Thanks for the heads up Vunce. I will start reducing the windings to make my 2.5uH inductor a 1uH inductor and then reduce the OD of the legs to 18awg so they will fit.
MM
MM
Hi Folks,
Just a reminder that the boards will be arriving soon but only a fraction of people who signed up have sent me payment for the shipping. Here is the list so far from the Swap Meet thread for the logistics.
Here is the list of people who have sent me shipping payment:
Dibya’s TDA7293 Xmas amp by Jhofland - Giveaway
Just a reminder that the boards will be arriving soon but only a fraction of people who signed up have sent me payment for the shipping. Here is the list so far from the Swap Meet thread for the logistics.
Here is the list of people who have sent me shipping payment:
Jlevro
Astromo
Nautibuoy
kp93300
Signal lost
Chermann
Twocents
Invaderzim
Francois G
Tubesguy
Sixto
Angchuck
Dibya’s TDA7293 Xmas amp by Jhofland - Giveaway
Hi X, Thought I would add myself to the list.
Jlevro
Astromo
Nautibuoy
kp93300
Signal lost
Chermann
Twocents
Invaderzim
Francois G
Tubesguy
Sixto
Angchuck
Kokanee
Jlevro
Astromo
Nautibuoy
kp93300
Signal lost
Chermann
Twocents
Invaderzim
Francois G
Tubesguy
Sixto
Angchuck
Kokanee
Hi X, that's a very helpful diagram. I agree with all the comments about isolating grounds... I am mostly unfamiliar with the buffer (whether it's an off-the shelf or custom item - essentially how to buy or make one?)... also i have not previously seen using a second NTC and 22 uF MKP in parallel connecting the clean ground form the secondaries to chassis. (see red dashed outline added to your diagram) I understand the use of GLB's everywhere else, just haven't seen an NTC used in this way before.
Thanks! - Six.
Thanks! - Six.
It’s not a trick but a fortunate case that adding a buffer in between my signal source and amp cleaned things up. The buffer has a ground loop breaker to isolate dirty vs clean ground (as do all the other circuits). The buffer happens to have its own separate wall power supply and an isolated DCDC step up dual rail PSU (Murata). Here is sketch of my setup.
Attachments
I believe the buffer is this one:
BTSB Buffer SE/Bal to SE/Bal Buffer | Etsy
BTSB Buffer - SE/Bal to SE/Bal Buffer GB
BTSB Buffer SE/Bal to SE/Bal Buffer | Etsy
BTSB Buffer - SE/Bal to SE/Bal Buffer GB
Hi X, that's a very helpful diagram. I agree with all the comments about isolating grounds... I am mostly unfamiliar with the buffer (whether it's an off-the shelf or custom item - essentially how to buy or make one?)... also i have not previously seen using a second NTC and 22 uF MKP in parallel connecting the clean ground form the secondaries to chassis. (see red dashed outline added to your diagram) I understand the use of GLB's everywhere else, just haven't seen an NTC used in this way before.
Thanks! - Six.
The NTC (8D-20 or CL-60) provides a nominal 8ohm to 10ohm resistance when cold. Just like a resistor. However, if there is a catastrophic fault and full current needs to shunt to ground, the NTC heats up and is about 0.5ohm to allow the current to safely get dissipated. Alternatively, two anti parallel diodes conduct when voltage is greater than 0.6v and allow more current to flow. The 22nF (or 100nF) cap is there as an RF shunt to reduce radio noise. You will need really big diodes to handle 10A currents and the single NTC is more cost effective and compact way to do this.
Someone else posted the link to the buffer.
Elna Silmic II
Hi Dibya and other builders,
Mouser does not have any of the Nichicon 100uF 50V caps for C16 in stock at present. Can I use the Elna Silmic II caps in the above quote for all caps C16, C5, C6, C9, C11 even though C5, C6, C9, C11 are supposed to be 220uF. I just happen to have these caps on hand.
Thanks for the help,
Myles
Secret Sauce in the recipe:
Want a 50W Tube like Amp to drive your bookshelf speaker with less than 1% THD?
* Use Desktop Class A or Pocket Class A Headphone amp by XRK971 as a
Preamp
* Replace C5 and C11 with Elna Silmic II 100uf 50v ( I still have no explanation how PSU cap effect sounds)
Hi Dibya and other builders,
Mouser does not have any of the Nichicon 100uF 50V caps for C16 in stock at present. Can I use the Elna Silmic II caps in the above quote for all caps C16, C5, C6, C9, C11 even though C5, C6, C9, C11 are supposed to be 220uF. I just happen to have these caps on hand.
Thanks for the help,
Myles
Jlevro
Astromo
Nautibuoy
kp93300
Signal lost
Chermann
Twocents
Invaderzim
Francois G
Tubesguy
Sixto
Angchuck
Kokanee
diy.tiger (Store order)
Hi Dibya and other builders,
Mouser does not have any of the Nichicon 100uF 50V caps for C16 in stock at present. Can I use the Elna Silmic II caps in the above quote for all caps C16, C5, C6, C9, C11 even though C5, C6, C9, C11 are supposed to be 220uF. I just happen to have these caps on hand.
Thanks for the help,
Myles
Hi Myles,
Go ahead , give 100hrs of burn in as otherwise silmic may sound bit muddy reason I prefer Muse caps as they don't require ingredient called patiance, you can't buy patience from mouser, digikey and rs components unfortunately.
Thanks for the info Dibya. I think I will try the 100uF Elna SII caps I have on hand at C16, C5 , C11 and leave C6, C9 as 220uF as in the BOM . Saves a few $$
MM
MM
It’s not a trick but a fortunate case...
Thanks guys for the Christmas' gift!
Wondering if you tried a regulated PSU instead of the 'simple' All Cee’s one?
I think the TDA7293 has a decent PSRR so not sure if a regulated supply would do much more. I can’t remember if Vunce tried a SMPS (which might be regulated).
Ok, got it Dibya. Thanks 
As for the DC servo:
In the #1 post it is written "Note that if populating the DC servo, C17 and C2 should be replaced with jumpers."
In the build shown in the #171 post, C17 is not replaced by a jumper.
What would be the best practice?

As for the DC servo:
In the #1 post it is written "Note that if populating the DC servo, C17 and C2 should be replaced with jumpers."
In the build shown in the #171 post, C17 is not replaced by a jumper.
What would be the best practice?
C17 is a bypass cap for C2.
C2 has a jumper installed which negates any effect C17 would have.
X just hasn’t removed the film cap yet. 😀
With a fresh unpopulated board, a jumper in C2 is sufficient. Leave C17 empty.
C2 has a jumper installed which negates any effect C17 would have.
X just hasn’t removed the film cap yet. 😀
With a fresh unpopulated board, a jumper in C2 is sufficient. Leave C17 empty.
Last edited:
Haha, lazy me. It doesn’t hurt to leave it in if you accidentally installed it by mistake.
X just hasn’t removed the film cap yet.
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