4 Valve amp - UK Vintage Radio Repair and Restoration Discussion Forum

murphyv310 · 22nd Sep 2008, 9:14 pm

Hi.
For quite a while I have thought about making valve amps while I have been off ill.
Years ago I built some amps for friends using EF86, ECC83 & two 6L6 with a GZ30 rectifier. I know that at least two amps are still in use with no faults in at least fifteen years.

Iv'e set about building a different amp using a 6BA6, 6SN7 & 2 of 6V6GT. Instead of a valve HT rectifier I am using 2 IN5408 rectifiers and smoothing rated at 450v. All components are modern except the Transformers which are Gardiners NOS. The amp is loosely based on the Brimar VA10 design.
The performance is stunning and is running 6 watts RMS with less than 1% distortion.
here are some pictures, note the temporary position of the volume control as I need some aluminimum to finish the front panel.
Trevor

murphyv310 · 22nd Sep 2008, 9:15 pm

And the last five
Trev

Neil F · 23rd Sep 2008, 9:42 am

Lovely tidy work, Trevor

If it sounds half as good as it looks it'll have been well worth the time it must have taken. Are you going to build it a sister so you can do stereo?

murphyv310 · 23rd Sep 2008, 2:27 pm

Quote:

Originally Posted by Neil F

Are you going to build it a sister so you can do stereo?

Hi Neil.
I think I will build a stereo version, but I now need to look out for a pair of o/p transformers and some more octal bases.
The chassis I used was from an old crystal calibrator, but my local engineering shop is making up some chassis for me, iv'e got some step drills which are great for the bigger holes.
This amp was built in a weekend so they dont take too long.
Trevor

Tim · 23rd Sep 2008, 2:46 pm

Excellent work.

I'm not worthy, I'm not worthy...............

dominicbeesley · 25th Sep 2008, 11:49 am

Lovely job!

Any chance of a circuit diagram?

Dom

mark pirate · 25th Sep 2008, 8:13 pm

Lovely job Trevor, i love how neatly you have wired it

I look forward to seeing a stereo version!
Keep up the good work

Mark

Mike Phelan · 26th Sep 2008, 8:38 am

What a great job, Trevor! The underchassis layout is as good as a Quad.
Is there a preamp on the way?

Phil G4SPZ · 26th Sep 2008, 9:34 pm

Pity I didn't see that when I visited, Trevor! That amp looks a really neat professional job. Who needs stereo anyway?

PM sent about the records, too. Cheers,

Phil

22nd Sep 2008, 9:14 pm	#1
murphyv310 Dekatron Join Date: Sep 2006 Location: Kilmarnock, Ayrshire, UK. Posts: 5,422	4 Valve amp Hi. For quite a while I have thought about making valve amps while I have been off ill. Years ago I built some amps for friends using EF86, ECC83 & two 6L6 with a GZ30 rectifier. I know that at least two amps are still in use with no faults in at least fifteen years. Iv'e set about building a different amp using a 6BA6, 6SN7 & 2 of 6V6GT. Instead of a valve HT rectifier I am using 2 IN5408 rectifiers and smoothing rated at 450v. All components are modern except the Transformers which are Gardiners NOS. The amp is loosely based on the Brimar VA10 design. The performance is stunning and is running 6 watts RMS with less than 1% distortion. here are some pictures, note the temporary position of the volume control as I need some aluminimum to finish the front panel. Trevor Attached Thumbnails __________________ Cheers, Trevor. MM0KJJ. RSGB, GQRP, WACRAL, K&LARC. Member

22nd Sep 2008, 9:15 pm	#2
murphyv310 Dekatron Join Date: Sep 2006 Location: Kilmarnock, Ayrshire, UK. Posts: 5,422	Re: 4 Valve amp And the last five Trev Attached Thumbnails __________________ Cheers, Trevor. MM0KJJ. RSGB, GQRP, WACRAL, K&LARC. Member

23rd Sep 2008, 9:42 am	#3
Neil F Retired Dormant Member Join Date: Oct 2003 Location: Leicester, UK. Posts: 143	Re: 4 Valve amp Lovely tidy work, Trevor If it sounds half as good as it looks it'll have been well worth the time it must have taken. Are you going to build it a sister so you can do stereo?

23rd Sep 2008, 2:46 pm	#5
Tim Dekatron Join Date: Jan 2003 Location: Bradford on Avon, Wiltshire, UK. Posts: 3,310	Re: 4 Valve amp Excellent work. I'm not worthy, I'm not worthy............... __________________ "Nothing is as dangerous as being too modern;one is apt to grow old fashioned quite suddenly."

25th Sep 2008, 11:49 am	#6
dominicbeesley Octode Join Date: Nov 2004 Location: Hebden Bridge, West Yorkshire, UK. Posts: 1,885	Re: 4 Valve amp Lovely job! Any chance of a circuit diagram? Dom

25th Sep 2008, 8:13 pm	#7
mark pirate Dekatron Join Date: Mar 2008 Location: Worthing, West Sussex, UK Posts: 5,185	Re: 4 Valve amp Lovely job Trevor, i love how neatly you have wired it I look forward to seeing a stereo version! Keep up the good work Mark

26th Sep 2008, 8:38 am	#8
Mike Phelan Dekatron Join Date: Nov 2003 Location: Near Leeds, West Yorkshire, UK Posts: 4,609	Re: 4 Valve amp What a great job, Trevor! The underchassis layout is as good as a Quad. Is there a preamp on the way? __________________ Mike.

26th Sep 2008, 9:34 pm	#9
Phil G4SPZ Dekatron Join Date: Apr 2005 Location: Bewdley, Worcestershire, UK. Posts: 4,748	Re: 4 Valve amp Pity I didn't see that when I visited, Trevor! That amp looks a really neat professional job. Who needs stereo anyway? PM sent about the records, too. Cheers, Phil __________________ Phil Optimist [n]: One who is not in possession of the full facts