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Old 26th August 2008, 10:10 PM   #1
cjkpkg is online now cjkpkg  United States
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Default Long time lurker - first build a tubelab Simple SE

I have ordered all the necessary parts per George's recommendations for the Simple SE.

For power I went with an Allied 6K56VG
For OPT's I went with Edcor XSE15-8-5K's

output tube 6L6GC-CHIN
driver tube 12AT7-JJ
rectifier tube 5AR4-Ruby

I have seen many great builds on this site and I plan to use a wood frame with a steel top panel that the guts will be mounted to.

I have one outstanding question as to the appropriate amp rating for the main incoming power fuse. If someone could recommend an appropriate amperage I would appreciate it.

Thanks!
Carl
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Old 27th August 2008, 12:42 AM   #2
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Hey Carl,
good to see someone else is having a go at a Simple SE! I'm about to put orders in for some goodies to build one myself (but with EL34's) so I'll keep an eye to see how you're going with yours
Good luck
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Old 27th August 2008, 01:08 AM   #3
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Default Re: Long time lurker - first build a tubelab Simple SE

Quote:
Originally posted by cjkpkg
I have seen many great builds on this site and I plan to use a wood frame with a steel top panel that the guts will be mounted to.

I have one outstanding question as to the appropriate amp rating for the main incoming power fuse. If someone could recommend an appropriate amperage I would appreciate it.
I think I put a 1 1/2 amp slow blow in mine, because that is what was laying around. I'd probably be better off with a 2 amp fast blow, and I hope I remember to pick up a pack the next time I'm at the hardware store.

I like the wood box / metal top approach. That's what I used for mine. I used half inch metal standoffs on inch long #8 machine screws to mount the board to the underside. All the board components are mounted on the reverse side, opposite the tube sockets. I've got a long thread with plenty of photos here.

Be sure to post some photos when you are done.
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Old 27th August 2008, 06:40 AM   #4
cjkpkg is online now cjkpkg  United States
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I just finished soldering on the resistors except for 2 that digikey did not have. I have an order in with Mouser for the rest of the misc items and the 2 resistors. I also did all the caps except for the 2 coupling caps. I'm starting out with the Mallory ones Mouser has and will upgrade to the Auricaps maybe eventually...

The smallest 125V fuses I could find at Mouser were the 3A quick blow ones so I went with those - I figured 3A should be OK...

The tube sockets should be here shortly from Vintage Electric along with the tubes.

So far the longest lead time item are the Edcor OPT's...they wont ship for a couple weeks...

Thanks for the support
Carl
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Old 27th August 2008, 03:16 PM   #5
cjkpkg is online now cjkpkg  United States
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Some pics of the progress...I have decided to go with the reverse mount method for the caps for the final enclosure look I want.
Click the image to open in full size.
Click the image to open in full size.

Looks like almost everything but the OPT's will be here for the weekend.
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Old 27th August 2008, 11:36 PM   #6
chrish is offline chrish  Australia
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If you are doing an under chassis mount, that is tubes sticking out of the top of the chassis, I would suggest that it might be easier to mount those big 5 watt resistors on the back side of the board. They might be a little close to the top of the chassis on the front side of the board, or you may find that they sit too high and wont allow your sockets to sit flush with the chassis. Also, if you decide to add a choke at a later stage you can snip that 150R resistor off without having to unmount the board, or if you decide that you want to change the value of those cathode bias resistors.

Just my 2c worth. Good luck with the build, it is a great amp!

Chris
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Old 27th August 2008, 11:36 PM   #7
cjkpkg is online now cjkpkg  United States
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I have been scheming the layout of the top plate. Still plan on metal top with wood frame base.

Click the image to open in full size.
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Old 28th August 2008, 01:24 AM   #8
cjkpkg is online now cjkpkg  United States
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Yeah...I was looking at Ty Bower's post here this morning and noticed that the only thing he mounted topside were the tube sockets...I wish I had taken a closer look at that...

The large resistors should be easy enough to move and/or cheap enough to replace if I botch up the removal...I'll know better by Friday when the rest of the components arrive.
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Old 28th August 2008, 01:41 AM   #9
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I have been recovering from surgery so I missed the start of this thread. I am not even supposed to be out of bed now, so I will be seen here sporadically over the next few days.

First off, I see that you are planning to use a 6K56VG power transformer and 6L6GC output tubes. The 6K56VG will produce about 300 to 320 volts of B+ which will work with 6L6GC's but the output power may be lower than you expect. Most builders use the 6K7VG which will produce 450 to 460 volts. This will put 400 to 430 volts across the 6L6GC. You may want to allow room on your chassis for future upgrades. If you use the 6K56VG you will need to change the 560 ohm cathode resistors to 300 ohms to get enough current through the tubes.

Second, the board should fit under the chassis with the resistors on the top. I have built several amps that way.

Third, I use a 2 amp fuse from Radio Shack in my amps. They have reliably blown in the cases where I have done something stupid.
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Old 28th August 2008, 02:19 AM   #10
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Your layout looks traditional, and should work well. I would have liked to have done the same on mine, but the aluminum plate I had on hand was too small. I gave extra consideration to where wires might be routed underneath the chassis, and tried to decide whether or not something might be blocking easy entry to one of the Phoenix connectors. I found that including the locations of the Phoenix connectors in my chassis layout was useful.

I wouldn't worry about the top side mount of the cemented resistors. As George says, there ought to be enough clearance. On mine, 1/2" standoffs were perfect to get a flush appearance on the octal sockets. As long as your cemented resistors sit no higher than 1/2" off the top of the board, you should be golden. You can always move them last minute if need be. Chris makes a fair point about having access to them in the future, but I'd counter by asking how long it really takes to pull the board. With the Phoenix connectors, it isn't like anything needs to be unsoldered. I could probably pull the whole board out in five minutes, and wire it back up in ten.

I'd put the CFB and UL switches in a different location, most likely closer to the back. You don't really want to be switching them while the amp is running, and making them slightly less accessible reduces the temptation. Besides, they get wired in between the speaker binding posts / output transformers / back side of the circuit board. Where you've place them now requires wiring to run back and forth across the underside of the chassis.

While I'm babbling on about wiring, you might consider taking a printed copy of your proposed chassis layout and a couple of colored pencils. Try sketching in where the wiring will go, and see if you feel comfortable with your plan.

With regards to the 300 volt power supply, George mentioned something about reducing the size of R14 and R24. Otherwise the CCS might run out of headroom. I'd think a 6L6GC would work OK with a 300 volt supply. The RCA data sheets show cathode bias with 300 volts plate, 220 ohm cathode resistor. Load resistance is 4.5K, and output is 6.5 watts at 11% THD.
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