Output tube swap results in no change...
I'm still hearing music, just very faint and very distorted.
I am going to walk away and try again tomorrow, as I feel I am starting to chase my tail.
In the interim, if anyone can come up with some clever ideas as to what is wrong, I'm all ears.
Maybe I should pull out the sig gen and scope and have a thorough, methodical examination of what is happening along the chain...
Thanks everyone for the help/ideas. Hopefully with a clear head I will get my head around the problem with your help.
I think it is time for one of my freshly home-brewed IPA's.
Until tomorrow,
Bryan
I'm still hearing music, just very faint and very distorted.
I am going to walk away and try again tomorrow, as I feel I am starting to chase my tail.
In the interim, if anyone can come up with some clever ideas as to what is wrong, I'm all ears.
Maybe I should pull out the sig gen and scope and have a thorough, methodical examination of what is happening along the chain...
Thanks everyone for the help/ideas. Hopefully with a clear head I will get my head around the problem with your help.
I think it is time for one of my freshly home-brewed IPA's.
Until tomorrow,
Bryan
If your transformer measures .5 ohms, and you are reading .2 ohms at the speaker terminals, something is not right. The reading should be at least as high as the transformer resistance. It is possible that your meter can not accurately measure a low resistance due to resistance in the leads, but it is also possible that you have a short. If you run out of things to try, disconnect all wiring from the transformer secondary, and hook the speaker up directly to the transformer with clip leads. .5 ohms is not totally out of line, I measure .4 ohms on an 80 watt P-P transformer, and .7 on a 10 watt Electra-Print SE.
The fact that you see a bright spot in the tube that increases when you turn it up says again that the driver is working. It also says that something in the output stage is wrong. Maybe it is a bad tube, but I would double check the grid and plate leads before trying another tube. The "spot" could be caused by a short or a bad transformer.
I tried the 9 volt battery test on the Edcor transformer - Yamaha speaker combo that is here on the bench and the click is loud enough to be heard in the next room. These are not efficient speakers.
The other OPT produce a very audible clicking with the 9volt trick.
I will swap and see what happens tomorrow. I am starting to think very bad thoughts...
On another note, this transformer was banged around in shipping, and the plastic cap where the terminals are was dislodged. Could it be possible that there was some sort of mechanical occurance here that would cause the short other than electrical....
Maybe if I pull it apart???
Ugh... UGH!
Much better today!
I replaced the OPT with the alternate, and sure enough, no music. I then removed the wires connecting the OPT to the speaker terminals, and replaced with clip-leads directly from the OPT to the speakers. 9 volt battery test worked. I powered up the amp and it worked. Music played just wonderfully through the beat up old test speaker, which has been on its last leg for a long long time.
Never the less, I swapped back to the original OPT, with clip-leads directly to the speaker. 9 volt test check! Music, check.
So, no blown OPT (THANK GOD!).
The only fault I can find in the wiring of the speaker terminals is that I drilled their mounting holes through the wood of the breadboard. There is a few cm between the posts, but maybe this was the source of the problem? The only other thing it could be was a bad solder joint.
That said, I am going to tidy up things a bit and then try some listening test.
First impression is that the low end response is very present, even through the beat test-speaker.
I'll report back with more time listening.
Thanks All,
BK
Hey Guys,
I decided to post a photo of the monster I've been working on. I feel like a proud father with his new son.
The previous problem with the OPT was a small sloder lug on the underside of the speaker terminal had moved while tightening the bolt and made contact with the other terminal resulting in a short. Good call guys!!! Thanks.
Anyway, he works and I have never been happier listening to just one channel.
Initial observations are that the gain is low (but we all know that was going to be an issue). I have played the amp through my AV speakers which are 90dB and the volume capability is fine. They get pretty damn loud, loud enough to fill the room with ease, but the volume pot is near its limits at this point. I may need to tweak with the input tube in the future.... More measurements and tweaks for another day....
Once I burn it in a little more (ie am sure it is working fine for more than 20 minutes) I will attach her to the ProAc's and see how it sounds. If the test speaker is any indication, I will be happy!
Thanks again for everyones assistance. If any of you make it to the NYC area, home-brews await you!
BK
I decided to post a photo of the monster I've been working on. I feel like a proud father with his new son.
The previous problem with the OPT was a small sloder lug on the underside of the speaker terminal had moved while tightening the bolt and made contact with the other terminal resulting in a short. Good call guys!!! Thanks.
Anyway, he works and I have never been happier listening to just one channel.
Initial observations are that the gain is low (but we all know that was going to be an issue). I have played the amp through my AV speakers which are 90dB and the volume capability is fine. They get pretty damn loud, loud enough to fill the room with ease, but the volume pot is near its limits at this point. I may need to tweak with the input tube in the future.... More measurements and tweaks for another day....
Once I burn it in a little more (ie am sure it is working fine for more than 20 minutes) I will attach her to the ProAc's and see how it sounds. If the test speaker is any indication, I will be happy!
Thanks again for everyones assistance. If any of you make it to the NYC area, home-brews await you!
BK
Attachments
What color 'ya gonna stain the board?
Don't you think you should have left room for serviettes and utensils (plastic recommended). So how many can this amp serve? I've heard of dinner by candle light but by DHT?
Now that I got the cornball jokes out of the way. I'm very glad you got it working! I'm interested in seeing it after it is in it's final form.
Don't you think you should have left room for serviettes and utensils (plastic recommended). So how many can this amp serve? I've heard of dinner by candle light but by DHT?
Now that I got the cornball jokes out of the way. I'm very glad you got it working! I'm interested in seeing it after it is in it's final form.
Thanks Guys,
I am going to hook her up to the ProAc today and give a listen... My main concern was stability/faults before I attach anything to my "good" speakers. So far I've played her for a couple of hours or so without any signs of problems.
My listening impression will be in mono as only one channel is breadboarded, but I should be able to hear a lot from one channel. This will admittedly be my first SET listening experience, compared to all sorts of SS and PP amps. Very exciting that it is my own creation as well. Hopefully I wont be too biased.
Thanks Again guys for all the help. I wouldnt be here without all of the great assistance from each of you. This is a valuable community filled with gewnuinely kind and VERY knowledgable individuals...
BK
I am going to hook her up to the ProAc today and give a listen... My main concern was stability/faults before I attach anything to my "good" speakers. So far I've played her for a couple of hours or so without any signs of problems.
My listening impression will be in mono as only one channel is breadboarded, but I should be able to hear a lot from one channel. This will admittedly be my first SET listening experience, compared to all sorts of SS and PP amps. Very exciting that it is my own creation as well. Hopefully I wont be too biased.
Thanks Again guys for all the help. I wouldnt be here without all of the great assistance from each of you. This is a valuable community filled with gewnuinely kind and VERY knowledgable individuals...
BK
Chris,
Thanks for asking...
Well, so far so good. I'm running the 845 at about 1040VDC / 70mA. The 300B is biased at 375VDC / 45mA. Everything has been stable and no breakdowns...
The sound is very good from what I can tell. The bass is prominent and easy to follow. The mids are very warm and the highs are clear/crisp but not brash. Piano sounds AMAZING. Let me also say I suck at describing sound like one would like to see from a magazine. Overall I am very pleased with the sonics, but I do have a couple concerns.
The sensitivity is low. I think I will need to change the input to get a little more gain. She has plenty of volume capability in A1, but I am getting pretty high up there with my stepped attenuator in the preamp. I havent measured the voltage at the input with listening volumes tthat work for the room, but I imagine it is pretty high.
That said, I am going to start investigating a few possible alterations for the input. Maybe the 6sl7. Possible a ccs loaded triode (not sure about this as of yet). SRPP???
I am open to any other ideas anyone thinks will work well in this amp.
If you have any specific questions, maybe I can give you a more direct answer.
At the end of the day, I am very happy!
Thanks for asking...
Well, so far so good. I'm running the 845 at about 1040VDC / 70mA. The 300B is biased at 375VDC / 45mA. Everything has been stable and no breakdowns...
The sound is very good from what I can tell. The bass is prominent and easy to follow. The mids are very warm and the highs are clear/crisp but not brash. Piano sounds AMAZING. Let me also say I suck at describing sound like one would like to see from a magazine. Overall I am very pleased with the sonics, but I do have a couple concerns.
The sensitivity is low. I think I will need to change the input to get a little more gain. She has plenty of volume capability in A1, but I am getting pretty high up there with my stepped attenuator in the preamp. I havent measured the voltage at the input with listening volumes tthat work for the room, but I imagine it is pretty high.
That said, I am going to start investigating a few possible alterations for the input. Maybe the 6sl7. Possible a ccs loaded triode (not sure about this as of yet). SRPP???
I am open to any other ideas anyone thinks will work well in this amp.
If you have any specific questions, maybe I can give you a more direct answer.
At the end of the day, I am very happy!
Bryan...I am glad the amp is working out nicely for you..
The first Gain stage needs be roughly 50 for a 1V input signal...
Give the 6SL7 a try...the ciruit I described in a earlier post...try it and see if you like it... Keep in mind that the grid resistor for the 300B is in parallel with the plate resistor for the first stage tube....so you need to keep an eye on that so it doesn't load down the first stage..which would lower the Gian and increase the distortions...
Chris
The first Gain stage needs be roughly 50 for a 1V input signal...
Give the 6SL7 a try...the ciruit I described in a earlier post...try it and see if you like it... Keep in mind that the grid resistor for the 300B is in parallel with the plate resistor for the first stage tube....so you need to keep an eye on that so it doesn't load down the first stage..which would lower the Gian and increase the distortions...
Chris
Thanks Chris,
I'll give the 6sl7 a try, once I source a couple units to experiment with. Any preferrence as to which tpe to buy? I'm shooting for an input sensitivity of about 2, but hey, whats a volt or so.
Also, I was reading back about your comment in regard to the CMC in the fillament supply. I've tried it both ways, and I honestly feel there is a difference for the better with the CMC at the end of the filter. Have you ever tried the choke in this position?
I'm not sure about the science behind the placement, but I have seen others do it as well. Welbourne labs has a CMC choke in this location as part of their upgrade path for the teraplane.
Anyone esle have any experience with CMC palcement at this location?
Any and all input is always appreciated.
Thanks,
BK
I'll give the 6sl7 a try, once I source a couple units to experiment with. Any preferrence as to which tpe to buy? I'm shooting for an input sensitivity of about 2, but hey, whats a volt or so.
Also, I was reading back about your comment in regard to the CMC in the fillament supply. I've tried it both ways, and I honestly feel there is a difference for the better with the CMC at the end of the filter. Have you ever tried the choke in this position?
I'm not sure about the science behind the placement, but I have seen others do it as well. Welbourne labs has a CMC choke in this location as part of their upgrade path for the teraplane.
Anyone esle have any experience with CMC palcement at this location?
Any and all input is always appreciated.
Thanks,
BK
Bryan...
As for best sounding 6SL7 tubes... I am not the best expert on that, but i am sure there are plenty of people here who can help with that..
My best experience with 6SL7 tubes have been with the old Sylvania ones that came in a green and black box... looked like early 1950's...
Also the old RCA ones are good....
As for the CM choke location....go with what your ears tell you is best...
Chris
As for best sounding 6SL7 tubes... I am not the best expert on that, but i am sure there are plenty of people here who can help with that..
My best experience with 6SL7 tubes have been with the old Sylvania ones that came in a green and black box... looked like early 1950's...
Also the old RCA ones are good....
As for the CM choke location....go with what your ears tell you is best...
Chris
Bryan said:
Get Sovtek 6SL7s. I tried 'em, and the design results I got from Sovtek 6SL7s and RCA data sheets were spot on, so these are real 6SL7s. Also, not the least bit microphonic as sharp rapping didn't cause any disturbances when o'scoping the output. Helluvalot less expensive than NOS, and NOS isn't always the "magic word": lots of US made 6SL7s (and 6SN7s) are very microphonic.
Hey Guys,
All is good with the amp, and it is nearing it's final stage.
I am currently designing PCD boards for the fil regs, fan voltage source, bias curcuitry, etc etc. Once that is done, I plan to work on layout of the PS.
I am going to make this a 4 chassis monster. Individual PS and Audio chassis for each channel.
I need advice!
I don't think I will be able to get all the iron, caps, and tubes for the PC on the standard Welbourn labs enclosures. These are what I have used in the past. So, I need something similar, but larger. I will have FPE make a top-plate, and hang that on the enclosure, with parts suspended above and below the top-plate. I need something strong, and comercially available, as I am not good with wood work. That said, does anyone have any good suggestion for the chassis system?
Thanks,
Bryan
All is good with the amp, and it is nearing it's final stage.
I am currently designing PCD boards for the fil regs, fan voltage source, bias curcuitry, etc etc. Once that is done, I plan to work on layout of the PS.
I am going to make this a 4 chassis monster. Individual PS and Audio chassis for each channel.
I need advice!
I don't think I will be able to get all the iron, caps, and tubes for the PC on the standard Welbourn labs enclosures. These are what I have used in the past. So, I need something similar, but larger. I will have FPE make a top-plate, and hang that on the enclosure, with parts suspended above and below the top-plate. I need something strong, and comercially available, as I am not good with wood work. That said, does anyone have any good suggestion for the chassis system?
Thanks,
Bryan
Blast from the Past....
WOW....
What a trip. I just re-read my entire thread and wow, what a trip down memory lane.
Amazingly, no more progress on the amp. I've been up to all sorts of things over tha past several years (graduating, moving, buying a house, building a brewery, building a smoker to compliment the brewery, getting married, getting pregnant) that I didn't have a chance to pull the bread board out of storage and finish her off.
With winter approacing, I am thinking that it may be time to finish off this project, or at least start fooling around with it again.
That said, what is new in the world of SET 845s?
Hope all are well.
Best,
Bryan
WOW....
What a trip. I just re-read my entire thread and wow, what a trip down memory lane.
Amazingly, no more progress on the amp. I've been up to all sorts of things over tha past several years (graduating, moving, buying a house, building a brewery, building a smoker to compliment the brewery, getting married, getting pregnant) that I didn't have a chance to pull the bread board out of storage and finish her off.
With winter approacing, I am thinking that it may be time to finish off this project, or at least start fooling around with it again.
That said, what is new in the world of SET 845s?
Hope all are well.
Best,
Bryan
Nothing seems to be new in the world of transmitting tube amps. Seems like most people are put off by the high voltage PS.
I've still got my mono block 211 amps I built back in 2001 and I have two Chinese 845 amps I tinker with that actually do not sound too bad.
I was thinking of throwing up a design, for a simple to build stereo 845 amp, with parts list, to illustrate to people interested in transmitting tube amps that one can be built for not much more than a 300B stereo amp.
I've still got my mono block 211 amps I built back in 2001 and I have two Chinese 845 amps I tinker with that actually do not sound too bad.
I was thinking of throwing up a design, for a simple to build stereo 845 amp, with parts list, to illustrate to people interested in transmitting tube amps that one can be built for not much more than a 300B stereo amp.
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