For output tubes, I'd be very surprised. For input tubes (and when you're sure the hum is not caused by a ground problem or something), a good DC regulator can help the noise floor to be lower. But that means possibly another transformer with voltage and current high enough to get the regulator operate adequately.
If you used the Edcor CXPP output transformers then you might have a similar problem that I had.
Removing the capacitors in the compensation network fixed it right up.
My SPP humms a bit without an input connected.
As soon as I short the input or connect a source the humm goes away.
After that, the only humm I hear is the physical humm from the power transformer.
Removing the capacitors in the compensation network fixed it right up.
My SPP humms a bit without an input connected.
As soon as I short the input or connect a source the humm goes away.
After that, the only humm I hear is the physical humm from the power transformer.
In older days, it was not that uncommon to take DC from the cathodes of a pair of 6BQ5, and use it to power the filaments of a 12AX7, or similar, tube in a phono stage, so, a separate transformer is not always required.
I haven't looked at the SPP board that close; I have no idea whether or not it could be adapted for that, or if it would even be worth the effort, but it's kind of a neat trick ....
Win W5JAG
Hi,
I just finished my SPP and everything was working for the first moment. Then i realised some smoke after a while (approx 5min.) and I turned it off. I use a toroid with 300-0-300 that has 330V without the tubes. Adding all tubes i get 350 before and 315V after R1=220ohm (R1 is getting really hot). The voltages look ok for me. Is R1 with 5W a little bit underrated ? As rectifier i use a 5U4G.
I just finished my SPP and everything was working for the first moment. Then i realised some smoke after a while (approx 5min.) and I turned it off. I use a toroid with 300-0-300 that has 330V without the tubes. Adding all tubes i get 350 before and 315V after R1=220ohm (R1 is getting really hot). The voltages look ok for me. Is R1 with 5W a little bit underrated ? As rectifier i use a 5U4G.
When people substitute components other than recommended, it should come as no surprise there could be issues. In such case, one would hope the discrepancy would be the first place to look, and correct, before asking for help. That said:
A simple power calc reveals the following:
P = U^2/R = 35^2/220 = 5.6W
Yeah, it's cooking. Like Einric said, the specified component should be used. Choke (with R1 removed) is even better.
I used a Hammond 159R choke (6H, 150 ohm, 200ma) instead of the R1 resister and it works fine. No heating problems.
But I did have a problem with the B+ being too high so ended up adding an RC filter before the choke (parallel 430 ohm and 60uF). B+ is now around 300v so the EL84's should last longer.
Another option is to remove R1 and use a larger power resistor (maybe 10w) off board instead of a choke. Would keep the heat away.
But I did have a problem with the B+ being too high so ended up adding an RC filter before the choke (parallel 430 ohm and 60uF). B+ is now around 300v so the EL84's should last longer.
Another option is to remove R1 and use a larger power resistor (maybe 10w) off board instead of a choke. Would keep the heat away.
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CNAU:
I have had the SPP running for a few years now. I checked recently and R1 had "died" a fiery death. I replaced it but I am going to follow your example and and use a choke. I have the schematic from a while back (see below link). Where does the choke go? Thanks!
Marco
http://www.diyaudio.com/forums/tubelab/148694-tubelab-simple-36.html#post2568175
On the topic of chokes I got my SPP up and running the other week and it arc'd the rectifier tube pretty quick. I had bought a Hammond CXC100-5H-200MA choke and realized it's 58ohm, far short of the 150R needed. Is there any solution to this or do I just need a different choke?
While I'm at it, I've been reading back thru this thread and can't find the proper way to add in the supplement motor run cap. One side goes to ground, is the other on L1-1 or L1-2?
While I'm at it, I've been reading back thru this thread and can't find the proper way to add in the supplement motor run cap. One side goes to ground, is the other on L1-1 or L1-2?
The motor run cap is in parallel with C2. If you look at the traces in the image I posted above you can see that L1-1 goes to the positive terminal of C2 so that is where you would hook up one side of the motor run cap. The other goes to ground as you mentioned.
With only a 59 ohm choke your voltage may be too high for the tubes. Can't really comment on if this would result in arcing of the rectifier tube. I usually use a CL-90 on the mains to slow startup. You may be able to use a resistor in series with the choke but someone with more knowledge should comment on that. As mentioned earlier I used an additional RC stage to lower my B+.
With only a 59 ohm choke your voltage may be too high for the tubes. Can't really comment on if this would result in arcing of the rectifier tube. I usually use a CL-90 on the mains to slow startup. You may be able to use a resistor in series with the choke but someone with more knowledge should comment on that. As mentioned earlier I used an additional RC stage to lower my B+.
Well, I just built a second SPP. Now I have 2 SPP and 2 SSE amps functioning.I simply wanted to build working amps out of some of many parts lying around.Really a great sounding little amp.Using a set of Olson AM240 integrated 7189 output transformers, running in triode mode.Question is,where will all this stuff end up?Will a new generation appreciate as much as we have? They will I trust.
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Posting here to avoid a new thread.
My SPP was functioning fine, but I moved it recently and hooked it up directly to a CD player and new speakers, 8 ohm.
Now I have an odd issue: motorboating at the extremes of the volume control (max and min) and the volume is the same. As the volume level for motorboating is approached there is a bit of electrical hum audible.
The motorboating is like pulses of static.
No smells of anything cooking.
Sound quality is also a bit degraded.
I hope to have time to take it apart soon, and test without feedback and the volume control, but was hoping this might be a know issue to somebody out there.
My SPP was functioning fine, but I moved it recently and hooked it up directly to a CD player and new speakers, 8 ohm.
Now I have an odd issue: motorboating at the extremes of the volume control (max and min) and the volume is the same. As the volume level for motorboating is approached there is a bit of electrical hum audible.
The motorboating is like pulses of static.
No smells of anything cooking.
Sound quality is also a bit degraded.
I hope to have time to take it apart soon, and test without feedback and the volume control, but was hoping this might be a know issue to somebody out there.
Did you manage to take your amp apart and experiment with it? Mine was also motorboating until I disconnected GNF. Funny enough it was motorboating only on higher volume levels when feedback compensation capacitor was *not* soldered to the board.
Hi Grey1,
No, I have not had the chance to dedicate the time to getting it going properly again. I also have an SSE, and that is satisfying my musical needs for now.
I have been wondering where I should be going with my hobby. I am clearly a signed up member of Tube-aholics Anonymous, and wonder whether I need to invest a bit more in equipment so I have better investigation tools. I have been looking at some of these compact oscilloscopes, and by the looks of it $200 should be plenty to get me up and running with signal tracing capabilities.
I would really like to be able to examine the quality of the signal, and fine tune feedback, for instance.
Now I have this hobby, I find I am yearning for the winter months, so I can indulge myself without being guilty that my priorities are skewed.
Thanks for the pointer about GNF. I am 99% sure that it is just a question of checking the wiring. This was my first project, and I have another 3 under my belt now, so I think I have improved my skills a bit along the way. It is both channels, which implies some basic grounding or screening problem.
No, I have not had the chance to dedicate the time to getting it going properly again. I also have an SSE, and that is satisfying my musical needs for now.
I have been wondering where I should be going with my hobby. I am clearly a signed up member of Tube-aholics Anonymous, and wonder whether I need to invest a bit more in equipment so I have better investigation tools. I have been looking at some of these compact oscilloscopes, and by the looks of it $200 should be plenty to get me up and running with signal tracing capabilities.
I would really like to be able to examine the quality of the signal, and fine tune feedback, for instance.
Now I have this hobby, I find I am yearning for the winter months, so I can indulge myself without being guilty that my priorities are skewed.
Thanks for the pointer about GNF. I am 99% sure that it is just a question of checking the wiring. This was my first project, and I have another 3 under my belt now, so I think I have improved my skills a bit along the way. It is both channels, which implies some basic grounding or screening problem.