Amp too good for DIYaudio.

[AndyG.]

Dear Koifarm,

I try to build your Amp, but my progress will be kind of slow. Now I do have the PCBs on hand. (5c-6c input, 6c Power)
Plan is to build a small low power amp for tweeter - 19V supply. As I ordered 10 sets of PCBs, I will start with on pair 10A FETs on the 6c.

Some questions:
- C1,C2: Spacing is 5mm, I have not found any 4.7uF fitting into this space - do you have any hints for me?
- L1/R31: Can you describe please how you built this? Wire diameter, the carrier (dont know how to get it) is it a 5 W MOX, or ordinary wire resistor (I found these square ones, but not sure if they are ok - inductivity?)
- Any considerations, if I just drop in one pair instead of 2 pair FETs?

Thank you so much!
Andy

 

[Koifarm]

Hallo Andy,

Good to see you are building the Trex amp.

For C1/C2 I used Wima mks2 5mm.

L1 is 16 wdg around 10mm drill of 1mm CuE, with a 10 ohm/5 Watt wirewound resistor.
I used a 3d printed support for that.

STL file to print yourself, see below

For low power output (<50Watt) you can use 10n20/10p20.
At 19V and 8ohm expect max. 8Watt.

 

[AndyG.]

Hey Koifarm,

thank you for all the info and the STL - phantastic. Will print it.
Ahh and its an MKS - was not looking for them :-D

Cheers!
Andy

 

[EricfromSonocus]

The layout, topology, documentation.. its all beautiful and masterful, thank you. Truly top notch quality. If i ever need a new amp i will definitely build this one.

Ive been using nothing but composite amps for over a decade now. First myrefc, then miniref, then one of my own devising that was miniref with 3 3886 current pumps and lm317 337 reg. I preferred overcompensated older opamps because with them the pumps were easier to tame. Your amp's probably one level above them.

And no need for over the top protection scheme unless its a public use amp. With a well designed amp its only user error that can cause damage

 

[Koifarm]

Did also my share of composite lm3886.

Because I use for 30 years only active multi way setups, I like to have the amps build with the same topology.

Latest amps are the trex lat fet amps, they have for me best detail and dynamics without losing depth and warmth until yet.

This I used in the past:

- 2n3055 philips design.
- hypex active home(analog)
- tube amps pp kt88, pp el34, se 300b, se 813, pp el84.
- hypex ucd 180, 400, 700
- comp lm3886.
- purifi 1et400a and hypex ncore500.

And now Trex amps.

 

[AndyG.]

Dear Koifarm,
Vacation is over, other projects closed (automatic whirlpool water treatment system)...I am back!


Now I am putting together bits and pieces (Spoolhoulders I already got, EXICONs as well...) and I skipped the 19V version - 8W is a bit thin. Moving up to 34V.

I read about your latest version, and I think you attached only the 4 transistor version in post 80. As I am a bit on a space budget, would it be possible for you to share the 2 transistor version (60mm width) of your latest mod?

Thank you and cheers,
Andy

Edith: I read again through the full thread and found the 2d to be a perfect candidate for my first step. I think I even have the same heatsinks you used in the 2d and I like the compact size of it. ;-)

 

[mlloyd1]

How does the clipping and recovery behavior look for this design?

 

[AndyG.]

@Koifarm
I am on my mission to put together all the components for the 2d and thoughts its easy for me but it give me a bit of challenge.
Today I searched though the web to find a suitable capacitor for C11/C17. Gerber give me 25mm diameter / 10mm hole pitch. A 4700uf 63V will not fit there. Running on 36V DC, a 50V should be also good enough, but I did not find a high capacity one - may I ask what choice you took/obtain them?

Any other hint for component selection? I am a bit unsure on the capacitor types as well...

CHeers and thank you!
Andy

 

[egellings]

I marvel at those impressive specs, but have to take issue with their significance to good sound quality. They are so much better than human hearing can appreciate that I see no reason to pursue them beyond a certain point other than achieving engineering excellence.

 

[lgqliu]

Update Trex 4b .

As promised the files for the big version.

View attachment 497230

Schematic

View attachment 497234

Attached also gerber files for ordering the PCB.

View attachment 497233

And in the attachments LTspice simulation.

This PCB you can also use for previous versions:

- When use only one 10N20 and 10P20 you get 65Watt amp using +/- 36V power supply.( Trex 2C).(also lower cost)
- When use two 10N20 and 10P20 or one 20N20 and 20P20 you get 150Watt using +/- 48V power supply.
- When using two 20N20 and 20P20 you get 350Watt amp using +/- 65V power supply.( Trex 4B).

I am using as power supply one Hypex SMPS 1200A400 for one Trex 4b board.

Blockschematic of one channel.

View attachment 497244




Ronny

I am also puzzled by the function of transistor T4. If transistor T1 forms a current mirror, shouldn't resistors of appropriate resistance values also be connected in series with the emitters, respectively?

 

[lgqliu]

And a newer version T-rex 5c with XLR and rca input and DC protection.
And even better thd (0.000045%).

For Q1 you can also use OPA1656 on adapter.
My subjective opinion is, I like this amp better then ncore500 and purifi 1et400a. Even better then my SE FU13 tube amp.

View attachment 513258

View attachment 513264

View attachment 513259

View attachment 513260

View attachment 513261

View attachment 513262

This version of the design looks good.

 

[Koifarm]

Development continous.

Smd versions of input board and output board.

Balanced version can also adapt RCA adapter.
With RCA adapter it automatic adapts gain.

 

[Koifarm]

How does the clipping and recovery behavior look for this design?

It is a kind of soft clipping and direct recovery.