Tír Na HiFi

randytsuch wrote: ↑Fri Sep 29, 2017 5:05 pm Hmmm. Higher voltage = more batteries and higher expense.

Sounds like you guys are making another run at my wallet lol

yea the batt expense is killer
we could do with another ps solution
is just so easy to cheat using the lifepo4

nige2000 wrote: ↑Fri Sep 29, 2017 6:10 pm

randytsuch wrote: ↑Fri Sep 29, 2017 5:05 pm Hmmm. Higher voltage = more batteries and higher expense.

Sounds like you guys are making another run at my wallet lol

yea the batt expense is killer
we could do with another ps solution
is just so easy to cheat using the lifepo4

By the time you costed an "equivalent" ps solution, I think makes lifepo4 look very appealing. And for some apps I don't know if there is anything as good, at any cost.
And A123 lifepo4's are actually getting cheaper over here, so it's not as bad as it used to be.

Nige,
How close is your PS to the amp? If you move the PS relative to Amp do you get a change in hum or SQ?
In other words, could it be magnetic field or other radiated disturbance?

jkeny wrote: ↑Fri Sep 29, 2017 6:40 pm Nige,
How close is your PS to the amp? If you move the PS relative to Amp do you get a change in hum or SQ?
In other words, could it be magnetic field or other radiated disturbance?

nah i just really half assed the supply

bypassing my half assed supply with bench supply and the the battery pack i did further subjective testing

feeding gain stage and output stage from battery pack showed substantial improvement with higher voltage (tested up to 36v)
putting the gain stages on the battery pack and the output stage solely on bench supply at same voltage ie 36 v
sound was flatter, tamer and less resolution
tested that between 16v to 64v,
no decent performance until 24v
as voltage raised it sounded more like it did with the battery pack
id say 30v is a minimum
40v is a plausible target given enough heatsinking
any more voltage is going to be difficult to dissipate
at 64 v sounded great but maybe not just as good as the battery pack at 36v,
id imagine after half an hour of 60 odd volts i could sear a steak on the heatsink

the power supply from the group buy amp would work wonders in this,
though the heatsinking would have to be more than doubled i recon

tonights the best i've heard this amp

Have you thought about using this amp with the output transformer to step the voltage down? If you did that then you could reduce the bias current (as the load is higher impedance). Its a great way to run at higher voltage without extra heat. Mind you we'd need a revised design for the gain stage as that tops out at 40V I think.

No hadn't thought of it yet
Your brain works slot faster than mine

Think there'll be diminished returns after 40 v as the difference between 30 and 40 v seems to be more than the difference between 40 and 64v

With the tx i have i think I've some that will take 60v but definitely have some that take 30

Were you running the gain stage at 60V?

Ha ha
Not something i wouldn't try but not yet

So I have this crazy idea

Deleted my first idea, because I'm pretty certain it was wrong.

Now I'm wondering if the voltage developed by R4/R5 is what controls the idle current?

I want to lower the idle current by about 10 times, maybe a little more.

Looking to build a battery powered portable head amp, something like xrk's but better lol.

Was thinking maybe use one or two lifepo4 batteries and a then cap multiplier to raise the voltage up to 16VDC.

Randy