Thanks guys. My questions have been answered. I will keep an eye on the progress with the MOSFETs. I have a drawer full of them myself. I'll save my questions about the genuine OS designs for the new thread. Hopefully that one will stay on course.
Blessings, Terry
Blessings, Terry
Hi Valery,
Great work!
Have you considered replacing the EF or double EF with MosFet drivers?
...Jim
Great work!
Have you considered replacing the EF or double EF with MosFet drivers?
...Jim
I think MOSFET drivers would be wasteful of voltage efficiency and I doubt the VAS would be able to drive it any easier since the gate capacitance is really big with almost any FET. Lightly loaded EF stages work very well as a buffer.
First picture is 1KHz loopback spectrum
Cheers,
Valery
What's true rms value of the output signal from card from 1. pic (loopback)?
+1 (soundwise for me, no idea about measuring results)
http://www.diyaudio.com/forums/soli...n-subwoofer-wideband-duty-13.html#post3382545
Really interest this problem.
MOSFET driver, which are the best we need? 2SK216/2SJ79 is very hard to find.
What's about IRf6xx, like IRF610/9610?
MOSFET driver, which are the best we need? 2SK216/2SJ79 is very hard to find.
What's about IRf6xx, like IRF610/9610?
The Low TIM hybrid is playing. Sounds very nice but one channel is noticeabely louder. I can see it on the bias too. I tried swapping tubes and there is no change. Must be something else. Maybe I missed changing one of the resistors. With so many changes it is sure possible I missed something. I'm attaching a photo of it playing. Pardon the rats nest.
Blessings, Terry
Blessings, Terry
Attachments
Terry,
Do you have any subjective impressions (opinions??) to share regarding the sound of the tube IPS versus say the Wolverine IPS?
Do you have any subjective impressions (opinions??) to share regarding the sound of the tube IPS versus say the Wolverine IPS?
I found the issue. For some reason, I had 100k in the feedback resistor. Should be 47K. Now all is good.
Carl,
I did do a little A/B comparison with a Honey Badger. Very, very close. I need a little more time to do more critical listening. I'll get back tomorrow.
Blessings, Terry
Carl,
I did do a little A/B comparison with a Honey Badger. Very, very close. I need a little more time to do more critical listening. I'll get back tomorrow.
Blessings, Terry
Thanks. I feel like a load has been lifted. There is a lot more to getting the hybrid working with needing the heater transformer and needing the delay for the speaker protection. It does sound very nice.
Final schematic as built (single EF - 2-nd option)
Here we go. That's the one I like the best.
Single EF, but built on the "second" pair (NJW0281/0302), working at 15 mA, sitting on a local heatsink with Q103 driver Vbe transistor, as designed originally. C108 is still in place (it was just difficult to draw the red box without touching it). R113 is two 1K resistors in parallel (we need 500 ohm here). I have put CSA and CSB 33pF caps "just in case" - it actually runs fine without them, but I feel safer with them in place 🙂
I think, having these drivers, it will run with 5 output pairs smoothly - I just don't have enough space at my test heatsink for 2 extra pairs.
VAS (at the front-end) runs at 5.6 mA.
Key measurements are good enough, sound is excellent. Same strong clean bass, highest level of micro-details. I also attach the hybrid front-end schematic as used with this OPS now (measurements are done for this combination, though the front-end's contribution in overall distortion is negligible).
I'm not keen to try the FET drivers at this time - they will require higher VAS current, Vbe spreader redesign and will "eat" some output swing headroom. I'm rather happy with what I've got at the moment. Enjoying the listening and soldering the second channel 🙂
Let me know if you have questions 😉
Cheers,
Valery
P.S. Added a picture of what the front side of OPS looks like...
Here we go. That's the one I like the best.
Single EF, but built on the "second" pair (NJW0281/0302), working at 15 mA, sitting on a local heatsink with Q103 driver Vbe transistor, as designed originally. C108 is still in place (it was just difficult to draw the red box without touching it). R113 is two 1K resistors in parallel (we need 500 ohm here). I have put CSA and CSB 33pF caps "just in case" - it actually runs fine without them, but I feel safer with them in place 🙂
I think, having these drivers, it will run with 5 output pairs smoothly - I just don't have enough space at my test heatsink for 2 extra pairs.
VAS (at the front-end) runs at 5.6 mA.
Key measurements are good enough, sound is excellent. Same strong clean bass, highest level of micro-details. I also attach the hybrid front-end schematic as used with this OPS now (measurements are done for this combination, though the front-end's contribution in overall distortion is negligible).
I'm not keen to try the FET drivers at this time - they will require higher VAS current, Vbe spreader redesign and will "eat" some output swing headroom. I'm rather happy with what I've got at the moment. Enjoying the listening and soldering the second channel 🙂
Let me know if you have questions 😉
Cheers,
Valery
P.S. Added a picture of what the front side of OPS looks like...
Attachments
Last edited:
Great job! I'm happy you like it
Hi Carl,
I have been listening to music all morning. I have the Low TIM hybrid on one side and the Honey Badger on the other of my A/B setup. I have tested with worship, jazz, country, rock, blues and techno. There is virtually no difference in sound between the two amps. To be sure that it wasn't just me, I had my son come in and listen. He is a worship leader and a fine musician. He was unable to detect when I changed amps. This is a complement by the way. The Honey Badger is one fine sounding amp.
I know my opinion isn't popular with a lot of the designers around here. All I can say is if you want to believe that your latest amp sounds better than your last, don't build a blind A/B setup. You may be very disappointed.
Blessings, Terry
I'm really surprised Terry that the tube front-end IPS sounds the same as all BJT IPS, that's really strange if not even very weird.
My First One V1.2 and V1.3 sounds noticeably different and there's a only a little difference among almost completely the same design. I can easily notice even if my input interconnect cable inside chassis is coax or twisted pair. 😕
It looks like I'm a "Golden Ear" or something's really wrong with me. 😀
Thanks reporting A/B test still4given, confess haven't got a A/B test setup myself i unplug/plugin when testing.
Wonder though that there virtually are no difference, to make sence i think okay all tested amps must have hit a certain good class/level (maybe signal source and speakers can't reveal difference).
Expect one of these better amps that sound virtually same that if A/B'ed against cheaper chipamp or maybe clean tubeamp that your A/B test setup would reveal a difference.
Wonder though that there virtually are no difference, to make sence i think okay all tested amps must have hit a certain good class/level (maybe signal source and speakers can't reveal difference).
Expect one of these better amps that sound virtually same that if A/B'ed against cheaper chipamp or maybe clean tubeamp that your A/B test setup would reveal a difference.