I am building my first tube amp, it's exciting and can seem daunting too. I am hoping not to make any costly mistake.
Transformers are Edcor XPWR035 and CXSE25-8-5K.
I intend to do a first build with tube rectification and affordable Sino tubes like 6L6.
I have salvaged caps. Would these do for C1 and C2?:
120uF 400V 105C
150uF 400V 85C
I am not sure about both the voltage rating for peak B+ and the temp rating as 85C seems low.
Transformers are Edcor XPWR035 and CXSE25-8-5K.
I intend to do a first build with tube rectification and affordable Sino tubes like 6L6.
I have salvaged caps. Would these do for C1 and C2?:
120uF 400V 105C
150uF 400V 85C
I am not sure about both the voltage rating for peak B+ and the temp rating as 85C seems low.
Here's an example of a good C1 what many use here.
380LX470M500H012 Cornell Dubilier | Mouser
To answer your question you need at the very least 450v caps @ C1 C2,
aux cap you can get on ebay here:
Run Capacitor 100 MFD 370V Round AC Electric Motor HVAC 370 Vac V Volts 100 Uf | eBay
Note that the 370v in the description is AC volts, you will be running DC after the rectifier and that cap is rated for 370*1.5 (roughly) = 555vdc so good there too.
Alligator clips leads for your multi-meter are your friends with this voltage.
Good luck with your build.
Cheers,
Bob
Thanks for pointing those out, Bob.
Yesterday, I took some time to fashion holes for the tubes, using a Dremel. That's far from ideal since the proper tool would have been a hole saw. Instead, I used the circular disc (no good), the stone abrasive (only good for very small areas to sand), and finally settled on the sand drum, one of which is completely eroded now.
The holes aren't very regular so there's more work to do.
I also started to look for the proper resistors to solder on the PCB board. I have a set of 1/4W resistors, but I am not sure I have the others that George prescribed liked the 5W and so on.
In between looking for parts and ordering new ones, I'll continue doing the chassis work. It's the first time I do this, including the metal work. I am more interested in the electronics rather than chassis work, but I still did my own speaker stands, so I am enjoying it more and more.
All terminals are soldered in. I really like that design since there will only be screws to turn rather than more soldering when assembling the system.
The chassis finish is envisioned to be a mix of glossy black and chrome for the upper plate, together with a strip of wood, and the faceplate as well as sides in wood too.
I intend to re-purpose a VCR head assembly as volume knob. This will require a strong bond to the potentiometer shaft.
Yesterday, I took some time to fashion holes for the tubes, using a Dremel. That's far from ideal since the proper tool would have been a hole saw. Instead, I used the circular disc (no good), the stone abrasive (only good for very small areas to sand), and finally settled on the sand drum, one of which is completely eroded now.
The holes aren't very regular so there's more work to do.
I also started to look for the proper resistors to solder on the PCB board. I have a set of 1/4W resistors, but I am not sure I have the others that George prescribed liked the 5W and so on.
In between looking for parts and ordering new ones, I'll continue doing the chassis work. It's the first time I do this, including the metal work. I am more interested in the electronics rather than chassis work, but I still did my own speaker stands, so I am enjoying it more and more.
All terminals are soldered in. I really like that design since there will only be screws to turn rather than more soldering when assembling the system.
The chassis finish is envisioned to be a mix of glossy black and chrome for the upper plate, together with a strip of wood, and the faceplate as well as sides in wood too.
I intend to re-purpose a VCR head assembly as volume knob. This will require a strong bond to the potentiometer shaft.
for tube socket holes - this is what works for me. I use these with a cheap Chinese table top drill press but they will work with a hand held drill. Hard to beat a perfect hole there!!
Titanium Nitride Coated Steel Step Drill Bit Set
Cheers,
Bob
Titanium Nitride Coated Steel Step Drill Bit Set
Cheers,
Bob
That's going to be difficult. You can try to put a flat piece of hard wood or MDF underneth and use a small hammer to flatten the worst bits. But it won't be perfect. If you're looking for a flawless surface, you may want to start over.
Good luck!
Michael
Initial chassis priming, painting and sanding and motor run cap.
Haha!
What I'll do for the IEC hole is use a medium thickness wood plate and drill several holes along the lines, then sand them until the IEC plug fits. The IEC plug, filter and fuse are salvaged from an old synthesizer.
Question: is the motor run cap necessary or optional?
Pre-primer sanding (you can probably discern a little layer of epoxy around the holes drilled for the transformer wires to prevent abrasion of the insulators):
Some primer after hammering out most of the kinks:
Several coats of primer:
Some good results with primer sanding on the lower left:
If only they made a square/rectangle one for IEC inlets.....
Haha!
What I'll do for the IEC hole is use a medium thickness wood plate and drill several holes along the lines, then sand them until the IEC plug fits. The IEC plug, filter and fuse are salvaged from an old synthesizer.
Question: is the motor run cap necessary or optional?
Pre-primer sanding (you can probably discern a little layer of epoxy around the holes drilled for the transformer wires to prevent abrasion of the insulators):
Some primer after hammering out most of the kinks:
Several coats of primer:
Some good results with primer sanding on the lower left:
Attachments
Last edited:
+1 on the stepped drill bit for round chassis holes.
I bought a Milwaukee 2-size set for about $60 and have had great results.
If only they made a square/rectangle one for IEC inlets.....
Greenlee makes a punch for that but it's not cheap.
Cheers,
Bob
Youbetcha...
Parts ConneXion - The authority on hi-fi DIY parts and components
They should have just about everything you need. I'd use them cept they are in .... ahem Canada Eh?
Cheers,
Bob
Hey Bob, I was just looking at them, built a temporary shopping list with 4 sockets, choosing the Teflon-composite silver PCB mounts, and the total is $33. Things add up quickly!
I think they only have expensive tubes, so I may have to get the sockets from them and source the tubes elsewhere for a more affordable price.
I think they only have expensive tubes, so I may have to get the sockets from them and source the tubes elsewhere for a more affordable price.
Right now Parts Connection have a 20% off almost everything including vacuum tubes.
They usually have this offer twice per year. These are the times when I get my
vacuum tubes from them. I have purchased several times over the past few years.
I find that even with the HST tax it is still cheaper than ordering from the USA.
I'm referring to tubes like Electro Harmonix, Sovtek, and reissue tubes like Tung Sol,
Gold Lion, Mullard and others.
The 20% off goes for other stuff as well - resistors, capacitors, connectors, etc.
Don't what kind of tubes you are looking for but you can try the sale here
Sonic Craft Specials
Sonic Craft Specials
I use the cheap Chinese ceramic versions for $2/pc they work fine. There's not going to be a sonic different between a $2 socket and a $10 gold pin ...
For tubes which tube are you thinking about using?? For driver I'd get an old stock 12AT7 - I don't like the sound of the reproduction (12AT7) tubes at all. The old stock sound very good and readily available look for Sylvania they should be in expensive and sound good. You can upgrade them later if you want to roll tubes in. Trust me on the new stock driver tubes they will make the amp sound like crap.
Cheers,
Bob