BOM's need updating

sweet & juicy SE amp for 1626 Darlings and the 6L6 family

Re: BOM's need updating

Postby jukingeo » Mon Mar 29, 2021 7:27 pm

vvelt wrote:Still haven't received a PM in my inbox. That's how it goes.


Wait wait. Didn't you mention that you got the other one? I did as I did before and replied to your PM. I checked it just now and it looks to have been sent. So that seems odd that I get your PM's right away. At any rate, I did say "Yes" to what we were discussing there. While I would give you my email address through a PM, now I am not sure if you are going to get it. So I don't know how to proceed if the PM's are that unreliable on your end. I am getting your pm messages fine.

The Mundorf Supreme's are good. With the Darling you could use another 400v cap.


Yes, given to what I was reading and doing comparisons on your suggestions as well, I think I will give the Mundorfs a try.

I have JAN 1626 tubes as well. Bought them several years ago and will finally put them to use. The boxes are cool, dating them to wartime.


All around the JAN's just look good and I agree that even the box is nice. I do have other 1626 tubes, but they are not as nice looking as the JAN tubes. They date back to wartime because the 1626 tube (as well as the 1629 eye tube) were popular in a radio transmitter that was used on most WII B series planes such as the B-17 bomber. The radio was used from the 30's well through the 50's. So naturally the armed forces had thousands made.

For cathode bypass caps, the ones in the BOM should be fine and they are long life high temperature rated. However, there are audio grade lytic caps available from Nichicon and Elna. See this page on Mouser that lists the different audio grade caps from Nichicon:

https://www.mouser.com/new/nichicon/Nichicon-Audio-Caps

The KZ or "Muse" series are larger and their lead spacing won't match up with the board. However their FG or "Fine Gold" series will work fine for the power tubes as long as you keep them away from the hot cathode resistors. These are rated for up to 100v. The KA series are high temp rated and go up to 50v. I ordered these from Digikey since Mouser was out of stock.


Yes, I had noticed that they were out of stock as well. The 220uf cap is also a bit larger in diameter. Most of the other 'audio grade' electrolytics have different body dimensions. Unlike the coupling caps (on the board) that have multiple mounting holes, there is only a single pair for the electrolytic caps. So after putzing around for a half hour on the Mouser site looking for alternatives that don't seem to fit, I have decided to stick with what is specified. Besides it is something I could always swap out later on.

Question: If I DID go with the better electrolytic caps, at a SMALLER value, say 47uf in place of the 100's for C5 and C6, and 100uf for C3 and C4, then I have noticed some of the audio grade caps do fit. However, lowering the capacitance in a circuit was something I never did before. I was always told to go higher in value (when it comes to power supplies), but it seems that most of those audio grade caps don't fit on the board, but going with a smaller package...IE lowering the capacitance would have them fit. But what would that do to the sound?

UFG2A101MHM
UKA1E221MPD1TD

With small orders on Digikey you can select the cheapest shipping method which is USPS and as long as it's under a certain weight it will go out that way.

I've read where film caps are great for bypass, but they're just too huge.


Well, I have noticed the difference in that pre-amp I built. But yeah, they are pretty darn big. That circuit was mostly point to point. I made it from a Paia "Tube Head" preamp, but I was so disappointed with the results and it had a hum in it that I couldn't get rid of. It was one of those low voltage circuits that only had 50 volts on the tube plates. (It used 12AX7's). I was so pissed off that I ended up chucking the circuit board and reused the tubes and followed the schematic for an SRPP line stage. It had a more appropriate 240volt B+ too. I had a tapped volume control and made a loudness compensator and I put a couple other filters in. I did want to put in bass / treble controls, but the circuit didn't have enough gain for that. So it had a simple tone control, a loudness contour and I added a switch so I could switch between two sets of inputs. The results were fantastic, and even more so when I put the Solen caps in it.

Surprisingly, it seems that Paia still carries the Tube Head:

https://paia.com/proddetail.php?prod=9305HSR

BTW, those Vishay/Draloric resistors are interesting. After reading the specs on them, they say they are fusible/safety resistors. Bonus circuit protection!

I also wanted to ask you how you mount the boards in terms of standoffs. I am going to be needing those as well.

Regards,
Geo
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Re: BOM's need updating

Postby vvelt » Tue Mar 30, 2021 8:27 am

Still no PM and I haven't sent one to you, so what did you get? Maybe it was just a notice that I commented on your post. I'll try sending you a test PM.

C5 and C6 should stay as 100uf in order to not roll off the bass. I used the FG Fine Gold on the Get SET Go and they fit fine on the board so I ordered these again from Digikey, I should get those today. I don't know how a larger value would affect the sound, but my board has 470uf's in there now. I think the 220uf's on the driver should stay as well. There's an online calculator for this you can play with:

https://www.ampbooks.com/mobile/amplifier-calculators/cathode-capacitor

For standoff's I ordered six 36-8414-ND. These are half-inch tall with a tapped end for a #6 screw and a threaded end for a nut. If you haven't populated your board yet MAKE SURE you have drilled your chassis so that the holes line up with the mounting holes on the board. These standoffs are very unforgiving if the holes don't line up. There is also a board outline you can print out on the Docs page.

The Vishay/Draloric's are good, I even use them in guitar amps. They're much nicer than those big square cement jobs.
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Re: BOM's need updating

Postby jukingeo » Tue Mar 30, 2021 10:28 pm

vvelt wrote:Still no PM and I haven't sent one to you, so what did you get? Maybe it was just a notice that I commented on your post. I'll try sending you a test PM.


I figured out what was going on. Thermion was the one that PM'ed me and I thought it was you and thus I ended up crossing conversations. So as I said in my return PM to you....OOOPS! Well, at least that cleared that up.

C5 and C6 should stay as 100uf in order to not roll off the bass. I used the FG Fine Gold on the Get SET Go and they fit fine on the board so I ordered these again from Digikey, I should get those today.


I am not set up with Digikey, but could do so. Do they have the 220uf caps too?

I don't know how a larger value would affect the sound, but my board has 470uf's in there now. I think the 220uf's on the driver should stay as well.


I think going bigger is usually OK, but going smaller, I wasn't sure of.

There's an online calculator for this you can play with:

https://www.ampbooks.com/mobile/amplifier-calculators/cathode-capacitor


That calculator is pretty cool, but it only shows a gain stage and not an output stage. So I don't know how that would figure out. At any rate, I did the example for a 12AT7 driver which would be similar to a 12SL7 and I figured out that you can drop the c3, c4 220uf bypass cap to 100uf. The response will roll off at 20hz, whereas with the 220uf the roll off happens below 10hz.

For standoff's I ordered six 36-8414-ND. These are half-inch tall with a tapped end for a #6 screw and a threaded end for a nut.


NICE! Thanks! That is better than what I had initially planned.

If you haven't populated your board yet MAKE SURE you have drilled your chassis so that the holes line up with the mounting holes on the board. These standoffs are very unforgiving if the holes don't line up. There is also a board outline you can print out on the Docs page.


Oh, I would have laid the unpopulated board out first and mark off the holes first, but I don't have a final cabinet as of yet. As I mentioned in another reply, I am probably going for a breadboard layout first.

The Vishay/Draloric's are good, I even use them in guitar amps. They're much nicer than those big square cement jobs.


How are they with heat? Do they heat up a lot? Wirewounds usually get VERY hot and C5,C6 are pretty close by.

Thanks for the info, you have been a big help with finding the parts. While this isn't the first time working with PCB's, it is for a tube amplifier. One of my concerns, especially with the 6L6 variant is that with the tube rolling I intend to do, if the sockets will loosen up eventually and break the solder connection on the PCB. Do you have a bracket to support the tube sockets as well (on your amps)?

Geo
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Re: BOM's need updating

Postby vvelt » Wed Mar 31, 2021 7:27 am

I believe the Muse and Fine Gold caps come in 220uf and greater. You'll have to check the size of these. Your low Hz response will always be limited by your output transformers and speakers, so aiming for 10hz may not work out.

All wirewounds get hot, that's their job, the Draloric's tolerate it well. You should stand these up off the board a little bit for ventilation, and some can be mounted on the backside of the board to keep them away from cooking other parts. I think there are some notes in the Docs about this. In fact, all parts should have a little stand-off from the board for resiliency. There's a good page of instructions that explain this on the TubeLab website.

http://tubelab.com/designs/tubelab-se/manual/getting-started

The sockets don't come loose from the board. Of course you'll never get them off either so make sure they're flat against the board and level before soldering them up, again this is in the TubeLab page. The biggest challenge with having tube sockets on the board is when you plug in your tubes and pull them out, this puts strain on the board. The DiyTube boards are excellent because they provide extra mounting holes near the tube sockets so that you don't flex the board. A lot of those cheap generic boards on eBay will only have 4 mounting holes in the corners. How many tubes can you roll with those before you break the traces on the board? The DiyTube boards are rock solid, and the Clementine board has 6 mounting holes. I've not had any issue with the Chubby Clem I built, and I've rolled 6L6, EL34, KT77's and various 6SL7's.
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Re: BOM's need updating

Postby jukingeo » Wed Mar 31, 2021 7:48 pm

vvelt wrote:I believe the Muse and Fine Gold caps come in 220uf and greater. You'll have to check the size of these. Your low Hz response will always be limited by your output transformers and speakers, so aiming for 10hz may not work out.


Indeed, I was thinking of that as well and I know the transformers roll off at 40hz, so using that little calculator, I could get by fine with a 100uf cap in that spot.

All wirewounds get hot, that's their job, the Draloric's tolerate it well. You should stand these up off the board a little bit for ventilation, and some can be mounted on the backside of the board to keep them away from cooking other parts.


This practice I am familiar with doing.

<< I think there are some notes in the Docs about this. In fact, all parts should have a little stand-off from the board for resiliency. There's a good page of instructions that explain this on the TubeLab website.

http://tubelab.com/designs/tubelab-se/manual/getting-started[/quote]

Having experience with kit building this was more or less a review for me. Nice information though and it gave me a good idea of the proper order of installing parts on tube based circuits.

The sockets don't come loose from the board. Of course you'll never get them off either so make sure they're flat against the board and level before soldering them up, again this is in the TubeLab page. The biggest challenge with having tube sockets on the board is when you plug in your tubes and pull them out, this puts strain on the board.


That is what I was worried about in addition to straining the solder connections. Which is why I was thinking about sockets with mounting flanges. I probably wouldn't need it on the Darling amplifier, but for the 6L6, it might be a good idea.

The DiyTube boards are excellent because they provide extra mounting holes near the tube sockets so that you don't flex the board. A lot of those cheap generic boards on eBay will only have 4 mounting holes in the corners. How many tubes can you roll with those before you break the traces on the board? The DiyTube boards are rock solid, and the Clementine board has 6 mounting holes. I've not had any issue with the Chubby Clem I built, and I've rolled 6L6, EL34, KT77's and various 6SL7's.


Well, if you don't think I need the mounting flanges then I will not be bothered. As it is, I am also going to have to get standoffs that hold the board up when I have the amplifier in its 'test mode' as the board will be mounted with the parts downward and supported from the base. In the final design of the amplifier, it would be supported from the top panel. The six mounting points on the board are good and it is nice that board has them, but I have noticed the thickness as well too.

I don't have many different 6SL7's, or in the case of the Darling 12SL7's. The latter I do have in NOS JAN. When it comes to NOS tubes, I usually try to go for the JAN ones first. They are mil-spec and just made better. Runners up would be the Sylvania Black Plate preamp tubes. I have some in 6SL7's but more in 6SN7's.

Regards,
Geo
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Re: BOM's need updating

Postby vvelt » Thu Apr 01, 2021 5:00 pm

I’ve swapped tubes in and out of my Chubby Clem plenty of times without problems. Your board will be fine.

For testing I plugged in the tubes first holding the board in my palm for support, then attached 2 “L” brackets to the bottom outer mounting holes, then attached the other end of the “L” brackets to a wooden board. This way the board is vertical and the tubes are sticking out sideways but this doesn’t bother them. Then I can get at anything on the backside of the board as well as the top. I did this with my GSG build as well.

The good 6SL7’s I have are old RCA’s and a JAN Phillips. I also have new production a Sovtek, which isn’t bad but not as nice as the others. I got a Sylvania on Reverb once, but it sounded terrible, I’m sure it was just a fluke. I’ve not tried the new Mullard or JJ.
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Re: BOM's need updating

Postby jukingeo » Thu Apr 01, 2021 8:09 pm

vvelt wrote:I’ve swapped tubes in and out of my Chubby Clem plenty of times without problems. Your board will be fine.


That is good to know.

For testing I plugged in the tubes first holding the board in my palm for support, then attached 2 “L” brackets to the bottom outer mounting holes, then attached the other end of the “L” brackets to a wooden board. This way the board is vertical and the tubes are sticking out sideways but this doesn’t bother them. Then I can get at anything on the backside of the board as well as the top. I did this with my GSG build as well.


That is an interesting way to set it up. With me, I think once I have the board constructed, I would prefer a standard vertical setup. From that point I can A/B tubes and transformers. If I did something on the board, it probably would be to change out C1 and C2 and those are right at the edge, so I can just 'tack' the caps in place, hanging down. So I could put an orange drop on one side and compare it to the Mundorf on the other side. Then by doing tests and gathering information, I can determine what I think sounds best. Once I have decided on everything, then I will put it in a chassis.

The Darling will be simpler using the results I have garnered from the "Chubby" tests, I would have already determined what will be good for caps and transformers. Granted I would do some additional tests with the Darling, but I am not going to be doing too much tube rolling with that amplifier as I have heard it time and again from those that built the amp that they like the sound of the JAN tubes. I do have other brand 1626 tubes just for testing, but I have a funny feeling I probably will end up sticking the JAN tubes myself.

The good 6SL7’s I have are old RCA’s and a JAN Phillips.


I might have some RCA's kicking around and I know I have Sylvanias. With the 6SN7s, I mostly have Sylvania Black Plates. I stumbled on a deal in getting a bunch of them for a good price.

I also have new production a Sovtek, which isn’t bad but not as nice as the others.


Sovtek is a nice, no nonsense tube. They are pretty reliable and sound good, but not great. I had found that Svetlana's are better when it comes to Russian tubes. In terms of newer tubes, I have almost exclusively retubed the guitar amps I worked on with Svetlana tubes. I used those mostly for outputs though, wheras for preamp tubes, I either used Sovtek or JJ. The latter was very popular with guitarists, however, I did have some issues with their EL34's and I don't like the bottle shape JJ uses for the EL34. However, for 6L6 tubes, the J.J.s were fine. Again, most of these tube tests I have done with commercial / guitar amplifiers. So hi-fi listening and driving a tube to it's max will probably be different as each field is going for a different type of sound. Naturally with a guitar amplifier, the tube's magic happens when you can 'play' the amplifier into that cusp of early distortion, something that you cannot do with a transistor amp. I used to create a circuit for the 6550 Marshall amplifiers that would put an extra 'crunch' or early clipping effect on the driver tube and this would allow the player to decide WHERE the amp starts to clip power wise. So if they wanted to practice and not blow everyone away, they could dial the control down for heavy clipping early on. It was a cool trick and I have tried it on a number of guitar amplifiers, but it seemed to work best on the 6550 Marshalls.

I got a Sylvania on Reverb once, but it sounded terrible, I’m sure it was just a fluke. I’ve not tried the new Mullard or JJ.


Probably was a bad tube. NOS Sylvanias usually are pretty nice sounding. Old Mullard is great too, but mostly for the miniature (9pin) tubes. They used a lot of those in European equipment. New Mullard must have come later as I wasn't exposed to it. However, I had some of the Fender guys want NOS Mullard pre-amp tubes and naturally, they paid a premium for them.

Speaking of guitar amplifiers, you might find this entertaining:

https://www.youtube.com/watch?v=DtpilZR-49o

The reason why I find this entertaining is because I was sitting in my seat waiting for that tube to go BANG! That is a good way to powder-keg an output transformer. You think the guy, knowing he has a problem, wouldn't run the amp so long like that? LOL! I can tell you that I have seen some whoppers too. Remember what I said about the J.J. EL34s? Well, one guy had a bad one and he brought his amplifier back and the thing must have red-plated so bad, it actually melted the glass! Naturally the glass pulled inwards and when it hit the red hot plate, the tube evacuated and completely shorted out. So he must have had the amplifier running quite a long time in a red plate condition for the glass to melt like that.

Regards,
Geo
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