letterbeacon
Well-known member
Haha! The coffee can as a shield is a great idea!
GroupDIY Bridge compressor.
- Thread starter DaveP
- Start date
Help Support GroupDIY Audio Forum:
I see that I need to change my brand of coffee now! You still using those alu boxes from Farnell for the case?
I think illustrating options in the schematic/manual is a good idea or you'll be bound to get bombarded with questions when folk attempt to build this...
Jay
I think illustrating options in the schematic/manual is a good idea or you'll be bound to get bombarded with questions when folk attempt to build this...
Jay
Jay,
Our CEO gets through quite a few for his expresso machine, they were just too nice to dump!
CPC branch of Farnell actually, I don't know what I'd do without them and pop-rivets!
http://cpc.farnell.com/jsp/level5/module.jsp?moduleId=cpc/256377.xml
I'll make sure the final schematic shows the possible switch options as you suggest.
best
Dave
Our CEO gets through quite a few for his expresso machine, they were just too nice to dump!
CPC branch of Farnell actually, I don't know what I'd do without them and pop-rivets!
http://cpc.farnell.com/jsp/level5/module.jsp?moduleId=cpc/256377.xml
I'll make sure the final schematic shows the possible switch options as you suggest.
best
Dave
Work continuing apace,
Finished the front panel today, I will probably leave it in plain metal finish. I did think of painting it in grey Hammerite for the vintage look, but that requires a primer for aluminium first. I managed to get a nice little U.S. 1940's ?? Marion mA meter, I'll print a new scale for it.
Lots of angle section secured with many tediously cut countersunk screws!
The main box will be secured to the front with heavy duty stainless steel self-tappers, with five transformers it has to be able to take the weight.
The wiring up starts next.
best
DaveP
Finished the front panel today, I will probably leave it in plain metal finish. I did think of painting it in grey Hammerite for the vintage look, but that requires a primer for aluminium first. I managed to get a nice little U.S. 1940's ?? Marion mA meter, I'll print a new scale for it.
Lots of angle section secured with many tediously cut countersunk screws!
The main box will be secured to the front with heavy duty stainless steel self-tappers, with five transformers it has to be able to take the weight.
The wiring up starts next.
best
DaveP
Thanks Guys,
Just worked out the layout for the transformers, had to make a sub-assembly for the bridge pair. They will be pre-wired and canned and mounted on a bracket so all I'll have to do is bolt the thing in. The transformers will all be internal and centrally mounted to even out the weight.
I shall be working on it over this long weekend after I've cut the grass and washed the car! Time to turn in now, more next week.
best
DaveP
Just worked out the layout for the transformers, had to make a sub-assembly for the bridge pair. They will be pre-wired and canned and mounted on a bracket so all I'll have to do is bolt the thing in. The transformers will all be internal and centrally mounted to even out the weight.
I shall be working on it over this long weekend after I've cut the grass and washed the car! Time to turn in now, more next week.
best
DaveP
This is how the two bridge transformers are going to be mounted inside the chassis. I have pre-wired both of them with colour-coded wire, so that when the wires emerge from the grommets they will just have to be matched colour for colour.
If the transformers were mounted on the back of the chassis they would lever a heavier load on the front panel. This sub-assembly leaves much more space within the chassis than other mounting schemes.
They will be mounted base-to-base but with the Ally bracket between to break the magnetic contact. .
I will now give them a coat of Hammerite to give a more professional look!
I'm starting on the tube bases and component wiring tonight and hope to make lots of progress over this long break.
best
DaveP
If the transformers were mounted on the back of the chassis they would lever a heavier load on the front panel. This sub-assembly leaves much more space within the chassis than other mounting schemes.
They will be mounted base-to-base but with the Ally bracket between to break the magnetic contact. .
I will now give them a coat of Hammerite to give a more professional look!
I'm starting on the tube bases and component wiring tonight and hope to make lots of progress over this long break.
best
DaveP
Hi Dave
About your diy transformer shields - do you expect they will do much to attenuate hum in the transformer?
Just wondering as I've never really been able to get much more than a 1db or 2 from my own signal transformer shielding efforts.
Regards
About your diy transformer shields - do you expect they will do much to attenuate hum in the transformer?
Just wondering as I've never really been able to get much more than a 1db or 2 from my own signal transformer shielding efforts.
Regards
Hi Alex,
All the levels through the transformers are pretty high, so I was thinking more about shielding the rest of the circuit than hum pick-up in them. You may be right that the shielding could be ineffective but I thought I ought to make the effort as they were inside the chassis, it would be too late or difficult to do later when it was finished.
This bridge arrangement must not have magnetic induction between the transformers or the compression ration will be reduced, so that was the primary reason for shielding them.
We have covered this before, but magnetic shielding is really a misnomer, its much more like a bypass channel than a brick wall. I liked the tins because of the rounded edges, magnetic field propagate from edges, so I'm told.
best
DaveP
All the levels through the transformers are pretty high, so I was thinking more about shielding the rest of the circuit than hum pick-up in them. You may be right that the shielding could be ineffective but I thought I ought to make the effort as they were inside the chassis, it would be too late or difficult to do later when it was finished.
This bridge arrangement must not have magnetic induction between the transformers or the compression ration will be reduced, so that was the primary reason for shielding them.
We have covered this before, but magnetic shielding is really a misnomer, its much more like a bypass channel than a brick wall. I liked the tins because of the rounded edges, magnetic field propagate from edges, so I'm told.
best
DaveP
Ah.
Thanks for the clarification. Interesting point regarding the magnetic induction in this type of compressor.
Just for info, I'm doing some of my own 'soup can' tests today on some troublesome siganl traffos I have going.
Looks like this unit will be a major looker with those beautiful vintage meters you have there.
Big fan of your metal work too.
Regards
Thanks for the clarification. Interesting point regarding the magnetic induction in this type of compressor.
Just for info, I'm doing some of my own 'soup can' tests today on some troublesome siganl traffos I have going.
Looks like this unit will be a major looker with those beautiful vintage meters you have there.
Big fan of your metal work too.
Regards
The layout of the major components is now finalised and the back panel componets fitted.
This is it from the inside, the two pots are the output stage balance and the meter zero.
All the DC tube heaters are now wired up, awaiting connection to the supply.
There is more room left inside the chassis than I expected....the power toroids are doubled up, just have to find a place for all those wires ???
The bridge transformer cases are now nicely "Hammered"
But the transformers not yet fitted, I forgot to take home some grommets for the wiring, have to finish the sub assemby during the week.
I'll post more pics as the build progesses, looks like maybe two weeks from the finish line?
best
DaveP
This is it from the inside, the two pots are the output stage balance and the meter zero.
All the DC tube heaters are now wired up, awaiting connection to the supply.
There is more room left inside the chassis than I expected....the power toroids are doubled up, just have to find a place for all those wires ???
The bridge transformer cases are now nicely "Hammered"
But the transformers not yet fitted, I forgot to take home some grommets for the wiring, have to finish the sub assemby during the week.
I'll post more pics as the build progesses, looks like maybe two weeks from the finish line?
best
DaveP
Hi Jay,
Yes it's provisionally finished in Excel, but I was waiting till I can say it's tested to spec before posting; that way it won't get messy if I have to make last minute changes.
Looking forward to the concert tonight, I'd like Paul to do "Her Majesty" off Sgt Pepper 8)
best
DaveP
Yes it's provisionally finished in Excel, but I was waiting till I can say it's tested to spec before posting; that way it won't get messy if I have to make last minute changes.
Looking forward to the concert tonight, I'd like Paul to do "Her Majesty" off Sgt Pepper 8)
best
DaveP
Wow,
this looks great! Pix are gone make me carving (is that right written?)
Put me on the list to test it in Germany; ohhh I'm stepping to far...
I'll have to ask my friend of heyday-studio... with out him it wouldn't make
any sense...
ROCK-ON!
this looks great! Pix are gone make me carving
(is that right written?)Put me on the list to test it in Germany; ohhh I'm stepping to far...
I'll have to ask my friend of heyday-studio... with out him it wouldn't make
any sense...
ROCK-ON!
Thanks for the offer Dr-J,
I will have to decline unfortunately, it's going to 2 studios in the UK then off to the USA for review and auction for the Forum. I need to get the project finished this year.
English is part Welsh, part Danish, part Saxon German, and part Norman French, so who's to say what's right? Maybe best to say "written right", than right written!
best
DaveP
I will have to decline unfortunately, it's going to 2 studios in the UK then off to the USA for review and auction for the Forum. I need to get the project finished this year.
English is part Welsh, part Danish, part Saxon German, and part Norman French, so who's to say what's right? Maybe best to say "written right", than right written!
best
DaveP
rafafredd
Well-known member
Hey Dave, congratulations on this great project.
How did you make the hammerite finish? It looks great!
How did you make the hammerite finish? It looks great!
Hi Rafa,
Hammerite is a brand of special paint in the UK.
It is made with different solvents from ordinary paint and dries with a hammered finish.
Forty years ago you could also get "black crackle" paint but I guess all these paints are bad for the environment.
Glad you like the project
best
DaveP
Hammerite is a brand of special paint in the UK.
It is made with different solvents from ordinary paint and dries with a hammered finish.
Forty years ago you could also get "black crackle" paint but I guess all these paints are bad for the environment.
Glad you like the project
best
DaveP
Progress to date,
Started to solder in the components P2P.
Hardest job so far was the new meter face.
Scanned in the original face 300 dpi.
Next I found the font online, nearest was an American 1931 font called Stymie.
Changed the lettering and numbers, laser colour printed exact size and pasted it onto the face.
Here's the finished meter.
A pro could have done it much quicker, it took me about 3 hours altogether!
Face is actually a pale cream, photo looks white for some reason.
Artwork is attached if anyones interested.
best
DaveP
Started to solder in the components P2P.
Hardest job so far was the new meter face.
Scanned in the original face 300 dpi.
Next I found the font online, nearest was an American 1931 font called Stymie.
Changed the lettering and numbers, laser colour printed exact size and pasted it onto the face.
Here's the finished meter.
A pro could have done it much quicker, it took me about 3 hours altogether!
Face is actually a pale cream, photo looks white for some reason.
Artwork is attached if anyones interested.
best
DaveP
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