I was going to also ask Vunce for a pair but then realized it’s cheaper to have 5 PCBs made at JLCPCB and have them shipped to Canada than buying a pair from someone in the US. It’s insane. Cost me $10 USD to have 5 done (red) including shipping to Canada. Pollution wise I’m not sure it’s the best option though...
Thanks for making your PCB available Cody 👍
Thanks for making your PCB available Cody 👍
Awesome, thanks for sharing measurements! The 1A4 point came about purely through listening and so I am glad to see measurements validate that somewhat. Can you also look at the phase of the second harmonic in both cases? REW provides that.
Agreed. I made the measures taking speaker+ from the big cap, and taking speaker- from ground. Based on experience measuring all my other amps, this setup yields negative phase second. REW displays it as 96deg, but historically that always indicates negative second. I believe Generg has also confirmed this using Diana.
Edit* in other words, I believe hooking it up as displayed in schematic and on the boards will yield overall phase inverted, and a positive second. I can also say I’ve tried it both ways and have a hard time deciding which I like best. They both sound really, really good.
Edit* in other words, I believe hooking it up as displayed in schematic and on the boards will yield overall phase inverted, and a positive second. I can also say I’ve tried it both ways and have a hard time deciding which I like best. They both sound really, really good.
I have tried both ways with my SIT amps and I prefer to have the sound project forward, out in front of the speakers. I believe that is positive phase. It sounds more realistic to me.
Sound stage with precise placement of instruments and voices is an "audiophile" thing. Live music does not have precise placement of sounds. Live music projects outward.
That is my opinion and I am sure many disagree with me.
Sound stage with precise placement of instruments and voices is an "audiophile" thing. Live music does not have precise placement of sounds. Live music projects outward.
That is my opinion and I am sure many disagree with me.
I imagine that each design and even each operating point gives different results. So, it is not a universal thing to reverse the speaker out. I tested all combinations on the TDV without looking at measured 2nd harmonic phase and settled on the two reversals mentioned earlier. On certain songs and albums, I do like to flip the signal input back to "in phase."
codyt, what's the 2nd harmonic phase at 1A7?
Ben, I don't think you are alone. Dave Griesinger calls it the "feeling of proximity" to the sound. This grabs the listeners attention and is highly valued.
Check out this presentation: http://www.davidgriesinger.com/The_Physics_of_auditory_proximity_2.pptx
Couple of selected conclusions:
I bet that the second harmonic helps the ear/brain combo to clarify or group reflections, thereby improving proximity or clarity.
codyt, what's the 2nd harmonic phase at 1A7?
Ben, I don't think you are alone. Dave Griesinger calls it the "feeling of proximity" to the sound. This grabs the listeners attention and is highly valued.
Check out this presentation: http://www.davidgriesinger.com/The_Physics_of_auditory_proximity_2.pptx
Couple of selected conclusions:
- Proximity – the perception that a source is acoustically close - is an important determinant of attention and recall.
- The ear detects proximity through the phase coherence of upper harmonics in the direct sound, which are randomized by early reflections.
I bet that the second harmonic helps the ear/brain combo to clarify or group reflections, thereby improving proximity or clarity.
Yes, Operating point definitely makes a difference. When trying to null the second in a pre or power amp, it’s fun to watch the phase number quickly flop as you pass the null ‘sweet spot’. In fact, I have one set of tubes for my 845 SE amp that - when set to prescribed Iq - do the exact opposite phase (one neg 2nd: one pos 2nd). Actually, it make for any interesting and enjoyable sound.
The TDV stuck consistently at negative phase 2nd when I adjusted Eq. In the measurement screenshots, you can see the phase deg just to the right of percentages of individual harmonics.
The TDV stuck consistently at negative phase 2nd when I adjusted Eq. In the measurement screenshots, you can see the phase deg just to the right of percentages of individual harmonics.
Having spent some time with TDV, I think I can offer some basic remarks and comparison...
All in all, an exceptional sounding amp. Easily holds its own with just about everything I have. It has a smooth, organic quality that I definitely associate with SE tube amps, but has lucidness and command of details that I think SIT followers really seem to nail (ask Ben Mah
It really does a superb job with details on the lower end. It's not the final word in bass slam or anything, but nobody would/should expect that. Being a follower, the FE/pre really makes an impact. So far, my favorite combo has been with the BA3 FE. I think it simply appreciates plenty of voltage gain. Every combo has been a winner though.
- a bit more organic and relaxed than Sony DIY PP VFET
- close cousin to the Sony SE DIY VFET
Yes, I really enjoy my single ended SIT followers.
It took a while to get to this point as I enjoyed other implementations of SITs, starting with the diyAudio push-pull Sony VFET amp, and then to a few variations of single ended common drain SIT amps, and also a DEF amp, the SissySIT. So I have heard quite a few SIT amps and they are all quite good, but the single ended SIT follower is the best implementation according to my ears.
I don't have any 2SK2087C but I am listening to my choke loaded 2SJ28 follower right now, and I would expect it to sound very much like a choke loaded 2SK2087C follower. It is a great choice for this hot summer. Then I have my SIT followers for the autumn, for the winter,..........
It took a while to get to this point as I enjoyed other implementations of SITs, starting with the diyAudio push-pull Sony VFET amp, and then to a few variations of single ended common drain SIT amps, and also a DEF amp, the SissySIT. So I have heard quite a few SIT amps and they are all quite good, but the single ended SIT follower is the best implementation according to my ears.
I don't have any 2SK2087C but I am listening to my choke loaded 2SJ28 follower right now, and I would expect it to sound very much like a choke loaded 2SK2087C follower. It is a great choice for this hot summer. Then I have my SIT followers for the autumn, for the winter,..........
Whoops, I meant to say that I built a few single ended common source SIT amps before I ended up building followers.
My question is, can THF51S be used in place of the more elusive K2087C? What would be the ideal Iq and supply voltage? Thanks.
I'm unaware of that combo being tested in this specific configuration, but I'm sure it'll work (see ra7's comments above). If I were going to take a crack at it, I'd probably start with 2R at R3 and work down. I'd probably put a 2-3A fuse between PSU and Vdc-in while I figured out operating points.