Is this impossible?

[david.rogers]

This may not be a new topic - feel free to flame me if it's a bore.....

Seems to me the main drawbacks of the old glass bottles are:

- the difficulty of handling very small signals - e.g. MC pickups - without hiss and/or hum. I await the results of the grand shoot-out with interest

- generating high power (75 - 100 watts) required to drive modern full range loudspeakers to produce something like the sound of a realistic orchestra in my living room

- wide frequency range - 10Hz - 100MHz(?)

Any of these is possible in isolation, but finding a design for a valve amp that delivers SET-like transparency with the oomph to drive B&W 801s or Wilson loudspeakers seems close to an impossibility - at least without needing a substation in my garage and a PS delivering 1000VDC or enabling me to do away with my ch boiler!

So.....what do our gurus think is the closest we can reasonably get to this spec? How about a 75W full range amp that could be built at reasonable cost (although an expensive O/T would be allowed as an exception to this rule). Maybe an transformerless design a la Futtermans?

Any suggestions?

[Clive]

It's not a drawback of old bottles, it's the drawback of some modern speakers that are hard to drive. What you ask for is possible and even available but why start off with expensive speakers that dictate such an expensive amp route when simpler (and probably even better sounding) speakers release you into a more reasonable valve amp world.

Where do you want to get to? Well, I wouldn't start from here.

[pre65]

Hi-i am no expert ! the way i am going is with more sensitive speakers.
My 89/90db KLS3 speakers are having to make way for 95db Adire HE10 to make a better match with 300b S/E and perhaps ,at a later date something even less powerful (than 8-9 watts).
an old adage is that with valve amps,the first watt is the sweetest,so why not try to borrow a sensitive pair and see what you think.got to be cheaper than building a monster amp i would think and hopefully better.

Philip

[david.rogers]

Well it's not really practicable or affordable for me to go the sensitive speakers route as I already have a pair of not especially insensitive speakers (needing c 50 - 60 watts to drive them properly). I spent years looking for speakers I felt I could live with for a long period, so am not likely to abandon them now!

[pre65]

Hi-at the end of the day you must proceed the way of your choice.

my personal opinion is as my last post.

with valves i am finding that "less is more"

Philip

[Clive]

You might find that a Chinese 805 amp putting out 40W will drive your speakers, often you need a little less power with valves than solidstate. I still fear that if you want all that SE gives then the crossovers in your speakers may restrict the sound somewhat.

[NickG]

I think you are onto a path of failure there. Yes, you could use a Mac or AR push pull amp for those speakers, or any other 6550/88 based PP design. Not sure actually what frequency response you need, it certainly is up to 100mhz.

IMHO, you are not going to get what a SET is good at with those speakers, yes you can get 50W from a set, but its such a difficult thing to do (just look at the problems Paul has had to work through to even have a breadboarded amp with that sort of output), and if you want to be below 1000v there are very very few choices, all will involve A2 and immense heater current, so thats another huge obstical to do right.

I don't know what speakers you have, but the chances are a SET to drive them and do it well may well involve as much money just for the transformers as your speakers cost you.

[Clive]

Frankly, I reckon you'd be best off with a meaty PP amp. Maybe 4 6550s per side. This sort of amp would suit the speakers more than an SE.

[Andrew]

Or an OTL.....speak to Dave the Vinyl Junkie, he's managed to get a sound he's very pleased (read works for him) with using OTLs and not particularly sensitive speakers. The OTLs he has are from a well-known competitor. I won't offend ours hosts by mentioning them by name.

cheers,

-- Andrew

[david.rogers]

Thanks for your comments guys. I always knew the answers that would come back would be along the lines of forget it, get a 300B SET amp and change your speakers! Well, for the record, my speakers cost £2500 and sound damn good on the end of an EL34 PP amp (C-J). However, the system DOES run out of steam on massive orchestral climaxes (well age gets to us all...snigger, snigger). I guess I am not looking for perfection but for something close to the best sounding (ok, ok) 50W per channel bottle amp. I built the WAD 70W EL34 paralleled amp - didn't like it! Something like the WAD 5881 amp with a bit more grunt would suit very well. If anyone can point me at a suitable design/schematic for me to breadboard I will be a happy bunny (Easter being upon us).

Cheers and thanks in advance......