frying them, but I guess they are careful not to play cannon shots through the 57s.
Thanks for all the input, folks! I do have a pair of 405-2s, with the voltage limiter installed. This reduces the output of the 405-2 to 50 watts into 8 ohms (20 volts maximum). For the price of a used 405-2 (around $250), the sound is amazingly good.
But, the 405-2s don't reveal the full glory of the Quad's legendary midrange. The best amp I've tried so far is the Macintosh MC275. A truly spectacular marriage of two audio legends. The Quad II is widely recommended, but it has such high distortion at even moderate volumes, I can't seriously consider using it.
I'm seriously considering installing the protection circuitry, but I'm worried about their audible effect on the sound.
Lists are great tools but just first base in this hobby.
I have no idea how good the hearing is of anyone that comes up with these lists or what their room, speaker placement and other gear is - in that order. I trust my ears only unless I am helping a friend set up speakers, in that case its his or her ears.
I listen around 85-90db with my 57's. Which means peaks above that getting close to their limits of 100db from what I have heard. They are a ridiculously easy load to drive compared to my other speakers.
As far as the 405 is concerned when put in a system that taxes that amp - I dont know never tried - maybe that is where some of the remarks come from. In my system with my panels I hit my db levels very easily. Its a piece of cake for the properly functioning 405 I think. For what you can buy them for anybody starting out with these speakers I think would be foolish to at least not give it a try with matching Pre and listen to what Quad "wanted you to hear". Then when u are ready get that nice little tube amp - there will always be someone waiting to buy your 405.
YMMV - My opinion only
When I had a stacked pair of %&'s I used an old Bell 2481 tube integrated,circa 1961 and stock 18 watts.
I also used the AtmaSphere S 30 OTL amp.
In my experience, a tube amp around 30 watts is fine.
Solid state amps around the same wattage have also been reccommended(Bedini 25/25 etc) but I've always found out that tube amps sound louder than their similar wattage solid state contemporaries.
Trying to push a 30 watt solid state amp to the same volume as a 30 watt tube amp may make for a nasty surprise.