It would be nice if you could use some form of revision control on your drawings/sims, so others can keep track of changes.
I took your latest Symasui 2.0 and modified it, to use for the AWH-048 form-factor design, so that it can be tested in a real situation.
Set the gain to match the original Pioneer design.
In the original design you posted, I saw some ringing on the negative edge and peaking on the frequency response curves?
The ringing gets worse on my implementation.
If you let me know the components you selected, I could add them to the sim as notes since I assume we do not have models for them.
See what you think
I took your latest Symasui 2.0 and modified it, to use for the AWH-048 form-factor design, so that it can be tested in a real situation.
Set the gain to match the original Pioneer design.
In the original design you posted, I saw some ringing on the negative edge and peaking on the frequency response curves?
The ringing gets worse on my implementation.
If you let me know the components you selected, I could add them to the sim as notes since I assume we do not have models for them.
See what you think
I do, among other vintage units. I'm trying to wrap my head with how it would sound with such a mod, it is an amazing unit as it is
I see you use MJL21193/4 - slow , some Sankens are 60mhz ! the 2 diodes should be between VAS LTP bases.
Your NFB resistors are too high value , more noise.
I might go your way and use the dual TTC004's in the VAS cascode for through-hole. Matching does not matter
on this cascode , it's just a high Z level shifter ... isolating the BC's from HV.
I'm "post OCD" on the sym ....
I do see that bit of ringing with SW or heavy clip. But , it is is well damped (stable).
MY simulation is in the zip - 1/2ppm !
OS
Your NFB resistors are too high value , more noise.
I might go your way and use the dual TTC004's in the VAS cascode for through-hole. Matching does not matter
on this cascode , it's just a high Z level shifter ... isolating the BC's from HV.
I'm "post OCD" on the sym ....
I do see that bit of ringing with SW or heavy clip. But , it is is well damped (stable).
MY simulation is in the zip - 1/2ppm !
OS
Attachments
I'm going to mod an OEM amp for these projects , using a old Sampson servo 500 chassis. But it has strait , flat standard 3U heatsinks.
How it would sound ??? Airy , effortless (with a big OPS). This small OPS would likely sound better than say a "Rockville" scam "3000W"
studio amp. For a bigger OPS , Wolverine OPS's will work with these designs .. Stuart made a 4 pair version , "Fireanimal" runs 4 pair
MT-200's and gets sub PPM @ 400W !!
OS
Yeah I had the clamp diodes wired up incorrectly, fixed.
Since we are using the exsiting sx-1250 infastructure, we are forced to use the slow MJ2119x or original 2SBxxx/2SDxxx devices. Will try to make the best out of what we have to work with.
We could reduce the NFB and input impedance a bit (47k) and still retain the same gain
I just chose what they used originally since they want a high input R(62k)
Since we are using the exsiting sx-1250 infastructure, we are forced to use the slow MJ2119x or original 2SBxxx/2SDxxx devices. Will try to make the best out of what we have to work with.
We could reduce the NFB and input impedance a bit (47k) and still retain the same gain
I just chose what they used originally since they want a high input R(62k)
I have the wolverine boards, impressive work, i got them just more for curiosity and for learning, especially since I realized that I don't need another behemoth. I will rather go with the symasui... I like your approach very much, a sleeper unassuming amp sounds like fun!
Not so short, NFB trace is quite long. I prefer NFB trace as short as possible.😉
Hipocrates, if you want to be involved and beta test my symasui2.0 version designed for a sx-1250,
I could supply you pcbs to try out, can you do the smt soldering?
I could supply you pcbs to try out, can you do the smt soldering?
R20 to Q5 = 20mm ? That's long ?
I see where you could say ALL the NFB traces are long , NFB goes the whole length of the OPS board.
I was passed over on the wolverine ... good ! I use that thread to see what 20K$ fancy test rigs find out.
What I found out , i recycle in the "post wolverine " design.
On this IPS , it's a VFA - just 1mA through R20/21. High Z Q5's trace is just near the clamp diodes and cascodes.
On the CFA , 80mA is way more. On all , I only allow reduced signals to pass anywhere near any high Z circuitry.
I keep those big CFA resistors away from anything and put them near the VAS/interface socket.
It works out good , Wolverine is 1/2PPM at 100's of watts.
I have to do the CFA Hellraiser again (next). I will isolate those pesky big resistors and even make the CFA ground selectable
between G1 / G2. Then during testing - finalize it. I use solderable bridges to do this. Those bridges are under Q8.
I will use another dual BJT P/N package for Q7/8 on the Hellraiser.
OS
I see where you could say ALL the NFB traces are long , NFB goes the whole length of the OPS board.
I was passed over on the wolverine ... good ! I use that thread to see what 20K$ fancy test rigs find out.
What I found out , i recycle in the "post wolverine " design.
On this IPS , it's a VFA - just 1mA through R20/21. High Z Q5's trace is just near the clamp diodes and cascodes.
On the CFA , 80mA is way more. On all , I only allow reduced signals to pass anywhere near any high Z circuitry.
I keep those big CFA resistors away from anything and put them near the VAS/interface socket.
It works out good , Wolverine is 1/2PPM at 100's of watts.
I have to do the CFA Hellraiser again (next). I will isolate those pesky big resistors and even make the CFA ground selectable
between G1 / G2. Then during testing - finalize it. I use solderable bridges to do this. Those bridges are under Q8.
I will use another dual BJT P/N package for Q7/8 on the Hellraiser.
OS
Attachments
Different way to compensate it. lag- lag .... lead at FB ? Still has the same OLG phase ... and Thd.
What is the difference , or improvement by changing the phase relationship in the audio band ?
OS
What is the difference , or improvement by changing the phase relationship in the audio band ?
OS
Last edited:
According to the Bode criterion, the feedback amplifier is absolutely stable if, at all frequencies at which the loop gain LFR is greater than zero (it lies above the frequency axis), the phase shift determined by the LFC is less than 180. https://studfile.net/html/2706/58/html_W91MapwhIP.VTl5/img-Kztjgn.png
You nailed it , Printnik. I guess I'll have to figure out transfer functions !
My simple 2- pole does not oscillate , but your method gives a whopping 90db OLG @ 20K without oscillating.
I'm going to hold back on the Symasui and get the two originals done (below).
I'm finally at the point where I was before my HDD failed.
OS
My simple 2- pole does not oscillate , but your method gives a whopping 90db OLG @ 20K without oscillating.
I'm going to hold back on the Symasui and get the two originals done (below).
I'm finally at the point where I was before my HDD failed.
OS
Attachments
Last edited:
This is mine VFA from 2014 (or around ) with LSK389 and TT output transistors and with simulated THD below ppm level at all frequences and output power.
I still listening sometime (to many finished amps 😊). https://www.diyaudio.com/community/threads/thermaltrak-tmc-amp.182554/
I still listening sometime (to many finished amps 😊). https://www.diyaudio.com/community/threads/thermaltrak-tmc-amp.182554/
