Valve amp enthusiasts?

Jonny69 · 21-12-2011, 19:24

The "Imagine it's 1996/97...........there was no internet" thread on OcUK got me thinking. I used to do a lot of things before the internet, which I don't do now, and one of them was building home hi-fi and PA equipment. I built a stereo Maplin Millennium valve amp in 1996, which is a pair of EL34 valves in push-pull like the old Mullard amps. I ran it for a year or so until the mains transformer blew and replaced it in my final year at university. It eventually blew again and I couldn't get a new transformer because Maplin discontinued them, so it has sat on the sideboard at home ever since.

A couple of years ago I noticed the guy who originally designed the Millennium amp had a website so I contacted him about it. He basically said the original spec was downgraded by Maplin to save money and the transformer was only powerful enough to supply a mono amplifier. I'd been driving a stereo pair which was constantly overloading it, hence it kept blowing. He did however have some proper spec ones. I didn't buy one at the time, but I returned today to find he's got a Paypal plugin and so I ordered away...

Here is the amp and in a couple of weeks I'll be able to get it up and running again, just like the old days...

SidewinderINC · 21-12-2011, 20:03

Do you mean EL34 valves?

3 transformers?! that's rather crazy.

I like!

Jonny69 · 21-12-2011, 21:20

Yep, typo. EL34 power valves on the output stage. The other two are an ECC83 triode and an EF86 pentode, which handle the audio splitting and pre-amplification.

Three transformers, because one supplies the power to everything (the one on the left) and the other two are the output transformers for the EL34's, which take out the 350V DC.

volospian · 22-12-2011, 10:50

Sweet! I'm on the verge of buying a kit to build a 5w mono amp for my guitar. I currently have a Blackstar HT5, which is tube (ECC83, 12BH7) with some circuitry to enable the "Infinite Shape Feature", but I fancy playing with a simpler tube setup, like this.

I've been thinking about it for ages, but not got around to it yet. I'd need to build a cab to go with it, but then I could select the speaker that I want and so on...

Jonny69 · 22-12-2011, 20:07

If you want to build from scratch, this is where I got the transformer from: http://livinginthepast-audioweb.co.uk/transformers.php

They do a 5W tranny for use in class A with a single EL84. There are loads of EL84 circuits out there and the valves are easy to get. There's a couple of circuits on that site, but I've also got a load in my old Marconi book. Let me know and I can scan them in if you want

volospian · 22-12-2011, 21:40

I was thinking of trying a kit first, as all the parts I need are there and there are full instructions, so I can get used to valves before fiddling with translating diagrams to physical connections. I've done that before with stompboxes, but I'd like a bit more experience before fiddling with high voltages

Feek · 23-12-2011, 07:35

That's my valve amp, it has a single 4CX800 with up to 1000 Watts output on all bands, 1.8MHz to 50MHz. I never run more than 400 Watts though.

SidewinderINC · 23-12-2011, 14:20

Quote:

Originally Posted by volospian

I was thinking of trying a kit first, as all the parts I need are there and there are full instructions, so I can get used to valves before fiddling with translating diagrams to physical connections. I've done that before with stompboxes, but I'd like a bit more experience before fiddling with high voltages

http://www.18watt.com/

I've been toying with the idea for ages

Jonny69 · 26-12-2011, 16:54

Don't know whether you've taken any old electronic equipment apart before, but it's quite different to modern stuff. Often there are no circuit boards and everything is wired up on tag boards. It's dead easy to translate valve circuits onto them, especially because valve circuits are quite basic

Nutcase · 27-12-2011, 10:11

I did my work experience for a valve supply company (and then worked for them during the summer holidays). They had loads of old stock decent branded valves, but were also rather naughty. Buy in chinese made ones, scrub off the branding and re-brand as their own premium items

Was a very interesting job.

21-12-2011, 19:24	#1
Jonny69 Noob Join Date: Oct 2006 Location: Socialist Republik of Kent Posts: 5,032	Valve amp enthusiasts? The "Imagine it's 1996/97...........there was no internet" thread on OcUK got me thinking. I used to do a lot of things before the internet, which I don't do now, and one of them was building home hi-fi and PA equipment. I built a stereo Maplin Millennium valve amp in 1996, which is a pair of EL34 valves in push-pull like the old Mullard amps. I ran it for a year or so until the mains transformer blew and replaced it in my final year at university. It eventually blew again and I couldn't get a new transformer because Maplin discontinued them, so it has sat on the sideboard at home ever since. A couple of years ago I noticed the guy who originally designed the Millennium amp had a website so I contacted him about it. He basically said the original spec was downgraded by Maplin to save money and the transformer was only powerful enough to supply a mono amplifier. I'd been driving a stereo pair which was constantly overloading it, hence it kept blowing. He did however have some proper spec ones. I didn't buy one at the time, but I returned today to find he's got a Paypal plugin and so I ordered away... Here is the amp and in a couple of weeks I'll be able to get it up and running again, just like the old days... __________________ Last edited by Jonny69; 04-02-2012 at 22:34.

21-12-2011, 20:03	#2
SidewinderINC Joey Tempest Join Date: Sep 2007 Location: Gravesend. Posts: 2,751	Do you mean EL34 valves? 3 transformers?! that's rather crazy. I like! __________________ No Sig.

21-12-2011, 21:20	#3
Jonny69 Noob Join Date: Oct 2006 Location: Socialist Republik of Kent Posts: 5,032	Yep, typo. EL34 power valves on the output stage. The other two are an ECC83 triode and an EF86 pentode, which handle the audio splitting and pre-amplification. Three transformers, because one supplies the power to everything (the one on the left) and the other two are the output transformers for the EL34's, which take out the 350V DC. __________________

22-12-2011, 20:07	#5
Jonny69 Noob Join Date: Oct 2006 Location: Socialist Republik of Kent Posts: 5,032	If you want to build from scratch, this is where I got the transformer from: http://livinginthepast-audioweb.co.uk/transformers.php They do a 5W tranny for use in class A with a single EL84. There are loads of EL84 circuits out there and the valves are easy to get. There's a couple of circuits on that site, but I've also got a load in my old Marconi book. Let me know and I can scan them in if you want __________________

23-12-2011, 07:35	#7
Feek ex SAS Join Date: Jun 2006 Location: JO01ou Posts: 10,062	That's my valve amp, it has a single 4CX800 with up to 1000 Watts output on all bands, 1.8MHz to 50MHz. I never run more than 400 Watts though. __________________

22-12-2011, 10:50	#4
volospian Vodka Martini Join Date: May 2009 Posts: 786	Sweet! I'm on the verge of buying a kit to build a 5w mono amp for my guitar. I currently have a Blackstar HT5, which is tube (ECC83, 12BH7) with some circuitry to enable the "Infinite Shape Feature", but I fancy playing with a simpler tube setup, like this. I've been thinking about it for ages, but not got around to it yet. I'd need to build a cab to go with it, but then I could select the speaker that I want and so on...

22-12-2011, 21:40	#6
volospian Vodka Martini Join Date: May 2009 Posts: 786	I was thinking of trying a kit first, as all the parts I need are there and there are full instructions, so I can get used to valves before fiddling with translating diagrams to physical connections. I've done that before with stompboxes, but I'd like a bit more experience before fiddling with high voltages

26-12-2011, 16:54	#9
Jonny69 Noob Join Date: Oct 2006 Location: Socialist Republik of Kent Posts: 5,032	Don't know whether you've taken any old electronic equipment apart before, but it's quite different to modern stuff. Often there are no circuit boards and everything is wired up on tag boards. It's dead easy to translate valve circuits onto them, especially because valve circuits are quite basic __________________

27-12-2011, 10:11	#10
Nutcase Moonshine Join Date: Dec 2006 Location: Chelmsford, innit! Posts: 3,979	I did my work experience for a valve supply company (and then worked for them during the summer holidays). They had loads of old stock decent branded valves, but were also rather naughty. Buy in chinese made ones, scrub off the branding and re-brand as their own premium items Was a very interesting job.