OK, I switched over to the the Hammond 274BX 115v primary winding (grey / white) and now the numbers are more like what I expected:
B+ = 450v
Cathode v = 34.5v
Cathode R = 680
Cathode I = 50.7mA
Dissipation = 20.6W
I am going to enjoy it like this while I wait for a roll of solder to be delivered, at which point I will stain the wood frame, then install and wire the meters and call it done.
I am extremely happy with the way things have gone so far! Thanks to George for creating this amplifier and supplying the boards, BOM, instructions and ongoing support. Thanks also to everyone who has helped me along the way!
B+ = 450v
Cathode v = 34.5v
Cathode R = 680
Cathode I = 50.7mA
Dissipation = 20.6W
I am going to enjoy it like this while I wait for a roll of solder to be delivered, at which point I will stain the wood frame, then install and wire the meters and call it done.
I am extremely happy with the way things have gone so far! Thanks to George for creating this amplifier and supplying the boards, BOM, instructions and ongoing support. Thanks also to everyone who has helped me along the way!
Been doing more critical listening, with a wider range of music. At this point I am not sure if "SET sound" is for me or not. I sure spent a lot of money to get to this point so I am certainly not ready to declare a final verdict. It really does sound different in a good way with very specific types of music, but I have easily found its weak points with other tunes. I am going to try UL mode and CFB. I suspect I will go ahead and install switches for these because as it stands (in triode with no feedback) the amp is really only in it's "zone" with vocals and light jazz, IMO.
I am also very curious about the Chinese OPTs. I really want to try them and see if I can even tell a difference.
I am also very curious about the Chinese OPTs. I really want to try them and see if I can even tell a difference.
Same experience with SE tube amps and DHT amps - they really sound magical with certain genres.
Good idea.
Wired up UL mode about an hour ago. Holy crap, the power/gain difference is immediately obvious! I can't turn up my pre-amp nearly as much as I needed to in triode mode. However, when it does get loud it seems to hit higher distortion quite a bit quicker. I guess that's where the CFB will help.
Not a scientific test, but those are my first impressions. Oh, and there is faint but audible hum/buzz now, especially in the left channel. It isn't terrible - need to have my ear right up to the cone to hear it but it wasn't there in triode mode.
Note: My left speaker drivers are less than a foot from the Hammond power transformer, which has its own internal buzz - but as I said, I didn't hear it before...
Not a scientific test, but those are my first impressions. Oh, and there is faint but audible hum/buzz now, especially in the left channel. It isn't terrible - need to have my ear right up to the cone to hear it but it wasn't there in triode mode.
Note: My left speaker drivers are less than a foot from the Hammond power transformer, which has its own internal buzz - but as I said, I didn't hear it before...
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Very bad news.
My amp was playing in the living room just now (I am in the den) and my daughter asked "did you just hear that?" I asked "hear what?" and she said "the music just made a really bad noise".
I dashed to the living room to find magic smoke rushing out of my amp and that terrible smell... music still playing...
Shut off and unplugged immediately. No obvious signs of failure on the bottom side of the board.
Great. Here we go. Not the time to look at it because I am on my second drink and now very unhappy. How could hooking up UL mode break things this badly? Oh, I noticed the OPTs were much warmer than usual, too.
My amp was playing in the living room just now (I am in the den) and my daughter asked "did you just hear that?" I asked "hear what?" and she said "the music just made a really bad noise".
I dashed to the living room to find magic smoke rushing out of my amp and that terrible smell... music still playing...
Shut off and unplugged immediately. No obvious signs of failure on the bottom side of the board.
Great. Here we go. Not the time to look at it because I am on my second drink and now very unhappy. How could hooking up UL mode break things this badly? Oh, I noticed the OPTs were much warmer than usual, too.
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Oh no, sorry to hear about the magic smoke. I know it's discouraging, but I can almost promise you it's something relatively cheap and simple. The fact that your amp was playing when you switched it off is certainly encouraging.
I had something similar occur with my Tubelab SE-II about a week after completion. I was listening to it one evening when I noticed that something didn't sound right; sort of a fuzziness to the overall sound. That's when I decided to check the bias of the 2A3 output tubes - and discovered they were drawing 120 mA of plate current each! A quick calculation showed there was absolutely no bias on the grids, and the tubes were in runaway. I turned the amp off and went to bed in disgust.
A look at the board the next morning showed nothing obviously wrong. At George's suggestion I measured all of the resistors in the bias supply and found a 270 Ohm resistor that read about 3 Megohms. A closer look under magnification revealed a microscopic crack almost in the exact middle. I replaced the offending part with a 5W wirewound cement job and it's been fine ever since. George later determined that the specified part couldn't take the current surge at startup and has since specified a beefier part.
I know it sucks, but I'm sure you'll get it straightened out soon. Just take your time and don't hesitate to ask for help if you need it.
Edit: I just noticed that you used binding posts to mount your cathode resistors and coupling caps. If you haven't already, it might be a good idea to check those connections. I just ran across this post from George (#24) from a couple of years back that might hint at what happened. It may or may not be the cause, but it's worth checking for sure.
I had something similar occur with my Tubelab SE-II about a week after completion. I was listening to it one evening when I noticed that something didn't sound right; sort of a fuzziness to the overall sound. That's when I decided to check the bias of the 2A3 output tubes - and discovered they were drawing 120 mA of plate current each! A quick calculation showed there was absolutely no bias on the grids, and the tubes were in runaway. I turned the amp off and went to bed in disgust.
A look at the board the next morning showed nothing obviously wrong. At George's suggestion I measured all of the resistors in the bias supply and found a 270 Ohm resistor that read about 3 Megohms. A closer look under magnification revealed a microscopic crack almost in the exact middle. I replaced the offending part with a 5W wirewound cement job and it's been fine ever since. George later determined that the specified part couldn't take the current surge at startup and has since specified a beefier part.
I know it sucks, but I'm sure you'll get it straightened out soon. Just take your time and don't hesitate to ask for help if you need it.
Edit: I just noticed that you used binding posts to mount your cathode resistors and coupling caps. If you haven't already, it might be a good idea to check those connections. I just ran across this post from George (#24) from a couple of years back that might hint at what happened. It may or may not be the cause, but it's worth checking for sure.
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Oh no, sorry to hear about the magic smoke. I know it's discouraging, but I can almost promise you it's something relatively cheap and simple. The fact that your amp was playing when you switched it off is certainly encouraging.
I had something similar occur with my Tubelab SE-II about a week after completion. I was listening to it one evening when I noticed that something didn't sound right; sort of a fuzziness to the overall sound. That's when I decided to check the bias of the 2A3 output tubes - and discovered they were drawing 120 mA of plate current each! A quick calculation showed there was absolutely no bias on the grids, and the tubes were in runaway. I turned the amp off and went to bed in disgust.
A look at the board the next morning showed nothing obviously wrong. At George's suggestion I measured all of the resistors in the bias supply and found a 270 Ohm resistor that read about 3 Megohms. A closer look under magnification revealed a microscopic crack almost in the exact middle. I replaced the offending part with a 5W wirewound cement job and it's been fine ever since. George later determined that the specified part couldn't take the current surge at startup and has since specified a beefier part.
I know it sucks, but I'm sure you'll get it straightened out soon. Just take your time and don't hesitate to ask for help if you need it.
Edit: I just noticed that you used binding posts to mount your cathode resistors and coupling caps. If you haven't already, it might be a good idea to check those connections. I just ran across this post from George (#24) from a couple of years back that might hint at what happened. It may or may not be the cause, but it's worth checking for sure.
Thanks for the moral support and advice! There was enough smoke that I am hoping the problem is obvious when I get the board out and inspect it. If not, well I guess I will be getting more bang for my buck in "entertainment" from this amp.
Trying to smile but not managing it yet.
Cheers! I'm going to take your advice but I am already well on my way to a bit of a rough morning tomorrow.
Well I was gonna suggest you have a third and reverse the unhappiness trend, but I see you needed no such goading!
When an electrolytic capacitor vents, they will "smoke" for a long time, and really stink the place up. If you're lucky ( in a relative way ) there will be tell tale evidence on whatever is right below the cap, I'd look at the cathode bypass caps on the power tubes (s) ...
OPT's really don't get hot, other than picking up radiant heat from what's around them. Just speculating, but this and you stating it was distorting early, you might have had a tube running away and smoking parts was a secondary failure from too much current going through the tube ( s ) ...
edit: I am assuming you have 500 volt filter capacitors in the power supply. If you have 450 volt capacitors, one or both of those could have let go ...
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Oh no cogitech!
But, I think you're approaching it the right way: get some distance from it, and clear your mind.
I don't want to tread where I have no business commenting, but... maybe stay in basic triode mode for a week or two to shake everything down real good.
Personally, mine seems to be working so far; I feel very lucky, and I'm not touching anything!
You'll get it sorted out.
But, I think you're approaching it the right way: get some distance from it, and clear your mind.
I don't want to tread where I have no business commenting, but... maybe stay in basic triode mode for a week or two to shake everything down real good.
Personally, mine seems to be working so far; I feel very lucky, and I'm not touching anything!
You'll get it sorted out.
I've just removed the board from the chassis and done a full visual inspection of all components. Absolutely no obvious signs of failure anywhere.
The OPTs were not hot, they were warm - which I noted as being unusual because they basically remained at room temperature when I ran the amp in triode mode. The amp ran for quite a few hours in triode mode without any issues at all.
Yes, all the PS caps are 500v.
So the facts currently are:
1) The amp ran for hours without issue in triode mode
2) I switched to UL mode (simply connected the UL taps to the board), powered it up and played some tunes - there was a hum/buzz that had not existed in triode mode
3) A couple hours after, my daughter heard "a bad sound" and notified me
4) I rushed in and noticed magic smoke, immediately killed the power and unplugged it
5) I felt all the transformers and noted that a) the power transformer was hot as usual, b) the OPTs were unusually warm and one was definitely warmer than the other
6) There are zero signs of component failure, heat, burning on the SSE board
7) There are signs of heat/burning on the wires connected to the ground terminal of my power input connector - however, these were already there due to a mishap during testing when I accidentally arced the terminals with my alligator clip.
8) The fuse is intact
I have no idea where to go from here.
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Yes.
By the way I checked the solder joints on the binding posts and they are all solid.
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