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Amplifier Modules and PCBs For Sale

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jimk04

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Joined 2018
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JLesterP said:
Nice :) Also place fuse to the secondary side of your power supply, the SCR circuit will self-destruct at 62V DC input. (if your area has unstable mains). The TVS diode will start to conduct at 53V DC so it will catch some DC transients. (So don't worry :) )
Click to expand...

What fuse would you recommend Lester please?

Listening to this track last night

https://open.spotify.com/track/00XoyOnSy2QjEr4p9kis1I?si=ISIANwKbTb6lfrIDeOts8A

And the tune after ...called Arctica

I heard some slight cicks in the upper registers. It is a very 'tinkly' album st times and so I wandered if they are just part of the music that I havent noticed before but then I thought they sounded a bit like DC clicks....although not heavy ones.

Would this have anything to do with the TVS diode you mention?

I can easily swap out the ideal rectifier for the traditional one for testing.

I thought the amp was sounding great though with maybe better bass than my 3e board. You're comment on the inductors on your very 1st 3255.....look like the same Sagami type as on my 3e board and yeas they got really warm on mine too. This morning having been powered up for 18 hours and sitting idle overnight the inductors and big caps on your board are barely above ambient to touch and the chip heatsink is barley warm. Good signs. Especially given the higher input voltage over what I used with the 3e.
 
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Deleted member 148505

I suggest that you get the 6.8uH VER2923-682KL for 36V supply.

Here's my TPA3251 with coilcraft 6.8uH. Latest shipment will have all the mods applied so no need to modify any values. I configured it such that the PFFB sound will not deviate much from non-PFFB, just improvement in high registers and slightly softer sound.


@Pete
PFFB works with 6.8uH without any modifications, though I just tested it on 36V to 41V.

Few months ago using 6.8uH + 0.68uF. I changed c_fb_out to 1nf and osc freq to 600kHz (same with slaa788a) and it didn't work.

With c_fb_out to 220pF and osc freq to 450kHz, 6.8uH + 0.68uF works well.

Regards,
Lester
 

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Deleted member 148505

jimk04 said:
What fuse would you recommend Lester please?
Click to expand...

You can use 10A to 12A slow blow fuse.

Make sure that faston connections to wires are not just crimped but also soldered.

For speaker connections make sure that they are tight, else you will experience some turntable-like scratch noise.
ricyuyc said:
@JLesterP
What is the maximum diameter of the 4 tank caps?
Thank You.
Click to expand...

Max dia is 18mm, min voltage 50V
 
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Deleted member 148505

454Casull said:
What uF are the bipolar caps currently selected? "Option A" currently showing 22 uF, still the current spec?

And where do we stand on adjustable gain for the TPA3255 units you are restocking with?
Click to expand...

I will update actual pic for partially assembled tpa3251 module which will show correct parts.

The upcoming module with split supply will use 10uF Elna Silmic II on the inputs.
It will have a fixed gain of 1.5x. No adjustable gain, so users should desolder the 0603 resistors to change the gain.
 
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Deleted member 148505

1st pic - left channel
2nd pic - right channel

I will investigate the lower 2nd and 4th harmonic on left channel.

I placed a clamp meter in the speaker out to make sure that I'm getting 5W at 4 ohms. (1.1 Amperes)

I haven't upgraded my soundcard interface so I'm not sure if this will be the final result.

But I think the THD+N performance will breach 100dB (or better) at 5W 4 ohms.
 

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4

454Casull

Member
Joined 2004
JLesterP said:
I will update actual pic for partially assembled tpa3251 module which will show correct parts.

The upcoming module with split supply will use 10uF Elna Silmic II on the inputs.
It will have a fixed gain of 1.5x. No adjustable gain, so users should desolder the 0603 resistors to change the gain.
Click to expand...
Ah, man, I don't have hot tweezers. :(

Re: input caps, would they see any reverse voltage whatsoever?
 
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4

454Casull

Member
Joined 2004
JLesterP said:
1st pic - left channel
2nd pic - right channel

I will investigate the lower 2nd and 4th harmonic on left channel.

I placed a clamp meter in the speaker out to make sure that I'm getting 5W at 4 ohms. (1.1 Amperes)

I haven't upgraded my soundcard interface so I'm not sure if this will be the final result.

But I think the THD+N performance will breach 100dB (or better) at 5W 4 ohms.
Click to expand...
Whew! Definitely can't be disappointed at all with this, seems like you're getting pretty much to the limit of the chip.

When you say "speaker out", are you actually using a speaker as your load? You need to make sure, if you haven't already, that the impedance is measured accurately at your driving frequency then.
 
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Deleted member 148505

I'm using a resistive dummy load for testing. What worries me is that when I put the test leads right at the module, I'm getting the best THD. But when I put the test leads at the dummy load, the performance is getting worse. Maybe when I send this to ASR, it will have worse performance (like AIYIMA A07) lol.
 
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