USSA 5B THD
Hi meanie
THD taken into 8 ohms for 1W , 6W and 10W rms with my bench power supply.
I have included 10KHz square wave into 8ohms and 1uF in parallel.
Note that the Exicon mosfet of the original USSA5 are quite easy to find and Profusion distributor ships very quickly.
The USSA5B sounds different than the USSA5 based on the first listening sessions I had this weekend and this is not surprising for me. But break-in is not completed...
Fab
Hi meanie
THD taken into 8 ohms for 1W , 6W and 10W rms with my bench power supply.
I have included 10KHz square wave into 8ohms and 1uF in parallel.
Note that the Exicon mosfet of the original USSA5 are quite easy to find and Profusion distributor ships very quickly.
The USSA5B sounds different than the USSA5 based on the first listening sessions I had this weekend and this is not surprising for me. But break-in is not completed...
Fab
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Group buy status:
Fab - 4 pcs
Vunce - 2 pcs- USA :15$ , PAID, shipped
Meanie -4 pcs- Singapore: 11$, paid , shipped
Brianco -2 pcs- UK: 11$ PAID, shipped
Boba1000 -2 pcs- USA:15$ (tracking), paid , shipped
FAA -2 pcs - USA: need postal code
Coolnose - 2 pcs- France: 11$, paid, shipped
Funke and Speedy - 6 pcs- Germany: 11$, paid, shipped
Gary s - 2 pcs- Australia: 12$, paid, shipped
Potstip - 2 pcs- Turkey: 12$
mbrennwa - 2 pcs- - Switzerland: 11$, paid, shipped
Bfpca - 2 pcs - Canada : paid , shipped
Praudio - 2pcs - Canada : paid
Randytsuch - 2 pcs - USA: 15$ (with tracking) , paid, shipped
Hallcon83 - 2 pcs - USA Texas: 8 , paid
Myl - 2 pcs - Hong Kong : 15$ , paid
Total pcbs: 40/40
Reserve list:
Arthur - 2pcs - Hong Kong :
Add 1$ for packing
Add 16$ for each pcb pair
Add 2$ for PayPal fee but only if gift not selected for reason
All in CAD $
Next shipment probably next weekend.
FAA and potstip, please get back to me for payment.
This pcb is really a bargain for that price and it comes with a full step-by-step build manual.
Fab
Fab - 4 pcs
Vunce - 2 pcs- USA :15$ , PAID, shipped
Meanie -4 pcs- Singapore: 11$, paid , shipped
Brianco -2 pcs- UK: 11$ PAID, shipped
Boba1000 -2 pcs- USA:15$ (tracking), paid , shipped
FAA -2 pcs - USA: need postal code
Coolnose - 2 pcs- France: 11$, paid, shipped
Funke and Speedy - 6 pcs- Germany: 11$, paid, shipped
Gary s - 2 pcs- Australia: 12$, paid, shipped
Potstip - 2 pcs- Turkey: 12$
mbrennwa - 2 pcs- - Switzerland: 11$, paid, shipped
Bfpca - 2 pcs - Canada : paid , shipped
Praudio - 2pcs - Canada : paid
Randytsuch - 2 pcs - USA: 15$ (with tracking) , paid, shipped
Hallcon83 - 2 pcs - USA Texas: 8 , paid
Myl - 2 pcs - Hong Kong : 15$ , paid
Total pcbs: 40/40
Reserve list:
Arthur - 2pcs - Hong Kong :
Add 1$ for packing
Add 16$ for each pcb pair
Add 2$ for PayPal fee but only if gift not selected for reason
All in CAD $
Next shipment probably next weekend.
FAA and potstip, please get back to me for payment.
This pcb is really a bargain for that price and it comes with a full step-by-step build manual.
Fab
Hi Fab,
Good to hear that the USSA5B is running and you have found the time for the first listening sessions.
Already nervous and curious to hear more about it and if it is worth to build a second one for comparison to the original USSA5.
Could you describe your first impressions, was it better or worse than expected, what are differences sound wise, ....!?
If FAA or potstip are not interested in your PCB anymore and no one else is interested (need one),
and we keep the plan that I will build an USSA5B too, than you could put me on the reservation list for one pair of them.
Keep on going!
André
Hi André
I prefer not to post my first impressions when break-in is not completed. Since I use the same chassis and PSU as my USSA5 for the USSA5B then I cannot do an A/B comparison... In general I prefer to post others impressions since the designer may be biased....for that purpose I am trying to go to my friend shortly since he has an USSA5. In the end, since they will sound different I expect that it could be a matter of preferences based on taste and setup at home.
For sure I will put you on the reserve list and keep you posted on more listening impressions. As a teaser, it has the typical bass of good power bjt as output.
Thanks for encouragement.
Fab
I prefer not to post my first impressions when break-in is not completed. Since I use the same chassis and PSU as my USSA5 for the USSA5B then I cannot do an A/B comparison... In general I prefer to post others impressions since the designer may be biased....for that purpose I am trying to go to my friend shortly since he has an USSA5. In the end, since they will sound different I expect that it could be a matter of preferences based on taste and setup at home.
For sure I will put you on the reserve list and keep you posted on more listening impressions. As a teaser, it has the typical bass of good power bjt as output.
Thanks for encouragement.
Fab
I am thinking of using two 24 VDC switching PSUs (bricks) to get +/-24 VDC. Then use CLC filtering to get clean DC rails.
Here is what i intend to do on my next USSA5.1&B version.
On the first USSA5 build, all the components was bought with exact quantity as per BOM, so i got no chance to match any of the BC transistors for hfe values. Yet it performs so well. I listens to it more than any other amps i have on hand.
I will do hfe selection now, and i do have a batch of 1943/5200, so i can select them too.
Then i will get more Sanken bjt and do the same.
Once all amps are built, lets call them : The GOOD, BETTER and BEST.
The BEST will naturally be my reference set.
The BETTER will drive the mid and high tweeters.
The GOOD will drive the woofers.
Time for active XO and Bi-amping. Something that i have never try before.
But all above take time...
On the first USSA5 build, all the components was bought with exact quantity as per BOM, so i got no chance to match any of the BC transistors for hfe values. Yet it performs so well. I listens to it more than any other amps i have on hand.
I will do hfe selection now, and i do have a batch of 1943/5200, so i can select them too.
Then i will get more Sanken bjt and do the same.
Once all amps are built, lets call them : The GOOD, BETTER and BEST.
The BEST will naturally be my reference set.
The BETTER will drive the mid and high tweeters.
The GOOD will drive the woofers.
Time for active XO and Bi-amping. Something that i have never try before.
But all above take time...
This is not a preferred solution to have extension leads and more especially if the are long. For sure the gate/base resistors must be very close to the transistor lead. This is mainly to prevent oscillation. As a sanity test you should check with a scope with a resistive/capacitive load for a 10KHz square wave (for example) if you really go that way.
The pcb layout has been designed to have a good placement for the output transistors on a usual size heatsink (300mm length) for more optimal heat distribution.
However you can have transistors (positive and negative sides of circuit ) on different heatsinks since they have their respective thermistor.
The drivers and output transistors must be on the same heatsink with the thermistor.
Fab
P.s. if you want to use your Aleph style heatsinks maybe install pcb on the corner in between 2 heatsinks with an 45deg angle....just a silly idea maybe ...
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