Hi, new to the forum (first tube amp as well!), and I'm looking for some answers from someone who has built an SPP in the past.
Got my board built, now I'm working on getting the case wired up. I'm also still waiting on the transformers from Edcor. (3 weeks and counting!)
My main question is how to wire this thing up so that I can utilize a UL / Pentode switch. The instructions on the tubelab website aren't quite as detailed for the SPP as they are for the SSE. I've looked at a schematic that I found somewhere on this site, and it looks to me that I will need two DPDT switches in order to accomplish this, one for each channel.
Is there anyone that can confirm this? Any caveats I may not have seen?
Got my board built, now I'm working on getting the case wired up. I'm also still waiting on the transformers from Edcor. (3 weeks and counting!)
My main question is how to wire this thing up so that I can utilize a UL / Pentode switch. The instructions on the tubelab website aren't quite as detailed for the SPP as they are for the SSE. I've looked at a schematic that I found somewhere on this site, and it looks to me that I will need two DPDT switches in order to accomplish this, one for each channel.
Is there anyone that can confirm this? Any caveats I may not have seen?
Hello:
I am in the exact same boat, transformers and wiring 🙂. I ordered the transformers before Christmas, but Edcor was already in shut down mode , so they did not start until the new years, hence 3 weeks in, just as you.
I have a couple of sketches drawn that I found here on the forums that show the connections but I have not studied them yet. I will try to see if I can post. I don't know who the original poster was, so please forgive me for posting them again.
Marco
I am in the exact same boat, transformers and wiring 🙂. I ordered the transformers before Christmas, but Edcor was already in shut down mode , so they did not start until the new years, hence 3 weeks in, just as you.
I have a couple of sketches drawn that I found here on the forums that show the connections but I have not studied them yet. I will try to see if I can post. I don't know who the original poster was, so please forgive me for posting them again.
Marco
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The switches are wired in the same manner as the SSE. You either need two DPDT switches, or a 4PDT switch. I found such a switch in a box of switches passed out by a vendors rep for C and K switches. It is a miniature toggle switch only rated for 250 VAC, but I tried it anyway and it hasn't fried yet. I don't recommend this though.
The UL/pentode switch will see a bit over 400 volts between its terminals and ground. The 250 VAC switch you show is rated for 250*1.41=352 volts so technically it is a bit short in voltage handling capability. It however is about 4 times the size of the tiny little switch that I used, so it should be OK.
If you use it make sure that the metal part of the case is well grounded. There should be a wire running from whatever metal the switch is mounted in to the center pin on the power receptacle. This way if the switch fries it will blow the fuse rather that apply voltage to the handle.
If you use it make sure that the metal part of the case is well grounded. There should be a wire running from whatever metal the switch is mounted in to the center pin on the power receptacle. This way if the switch fries it will blow the fuse rather that apply voltage to the handle.
First off, thanks everyone. After reading the requirements for the UL/Pentode switch, I have decided to forgo the switch for now. I may change my mind on that in the future, we'll see.
Anyway, I have a question about connecting the Feedback for this amp. I have been working from the schematics drawn up by Ian444 (SimplePPschemUL.gif Photo by birdy81260 | Photobucket). Unfortunately, whenever I connect the secondary output to L_FB-1 or R_FB-2, I get a huge squealing noise.
I found some help on this in this post: http://www.diyaudio.com/forums/tubelab/148694-tubelab-simple-p-p-58.html#post3482585 , which suggested swapping the PRI_1 and PRI_2 secondary connections. This did change the noise that came out- instead of the squealing noise, I now get a rhythmic scratchy popping noise.
If I just disconnect L_FB-1 and R_FB-2, then the amp seems to work...? I have also seen documentation (For the SSE) that shows the L_FB-1 / R_FB-2 nodes shorted to their corresponding FB node. I installed some 470uF capacitors for C101/C201. I'm really quite puzzled as to how I should connect this. Any help would be appreciated.
Thanks!
Anyway, I have a question about connecting the Feedback for this amp. I have been working from the schematics drawn up by Ian444 (SimplePPschemUL.gif Photo by birdy81260 | Photobucket). Unfortunately, whenever I connect the secondary output to L_FB-1 or R_FB-2, I get a huge squealing noise.
I found some help on this in this post: http://www.diyaudio.com/forums/tubelab/148694-tubelab-simple-p-p-58.html#post3482585 , which suggested swapping the PRI_1 and PRI_2 secondary connections. This did change the noise that came out- instead of the squealing noise, I now get a rhythmic scratchy popping noise.
If I just disconnect L_FB-1 and R_FB-2, then the amp seems to work...? I have also seen documentation (For the SSE) that shows the L_FB-1 / R_FB-2 nodes shorted to their corresponding FB node. I installed some 470uF capacitors for C101/C201. I'm really quite puzzled as to how I should connect this. Any help would be appreciated.
Thanks!
Update:
Anyone having a similar problem, try removing your C101/C201 capacitors. Without them installed, everything works wonderfully.🙂 Apparently the 470pF capacitance value is too high for my amp.
Even better, try the amp before installing them!
Anyone having a similar problem, try removing your C101/C201 capacitors. Without them installed, everything works wonderfully.🙂 Apparently the 470pF capacitance value is too high for my amp.
Even better, try the amp before installing them!
Even better, try the amp before installing them!
In the build instructions on his website, George advises to build and listen first, and then install the feedback compensation caps if needed. 🙂
Good to know that you have got the amp up and running.
Im a bit perplexed also considering this is a beginner build there is no wiring hookup on the websight for the SPP
What tube does the SPP use for gain/phase splitting? Been thinking of building one of these with a set of old iron from a Heathkit EL84 amp. I have the original Mullard GZ34 from the amp.
TIA, Steve
TIA, Steve
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