Sims are nice, thanks, Mooley. Nicest performance of a single supply fully complimentary amp I have seen.
The real world has RF interference in it. The 0.1 ohm and the two 680 pf at the output on DX appear to be an attempt to stop RF, but is rather unique and feeble. What is working in my location on the ST120 is 15 turns of wire between output transistors and C25, plus 1000 ohms 3 Watt series 0.1 uf ceramic cap across the output jacks, dual banana jack/binder posts. Both the ST120-PC15-djoffe bias side, and the AX6 driver side, are dead quiet in my location which is 3 miles from half the radio stations AM & FM in the metro area. Also, the amp is in a steel case with a perforated steel cover. Even with that I was picking up multiple radio stations on AX6 side with 4 m of RCA cable from mixer and C12 at 33 pf, but changing C12 to 68 pf killed that - unless the mixer is turned off before the amp.
The 2 A bias current with speaker connected, check to see if RF oscillation occurs at the same time with analog meter AC scale+DC blocking cap. If so try C13 & c14 @ 47 pf instead of 7.5 pf.
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Have to admit that in simulation it does seem pretty stable. Layout and grounding is everything though.
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hi mooly,
I installed ltspice and can run dc analysis.
I can't run Ac analysis or freq.resp, nothing appears on the graph....I used your file...can you help me?
I installed ltspice and can run dc analysis.
I can't run Ac analysis or freq.resp, nothing appears on the graph....I used your file...can you help me?
Have you followed the link in my signature line on how to use LT ? Have a look at post #7 in that thread.
If the graph has appeared then you need to place and click the cursor on to the point of interest (the amp output).
Did you install LT IV (the original version) or LT XVII ? There are some slight differences in operation.
If the graph has appeared then you need to place and click the cursor on to the point of interest (the amp output).
Did you install LT IV (the original version) or LT XVII ? There are some slight differences in operation.
have fun.
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HI bigun,
would be amazing if you attach the final and definitive schematic of your amp
do you plan to build it ?
will you make your own pcb design ?
I know this is an old thread, but since I actually built the DX-Trust I am curious about your findings. My build is described in the main thread, starting from here:
https://www.diyaudio.com/forums/solid-state/141744-trust-delicious-dx-amplifier-8.html#post3526853
Mine is built according to the plans except for 2uF at the input, 8800uF at the output and has an inverted bias servo. It also has a different homemade pcb. Please see the comments in the main thread.
@cucico
Did you finish your build, and what are your impressions?
@Mooly
Thank you for your insightful simulations. Regarding the reported "thin" sound I also suspected C5 to be a bit small. I may change it for a bigger value next time I open the box for service/upgrade, one channel at the time.
I never had any oscillations or other bad things, except for some faint hum in the left channel, most likely caused bu close proximity to the transformer. Rearranging the signal wire helped somewhat. Otherwise it works well, maybe not the richest in bass, but it's hard to say since I don't have another amp to compare it to. Some recordings work very well indeed.
https://www.diyaudio.com/forums/solid-state/141744-trust-delicious-dx-amplifier-8.html#post3526853
Mine is built according to the plans except for 2uF at the input, 8800uF at the output and has an inverted bias servo. It also has a different homemade pcb. Please see the comments in the main thread.
@cucico
Did you finish your build, and what are your impressions?
@Mooly
Thank you for your insightful simulations. Regarding the reported "thin" sound I also suspected C5 to be a bit small. I may change it for a bigger value next time I open the box for service/upgrade, one channel at the time.
I never had any oscillations or other bad things, except for some faint hum in the left channel, most likely caused bu close proximity to the transformer. Rearranging the signal wire helped somewhat. Otherwise it works well, maybe not the richest in bass, but it's hard to say since I don't have another amp to compare it to. Some recordings work very well indeed.
yes, it's exactly what I'm looking for.
I think that if someone looks at dx trust schematics, can surely improve it.
I would start from R13.....
I am working on a 52 year old Pioneer SX-1000TA and the power amp section is almost the same as the diagram above. Amazing.
(Don’t know if I’ll grt it going, but I’m giving it a try!)
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