Greeting all!
I'm going to pick up a K12G tube kit and I want to upgrade all the transformers to Edcor. Does anyone know which edcor models are best drop-in replacements to the stock ones? This would include two output transformers and one power transformer.
Also, are there exact instructions for how to install them? Ive searched around for info, but haven't found the authoritative response. I'm also new to DIY audio, so handholding is greatly appreciated, 🙂
I'm going to pick up a K12G tube kit and I want to upgrade all the transformers to Edcor. Does anyone know which edcor models are best drop-in replacements to the stock ones? This would include two output transformers and one power transformer.
Also, are there exact instructions for how to install them? Ive searched around for info, but haven't found the authoritative response. I'm also new to DIY audio, so handholding is greatly appreciated, 🙂
Here's a recent thread: http://www.diyaudio.com/forums/tubes-valves/217665-s5-k-12g-output-trans.html
jeff
jeff
Hi Jeff, There are several choices that largely depend on your budget and the chase or chassis you plan on using. Here are my picks
For outputs
GXPP10-6-10K ($28)
GXPP10-6-8K ($28)
CXPP-MS-10K ($44)
CXPP-MS-8K ($44)
For power
XPWR 236 ($44)
XPWR012 ($43) (need to series the 6 and 5 volt heater windings)
XPWR264 ($63) (a bit of overkill)
The best IMO for outputs is the CXPP10-MS-10K
The Best IMO for the power is the XPWR 236
All the outputs have ultra linear screen taps and I recommend you use them that way. PM me for details if you are interested
I completely rebuilt a K-12 (modified circuit as well) using the XPWR 236 and CXPP10-MS-10K transformers. A really big step up.
EDIT: I just saw the other posting....pass on the Hammonds.. I used them and while better they were not as good as the EDCORS.
For outputs
GXPP10-6-10K ($28)
GXPP10-6-8K ($28)
CXPP-MS-10K ($44)
CXPP-MS-8K ($44)
For power
XPWR 236 ($44)
XPWR012 ($43) (need to series the 6 and 5 volt heater windings)
XPWR264 ($63) (a bit of overkill)
The best IMO for outputs is the CXPP10-MS-10K
The Best IMO for the power is the XPWR 236
All the outputs have ultra linear screen taps and I recommend you use them that way. PM me for details if you are interested
I completely rebuilt a K-12 (modified circuit as well) using the XPWR 236 and CXPP10-MS-10K transformers. A really big step up.
EDIT: I just saw the other posting....pass on the Hammonds.. I used them and while better they were not as good as the EDCORS.
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Why buy that kit when your replacing the transformers and so paying big bucks for non standard no longer produced tubes and a PCB?
Maybe look at 17W/CH diytube.com ST-35 PCB using even better (another big step up from the above mentioned upgraded ones) output transformers and in production tubes from Triode Electronics whom sells a whole kit if wanted. Or you could use the Edcors to save $. Add Dave Gillespie's EFB mod on the Tronola Electronics site for the best sonics and tube life.
Also consider tubelab.com George Anderson's Nice EL84 PP PCB and kit of parts to populate the board as it is well regarded also. He also has a helpful Forum on this site also.
Maybe look at 17W/CH diytube.com ST-35 PCB using even better (another big step up from the above mentioned upgraded ones) output transformers and in production tubes from Triode Electronics whom sells a whole kit if wanted. Or you could use the Edcors to save $. Add Dave Gillespie's EFB mod on the Tronola Electronics site for the best sonics and tube life.
Also consider tubelab.com George Anderson's Nice EL84 PP PCB and kit of parts to populate the board as it is well regarded also. He also has a helpful Forum on this site also.
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Cool! I'll check that out too. The K12G was attractive to me as a nice 1st tube project. I've read great things about it, and the initial cost of $200 certainly eases entry into the hobby. My plan was to build the stock one on the pine board just to make sure it works. Then upgrade to the Edcor transformers, which look amazing... and try to build a proper chassis for it. I'm very new to DIY electronics and definite want to ease into it with best chances for success. 🙂
I forgot about Pete Millet and he posts on this site. His very popular Engineer's Amp (Big Red Board) with a PCB for it may be a a good diy project to look at also! It uses old TV tubes and new production could be subbed if need be also. Some have gotten amazing power out of it with bigger output tubes still from TV's, and there is a huge thread on this forum about it, He has other PCB's with the simpler maybe more suitable. to check out also, and he has a a great web site with lots of books to download for info.
I should mention previously mentioned George's tubelab.com also has SE and SET PCB's that are very popular. If close to 10W/CH the Simple SE has been very popular with new people as it is simpler with only one output tube per channel and less parts. It uses affordable in production tubes also and with the Edcor GX series also except the SE versions you can build a very affordable SE amp. SE or SET is actually the way the first amps started with PP coming later for more power.
As your learning the Output Transformer is key to the sonics of a tube amp so you have to spend wisely.
You will also come across the virtues of SE or SET vs PP.
I should mention previously mentioned George's tubelab.com also has SE and SET PCB's that are very popular. If close to 10W/CH the Simple SE has been very popular with new people as it is simpler with only one output tube per channel and less parts. It uses affordable in production tubes also and with the Edcor GX series also except the SE versions you can build a very affordable SE amp. SE or SET is actually the way the first amps started with PP coming later for more power.
As your learning the Output Transformer is key to the sonics of a tube amp so you have to spend wisely.
You will also come across the virtues of SE or SET vs PP.
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What speakers are you going to drive? What nominal impedance?
Do you want to squeeze a bit more power out,or are you wanting to optimize distortion?
Based on the Philips data sheet, I'd recommend 10K plate to plate. 8K will give you a bit more power out, at more distortion.
I've found that the GXPP series in the 15W class to be excellent when used at lower power levels (10W amp) as you get better low frequency extension before core saturation sets in.
http://www.r-type.org/pdfs/ecl86.pdf
Look at the later pages showing 8.2K and 9.1K P-P load vs distortion. Distortion is way lower at 9.1K, and will most likely be lower at 10K as well. Unfortunately they don't give a plot of distortion harmonics vs load impedance.
With regards to obsolescence, buy a spare set of tubes off ebay, Cut back on your plate dissipation to 75%, and enjoy the amp for 20 - 30years (you will need to re-cap it in the interim).
Do you want to squeeze a bit more power out,or are you wanting to optimize distortion?
Based on the Philips data sheet, I'd recommend 10K plate to plate. 8K will give you a bit more power out, at more distortion.
I've found that the GXPP series in the 15W class to be excellent when used at lower power levels (10W amp) as you get better low frequency extension before core saturation sets in.
http://www.r-type.org/pdfs/ecl86.pdf
Look at the later pages showing 8.2K and 9.1K P-P load vs distortion. Distortion is way lower at 9.1K, and will most likely be lower at 10K as well. Unfortunately they don't give a plot of distortion harmonics vs load impedance.
With regards to obsolescence, buy a spare set of tubes off ebay, Cut back on your plate dissipation to 75%, and enjoy the amp for 20 - 30years (you will need to re-cap it in the interim).
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Pete Millet's 'engineer's amplifier' is definitely a great candidate:
DCPP Amp
Thanks for pointing that out, @rmyauk! I see that Edcor has a separate project site for the required transformers:
https://www.edcorusa.com/pm-100
I've got a lot of reading ahead of me to better understand what I'm getting myself into. 😉 I'll probably stick with the K12G initially. I like the idea of getting a single package that has all the necessary pieces to get started. After that - on to the 'engineers amp'.
I'm planning to drive a pair of NHT super zero's (8 ohm) that I've had for ~20 years. This is all mostly just for fun.
Thanks for all the great guidance!!! This is quite a useful forum! 🙂
DCPP Amp
Thanks for pointing that out, @rmyauk! I see that Edcor has a separate project site for the required transformers:
https://www.edcorusa.com/pm-100
I've got a lot of reading ahead of me to better understand what I'm getting myself into. 😉 I'll probably stick with the K12G initially. I like the idea of getting a single package that has all the necessary pieces to get started. After that - on to the 'engineers amp'.
I'm planning to drive a pair of NHT super zero's (8 ohm) that I've had for ~20 years. This is all mostly just for fun.
Thanks for all the great guidance!!! This is quite a useful forum! 🙂
If you want to do the simple PP type of amp first, you really owe yourself to really try an EL84 PP amp first for the great sonic qualities of the EL84/6BQ5 tubes that can't be beat in that power range. Either the ST-35 or the tubelab PP ones can be had with a kit of parts so that makes it just as easy as all you have to buy are the OPT's and PS trans. For close to the same kind of $ you are going to spend you will not regret the greater sonics and power!
A used Dynaco SCA-35 is another affordable way to go as it can be easily recapped etc.
A used Dynaco SCA-35 is another affordable way to go as it can be easily recapped etc.
Hello,
I'm considering upgrading my K-12G to the EDCOR transformers Bruce recommended in this thread (CXPP10-10K/XPWR 236) but overwhelmed on how they would be connected.
Would someone be kind enough to let me know how to go about hooking them up to the existing board?
Thank you!
I'm considering upgrading my K-12G to the EDCOR transformers Bruce recommended in this thread (CXPP10-10K/XPWR 236) but overwhelmed on how they would be connected.
Would someone be kind enough to let me know how to go about hooking them up to the existing board?
Thank you!
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