Eliad,
Some examples of the dimensions for the heatsink for each channel:
Of course it can be larger like 4U 400mm.
The fins should be around 40mm long, and the "base plate" (flat part) of the heat sink should be 8-10mm thick. It is important that the fins should be vertically oriented, allowing the hot air to freely move upwards.
I prefer a chassis that is 350mm to 400mm deep, as such a case gives more room to place the power supply boards and transformers.
Btw, you will also have to drill and tap the flat part of the heat sink to screw in the stand-offs that will hold the PCB, and also for the lateral FETs and other parts as shown in ggetzoff's build pic in post #5 of this thread ((attached here also for your reference). Looks like 10 such holes need to drilled and tapped per channel.
With a standard CRC type power supply like one that can be built with the Project16 PSU PCB, power transformers with two (02) secondaries of 18V AC or 20V AC should be sufficient for this amplifier; if you are to go with a dual-mono configuration (one power supply PCB for each channel) a VA rating of 250-300 VA is recommended. So you will need 2 transformers of 250-300VA, 18V Ac or 20V AC voltage.
Some examples of the dimensions for the heatsink for each channel:
- 125mm tall x 400mm long (~3U 400mm)
- 165mm tall x 300mm long (~4U 300mm)
- 150mm tall x 350mm long.
Of course it can be larger like 4U 400mm.
The fins should be around 40mm long, and the "base plate" (flat part) of the heat sink should be 8-10mm thick. It is important that the fins should be vertically oriented, allowing the hot air to freely move upwards.
I prefer a chassis that is 350mm to 400mm deep, as such a case gives more room to place the power supply boards and transformers.
Btw, you will also have to drill and tap the flat part of the heat sink to screw in the stand-offs that will hold the PCB, and also for the lateral FETs and other parts as shown in ggetzoff's build pic in post #5 of this thread ((attached here also for your reference). Looks like 10 such holes need to drilled and tapped per channel.
With a standard CRC type power supply like one that can be built with the Project16 PSU PCB, power transformers with two (02) secondaries of 18V AC or 20V AC should be sufficient for this amplifier; if you are to go with a dual-mono configuration (one power supply PCB for each channel) a VA rating of 250-300 VA is recommended. So you will need 2 transformers of 250-300VA, 18V Ac or 20V AC voltage.
Attachments
Last edited:
Yes, after reading so far it looks the better option is 2 transformers and 2 CRC power supplies. I am thinking using Antek toroidal transformers. From what I read so far an 18VAC probably would be better than the 20V since a lower voltage seems to improve the Class A operation of the USSA-5.0
If you’re located in the USA, Antek is your best option for transformer choices and pricing. Toroidy makes beautiful trafo’s but shipping to US is killer!
I’d recommend 4U height as minimum, big heatsinks are a Class A amps best friend 😉. Not a choice to skimp on and regret later.
I’d recommend 4U height as minimum, big heatsinks are a Class A amps best friend 😉. Not a choice to skimp on and regret later.
I used the R21 add-on modules in my Bliss amp and am very happy with it.
To be fair, I didn't replace a power supply with them, so I don't have a comparison Before and After.
My USSA-5 uses a capacitance multiplier based psu (SLB), this amp is one of my favs. Can Tombo's design further improve the sound? I wouldn't know unless I swapped supplies, not something I'm willing to do to this amp. The chassis is specifically designed for the components inside, swapping PSU's would basically mean rebuild the whole amp 😳.
I'm in the process of building another amp using four of Tombo's new R25 modules
.
To be fair, I didn't replace a power supply with them, so I don't have a comparison Before and After.
My USSA-5 uses a capacitance multiplier based psu (SLB), this amp is one of my favs. Can Tombo's design further improve the sound? I wouldn't know unless I swapped supplies, not something I'm willing to do to this amp. The chassis is specifically designed for the components inside, swapping PSU's would basically mean rebuild the whole amp 😳.
I'm in the process of building another amp using four of Tombo's new R25 modules
.Attachments
I might found the chassis. It looks it might fit the requirements
https://www.aliexpress.us/item/3256...rl=scene:search|query_from:#nav-specification
https://www.aliexpress.us/item/3256...rl=scene:search|query_from:#nav-specification
Judging from the photos, the fins of the heat sinks seem relatively short to me and the thickness of the plate quite thin.
Modushop has the 4U Dissipante and 4U MiniDissipante. Not sure if there is a significant difference between the 2 in regards to the heatsinks. I am wondering how this current politics would affect shipping from Italy.
For transformer, I already have one Antek https://www.antekinc.com/au-2218-200va-18v-transformer/. If this is a correct one then I need to buy one more. I will get the softstart and speaker protection PCBs from diyaudio store. I still have to decide on the Power supply. From what I read I should get LT4320 based board with CRC filter.
Also, I have been reading the manual, it looks some of the components on my partially populated USSA-5 should not be there at this stage of the build. I guess I should remove some of the components and start with first stage of adjusting the board. I do not not enough electronics to figure out if I dont need to remove components in order to start adjustments from the beginning.
For transformer, I already have one Antek https://www.antekinc.com/au-2218-200va-18v-transformer/. If this is a correct one then I need to buy one more. I will get the softstart and speaker protection PCBs from diyaudio store. I still have to decide on the Power supply. From what I read I should get LT4320 based board with CRC filter.
Also, I have been reading the manual, it looks some of the components on my partially populated USSA-5 should not be there at this stage of the build. I guess I should remove some of the components and start with first stage of adjusting the board. I do not not enough electronics to figure out if I dont need to remove components in order to start adjustments from the beginning.
Yes , any amp is only as good as the power supply .
1 ) Suggest , having a look what FAB used in the Galion TS A20 which he designed - see post #2,042
He's used dual CRC power supplies with 4 x 47,000uF per channel .
If you go with with this , you'll probably want two 250VA or 300VA transformers , with dual 18Vac + 18 Vac secondaries
which will give +/- 24 Vdc voltage rails .
2 ) Or look at what Nikos used in Post #2,044 ( His amp that used heat sinks ) .
For power diodes he's used LT4320 's and MOSFET's , and the transistors under the board suggest a capacitance multiplier circuit was used .
This looks similar to SMB ( Smooth Like Butter) supply boards .
If you go with a LT4320's know that the voltage drop across the MOSFET's is lower than power diodes .
However , know there is a " drop out " voltage across the bi power transistors .
This will affect the selection of the transformers .
For this you'll probably want two 250 VA or 300VA transformers with dual 20 Vac + 20 Vac secondaries .
3 ) Here is an idea I was thinking of . Maybe people could comment on this
- AnTek 600 VA transformer with 18 Vac + 18 Vac secondaries
- Diodes de Jour
- The ESR of those computer grade electrolytic caps is very low - something in the order of 0.004 ohms
- so they can handle the brunt of the ripple . But make sure your case has enough clearance for the height of these ... and they are expensive ... ouch !
- Then Hammond 159ZL chokes with 0R22 dampening resistors .
- with the chokes , probably want to use Belden 19364 cable for the internal AC wiring because it has a foil shield
- Then each USSA Amp gets its own bank of supply caps .
Attachments
Eliad,
There are 2 types of Antec Transformers listed on the site:
https://www.antekinc.com/as-2218-200va-18v-transformer/
https://www.antekinc.com/au-2218-200va-18v-transformer/
Check which one you have. The voltage and VA rating should be ok for your build. The AS series description on their website mentions "The 200VA toroidal audio power transformers have static shield between primary and secondary coils to improve the isolation and noise interference." - Do not see this in the AU series.
Regarding LT4320 option, it has some technical benefits like less voltage loss and no diode switching noise, but the cost is higher. Many good amps have been made using standard rectifiers followed by CRC.
There are 2 types of Antec Transformers listed on the site:
https://www.antekinc.com/as-2218-200va-18v-transformer/
https://www.antekinc.com/au-2218-200va-18v-transformer/
Check which one you have. The voltage and VA rating should be ok for your build. The AS series description on their website mentions "The 200VA toroidal audio power transformers have static shield between primary and secondary coils to improve the isolation and noise interference." - Do not see this in the AU series.
Regarding LT4320 option, it has some technical benefits like less voltage loss and no diode switching noise, but the cost is higher. Many good amps have been made using standard rectifiers followed by CRC.
Last edited:
Eliad ,
Regardless or which power supply you decide to go with , its important to know that the first bank of electrolytic caps
takes the brunt of the ripple . This ripple causes power to be dissipated inside the caps , and this affects their life time .
So for the first bank of caps , look for caps with a low ESR and a temp rating of 105oC is preferred over 85oC .
Also , the higher the total capacitance , the lower the ripple .
.
Regardless or which power supply you decide to go with , its important to know that the first bank of electrolytic caps
takes the brunt of the ripple . This ripple causes power to be dissipated inside the caps , and this affects their life time .
So for the first bank of caps , look for caps with a low ESR and a temp rating of 105oC is preferred over 85oC .
Also , the higher the total capacitance , the lower the ripple .
.
The heatsinks are the exact same ones, the main difference is the width of the chassis: the MiniDissipante is less wide.
At the moment we have not received any complaint from customers about extra duties. The only thing which has changed since the start of 2025 are the shipping charges which have increased more than expected.
Ι make my own boards cap multiplier with classic diodes STPS20M60 Schottky Vf 0.37V rectifiers 2.6A Bias for my AN 39 1-3mv ripple.
Attachments
Last edited: