Toshiba MOSFETs with a twist

[Derek]

the mosfets might benefit from been further apart they get rather hot?
maybe just run wire?

As a curious reader and one of the lucky people to hear this amp in progress, I'd follow Nigel's advice and run the Mosfets off of the PCB and maybe onto a heat spreader then bolt it a heatsink, they get shockin' hot.
(just an observation guys, no criticism implied.)

[nige2000]

the mosfets might benefit from been further apart they get rather hot?
maybe just run wire?

As a curious reader and one of the lucky people to hear this amp in progress, I'd follow Nigel's advice and run the Mosfets off of the PCB and maybe onto a heat spreader then bolt it a heatsink, they get shockin' hot.
(just an observation guys, no criticism implied.)

the pcb is for the headphone amp, not the speaker amp
its about half the current but the heatsinking will be around halfsize aswell so still hot

have u any subjective thoughts on the sound of the two speaker amps?
might be better than my description

[abraxalito]

i had a few of these lying about audiowind sp-2
http://www.audiowind.com/pdf/A-240LM.pdf
used two of them (just the negative half) for the gain stages

Fairly bog-standard implementation of LM317/337 which is a disaster for HF line rejection on the -ve rail due to the LM337 having poor rejection at HF. Even a passive RC on the input could lift the line rejection by more than 20dB. I also use LC filtering after 3 term regs.

briefly connected up a batt pack for gain stage for a quick haphazard test and got a good lift in sq
that i wasnt overly surprised with

Right, predictable.

i tried a batt on the tk13 headphone amp and there was very little improvement
so i was surprised there was a lesser but substantial improvement by powering the tk50 with batt
seemed to be a cleaner sound or a lower noise floor, better decay, reverb etc, dynamics unchanged

This is useful feedback for when I get off DACs and back to amps again.

[Derek]

the pcb is for the headphone amp, not the speaker amp
its about half the current but the heatsinking will be around halfsize aswell so still hot

have u any subjective thoughts on the sound of the two speaker amps?
might be better than my description

I had a sneaky feeling I was getting it wrong.

The Mosfet amp is very fast, accurate, dynamic, great detail, front to back sound-stage is impressive. Singer in front of you, drummer in the drum-booth way at the back. However it's lacking in body and bottom end. There's an early bass roll-off keeping the amp from fattening the sound.

The battery powered Class A is a different beast. Full sound without being lush, great dynamic detail and accuracy.
Eases off on the immediacy, of the Mosfet. Full sound-stage with instrument placement locked in.
It delivers a full deep sound with great bass extension. Lends timbre to both vocal and instruments, allowing the listener to "see" the musicians rather than just the instruments.

Hope this helps.

[randytsuch]

next attempt, this one is better for grounds and power routing, I think.

[frd1996]

Randy, here's just an idea:

hotbuff1.jpg (80.17 KiB) Viewed 884 times

[randytsuch]

Thanks for that frd.

Your layout is much cleaner than mine, will steal much of what you did.

[nige2000]

that looks good to me

learning pcb design should be on my agenda too

did some more batt testing on the tk50 amp

think batt would go a long way on narrowing the sound gap between these two batt amps

3.8 amps is pretty hungry for both channels there is quite the spark connecting up the battery pack

mono or dual mono supplies is the only way that could work heat and charging wise on batt packs

[randytsuch]

Any idea how much power the HP amp uses?

Wondering how many amps of 16V I need for the power supply.

I was calculating the power rating required for R2, and I must be doing something wrong because I'm getting a very high power number.

If your tk50 uses 3.8A, the hp amp must be much less.

Randy

[abraxalito]

Any idea how much power the HP amp uses?

Its for you to decide by selecting the appropriate supply voltage and bias current for your particular load impedance.

Wondering how many amps of 16V I need for the power supply.

With 16V supply I'd guess you're feeding high impedance (say >250ohm) headphones? If so you'll need a gain stage too, not just the HP amp.