Ok so after some fidling I have a few conclusions. The left channel or channel closest to the PT hums more with the volume down low. I've swapped the tubes around and its definitely not the tubes. I've narrowed it down to the PT being too close to board or perhaps its the filament wire that partially runs over the output section? I'll keep tinkering.
Despite the hum the sound is very nostalgic and dare I say lovely. In low light and with a drink in hand I can't stop tapping my feet. The Highs don't shimmer, however they blend lovely with what ever genre of music I play.When I iron out some of the kinks i will post the pics and proper review.
Shorting the input
Russell,
When I do that the hum free channel attenuates a little and distorts. Have you encountered that before? So at the min only one channel plays the other just hums.
Russell,
When I do that the hum free channel attenuates a little and distorts. Have you encountered that before? So at the min only one channel plays the other just hums.
descent progress
Russel thank you so much for your help with the wiring. I've been so busy with work that I haven't even checked my Facebook in ages. That aside I managed to put aside sometime to fix a few niggles with the amp it's not perfect but the sound is...dare I say charming.
I need to replace the volume pot as I'm getting some nice with the vol low down and One channel also plays abit lower than the next. One of my rft 12at7 valves fell on the ground so I need to get another matched pair.
Apart from what I mentioned the sound is very transparent, vivid and realistic. Guitar solos and sax singles sound just superb. The Diana Krall "Love Scenes" album is almost magical on it. However on bassier tracks the amp does fall short but that can be down to my OPTS which are Hammond. I wished I spent more on the Edcors like I was advised or the triode dynaco clones.
Overall it's a great midrange sounding amp. It was fun to build and I'm going to enjoy tweaking it.
Here are some pictures.
Russel thank you so much for your help with the wiring. I've been so busy with work that I haven't even checked my Facebook in ages. That aside I managed to put aside sometime to fix a few niggles with the amp it's not perfect but the sound is...dare I say charming.
I need to replace the volume pot as I'm getting some nice with the vol low down and One channel also plays abit lower than the next. One of my rft 12at7 valves fell on the ground so I need to get another matched pair.
Apart from what I mentioned the sound is very transparent, vivid and realistic. Guitar solos and sax singles sound just superb. The Diana Krall "Love Scenes" album is almost magical on it. However on bassier tracks the amp does fall short but that can be down to my OPTS which are Hammond. I wished I spent more on the Edcors like I was advised or the triode dynaco clones.
Overall it's a great midrange sounding amp. It was fun to build and I'm going to enjoy tweaking it.
Here are some pictures.
Attachments
Kerontt, I found the rft 12AT7's to be stronger in midrange and treble, and weaker in bass, compared to my other branded 12AT7's. If your system needs stronger bass I suggest trying any other different brand. Using matched tubes isn't really necessary IMO, the cathodyne phase splitter does not make gain. If you really wanted matched preamp tubes, its the 2nd triode of each 12AT7 tube (pins 6, 7 and 8) that need to be matched to each other. It will only affect the balance between the left and right speaker, you could always buy 3 un-matched and swap them around if the L-R balance was noticeably out.
Very nice build!
Hello
I got a Simple PP kit maybe two years ago and I am now ready to start putting it together . This is my first try at building a tube amp . I am about to order the Transformers from EDCOR and I would like to find out if the XPWR007 or XPWROO8-120 Power Transformers and the CXPP25-MS-7.6K Output Transformer are still the best choices or are there better or more suitable EDCORS now being used . I would really appreciate some advice before confirming my order . Also is there anyone selling a top plate with the tube holes already bored out , or is a stencil available . Thanks
I got a Simple PP kit maybe two years ago and I am now ready to start putting it together . This is my first try at building a tube amp . I am about to order the Transformers from EDCOR and I would like to find out if the XPWR007 or XPWROO8-120 Power Transformers and the CXPP25-MS-7.6K Output Transformer are still the best choices or are there better or more suitable EDCORS now being used . I would really appreciate some advice before confirming my order . Also is there anyone selling a top plate with the tube holes already bored out , or is a stencil available . Thanks
jasoun,
Let the experts chime in, but OPTs and XPWR008 look like good choices. I have the same OPTs, and my power transformer is the 240v version of the XPWR008.
Have you got the pdf of the PCB from the Tubelab website? That can help you do the holes for the top plate - you can find it here:
http://www.tubelab.com/AssemblyManualSimpleP-P/StartHere_SPP.html
Let the experts chime in, but OPTs and XPWR008 look like good choices. I have the same OPTs, and my power transformer is the 240v version of the XPWR008.
Have you got the pdf of the PCB from the Tubelab website? That can help you do the holes for the top plate - you can find it here:
http://www.tubelab.com/AssemblyManualSimpleP-P/StartHere_SPP.html
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Re- The Power Transformer for Simple PP , what is the difference in output or any other performance difference between using the EDCOR XPWR007 or XPWROO8-120 Power Transformers . I see where most people use the 008 but then they comment on the tubes being very near to there limit . Reliability is very important for me , will I be giving up much in performance if I go with the safer 007 .
Thanks
Thanks
jasoun,
If you check the Tubelab "Tubes and Transformers" page for the Tubelab PP, George recommends a transformer capable of 640-650 VCT - IIRC the XPWR008 is 600VCT (300-0-300).
http://www.tubelab.com/AssemblyManualSimpleP-P/TubesAndTransformers_SPP.htm
If I am not wrong a few of the folks ran into problems with the rectifier, and I recall reading that the Sovtek 5AR4 does a good job in this design, and that is what I am using
If you check the Tubelab "Tubes and Transformers" page for the Tubelab PP, George recommends a transformer capable of 640-650 VCT - IIRC the XPWR008 is 600VCT (300-0-300).
http://www.tubelab.com/AssemblyManualSimpleP-P/TubesAndTransformers_SPP.htm
If I am not wrong a few of the folks ran into problems with the rectifier, and I recall reading that the Sovtek 5AR4 does a good job in this design, and that is what I am using
Spp
Ian, thanks a lot mate. I've been so busy with work and being away that I haven't worked on the amp in ages. It's covered free from dust until I can do some more modding. I will change the rfts to jj perhaps. The outputs are cryo jj's and sound pretty good. High ones do you use?
Does one channel on your amp play considerably louder than the next? Regardless if I swallow the valves around I get the same channel playing louder and distorting faster. Could it be the pot? It 100k
Ian, thanks a lot mate. I've been so busy with work and being away that I haven't worked on the amp in ages. It's covered free from dust until I can do some more modding. I will change the rfts to jj perhaps. The outputs are cryo jj's and sound pretty good. High ones do you use?
Does one channel on your amp play considerably louder than the next? Regardless if I swallow the valves around I get the same channel playing louder and distorting faster. Could it be the pot? It 100k
It is unnecessary to remove the grid leak resistor, I prefer to leave it in place in-case of volume pot failure.
Well, this is the wiring diagram for the Hammond 1650FA OPT:
Each channel on the SPP has 3 sets of terminals for the OPTs. So for example, from left to right along the back of PCB:
Left Channel
- L-PRI_2
- 2 - V102 screen - primary blue/yellow wire
- 1 - V102 plate - primary blue wire
- L-PRI_1
- 3 - V101 screen - primary brown/yellow wire
- 2 - V101 plate - primary brown wire
- 1 - primary red wire
- L_FB
- 2 - Ground - secondary black wire
- 1 - Feedback - secondary (green, yellow, or white)
Right Channel
Please note that L_FB and R_FB are mirrored! Also note that if you do decide to use feedback (by installing C101/201), you may need to swap the PRI_1 and PRI_2 secondary connections on each channel to get the right phasing (leave the red wire where it is). I can't remember if I had to or not. You'll know if it's wrong if you get loud squealing out of your speakers with feedback connected.
- R-PRI_2
- 2 - V202 screen - primary blue/yellow wire
- 1 - V202 plate - primary blue wire
- R-PRI_1
- 3 - V201 screen - primary brown/yellow wire
- 2 - V201 plate - primary brown wire
- 1 - primary red wire
- R_FB
- 2 - Feedback - secondary (green, yellow, or white)
- 1 - Ground - secondary black wire
Russ,
For pentode connection, I would have to connect the following points to one another?
PRI_1-3, PRI_1-1, PRI_2-2
