Hi Fab,
You got it!
In addition to building the USSA3, I would also like to try the USSA5.1. And, I'm even considering FSSA2. Although I might skip this one, since Class A it's more my thing, and my speakers are fairly sensitive and easy to drive.
You got it!
In addition to building the USSA3, I would also like to try the USSA5.1. And, I'm even considering FSSA2. Although I might skip this one, since Class A it's more my thing, and my speakers are fairly sensitive and easy to drive.
You mean something like this....😉
But class AB with about 8W class A into 8 ohms.
This is only a simulation prototype concept thus do not use as-is.😱
Fab
But class AB with about 8W class A into 8 ohms.
This is only a simulation prototype concept thus do not use as-is.😱
Fab
Attachments
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I have removed my name because I made a bad error in my identification of the amp. models in my original post! 😱
What I want to build is two of the F5-USSA (with 2SK1530/2SJ201 Toshiba as I have a few sets of matched devices.) I now note that this variant has its own board.
I also want to build one off of theUSSA-3, B version.
IF colour choice exists, Banana Yellow is my choice!🙂
So my order is amended to:
Brianco....x2 sets forTOSHIBA outputsF5-USSA,
x1 set, but would take two sets, USSA-3B...with Sanken devices please where possible.
AnthonyA . 2 sets FSSA2 and 1 set ussa 3b+ Ntc, poly cap, sanken+ caddock
nfsgame - 1 set FSSA
Vunce - 1 set FSSA
Stretchneck - 3 sets fssa and 1 set ussa
ClaudeG - 1 set FSSA with Sanken
meanie - 1 set FSSA1 (toshiba driver)
zman01 - 1 set FSSA
touchdown - 1 set FSSA with Sunken
What I want to build is two of the F5-USSA (with 2SK1530/2SJ201 Toshiba as I have a few sets of matched devices.) I now note that this variant has its own board.
I also want to build one off of theUSSA-3, B version.
IF colour choice exists, Banana Yellow is my choice!🙂
So my order is amended to:
Brianco....x2 sets forTOSHIBA outputsF5-USSA,
x1 set, but would take two sets, USSA-3B...with Sanken devices please where possible.
AnthonyA . 2 sets FSSA2 and 1 set ussa 3b+ Ntc, poly cap, sanken+ caddock
nfsgame - 1 set FSSA
Vunce - 1 set FSSA
Stretchneck - 3 sets fssa and 1 set ussa
ClaudeG - 1 set FSSA with Sanken
meanie - 1 set FSSA1 (toshiba driver)
zman01 - 1 set FSSA
touchdown - 1 set FSSA with Sunken
Turbo USSA3B...
Not that easy to get matched LSK170/LSJ74 grade A with IDSS < 4.5ma...😀
This is only a concept but not a really practical amplifier. Even with low IDSS jfet the damping factor is low for a 80Wrms amplifier..🙄
I have found a possible way to increase the DF keeping same active parts and without adding new active parts but this can prove difficult to adjust...that is why it is dated from last April and not much work done until then...
Fab
Not that easy to get matched LSK170/LSJ74 grade A with IDSS < 4.5ma...😀
This is only a concept but not a really practical amplifier. Even with low IDSS jfet the damping factor is low for a 80Wrms amplifier..🙄
I have found a possible way to increase the DF keeping same active parts and without adding new active parts but this can prove difficult to adjust...that is why it is dated from last April and not much work done until then...
Fab
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USSA3B
USSA 3B is 25Wrms class A @8 ohms with 1.2A bias and +/-24Vdc.
I thought it was the FSSA thread😛
There is another thread for the USSA3B.
Fab
USSA 3B is 25Wrms class A @8 ohms with 1.2A bias and +/-24Vdc.
I thought it was the FSSA thread😛
There is another thread for the USSA3B.
Fab
F5-USSA
WoW this is quite a change from FSSA (100W class AB) to F5-USSA (<=25W class A). The latter is only an F5 with different parts and value but using USSA philosophy and of course using the 2SK1530/2SJ201. It was discussed in a now closed forum...It is somehow similar to EUVL design I believe. For the pcb I have simply used an F5 clone pcb from EBay and put my parts in.
Fab
P.S. I have found where I put the schematics on this forum:
Virtual Audition of Very Simple Quasi MOSFET Amp
Hi Brianco
WoW this is quite a change from FSSA (100W class AB) to F5-USSA (<=25W class A). The latter is only an F5 with different parts and value but using USSA philosophy and of course using the 2SK1530/2SJ201. It was discussed in a now closed forum...It is somehow similar to EUVL design I believe. For the pcb I have simply used an F5 clone pcb from EBay and put my parts in.
Fab
P.S. I have found where I put the schematics on this forum:
Virtual Audition of Very Simple Quasi MOSFET Amp
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Following Brianco's amended, I'll simply add my share: 🙂
Brianco....x2 sets forTOSHIBA outputsF5-USSA,
x1 set, but would take two sets, USSA-3B...with Sanken devices please where possible.
AnthonyA . 2 sets FSSA2 and 1 set ussa 3b+ Ntc, poly cap, sanken+ caddock
nfsgame - 1 set FSSA
Vunce - 1 set FSSA
Stretchneck - 3 sets fssa and 1 set ussa
ClaudeG - 1 set FSSA with Sanken
meanie - 1 set FSSA1 (toshiba driver)
zman01 - 1 set FSSA
touchdown - 1 set FSSA with Sunken
Analogico - 2 sets USSA3/5
Brianco....x2 sets forTOSHIBA outputsF5-USSA,
x1 set, but would take two sets, USSA-3B...with Sanken devices please where possible.
AnthonyA . 2 sets FSSA2 and 1 set ussa 3b+ Ntc, poly cap, sanken+ caddock
nfsgame - 1 set FSSA
Vunce - 1 set FSSA
Stretchneck - 3 sets fssa and 1 set ussa
ClaudeG - 1 set FSSA with Sanken
meanie - 1 set FSSA1 (toshiba driver)
zman01 - 1 set FSSA
touchdown - 1 set FSSA with Sunken
Analogico - 2 sets USSA3/5
Basic question to Fab - my understanding is that depending on the voltage of the transformer secondary, the output power of the FSSA amplifier will go up/down - it would be good to know an acceptable range for this.
FSSA
Good question zman01.
The preliminary build manual indicates +/-50vdc as recommended maximum.
Refer to post #9 showing schematics.
The input stage power dissipation including the TO-92 package provides the limiting factor which also is mainly aligned with the 2 pairs of output transistors (one dual die pair) for the conservative power capacity of the amplifier.
Thus it is based on the IDSS current of the Jfet which in turns gives about 70% of IDSS for ID with 20 ohms as RS of jfet.
Assuming that most of the jfet IDSS within range of a BL grade or B grade will be <10ma (12ma max) then I target to have no more than 175mw dissipation max (with no heatsink) for J1-J2-Q1-Q2. PSU voltage divided by 2 (using zener voltage of half of PSU voltage) gives equal dissipation between J1/Q1 and J2/Q2.
175mw/ 7ma= 25Vdc, then x 2 gives 50Vdc, +/- 50Vdc as PSU.
Note if your IDSS > 10ma then you can add a small heatsink to limit transistors temperature.
If your IDSS is in the low range then you can go a bit higher than +/-50Vdc but no more than 25Vdc at jfet thus zener voltage of 24vdc.
As for the minimum PSU voltage then you can go +/-25Vdc but the loss of voltage in the output stage will make less inefficient for power delivery.
+/-50Vdc gives about 125Wrms before clipping into 8 ohms.
+/-25Vdc gives about 20Wrms before clipping into 8 ohms.
Fab
Good question zman01.
The preliminary build manual indicates +/-50vdc as recommended maximum.
Refer to post #9 showing schematics.
The input stage power dissipation including the TO-92 package provides the limiting factor which also is mainly aligned with the 2 pairs of output transistors (one dual die pair) for the conservative power capacity of the amplifier.
Thus it is based on the IDSS current of the Jfet which in turns gives about 70% of IDSS for ID with 20 ohms as RS of jfet.
Assuming that most of the jfet IDSS within range of a BL grade or B grade will be <10ma (12ma max) then I target to have no more than 175mw dissipation max (with no heatsink) for J1-J2-Q1-Q2. PSU voltage divided by 2 (using zener voltage of half of PSU voltage) gives equal dissipation between J1/Q1 and J2/Q2.
175mw/ 7ma= 25Vdc, then x 2 gives 50Vdc, +/- 50Vdc as PSU.
Note if your IDSS > 10ma then you can add a small heatsink to limit transistors temperature.
If your IDSS is in the low range then you can go a bit higher than +/-50Vdc but no more than 25Vdc at jfet thus zener voltage of 24vdc.
As for the minimum PSU voltage then you can go +/-25Vdc but the loss of voltage in the output stage will make less inefficient for power delivery.
+/-50Vdc gives about 125Wrms before clipping into 8 ohms.
+/-25Vdc gives about 20Wrms before clipping into 8 ohms.
Fab
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You are welcome zman01.
Note also that using a separate PSU for the front stage instead of the on-board cap multiplier will increase the output power Of amp using only 5 to 7 Vdc more for this PSU. This Would put the clipping level further up.
Fab
Note also that using a separate PSU for the front stage instead of the on-board cap multiplier will increase the output power Of amp using only 5 to 7 Vdc more for this PSU. This Would put the clipping level further up.
Fab
Hi Fab,
Please count me down for a set of FSSA-2 PCBs + Sanken drivers.
That looks as a promising DIY project.
Thank you for that very exciting one.
Regards,
Kal
Please count me down for a set of FSSA-2 PCBs + Sanken drivers.
That looks as a promising DIY project.
Thank you for that very exciting one.
Regards,
Kal
Updated list for group buy
Hi Kalamin
Just added your name to the complete list here:
Brianco - ....x2 sets forTOSHIBA outputsF5-USSA,
x1 set, but would take two sets, USSA-3B...with Sanken devices please where possible.
AnthonyA . 2 sets FSSA2 and 1 set ussa 3b+ Ntc, poly cap, sanken+ caddock
nfsgame - 1 set FSSA
Vunce - 1 set FSSA
Stretchneck - 3 sets fssa and 1 set ussa
ClaudeG - 1 set FSSA with Sanken
meanie - 1 set FSSA1 (toshiba driver)
zman01 - 1 set FSSA
touchdown - 1 set FSSA with Sunken
Analogico - 2 sets USSA3/5
Kalamin - 1 set FSSA with Sanken
Note: assume I do not have USSA pcb at this moment.
@Brianco: please clarify if you require FSSA pcb.😕
And for the FSSA only related list:
AnthonyA . 2 sets FSSA2 and 1 set ussa 3b+ Ntc, poly cap, sanken+ caddock
nfsgame - 1 set FSSA
Vunce - 1 set FSSA
Stretchneck - 3 sets fssa and 1 set ussa
ClaudeG - 1 set FSSA with Sanken
meanie - 1 set FSSA1 (toshiba driver)
zman01 - 1 set FSSA
touchdown - 1 set FSSA with Sunken
Kalamin - 1 set FSSA with Sanken
That makes 24 pcbs. I can buy 30 pcbs to allow a few late inquiries. That should give probably less than 10$ CAD per pcb excluding shipping. Final Price to be confirmed.
Shipping will be a fixed price this time because only small variation between countries by Airmail no tracking.
All prices in CAD$:
Pcb (2) : <=20$
Packaging : 1$
Shipping : 14$
Sanken (4): 12$
Other parts (only special cases) by PM
Therefore, please send me a PM so I can give you my address for PayPal only payment. Also provide your e-mail and also home address for shipment.
I am working on the updated manual that will be sent after received payment.
Fab
Hi Kalamin
Just added your name to the complete list here:
Brianco - ....x2 sets forTOSHIBA outputsF5-USSA,
x1 set, but would take two sets, USSA-3B...with Sanken devices please where possible.
AnthonyA . 2 sets FSSA2 and 1 set ussa 3b+ Ntc, poly cap, sanken+ caddock
nfsgame - 1 set FSSA
Vunce - 1 set FSSA
Stretchneck - 3 sets fssa and 1 set ussa
ClaudeG - 1 set FSSA with Sanken
meanie - 1 set FSSA1 (toshiba driver)
zman01 - 1 set FSSA
touchdown - 1 set FSSA with Sunken
Analogico - 2 sets USSA3/5
Kalamin - 1 set FSSA with Sanken
Note: assume I do not have USSA pcb at this moment.
@Brianco: please clarify if you require FSSA pcb.😕
And for the FSSA only related list:
AnthonyA . 2 sets FSSA2 and 1 set ussa 3b+ Ntc, poly cap, sanken+ caddock
nfsgame - 1 set FSSA
Vunce - 1 set FSSA
Stretchneck - 3 sets fssa and 1 set ussa
ClaudeG - 1 set FSSA with Sanken
meanie - 1 set FSSA1 (toshiba driver)
zman01 - 1 set FSSA
touchdown - 1 set FSSA with Sunken
Kalamin - 1 set FSSA with Sanken
That makes 24 pcbs. I can buy 30 pcbs to allow a few late inquiries. That should give probably less than 10$ CAD per pcb excluding shipping. Final Price to be confirmed.
Shipping will be a fixed price this time because only small variation between countries by Airmail no tracking.
All prices in CAD$:
Pcb (2) : <=20$
Packaging : 1$
Shipping : 14$
Sanken (4): 12$
Other parts (only special cases) by PM
Therefore, please send me a PM so I can give you my address for PayPal only payment. Also provide your e-mail and also home address for shipment.
I am working on the updated manual that will be sent after received payment.
Fab
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