I am still here, but my "practical Gremlin" is the absence of C-cores so I can't wind my own output transformers and I find doing own OPTs quite an important DIY satisfaction factor.
I seems difficult to find any supplier and I made a try earlier during the winter to find a source but failed, for now am quite busy and will be so for another month but in may I will try to look into it again.
Would appreciate very much if anybody knows where to get C-cores.
Cheers Michael
Update:
The notification from Edcor finally came yesterday. The Power Trans. have been shipped! Wow that seemed like it took forever. My Electraprints are here waiting on their arrival!
Any updates on the BOM? Didn't see alot of additional input on the matter.
The notification from Edcor finally came yesterday. The Power Trans. have been shipped! Wow that seemed like it took forever. My Electraprints are here waiting on their arrival!
Any updates on the BOM? Didn't see alot of additional input on the matter.
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The Edcors arrived today. I hope I didn't undersize then too much as they look rather dinky next to the massive Electraprints. On most amps, these seem closer in size.
Here's a comparison:
For those who have never seen giant PP tranny's. Here's what they look like next to the OPT's on my Dynaco ST70.
Here's a comparison:
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
For those who have never seen giant PP tranny's. Here's what they look like next to the OPT's on my Dynaco ST70.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
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Well, you are comparing the relative size of an OPT to the power transformer on a stereo amp. You are building monoblocks, yes?
No, I was referring to other Monoblocks such as gregory's. Those ST70 pics were just to show how massive the Electraprints are in general.😱
They are monsters for sure. It's a little hard to tell because his OPTs are lying on their sides.
WOW!!! That's some serious iron! I can see now why people like to build big PP amps as monoblocks. What do those things weigh? Oh yes, if you don't mind my asking, what did those Electraprints run you?
Hey, long time no chat...
Despite the gorgeous summer weather that my wife hates me wasting when I could be doing something 'worthwhile', I've begun thinking about this amplifier project again and I wanted to start laying out a chassis.
I need advice since I am a tube newbie. Here's my first drawing. I would prefer to keep a square-ish shape rather than a long thin guitar amp style chassis shape. This one is about 8 x 10" as drawn.
The goal is to create something that will be dead simple for anyone to build with wood and a suitable slab of aluminum, using the stock BOM parts, but have ample room for "upgrades". On that note, how much bigger can high-end output transformers be -- within practical reason of course?
What needs changing here (and why?) Thanks!
[edit] Ooh... Just realized I didn't put any capacitors on the layout. I'll have to research their size/shape, etc.
[edit2] Also noticed the choke is infringing on one of the KT88 sockets. That obviously will not work.
..Todd
Despite the gorgeous summer weather that my wife hates me wasting when I could be doing something 'worthwhile', I've begun thinking about this amplifier project again and I wanted to start laying out a chassis.
I need advice since I am a tube newbie. Here's my first drawing. I would prefer to keep a square-ish shape rather than a long thin guitar amp style chassis shape. This one is about 8 x 10" as drawn.
The goal is to create something that will be dead simple for anyone to build with wood and a suitable slab of aluminum, using the stock BOM parts, but have ample room for "upgrades". On that note, how much bigger can high-end output transformers be -- within practical reason of course?
What needs changing here (and why?) Thanks!
[edit] Ooh... Just realized I didn't put any capacitors on the layout. I'll have to research their size/shape, etc.
[edit2] Also noticed the choke is infringing on one of the KT88 sockets. That obviously will not work.
..Todd
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Organized the way you have it will transfer quite a bit of hum from the power trafo to the OPT, through the air. To use this compact a lay out the power trafo must first be on its belly, with the coil sticking through a rectangular hole cut in the chassis. Then you must make a capital T with the OPT, across the short end of the power trafo core. You can safely mount the choke between the two trafo's. This is the classic Fender Bassman transformer layout and can be very quiet. But, you cannot cheat.
Means the power trafo must have all leads coming out one side of the coil, and a non foot cover plate must be obtained from Edcore and the current end bells must be removed. Save the isolation washers, the MUST be replaced in the same locations they are currently in.
Bud
Means the power trafo must have all leads coming out one side of the coil, and a non foot cover plate must be obtained from Edcore and the current end bells must be removed. Save the isolation washers, the MUST be replaced in the same locations they are currently in.
Bud
I have made a lot of amplifiers. It seems that my bigest mistake (and one I keep making) is making them too small. Small amps are much more prone to hum and signal coupling related issues. I have managed to beat that with careful layout and PC board construction. But the best layout can't solve the "too much heat in too small space" issue.
I have a Simple SE in a 10 X 12' box and it gets too hot. It uses 2 X KT88 a 12AT7 and a 5AR4, and likely dissipates a similar amount of heat. After running it for a few hours any part of the amp is hot, even the metal volume knob. The transformers and chassis deck can't be touched. It has been totally reliable though. The tight quarters make working on it a bit hard too.
I have a pair of "not high end" OPT's made by David Lucas before he started ripping everybody off. I plan to use these in my medium sized P-P project. They are rated at 60 watts and measure 3.75 inches across the core and 4.5 inches across the end bells.
Conventional wisdom holds that big power tubes like the KT88 should be spaced by an amount at least equal to their diameter.
Thanks all. Back to the drawing board.
I do want to keep it easy for off-the-shelf products, so I don't want to require any special orders from Edcor. Looking at standard Hammond boxes... How would, say, 8 x 16" or 10 x 17" work? Enough room to keep things quiet and cool?
Given what I've said for requirements, how would you guys approach laying out the hardware?
FYI: I think the latest schematic/BoM is here... MSG 809
..Todd
I do want to keep it easy for off-the-shelf products, so I don't want to require any special orders from Edcor. Looking at standard Hammond boxes... How would, say, 8 x 16" or 10 x 17" work? Enough room to keep things quiet and cool?
Given what I've said for requirements, how would you guys approach laying out the hardware?
FYI: I think the latest schematic/BoM is here... MSG 809
..Todd
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Hi Chrish, Yeah, it's on my 'to read' list. I'm still trudging slowly through the tube electronics theory books I have. Just haven't gotten to that one yet. 🙄
In the meantime, I checked out the Dynaco MkIII amp layout to see how the pro's did it... Almost the same -- except even more cramped! I suppose those amps got pretty hot, and hummed?
An externally hosted image should be here but it was not working when we last tested it.
I'll find some more examples of KT88 PP mono blocks (I hope) to see how their layouts were handled. Feel free to point me to any good ones that you know of.
..Todd
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How much humm you hear will depend on the sensitivity of your speakers. I have several amps with your suggested xfmr configuration with dc heaters and i can't hear the hum. You can see a 60Hz spike in the FFT however, which I m sure some is related to the coupling between transformers.
On the other hand my OPUS has the OPT in the flat orientation and I have a 60 Hz spike. I reasoned that to be the AC heaters. Can't hear the hum however.
On the other hand my OPUS has the OPT in the flat orientation and I have a 60 Hz spike. I reasoned that to be the AC heaters. Can't hear the hum however.
While making a measurement, turn the amp OFF. Unplug it even. Guess what. That 60 Hz spike doesn't go away. It's everywhere.
Darn power companies! I want to live in an area like some of the others here that don't have the spike. Audio Bliss.
Jeeze, you already said you can't hear it. Sounds like adequate bliss to me. 😉
Regarding the layout of this amp, here's my 2nd kick at the can... Any blunders here? (It seems the Edcor power tranny isn't belly-mount compliant.)
..Todd
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Taj, Check the kt88 specs, There are dimension and orientation conditions listed. I lent my MJ book out, will have to get it back, but there is also a good rules on placement around xfmrs.
While the OPT and PT are vertical endbells, the choke and filament xfmr can be laid on there side to avoid coupling. The choke is the one to watch as it runs near saturation.
Actually I liked the first sketch. You can keep the layout more symetrical that way.
While the OPT and PT are vertical endbells, the choke and filament xfmr can be laid on there side to avoid coupling. The choke is the one to watch as it runs near saturation.
Actually I liked the first sketch. You can keep the layout more symetrical that way.
Todd, I easily stuffed two channels of KT88 PP running 60 WPC using Edcor transformers on a 17" wide by 10" deep by 2" high black anodized chassis.
An externally hosted image should be here but it was not working when we last tested it.
I use two power transformers, one for each channel. Inside I have a number of PC boards. Three are for the power supplies. One is a filament and HV delay board. The other two are the left and right high voltage power supplies.
There is a single driver PC board for both channels mounted below the four 6SN7s in the center.
All four transformers sit on a 1/4" thick anodized aluminum plate that is bolted to the Bud chassis. I also have a 1/4" aluminum brace running under the center of the chassis from side to side to further increase rigidity. The aluminum Bud chassis is only about 0.050" thick and not as sturdy as I would like, so I added the plate aluminum.
As far as heat goes, the amp runs reasonably cool with the exception of the power transformers. The current draw is less than their ratings, but they do get pretty warm. This has nothing to do with the layout, but is inherent with the transformers. Edcor states that they are operating within their limits. I don't know how many hours I have on these, but they have been running flawlessly for me.
An externally hosted image should be here but it was not working when we last tested it.
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