An afternoon with valves

i recently completed a pair of these there also avaliable as a stereo pair complete with case for around £600.They kick out 90 watts and sound very nice.construction and set up is very straight folward,hardest bit was building the case's . ive got the instruction manual somewere as a pdf file if yer intrested
 
Last edited by a moderator:
Originally posted by penance
This is where my knowledge falls apart. The way i understand it is that it may not be so much power output but more so current delivery. With my electrical background this makes sense, but wireing houses doesnt realy apply to audio.
I currently have the Shearne amp, thats 60W, but rarely does it go above 11oclock position, i would rather have a lower sound level with better detail etc...
What i do want is control of those domes, whatever the volume.



Amen


Not always that easy to do tho
Click to expand...

I would be quietly confident that a 20w push pull amp with decent sized output transformers would go louder than the 60w shearne... although I havent heard the model.

My old 35w Beard P35 was louder and more powerful than my previous to that Musical Fidelity 80w per channel solid state amp into the 4 or so sets of speakers I tried it with.

Whichever amp you end up with, Im as confident as Robbo that you wouldnt have a problem with the products you're talking about, but it might give you reassurance to find out for yourself.


Cheers
Chris
 
Penance

Did you mention this to Greg. I believe he used (or maybe still does have) a Kat88 which is roughly what you are thinking of.
 
I wish it was as easy as that.

For instance the LS3/5a with a sensitivity of 82 dB would on paper need a lot of power. However I have read of 4w SET amps driving them, at least loud enough for the owner, and yet then reading how an old NAD 3020 didn't drive them very well. But the NAD could drive a pair of Isobariks well enough for some reviewers back in the 80's. Also Quad ELS57 partnered nicely by Quad II's (13watts) when other amps just curl up and die (the 57 goes down to 1 ohm in the upper trble region).

Really it is a case of suck it and see, so as ever it is down to personal auditioning.
 
Yes it really is not that simple, speakers which appear to be easy to drive sometimes don't respond well, and vice versa....

when engineers talk of 'drive', there are a few issues...

voltage drive, greater than the psu and it clips, usually, sensitivities are in terms of volts, so the more volts an amps psu, likely the more powerful it will sound, as power=volts AND current.

current drive, due to low impedance, more current needed, this is why you parallel lots of transistors to get more current.

Valves are appaling with current, the output tx converts the high anode volts to a lower volts, and the current correspondingly goes up.

now loads are not just resistive, they are capacitive and inductive, which means they vary with frequency, so you have to privide current to charge the capacitor of the cable, of the speakers, etc...

also, low impedances, say 4 ohms increase the ouput stages distortion, and can stress the feedback loop, too.

So when you see 'drive' it could be volts, current, capacitive load, 87 dbs type, 4 ohms type.....ah well.....
 
Dynaudios usually have quite a low impedance, but are not very reactive which at least gives an amp a chance. Any amp that gets close to doubling it's watts into lower impedances eg, 100 watts into 8 ohms, 180 watts into 4 ohms has a stiff supply and is suitable for speakers like Dynaudios. This model seems to work pretty well with solid state amps.

The problem comes when you get into valve amps which don't get close to this model {well ok the EARS do, but look at the transformers needed} but can often sound fast and driving into loads that they really have no right to be attempting. This is where Hi Fi seems to enter the role of the unexplained, and as rightly stated above we have to suck it and see. I agree that the old ELS are unbeatable with valves but the specs would say not.
 
I looked at the EAR amps Paul, :eek: slightly out my range unfortunately.

As many have mentioned, suck and see will be the case.

I did have a fleeting thought of a speaker change, but TBH the Dyns will stay :)
 
I would like to try a valve amp as an experiment at some point. I'd love to hear one of the World Audio Design integrated jobs as flinging one together is probably well within my capabilities.

One thing I don't really understand is how long valves actually last, and also how fast they spin the electric meter. At the moment I am attempting to build up a business that involves working mainly from home, so my system is in use almost constantly from when I wake up to when I go to sleep - I use it for both music and TV sound ââ'¬â€œ I don't play anything loud, but I'm always playing something! Would I be looking at high running costs were I to go over to a tube amp?

Tony.
 
Tony,

I cant talk about other amps, but my ARC CA50 integrated is 45 w/ch and uses 330w at maximum output and 190w at idle.

Valve life is rated at 2000 hours for the power valves and 5000 hours for the driver valves. It has 4 x 6550 power valves which are about £25 each and the driver valves (x4) are about £10 each. With my current usage, I am looking to replace valves every 12-18 month, so running costs dont work out too badly IMO.

If you are working from home and listen all day every day, it might work out a little expensive, but there are amps around which have longer valve life I believe.

Cheers, Robbo
 
well, the heaters are about 1.5 amps each, that is 6 amps for the power valves, but they are only 5 or so volts, so that is 30watts

on the anodes, typically 400 voltsx70mamps. = 30 watts each?? in my head that was, so you are looking 150 watts or so( 120 +30 ) give or take....seems a bit low, have I done something wrong...

anyway that for the leccy, 3 years for the power valves, t say £10 each for el34s, or £25 for 6550s = £40-£100 every 3 years,

and don't leave it on all the time, apart from sprogs, moggies, it will shorten the life, and could cause a fire if the worst happens

I have just bought 4x 6550s and 4x kt88s, from the US for £85 for the 8, post inc!!

maybe 5 years or more (or less if you are unlucky)
for the small ones.

Gives you an idea..best amp I have heard the wad 6550 thus far....

give it a go pen, you won't regret it and can always sell on ebay for a small loss.....
 
Last edited by a moderator:

Latest posts

Back
Top