Another TSE for me...
I built this one primarily because I had an unused pair of Lundahl LL1663/50mA on the shelf.
Operating point is 50mA at 350V B+.
THD is about 1.5% at 1W at 5% at about 8W.
Sounds really good and I like the lack of OPT on the top, which really showcases the 300B's.
I built this one primarily because I had an unused pair of Lundahl LL1663/50mA on the shelf.
Operating point is 50mA at 350V B+.
THD is about 1.5% at 1W at 5% at about 8W.
Sounds really good and I like the lack of OPT on the top, which really showcases the 300B's.
Attachments
Finished my second SPP, first one was with Hammond transformers that I enjoyed alot so decided to build an upgraded version with Hashimoto transformers. The only other splurge is the Mundorf 100uF polypropylene PSU capacitor.
I ran some measurements on my PC and it measures nicely.
0.07% THD @ 1W output
0.95% THD @ 10.5W output
The frequency response is very good, -0.3dB @ 20Hz and +0.1dB at 20kHz. (measured at 10W close to max output power. Notice the Y-axis is 1dB range)
10kHz square wave is nice too.
Only one thing is that I should have maybe spaced the output transformer a bit further away from the power tube. There is 1" clearance now, the opt gets slightly warm but not hot so I think it's fine.
I ran some measurements on my PC and it measures nicely.
0.07% THD @ 1W output
0.95% THD @ 10.5W output
The frequency response is very good, -0.3dB @ 20Hz and +0.1dB at 20kHz. (measured at 10W close to max output power. Notice the Y-axis is 1dB range)
10kHz square wave is nice too.
Only one thing is that I should have maybe spaced the output transformer a bit further away from the power tube. There is 1" clearance now, the opt gets slightly warm but not hot so I think it's fine.
Attachments
I've built alot of projects over the past few years so get asked alot about sound comparisons but unfortunately I don't have a great answer.
The previous SPP with Hammonds was used at my previous home, the room was small and untreated. I'm now in a new place, in a dedicated listening room that is much bigger and also has room treatments, so there are too many variables.
Hopefully I'll be in this place long term and so will be able to make informed comparisons going forward.
I did find the Hammond SPP enjoyable and did not feel anything was particularly missing or off in terms of sound. Ofcourse most of us don't settle so I decided to build one with more premium parts. One subjective thing I noticed with the Hashimoto (and I don't know how the room plays into this) is that the bass is amazing.
Measurements wise, the Hammond had similar THD performance (at 1kHz), but the square-wave was ugly and didn't get much better even with the compensation caps. It also went into instability with UL that required some trial and error to fix. The Hashimoto performs way better in that regard, with and without NFB, very nice square waves and no instability issues.
It definitely has better bandwidth and higher quality unit.
The Hashimoto PT is very quiet (you literally need to put your ear on it to hear any buzz) and gets a bit warm after hours of operation but never hot unlike the Hammonds.
A Hammond set (PT+OPT) costs ~$380 whereas the Hashimoto is probably close to $1000, about a $600 difference. If you're building a cheap amp for the garage or background music then the Hammond is sufficient, and in that case maybe even go with Edcor which is cheaper (and may perform better).
If you're planning on using this amp in the main system or in a listening room, then I would not hesitate to go with the Hashimoto. Ultimately $600 is not a big difference in DIY, and you'd be spending thousands on a retail amp that uses the same quality iron. It also upgrades the look of the amp (IMHO).
Hashimoto also has a smaller 15W P-P OPT, which is a few hundred dollars cheaper for a pair and could make a nice and cute amp (the 25W I used are massive compared to EL84's). I'm sure the FR won't be as nice to 20Hz though.
The previous SPP with Hammonds was used at my previous home, the room was small and untreated. I'm now in a new place, in a dedicated listening room that is much bigger and also has room treatments, so there are too many variables.
Hopefully I'll be in this place long term and so will be able to make informed comparisons going forward.
I did find the Hammond SPP enjoyable and did not feel anything was particularly missing or off in terms of sound. Ofcourse most of us don't settle so I decided to build one with more premium parts. One subjective thing I noticed with the Hashimoto (and I don't know how the room plays into this) is that the bass is amazing.
Measurements wise, the Hammond had similar THD performance (at 1kHz), but the square-wave was ugly and didn't get much better even with the compensation caps. It also went into instability with UL that required some trial and error to fix. The Hashimoto performs way better in that regard, with and without NFB, very nice square waves and no instability issues.
It definitely has better bandwidth and higher quality unit.
The Hashimoto PT is very quiet (you literally need to put your ear on it to hear any buzz) and gets a bit warm after hours of operation but never hot unlike the Hammonds.
A Hammond set (PT+OPT) costs ~$380 whereas the Hashimoto is probably close to $1000, about a $600 difference. If you're building a cheap amp for the garage or background music then the Hammond is sufficient, and in that case maybe even go with Edcor which is cheaper (and may perform better).
If you're planning on using this amp in the main system or in a listening room, then I would not hesitate to go with the Hashimoto. Ultimately $600 is not a big difference in DIY, and you'd be spending thousands on a retail amp that uses the same quality iron. It also upgrades the look of the amp (IMHO).
Hashimoto also has a smaller 15W P-P OPT, which is a few hundred dollars cheaper for a pair and could make a nice and cute amp (the 25W I used are massive compared to EL84's). I'm sure the FR won't be as nice to 20Hz though.
Another SSE Build
I just finished my SSE build. Big thanks to George for all his effort in the tubelab SSE.
I went with Hammond 278BX power transformer, 193J choke and 1628SEA output transformers. All parts sourced from digikey with the only "boutique" parts being the AuriCap coupling caps.
The board was very straightforward to stuff and assemble.
Some observations:
Turning it on without any load with solid state rectification produces more than 500V on the B+. Heard some whistling from the C2 capacitor as it is rated for 500V. At some point I will replace it with a 600V cap just in case.
By far, the biggest challenge was drilling the chassis. At the end, despite all the efforts, it was not aligned properly so had to do some grinding with a dremel to get the tube sockets to align.
The sound with KT88s is really good - shockingly good. Zero hum despite the underneath being a rats' nest of wires. Opted for a ultralinear mode with no CFB.
I just finished my SSE build. Big thanks to George for all his effort in the tubelab SSE.
I went with Hammond 278BX power transformer, 193J choke and 1628SEA output transformers. All parts sourced from digikey with the only "boutique" parts being the AuriCap coupling caps.
The board was very straightforward to stuff and assemble.
Some observations:
Turning it on without any load with solid state rectification produces more than 500V on the B+. Heard some whistling from the C2 capacitor as it is rated for 500V. At some point I will replace it with a 600V cap just in case.
By far, the biggest challenge was drilling the chassis. At the end, despite all the efforts, it was not aligned properly so had to do some grinding with a dremel to get the tube sockets to align.
The sound with KT88s is really good - shockingly good. Zero hum despite the underneath being a rats' nest of wires. Opted for a ultralinear mode with no CFB.
Great work, solid work! Now you are probably asking yourself why you waited so long to finish it….
Enjoy!
