3 Transistor HP Amplifier with low dist

[Rick PA Stadel]

Yes, lineup, a noble gesture, indeed -- thanks very much for that!

Cheers

 

[BucketInABucket]

Done works perfectly

 

[lineup]

Looks great.
And I bet it sounds lovely.

 

[BucketInABucket]

Thank you! Case doesn't even get warm, very happy with the sound too! Masking tape holding down the input cables is temporary as the switch broke so I just bridged the two pads of the JST connector...will have to replace it at some point and I'll come up with a more permanent solution for cable routing by then.

 

[avtech]

Very nice, you must be pleased with the end result!

 

[BucketInABucket]

Indeed, very happy with myself. Dad approves too!

 

[widea]

Done works perfectly

Looks great! How do you describe the sound?

 

[BucketInABucket]

How do you describe the sound?

I'm terrible at describing sound so bear with me, but so far, it sounds smooth and lovely a touch more euphonic than my JDS Atom too

 

[knauf1919]

Bingo!

 

[Rick PA Stadel]

Very nice!

 

[BucketInABucket]

Thanks guys! I just replaced the hard-soldered mains wiring with the intended Molex KK396 for safety it arrived in the mail yesterday, but I was too impatient to wait so I wanted to try it asap when my parts order arrived.

 

[sevenup2278]

Put the amp in a simple case, only have to decide which color led to use for the power indicator. I was thinking white...

Amp sounds fine by the way. Noise free, powerfull, and nice tone.

 

[knauf1919]

toss-up

I was wondering philosophically ... are there projects as good as the ones with the famous transistors that are no longer manufactured and sold at insensitive prices when you find them?

 

[avtech]

..
Original circuit had 1000uF. And this will work.
If you have 2200uF you should use this.
I now recommend 2200uF for 32 Ohms headphones.

This has been on my mind for a while, but I hadn't had a chance to explore it.

I redid the spice sim with the layout that I used for the previous (smaller) version that I made and the sim results were very close to the real deal. (THD% 0.00362 real versus 0.00346 Simulated).

I tried 2200uF and 3300uF for the output capacitors into a 32 ohm load.

Here are the results:

It seems that there is a marked difference when using the larger value for the output capacitors.

Now, it could just be an artefact of the sim, but it is definitely going to be worth testing the real world difference with the output caps.

 

[jasonRF]

That is an amazing agreement, which suggests the transistor models are quite good. Where did you get them?

Also, I’m curious what output voltage the measurements and sim were at.

Cheers!

Jason

 

[joensd]

I tried 2200uF and 3300uF for the output capacitors into a 32 ohm load.

At which frequency and input voltage?
Did you give any values for ESR or ESL for the caps?

With 50Ohms load just before clipping I can see a difference in THD between 1000µ and 2200µ but no improvement at 3300µ. (freq.:1k and Vin=1.2Vpp; ideal caps though)

Unfortunately I can´t do THD measurements yet but it would be fun to see any differences.
But why would be make it difference though at 1kHz?
Smaller capacitive reactance? Then I´d guess the type/model/brand of capacitor with its parasitics could make a bigger difference in the end.

 

[avtech]

Measurements were with a 1khz input and whatever voltage that would give an output of 1v peak.

The output caps in spice were originally selected as Nichicon or Panasonic or something but when I changed the values, it left behind ESR of 0.1 and ESL of 0.

No idea why the difference yet, but I'll be interested to make some measurements when I can get a chance.

 

[widea]

Just an update: I am still very happy with this amp, I use it every day.
My old DAC (a HRT Music Streamer II) is replaced by a Topping E30. Formula3HP is revealing enough to hear differences between the old DAC and the new one. A very good combination.

 

[avtech]

Good to see you're still enjoying yours widea.

Mine is still going strong and I still favour it over the Noir (T2), SHPA and the Hakuin. It's the only one that pairs nicely with my ESS422h headphones.

I might have something interesting on this topic coming next month..

 

[BucketInABucket]

I definitely favour mine over the JDS Atom recently got an E30 too, it's a nice little thing and cheap as chips.

I replaced the 2200uF Nichicon UFG I was using with 3300uF Panasonic FR, the sound seemed to get cleaner but it still has that nice SE class A smoothness.