Last weekend I finished my SE84 clone and now have over 20 hrs on it, so thought I'd write a report.
This project started out with me being really excited about the clear and open sound I got from my Pilot 402 and wanting to to try to scratch build a power amp using Pilot transformers. I found a trashed Pilot 602 locally and bought it for parts. I didn't have a SE tube amp at the time, so after giving it some thought I decided to build an SE amp instead of a second PP. So I parted out the amp and sold the PP OPT. Tried to sell the PT, but it didn't go. So, I started to look into what I might be able to build with it.
The PT is just a massive hunk of iron. It was designed to use SS rectification (no 5V tap) but the Pilot 602 schematic showed that it could produce 330VDC rectified. So, I started looking for SE schematics with lower B+ SS rectified voltage. Not many out there, I can assure you. I came up with a few from DIYAudioProjects.com including a 6V6 and a 6CY7, but then I discovered the Decware Zkit schematic and realized that it used SS rectification and a B+ of about 325-350V. I had been very interested in Decware SE84 from all the reviews from happy customers. I decided that THIS was the amp I wanted to build.
Total cost, not including tubes was $200. Mouser, Parts Express, Edcor. See the Decware Zkit BOM for part numbers. Thanks Steve Deckert!! You da man!
I used a Hammond aluminum chassis 15x7x3. Just a bit larger than the Decware chassis with plenty of room to spare.
I really like the Decware layout and was torn at how to lay mine out, but in the end, I decided like the asymmetrical look of the PS on one side and amp on the other side. Plus, I liked the clean look of hiding the input jacks and speaker binding posts in the back to hide wires.
I left room for a future tube diode if I wanted, but I've never had an SS rectified tube amp before and from reading about them, they kind of seem like they offer more advantages in terms of punch.
I used Edcor CXSE 25watt OPT on a previous SE amp. They were impressive, but very expensive and I think overkill. I wanted to see what the GXSE could do and trusted it because that is what Decware specifies in their Zkit. The Pilot 402 and DGSE1 amps both have small OPT yet still produce very full bass. I'm sure others will disagree, but I no longer feel it necessary to use giant iron...especially for my type of listening. I have NO regrets for using the GXSE. More on that in the review section.
I had to replace the 6watt 1K power resistor with a 50watt one because when I first fired up the amp, the 6 watt resistor started smoking. ????
Regrets or things I would do differently
1) I think a shorter chassis would be OK. 3" is quite tall and the metal is kind of thin. More of a tactile thing. It doesn't sag at all.
2) Smaller coupling caps. I had great luck with the Audyn 1200V cap on a previous preamp build. They sound great but they're huge.
3) NO stranded wire. I hate that stuff, but I was too cheap and lazy to go pick up some and ran my heater wires with stranded. Not a huge deal, but I just hate that it doesn't stay put and it makes for ugly soldering.
4) Belton Micalex tube sockets vs. ceramic. A lot of amp kits use ceramic, so I thought I'd give them a try. Normally I use Belton as my standard. Boy, what a mistake. These ceramic sockets suck. Grip well, but springy and hard to insert. And the gold retaining rings look very cheap and flimsy.
5) I honestly think I would buy the Zkit board and UFO OPT from Decware next time. It would save so much time to not have to build a chassis and do PtoP wiring. Heck, even integrating the board into the chassis wouldn't look half bad. I just don't like the idea of board mounted sockets.
This project started out with me being really excited about the clear and open sound I got from my Pilot 402 and wanting to to try to scratch build a power amp using Pilot transformers. I found a trashed Pilot 602 locally and bought it for parts. I didn't have a SE tube amp at the time, so after giving it some thought I decided to build an SE amp instead of a second PP. So I parted out the amp and sold the PP OPT. Tried to sell the PT, but it didn't go. So, I started to look into what I might be able to build with it.
The PT is just a massive hunk of iron. It was designed to use SS rectification (no 5V tap) but the Pilot 602 schematic showed that it could produce 330VDC rectified. So, I started looking for SE schematics with lower B+ SS rectified voltage. Not many out there, I can assure you. I came up with a few from DIYAudioProjects.com including a 6V6 and a 6CY7, but then I discovered the Decware Zkit schematic and realized that it used SS rectification and a B+ of about 325-350V. I had been very interested in Decware SE84 from all the reviews from happy customers. I decided that THIS was the amp I wanted to build.
Total cost, not including tubes was $200. Mouser, Parts Express, Edcor. See the Decware Zkit BOM for part numbers. Thanks Steve Deckert!! You da man!
I used a Hammond aluminum chassis 15x7x3. Just a bit larger than the Decware chassis with plenty of room to spare.
I really like the Decware layout and was torn at how to lay mine out, but in the end, I decided like the asymmetrical look of the PS on one side and amp on the other side. Plus, I liked the clean look of hiding the input jacks and speaker binding posts in the back to hide wires.
I left room for a future tube diode if I wanted, but I've never had an SS rectified tube amp before and from reading about them, they kind of seem like they offer more advantages in terms of punch.
I used Edcor CXSE 25watt OPT on a previous SE amp. They were impressive, but very expensive and I think overkill. I wanted to see what the GXSE could do and trusted it because that is what Decware specifies in their Zkit. The Pilot 402 and DGSE1 amps both have small OPT yet still produce very full bass. I'm sure others will disagree, but I no longer feel it necessary to use giant iron...especially for my type of listening. I have NO regrets for using the GXSE. More on that in the review section.
I had to replace the 6watt 1K power resistor with a 50watt one because when I first fired up the amp, the 6 watt resistor started smoking. ????
Regrets or things I would do differently
1) I think a shorter chassis would be OK. 3" is quite tall and the metal is kind of thin. More of a tactile thing. It doesn't sag at all.
2) Smaller coupling caps. I had great luck with the Audyn 1200V cap on a previous preamp build. They sound great but they're huge.
3) NO stranded wire. I hate that stuff, but I was too cheap and lazy to go pick up some and ran my heater wires with stranded. Not a huge deal, but I just hate that it doesn't stay put and it makes for ugly soldering.
4) Belton Micalex tube sockets vs. ceramic. A lot of amp kits use ceramic, so I thought I'd give them a try. Normally I use Belton as my standard. Boy, what a mistake. These ceramic sockets suck. Grip well, but springy and hard to insert. And the gold retaining rings look very cheap and flimsy.
5) I honestly think I would buy the Zkit board and UFO OPT from Decware next time. It would save so much time to not have to build a chassis and do PtoP wiring. Heck, even integrating the board into the chassis wouldn't look half bad. I just don't like the idea of board mounted sockets.
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