Just out if curiosity, what speaker model is this? 92 dB with 10 Ohm or higher sounds like a dream come true, so I'd like to look into this design a bit more and learn from it.
Hmmm. Looking at those specs: 95 dB/1W/1m is 2% efficiency. That is physically impossible in a 6 cuft enclosure with bass extension to 22 Hz (see attachment). Is this another fluke by an overly enthusiastic marketing department?
2SA1943 and 2SC5200 replacements?
Noob question – can TTA1943(Q) and TTC5200(Q) be used in place of 2SA1943-O and 2SC5200-O? I really don’t want to make any mistakes here. I ask because suppliers are out of stock and this post:
2SC5200 and TTC5200
Noob question – can TTA1943(Q) and TTC5200(Q) be used in place of 2SA1943-O and 2SC5200-O? I really don’t want to make any mistakes here. I ask because suppliers are out of stock and this post:
2SC5200 and TTC5200
Hi Twocents
In fact, the MJL1302 and MJL3281 (indicated in the manual BOM) are the preferred choice since they produce a little less THD than the 1943/5200. This was verified by myself in the USSA5B (or 3B) by THD measurement and also recently confirmed by peufeu in another thread/experiment.
I have not checked the TTA/TTC.
Fab
In fact, the MJL1302 and MJL3281 (indicated in the manual BOM) are the preferred choice since they produce a little less THD than the 1943/5200. This was verified by myself in the USSA5B (or 3B) by THD measurement and also recently confirmed by peufeu in another thread/experiment.
I have not checked the TTA/TTC.
Fab
Thanks Fab. Unfortunately the MJL’s are even more difficult to source. I see Digikey lists MJL1302A and MJL3281A as obsolete but looks like they have been replaced with the AG series, which is mostly out of stock. I assume AG is the same or better.
Diy was so much easier in pre-covid days.
Diy was so much easier in pre-covid days.
Hi Twocents
I think that the added G suffix is maybe only for no lead solder from the datasheet indication. The MJL series is probably very popular amongst commercial audio amplifiers…
I have ordered 2 MJL pairs about one month ago.
As you suggest, the low or depleted stock may be due to pandemic effect since electronic parts are missing ( car manufacturers are complaining about that) then peoples can buy stock by fear…..or to make money by reselling ?
If it is so, then it could prove difficult to get transistors in general….
Anyone have ideas about this situation?
Fab
I think that the added G suffix is maybe only for no lead solder from the datasheet indication. The MJL series is probably very popular amongst commercial audio amplifiers…
I have ordered 2 MJL pairs about one month ago.
As you suggest, the low or depleted stock may be due to pandemic effect since electronic parts are missing ( car manufacturers are complaining about that) then peoples can buy stock by fear…..or to make money by reselling ?
If it is so, then it could prove difficult to get transistors in general….
Anyone have ideas about this situation?
Fab
Last edited:
I am going to use the Dissipante 4UX400mm chassis for my build.
Dissipante 4U – diyAudio Store
I am wondering if substituting the UMS spec. heatsinks would be desirable? It appears that the UMS heatsinks are one piece heatsinks as opposed to what appears to be two piece heat sinks with the standard heat sinks. Is this correct and if so, would the UMS heatsinks be a better choice? Also do the USSA-5 boards happen to conform to the UMS standard dimensions?
Dissipante Substitution: UMS Heatsinks – diyAudio Store
Dissipante 4U – diyAudio Store
I am wondering if substituting the UMS spec. heatsinks would be desirable? It appears that the UMS heatsinks are one piece heatsinks as opposed to what appears to be two piece heat sinks with the standard heat sinks. Is this correct and if so, would the UMS heatsinks be a better choice? Also do the USSA-5 boards happen to conform to the UMS standard dimensions?
Dissipante Substitution: UMS Heatsinks – diyAudio Store
A quick question and help regarding my USSA5 amp.
Made as mono blocs is running now almost an year or so. But all of a sudden last week one of the channel, the offset seems to have jumped to 24vdc. I checked the TP4 and V- / TP2 and V+ I that the bias is pretty stable at 50-50.5mV hovering and using P1/2 I was able to adjust it easily to get to 50mV. All other test points seems to be within the range per the Fab's manual.
But the offset does not seem to have any effect via the P1/2 and right on powering its at 24 - 24.4vdc. Not sure what seems to have gone wrong as it was working fine so far.
Another observation is that the M2 gets hot immediately with power up whereas the M1 does not. I checked all the big mosfets, driver stage mosfets and transistors they seem to be alive and none failing. I do not see anything burnt up as well because of the heat as such. Any pointers to look at the issue will be helpful.
Some pics for reference.
Thanks
Made as mono blocs is running now almost an year or so. But all of a sudden last week one of the channel, the offset seems to have jumped to 24vdc. I checked the TP4 and V- / TP2 and V+ I that the bias is pretty stable at 50-50.5mV hovering and using P1/2 I was able to adjust it easily to get to 50mV. All other test points seems to be within the range per the Fab's manual.
But the offset does not seem to have any effect via the P1/2 and right on powering its at 24 - 24.4vdc. Not sure what seems to have gone wrong as it was working fine so far.
Another observation is that the M2 gets hot immediately with power up whereas the M1 does not. I checked all the big mosfets, driver stage mosfets and transistors they seem to be alive and none failing. I do not see anything burnt up as well because of the heat as such. Any pointers to look at the issue will be helpful.
Some pics for reference.
Thanks
Last edited:
Hi tmas
I believe that UMS for pre-drilled holes was created to fit the diystore pcbs which are mainly (but not all) Pass Diy pcb projects. Unfortunately, the USSA-5 pcb was not designed to fit with this heatsink holes position specifications. If it does - I have not verified - it would be a coincidence….
Good luck
Fab
Hi manniraj
You may have a failure….
if you have all good measurements as per the manual, the offset at output can not be as high as 24 VDC (PSU voltage ?)
Disconnect from speaker and from DC protection board first . Then Please specifically report all voltages below taken between:
TP9-TP10=
TP11-TP12=
TP7-TP1=
TP8-TP3=
TP5-TP1=
TP6-TP3=
TP1-TP2=
TP3-TP4=
OUT-GND=
You have a nice build by the way.
Fab
You may have a failure….
if you have all good measurements as per the manual, the offset at output can not be as high as 24 VDC (PSU voltage ?)
Disconnect from speaker and from DC protection board first . Then Please specifically report all voltages below taken between:
TP9-TP10=
TP11-TP12=
TP7-TP1=
TP8-TP3=
TP5-TP1=
TP6-TP3=
TP1-TP2=
TP3-TP4=
OUT-GND=
You have a nice build by the way.
Fab
Last edited: