Comepletely homebrew amp - UK Vintage Radio Repair and Restoration Discussion Forum

adibrook · 17th Mar 2007, 7:24 pm

It has been suggested several times that i should try to design and build an amp completly myself, without using random parts of other machines or just modefying other devices.

Well, now i think about it, maybe its NOT such an impossible task afterall.

The biggest problem for me is the actual structure to hold the circuitry. I didnt think i had the equipment or the space to build anything. But...since modefying that umbrella stand into a cab, and a few other jobs, i think its feasable to build my own amp!.

So far, hers what i'v come up with (this is just a crappy 20min paint diagram), it whould demonstrate the design of the device tho.

http://img.photobucket.com/albums/v4...k/ampcase1.gif

Rather than using a more conventional desing like Marshall heads and stuff, i think maybe this will be better.

The wood bits will be MDF i think. Chipbord is too weak at holding screws and plywood cant take screws into its edges. MDF is nice, dence and strong, and can take screws in any side or edge.

The shassis is a sheet of metal with a 90* bend. This is to minimise workign with sheet metal. If i tried to make anythging more complex than it will end up being a mess.

Cooling will be forced, since overkill is better than overheat. The way i plan to do it is drill holes in the shassis around the valve holders, and put in a fan that creates a gentle positive pressure inside the case, which will blow out of the holes, providing streams of cooling air aroudn the tubes, and as a bonus providing contant air movement over all components. Dust will be a problem i guess, but i'll have to live with that. The other day it hit 38* in a studio i was in

.

So, any opinions on this desing?

Thanks.

reelguy · 17th Mar 2007, 11:13 pm

Adi.
I haven't made anything like this for quite a few years,{Like 40} But one thing struck me.
Maybe you should design and build the actual amp first then see what size the cabinet might need to be. Also check that it works etc.
I shall watch with interest. Good luck
Peter W Reelguy.
PS, Where's me 'ammer and nails ! ?.

Paul Stenning · 18th Mar 2007, 10:25 am

I agree. Once you have the electrical design sorted out (not necessarily complete, but to the extent that you know what major parts are being used) then lay out the top panel and establish the size from that. I'm sure many of us have started a design with the case then had problems fitting it all in as it evolves.

adibrook · 18th Mar 2007, 11:44 am

Of course that is all to follow. I havnt come up with any mesurements yet.

What i'm more interasted in is generally opinions the design of the casing and shassis. Its pretty unconventional, since most radios and amps have shassis inside a wooden case. Whereas this has a wooden case with the top plate being the shassis, slightly lower than the top edges of the wood. I'v seen some hifi amps made simular to this. Also i believed i borrowed the idea of putting holes around valve bases for ventilation from a hifi amp (but that amp had no fan to encourage airflow).

By the way, the vertical part of the metal sheet is to fit controls etc. There will also be (not shown in diagram) a piece of sheet metal on the back holding the power connector and output jack sockets.

Station X · 18th Mar 2007, 12:09 pm

It wil take a long time to design and build a case like that. You might be better off buying a ready made chassis from somewhere such as Bluebell Audio:-

http://www.bluebellaudio.com/

Merlin · 23rd Mar 2007, 8:20 pm

Your design is do-able. I would orientate one of those upright transformers at 90 degrees to the other though, for minimal hum.
Also, plywood will take screws in its edge very well, though MDF is pretty easy to work i agree.
I actually really like your idea of having the trannies/valves mounted on top of the head for all to see- I hate hiding things in boxes! Better hope you don't have any really wild gigs though..!

By the way, I have a few blank, zinc-plated steel chassis made up, I'd be happy to sell you one (£16 inc post) photo: http://i81.photobucket.com/albums/j2...e/CIMG1452.jpg. I've also got turrets and board material for sale in the "parts for sale" section of this forum.

'LIVEWIRE?' · 24th Mar 2007, 7:50 pm

Quote:

Originally Posted by Station X

It wil take a long time to design and build a case like that. You might be better off buying a ready made chassis from somewhere such as Bluebell Audio:-

http://www.bluebellaudio.com/

This link doesn't appear to work. I have clicked on it twice in the past few minuites, and all I get is 'Internet Explorer cannot display the Web Page'

Station X · 24th Mar 2007, 8:47 pm

You're right. The link doesn't work. That is the correct url. It worked when I posted it. Let's hope it's just a glitch and the site reppears in a day or two.

mickjjo · 30th Mar 2007, 9:35 am

The Bluebell link seems to be working fine now:-

http://www.bluebellaudio.com/

Regards, Mick.

17th Mar 2007, 7:24 pm	#1
adibrook Retired Dormant Member Join Date: Dec 2004 Location: Weymouth, Dorset, UK. Posts: 377	Comepletely homebrew amp It has been suggested several times that i should try to design and build an amp completly myself, without using random parts of other machines or just modefying other devices. Well, now i think about it, maybe its NOT such an impossible task afterall. The biggest problem for me is the actual structure to hold the circuitry. I didnt think i had the equipment or the space to build anything. But...since modefying that umbrella stand into a cab, and a few other jobs, i think its feasable to build my own amp!. So far, hers what i'v come up with (this is just a crappy 20min paint diagram), it whould demonstrate the design of the device tho. http://img.photobucket.com/albums/v4...k/ampcase1.gif Rather than using a more conventional desing like Marshall heads and stuff, i think maybe this will be better. The wood bits will be MDF i think. Chipbord is too weak at holding screws and plywood cant take screws into its edges. MDF is nice, dence and strong, and can take screws in any side or edge. The shassis is a sheet of metal with a 90* bend. This is to minimise workign with sheet metal. If i tried to make anythging more complex than it will end up being a mess. Cooling will be forced, since overkill is better than overheat. The way i plan to do it is drill holes in the shassis around the valve holders, and put in a fan that creates a gentle positive pressure inside the case, which will blow out of the holes, providing streams of cooling air aroudn the tubes, and as a bonus providing contant air movement over all components. Dust will be a problem i guess, but i'll have to live with that. The other day it hit 38* in a studio i was in . So, any opinions on this desing? Thanks.

17th Mar 2007, 11:13 pm	#2
reelguy Heptode Join Date: May 2003 Location: Bexhill on Sea, East Sussex, UK. Posts: 746	Re: Comepletely homebrew amp Adi. I haven't made anything like this for quite a few years,{Like 40} But one thing struck me. Maybe you should design and build the actual amp first then see what size the cabinet might need to be. Also check that it works etc. I shall watch with interest. Good luck Peter W Reelguy. PS, Where's me 'ammer and nails ! ?.

18th Mar 2007, 10:25 am	#3
Paul Stenning Administrator Join Date: Dec 2002 Location: Cardiff Posts: 9,071	Re: Comepletely homebrew amp I agree. Once you have the electrical design sorted out (not necessarily complete, but to the extent that you know what major parts are being used) then lay out the top panel and establish the size from that. I'm sure many of us have started a design with the case then had problems fitting it all in as it evolves. __________________ Paul Stenning Forum Admin/Owner and BVWS Webmaster

18th Mar 2007, 11:44 am	#4
adibrook Retired Dormant Member Join Date: Dec 2004 Location: Weymouth, Dorset, UK. Posts: 377	Re: Comepletely homebrew amp Of course that is all to follow. I havnt come up with any mesurements yet. What i'm more interasted in is generally opinions the design of the casing and shassis. Its pretty unconventional, since most radios and amps have shassis inside a wooden case. Whereas this has a wooden case with the top plate being the shassis, slightly lower than the top edges of the wood. I'v seen some hifi amps made simular to this. Also i believed i borrowed the idea of putting holes around valve bases for ventilation from a hifi amp (but that amp had no fan to encourage airflow). By the way, the vertical part of the metal sheet is to fit controls etc. There will also be (not shown in diagram) a piece of sheet metal on the back holding the power connector and output jack sockets.

18th Mar 2007, 12:09 pm	#5
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,288	Re: Comepletely homebrew amp It wil take a long time to design and build a case like that. You might be better off buying a ready made chassis from somewhere such as Bluebell Audio:- http://www.bluebellaudio.com/ __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

23rd Mar 2007, 8:20 pm	#6
Merlin Retired Dormant Member Join Date: Apr 2006 Location: Shrewsbury, Shropshire, UK. Posts: 67	Re: Comepletely homebrew amp Your design is do-able. I would orientate one of those upright transformers at 90 degrees to the other though, for minimal hum. Also, plywood will take screws in its edge very well, though MDF is pretty easy to work i agree. I actually really like your idea of having the trannies/valves mounted on top of the head for all to see- I hate hiding things in boxes! Better hope you don't have any really wild gigs though..! By the way, I have a few blank, zinc-plated steel chassis made up, I'd be happy to sell you one (£16 inc post) photo: http://i81.photobucket.com/albums/j2...e/CIMG1452.jpg. I've also got turrets and board material for sale in the "parts for sale" section of this forum.

24th Mar 2007, 8:47 pm	#8
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,288	Re: Comepletely homebrew amp You're right. The link doesn't work. That is the correct url. It worked when I posted it. Let's hope it's just a glitch and the site reppears in a day or two. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

30th Mar 2007, 9:35 am	#9
mickjjo Rest in Peace Join Date: Jul 2004 Location: Dartford, Kent, UK. Posts: 1,661	Re: Comepletely homebrew amp The Bluebell link seems to be working fine now:- http://www.bluebellaudio.com/ Regards, Mick.