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Old 16th May 2008, 9:52 am   #1
smallspeed
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Default Valve amplifier advice for a newbie

Hi, its been a long standing ambition to build a valve amplifier, and Im hoping to do some research now so I can acomplish this during the autumn/winter this year.. I would like to build something with good stereo sound quality, but without spending an enormous amount of money first time around.

Can anyone recommend a circuit or type of amplifier I should consider, or should I just buy a kit from somewhere for my first go? I know a kit isn't really "homebrew" but if the kit route makes most sense for someone of my limited experience then any recommendations would be great..

Thanks in advance

Ben
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Old 16th May 2008, 11:48 am   #2
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Default Re: Valve amplifier advice for a newbie

Perhaps use circuit diagram for Radford STA25

I like this amp a lot and use JJ KT77 in it in place of the Mullard EL34. The JJs seem to be very nice in it and are so cheap. Souter can provide transformers for the STA25. The circuit diag is easily obtainable on the internet, possibly on this forum. I have it somewhere if you need it.

The STA25 has plenty of power for almost any speakers/ room and still retains superb sound quality.

Best regards
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Old 16th May 2008, 11:59 am   #3
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Default Re: Valve amplifier advice for a newbie

I suggest you look at the Mullard book "Circuits for Audio Amplifierrs" (1959-1963) which has full details for building a range of amplifiers from 3 to 20W.
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Old 16th May 2008, 12:17 pm   #4
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Default Re: Valve amplifier advice for a newbie

An American reprint of the Mullard book is currently available on the internet from Amazon at $16.95,
Jim
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Old 16th May 2008, 12:26 pm   #5
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Default Re: Valve amplifier advice for a newbie

Hi Ben,
It's worth having a look at Mike Holmes website http://www.livinginthepast.demon.co.uk/xformer.html where there's lots of information, circuits, parts & kits etc.
(N.B. I have no connection with this site but I am also thinking about building a valve amplifier and found it useful)

Andy
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Old 16th May 2008, 12:38 pm   #6
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Default Re: Valve amplifier advice for a newbie

thanks guys, will take a look at your sugestions.. im hoping to build something myself rather than buy a kit, so the references and links are great!
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Old 16th May 2008, 3:37 pm   #7
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Default Re: Valve amplifier advice for a newbie

Hi

It depends on what sort application you have for your amplifier. Is it for a small record player, a small or a large Hi-Fi system, public address system or Wembly Stadium.

Many designs exist, including the Mullard 5-10 and 5-20, and the Williamson. GEC also produced an Osram design.

You may find that the prices of the transformers somewhat daunting.

The Vellerman kits are avaialble from your local Maplins, Try a good Google for amplifiers.

Regards

ALAN
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Old 16th May 2008, 11:19 pm   #8
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Default Re: Valve amplifier advice for a newbie

I also wanted to build a valve amp and finally finished it two & a half years on. It was supposed to be a winter project but winter was busier than expected and it got left on the shelf. I considered a Velleman kit from Maplins but just couldn't justify an amp that cost around £500 to £600 and used something like eight EL34's! I finally cobbled together a circuit from articles found in various copies of Practical Wireless from the 60's and ended up with an amp with an EF86 then half an ECC83 and an EL84 per channel on an aluminium chassis from Maplins. It's not audiophile by any means, maybe not even hi-fi, but I think the THD might be in single figures! The thing for me was that I BUILT IT MYSELF and, I'll be honest here, I felt quite emotional when I fired it up for the very first time and, apart from connecting one of the output Tx's backwards, IT WORKED!! without fireworks or nasty noises!
I guess the point I'm making is that building a project like this can be as, if not more, rewarding as listening to the results. Hope this is helpful and good luck.
Cheers de Pete.
PS I don't think Maps do valve stuff any more, I might be wrong though.
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Old 16th May 2008, 11:22 pm   #9
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Default Re: Valve amplifier advice for a newbie

I built many amps from salvaged components in the 60's and 70's - the circuit topologies were generally borrowed from Leak and Rogers offerings of the time.
They all sounded great ( at the time !) , but of course valves are quite forgiving and many years later I realised that I had probably used low emission valves ,poorly matched transformers and some noisy resistors.
But the thrill was in starting with the unpromising box of bits and still getting some good sounds from the finished item.
The golden rule is ALWAYS get as good a quality output transfomer as possible. Many years ago I was informed by a then 'old hand' that in a good quality amp, the output transformer should be bigger than the mains transformer - This is probably an unaffordable goal nowadays !
As long as this component is of a reasonable standard and you ensure that with the negative feedback ( if used ) the amp remains stable, you can't go far wrong.
Use decent new components elsewhere, as they are fairly cheap these days. Don't bother with any of the esoteric stuff - You'll never hear any difference and the money you save can be lavished on the output tranny !
It's also worth buying Morgan Jones' book on valve amps - It's a good sensible read.


Andy

PS for sheer enjoyment value, try an amp with all octal valves - They're cheap to buy ( ie 6v6's 6SL7's etc ) and will look far more impressive than yer average EL84 or ECL86 offering !

Last edited by yestertech; 16th May 2008 at 11:28 pm.
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Old 16th May 2008, 11:36 pm   #10
mastermanx2001
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Default Re: Valve amplifier advice for a newbie

Sorry, Sowter is the correct spelling:

http://www.sowter.co.uk/acatalog/SOW...C_AMPS_15.html

Did not realise that they were quite that expensive though.
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Old 17th May 2008, 8:37 am   #11
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Default Re: Valve amplifier advice for a newbie

Quote:
Originally Posted by ALANS ANITAS View Post
Hi

Many designs exist, including the Mullard 5-10 and 5-20
If you only need it for domestic use, the Mullard 3-3 design does not cost a fortune and gives surprisingly good results for a single-ended jobbie.

I made one of these in the 1970s and used it for years, together with the Mullard preamp design.
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Old 17th May 2008, 8:58 am   #12
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Default Re: Valve amplifier advice for a newbie

Hi Ben
I was in a similar position a few months back & eventually built a Tubelab Simple SE
http://www.tubelab.com
It's kind of a half way house between a kit & scratchbuilding..you buy the circuitboard from George at tubelab (it was around £20) & buy the parts yourself using the parts list in the manual as a guide. The manual & the wiring diagrams on the site are a big help if like me you are new to this. I had NO previous electronics experience other than messing with old ebay heathkit amps & managed to build this. If you use the budget edcor output transformers (which sound nice) it is a relatively cheap build. I use EL34's & it drives my vintage 15" wharfedales very well. If you google Boozehound labs there is a great primer on tube(valve) amp building & some simple 6V6GT designs. If you have or can find/build some relatively sensitive speakers this will help.
All the best
Mike
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Old 17th May 2008, 1:28 pm   #13
dominicbeesley
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Default Re: Valve amplifier advice for a newbie

Just my twopeneth, I knocked on together from some second hand telly valves. The results are here: http://www.brahms.demon.co.uk/softwa...2_1/index.html

Once I'd got it working I forked out a whole £28 on NOS ELC82's. It's still going strong and still sounds good, though I've got nice efficient 1950's speakers.

I'm not saying that the above is a best way to go about things but it demonstrates that somebody with no real knowledge (I've learnt a bit more now by trial and error) and a tight budget can get something going, which might not work 100% first time but with a bit of messing you can get it to sing! You might not know much now but if you build something from scratch and design it yourself you'll learn a huge amount in a very short time, just be prepared for the odd minor disappointment along the way.

Boozehound mentioned above helped me enormously!

The main thing is are you after something that sounds good or are you after something to show off about to gold-plated audiofools? The extras might make a difference but only a very very tiny one. Using any proper AF valves, especially newer ones will always sound pretty good unless you make a real pigs-ear of things. You don't need Mullards or PX25's all very nice but stupidly expensive!

If you get stuck just post here or in components and circuits and you'll get loads of help!

Also attending some of the Radiophile/BVWS events and buying some of the "junk boxes" can get you enough parts to keep you going for years for a few quid that can set you back hundreds on ebay / maplins / rs etc

The books by Morgan Jones, Building Valve Amplifiers and Valve Amplifiers are expensive but giving huge amounts of detail not just on circuits but chassis building. For a bit less John Linsley Hood's Valve and Transistor Audio Amplifiers gives an excellent survey of various circuits.

Dom
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Old 19th May 2008, 11:50 am   #14
smallspeed
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Default Re: Valve amplifier advice for a newbie

thanks guys, a lot of info to be going on with there!.. I like the sound of purchasing a PCB and building on that; I will still gain the experience and knowledge of doing it and can move onto building something from scratch after that.. i will have a read up of the various websites adn things this evening

just an fyi, im looking for something to listen to around the house; single stereo input, stereo output to some reasonably small and efficient speakers.. Im not looking to shake the house down or wake the neighbours, but if it sounds 1/2 decent then I will be very happy. As much as anything its to get some experience and knowledge from doing rather than reading
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Old 19th May 2008, 5:34 pm   #15
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Default Re: Valve amplifier advice for a newbie

Ben
If you do decide to have a go at the Tubelab...it's worth having a search on the "Diyaudio" forum in the Tubes section for simpleSE, George is often posting help/advice on there & there are several builders who have posted their experiences of the build.
Mike
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Old 19th May 2008, 5:41 pm   #16
Whaam68
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Default Re: Valve amplifier advice for a newbie

This is what the Simple SE ended up like. I started with the smaller transformers & liked it so much I ended up shelling out for the larger ones...which are better but not massively so. The hardest part was the metalwork.
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