Your choices above are fine......
Are you planning on running the KT88's in UL or Triode? I suggest that you try triode even if you are planning UL.....less power but great sound, better distortion profile..etc. Since your speakers are 90db 6-8 watts may be plenty.
One thing with Hammond transformers are that they can run a little high on the output voltage, esp if your house mains voltage is high. The rectified voltage is 1.41x the AC output voltage (1.41x375V)=528V.....but this voltage is dropped by the forward drop of the 5AR4 and the resistance of the choke.
I did a quick PSUDII simulation assuming 80ma for each KT88 and another 20ma for the 12AT7's......I'm a bit rusty here but maybe not too far off. You should end up with around 450VDC.....maybe a little higher. You can adjust this voltage lower by using a smaller uf first cap after the 5AR4. Keep in mind that there is a max uf value for the first cap after the 5AR4, exceed this value and the rectifier may arc over and die. I think it may be around 68uf but I can't remember...
If you want more volts you can use SS diodes, they drop less volts......and as George mentioned in the build instructions current limiters at startup are a good idea. CL60's or CL90's are pretty typical and easy enough to wire in. SS diodes also don't have the constraint for the max value of the first capacitor like vacuum tube rectifiers do.
I would use 500V rated electrolytics in the power supply as well.
I would consider finding coupling caps that are 500V rated since you will be on the ragged edge with 450V caps, although they will have a little margin for over-voltage.
This is a great first project for a foray into tubes.
Are you planning on running the KT88's in UL or Triode? I suggest that you try triode even if you are planning UL.....less power but great sound, better distortion profile..etc. Since your speakers are 90db 6-8 watts may be plenty.
One thing with Hammond transformers are that they can run a little high on the output voltage, esp if your house mains voltage is high. The rectified voltage is 1.41x the AC output voltage (1.41x375V)=528V.....but this voltage is dropped by the forward drop of the 5AR4 and the resistance of the choke.
I did a quick PSUDII simulation assuming 80ma for each KT88 and another 20ma for the 12AT7's......I'm a bit rusty here but maybe not too far off. You should end up with around 450VDC.....maybe a little higher. You can adjust this voltage lower by using a smaller uf first cap after the 5AR4. Keep in mind that there is a max uf value for the first cap after the 5AR4, exceed this value and the rectifier may arc over and die. I think it may be around 68uf but I can't remember...
If you want more volts you can use SS diodes, they drop less volts......and as George mentioned in the build instructions current limiters at startup are a good idea. CL60's or CL90's are pretty typical and easy enough to wire in. SS diodes also don't have the constraint for the max value of the first capacitor like vacuum tube rectifiers do.
I would use 500V rated electrolytics in the power supply as well.
I would consider finding coupling caps that are 500V rated since you will be on the ragged edge with 450V caps, although they will have a little margin for over-voltage.
This is a great first project for a foray into tubes.
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One more thing...I would save the $$ on the Mullard and Auricaps and jump up one series of output transformers at Edcor if the budget can swing it. The boutique tubes and capacitors $$ would be better spent on the output transformer IMO....the XSE's are quite small and are going to have limited bass response.
Wow, thanks so much for the replies! This was all extremely helpful.
If i swap to these output transformers do i need to swap out any of the parts to match it?
Are you referring to the edcor GXSE15-8-5k? if so i think i can swing that one instead! hopefully i can find a pair sometime before April- the lead times for parts are crazy right now.
If i swap to these output transformers do i need to swap out any of the parts to match it?
Thanks for pointing me in the right direction with these caps. I'm still learning where to spend the money and where to save it.
I was planning on running in triode. It seemed like the least confusing thing for a first time builder like myself.
I'm having some trouble sourcing 1200 PIV diodes. There are no part numbers for them on the BOM and I'm not confident in finding a compatible part.
The same goes for the CSS digikey part number IXCP10m45s-ND. I can't seem to find those anywhere and I have a feeling it's not because they are scarce but because I don't quite know what it is I'm looking for.
I'm also under the impression I might not need these parts if I'm using a tube rectifier. Maybe SS rectifier is a simpler way to go?
Thanks again for the help!
lol you're right about that! maybe i'll pull the trigger on them tonight and by the time they show up I'll have the rest of this thing sorted outEdcor has a huge lead time right now. That's just the way it is. Plan accordingly
If you use a tube rectifier you don't need the 1200V FreD Diodes (fast recovery epitaxial diodes)
The 10m45s is the CCS (constant current source) for the long tailed pair phase splitter (I think...going from memory)....
It's made by IXYS......you want to the T0-220 thru hole package.....Mouser has 1 in stock and DigiKey has zero.....search either vendor for "10M45S" The good news is that Mouser has another 3217 pieces showing up on 1/2/2023!!!!! WOW!
As already mentioned......the GSXE series transformers (or any other SE 5K-8 ohm output transformer) is a drop-in replacement. The Frequency response for the XSE series is 70-18K and for the GXSE it's 40-18K. You want 40% taps on the transformer to run UL mode (both of these transformers have that, although the images confuse me a bit). Triode or UL are trivial in the wiring differences....you may want to play with both.....
The 10m45s is the CCS (constant current source) for the long tailed pair phase splitter (I think...going from memory)....
It's made by IXYS......you want to the T0-220 thru hole package.....Mouser has 1 in stock and DigiKey has zero.....search either vendor for "10M45S" The good news is that Mouser has another 3217 pieces showing up on 1/2/2023!!!!! WOW!
As already mentioned......the GSXE series transformers (or any other SE 5K-8 ohm output transformer) is a drop-in replacement. The Frequency response for the XSE series is 70-18K and for the GXSE it's 40-18K. You want 40% taps on the transformer to run UL mode (both of these transformers have that, although the images confuse me a bit). Triode or UL are trivial in the wiring differences....you may want to play with both.....
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The diodes can be 1n4007s. No need to use Schotkey's or such. You do want them & the cl-140 limiter if you are using tube rectification.
You can just jumper the connections & it will work, but you'll be removing some slow start & a bit of extra protection for the rectifier tube.
The CSS is not part of the power supply circuit & has nothing to do with tube or SS rectification.
It's an integral part of the driver circuit.
Yeah, if you are looking at this:
https://www.digikey.com/en/products/detail/ixys/IXCP100M45/2116766
Then it really is not in stock. Mouser doesn't have any either.
I am not knowledgeable enough to recommend a suitable replacement.
You can just jumper the connections & it will work, but you'll be removing some slow start & a bit of extra protection for the rectifier tube.
The CSS is not part of the power supply circuit & has nothing to do with tube or SS rectification.
It's an integral part of the driver circuit.
Yeah, if you are looking at this:
https://www.digikey.com/en/products/detail/ixys/IXCP100M45/2116766
Then it really is not in stock. Mouser doesn't have any either.
I am not knowledgeable enough to recommend a suitable replacement.
This is what I used for the 1200V SS rectifier diodes
https://www.digikey.ca/en/products/...=productdetail_CA&utm_cid=2223935&so=72798790
in my recent SSE build (about 2 months ago). Initially I thought of only using tube rectification but why not add the SS rectifier as well since it is so simple.
https://www.digikey.ca/en/products/...=productdetail_CA&utm_cid=2223935&so=72798790
in my recent SSE build (about 2 months ago). Initially I thought of only using tube rectification but why not add the SS rectifier as well since it is so simple.
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Here's an alternative 1200V Fred Diode that's a bit more affordable...
https://www.mouser.com/ProductDetai.../VS-HFA08TB120-M3?qs=F5EMLAvA7ID0I52a0WQIpw==
...and as mentioned earlier 1N4007 diode works too....they are 25 cents each........I would use the faster recovery flavor ..UF4007..they are 45 cents each. Both of these are 1000V rated parts.
The part Jsabev posted above is a super fast SiC (silicon carbide) diode with essentially a zero recovery time, so that's why the premium price.
https://www.mouser.com/ProductDetai.../VS-HFA08TB120-M3?qs=F5EMLAvA7ID0I52a0WQIpw==
...and as mentioned earlier 1N4007 diode works too....they are 25 cents each........I would use the faster recovery flavor ..UF4007..they are 45 cents each. Both of these are 1000V rated parts.
The part Jsabev posted above is a super fast SiC (silicon carbide) diode with essentially a zero recovery time, so that's why the premium price.
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Unrelated to this component talk...get yourself some clip leads for your multimeter(s). That allows safe "hands-off" measuring of the various voltages. Having 2-3 meters is REALLY handy when bringing an amp up for the first time. If need a meter or two the $6 Harbor Freight one will work.
Here is an example of some (Really nice Fluke) clip leads:
https://www.mouser.com/ProductDetail/Fluke/TL940?qs=8mPiuICODS9BwwLPep6DLA==
There are other brands like Pomona that are nice too......you can find cheaper ones but my experience is some of the cheaper alternatives are a pain to work with.
If you decide to just use the test probes on your meter, read the safety sticky in the tubes section. Never probe HV with 2 hands......get the ground lead attached to some metal and use one hand to carefully measure whatever you are measuring. Put your other hand in your pocket or better yet around your back grabbing a belt loop.
...or just get some clip leads...tube amps aren't worth dying for....
Here is an example of some (Really nice Fluke) clip leads:
https://www.mouser.com/ProductDetail/Fluke/TL940?qs=8mPiuICODS9BwwLPep6DLA==
There are other brands like Pomona that are nice too......you can find cheaper ones but my experience is some of the cheaper alternatives are a pain to work with.
If you decide to just use the test probes on your meter, read the safety sticky in the tubes section. Never probe HV with 2 hands......get the ground lead attached to some metal and use one hand to carefully measure whatever you are measuring. Put your other hand in your pocket or better yet around your back grabbing a belt loop.
...or just get some clip leads...tube amps aren't worth dying for....
Wow! good thing I waited until a total supply chain collapse to fulfill my dream of building my own system
I bought a couple of the IXYS parts on eBay so hopefully that works out!
This morning I pulled the trigger and ordered the GXSE15-8-5k output transformers you guys recommended.
I also ordered the Hammond Power transformer and choke as well as all the components for the PCB except the diodes, the coupling caps and the tubes and sockets- I'll sort that out this evening.
I'll prob go with these recommended diodes.
I suppose ill need some wire (duh) any recommendations there?
I guess while I wait for parts I can sort out the knobs, switches, fuse and all that other stuff George include on the other parts list.
I'll grab one of these as well! Not totally sure what to do with it yet but I'll learn!
Thanks again for all the recommendations and guidance!
This is great tip. I have one decent multimeter I use primarily on motorcycles. Maybe ill pick up a second cheap one and a couple sets of alligator clips too! I think safety is best practice here as I truly am a n00b. Thanks!
There may have been a bit of crossing information.
If you look at the PC board top, lower left, you'll see pads labeled D1, D2, D3, D4 & TR1
D1 & 2 are for the hexafreds for SS rectification.
D3 & 4 are where I was saying it's fine to use 1n4007 diodes. They are for some protection of the rectifier in case of a hot switch scenario.
TR1 is where the CL-140 lives.
The current limiters go on the AC mains input...don't worry about them, you'll figure that out later. They are easy to wire in.
I generally use either 600V or 1200V FreDs on my gear.......the reason for the 1200V PIV (peak inverse voltage) rating is that as these things switch on and off every 1/60th of a second ( or maybe 120 times a second..) sometimes there are large voltage spikes, and they can sometimes exceed 600V......George went to 1200V parts for this reason. Usually when powering up the amp, etc.
As far as wire goes, decent wire typically has it's specs inked on the jacket.....like UL listed, voltage rating, etc. Usually the common stuff is 300V rated, like the wires in a PC ATX power supply. You can also find wire that is 600V rated, it has a thicker jacket/insulator. If the jacket isn't inked with the voltage rating don't assume it's 600V. Teflon jacketed wire is usually rated for higher voltage but you don't really need this unless you want to spend the $$.
The other area is the input conductors from the RCAs to the board........these are sensitive to picking up noise. I sometimes use small Coax (RG179 or something?, can't remember.....or you can use the wires from a typical CAT5 ethernet cable. They are telfon coated twisted pairs.....almost free and work well for the inputs.
For the mains cable you can either hard-wire it into the chassis with a strain relief (look up heyco strain relief); you can buy these at McMaster-Carr or likely Digi-Key and Mouser, or better yet use an IEC 320 power inlet and use a modular power cord like the many that are laying around the house. I cannibalize dead computer power supplies for the IEC 320 power inlet, and they usually have some nice mains filtering on them too. I much prefer the screw in type over the snap in type....same goes for switches. I also use the wire from dead computer power supplies for lots of stuff, but you will need 600V rated wired from the transformers. In your case the wires on the transformer will be rated sufficiently.
I generally use either 600V or 1200V FreDs on my gear.......the reason for the 1200V PIV (peak inverse voltage) rating is that as these things switch on and off every 1/60th of a second ( or maybe 120 times a second..) sometimes there are large voltage spikes, and they can sometimes exceed 600V......George went to 1200V parts for this reason. Usually when powering up the amp, etc.
As far as wire goes, decent wire typically has it's specs inked on the jacket.....like UL listed, voltage rating, etc. Usually the common stuff is 300V rated, like the wires in a PC ATX power supply. You can also find wire that is 600V rated, it has a thicker jacket/insulator. If the jacket isn't inked with the voltage rating don't assume it's 600V. Teflon jacketed wire is usually rated for higher voltage but you don't really need this unless you want to spend the $$.
The other area is the input conductors from the RCAs to the board........these are sensitive to picking up noise. I sometimes use small Coax (RG179 or something?, can't remember.....or you can use the wires from a typical CAT5 ethernet cable. They are telfon coated twisted pairs.....almost free and work well for the inputs.
For the mains cable you can either hard-wire it into the chassis with a strain relief (look up heyco strain relief); you can buy these at McMaster-Carr or likely Digi-Key and Mouser, or better yet use an IEC 320 power inlet and use a modular power cord like the many that are laying around the house. I cannibalize dead computer power supplies for the IEC 320 power inlet, and they usually have some nice mains filtering on them too. I much prefer the screw in type over the snap in type....same goes for switches. I also use the wire from dead computer power supplies for lots of stuff, but you will need 600V rated wired from the transformers. In your case the wires on the transformer will be rated sufficiently.
I built a SSE over a decade ago and sold the stuffed board before ever powering it up.....so I'm gonna be rusty on the details. I sold it because I built two Tubelab SE's..a 300B version and a 45 version. The 300B version is my favorite amp.
It looks like Tony built his board with the caps and other tall stuff on the bottom...something else to consider depending on how you want to house the amp. Also be mindful of other HV stuff on the topside......it may be close to the underside of the top deck when mounting this way. On my Tubelab SEs I put pretty much everything except the tube sockets on the bottom; there are many ways to do this.
It looks like Tony built his board with the caps and other tall stuff on the bottom...something else to consider depending on how you want to house the amp. Also be mindful of other HV stuff on the topside......it may be close to the underside of the top deck when mounting this way. On my Tubelab SEs I put pretty much everything except the tube sockets on the bottom; there are many ways to do this.