que?
you mean - instead of cascoded JFets?
tricky - from few reasons :
- you need proper complement to BS170
-biasing them is problem , due to fact that JFets in F5 are depletion mode devices biased through degenerating resistors , while BS are enhanced mode devices , demanding positive voltage at gate ref. source , for N type .......and negative voltage on gate ref. source , for P type
you mean - instead of cascoded JFets?
tricky - from few reasons :
- you need proper complement to BS170
-biasing them is problem , due to fact that JFets in F5 are depletion mode devices biased through degenerating resistors , while BS are enhanced mode devices , demanding positive voltage at gate ref. source , for N type .......and negative voltage on gate ref. source , for P type
Again for the sake of experiment 3055 BJT output
Another stupid question again: has anybody tried chaning the Mosfets irpf240 to bipolars like the TIP3055? The pin-out of the pcb looks like the 3055 can be put in there just like that.
Because of the automatic current control the output stage will put out around 1 Amp just the same. At the 'gate' (base) of the TIP3055 now will be around .7 V (instead of 4V with mosfet). VR1 still can be uses to set-up the midpoint voltage. Correction of the current flowing through Q4 needs a lower value of R9, so change 1k into 150 or so.
Seems this could work just the same.
But .... from earlier attemps to build a 2-stage BJT power-amp I know that it is far more difficult to drive a 3055 with full swing than it is for the mosfet. That's the reason why hybrid amps always put mosfets after the tube stage.
So: anybody a clue if this is going to work (put out enough swing from the 2SK170 to drive the TIP3055 to 5 Watts)?
Another stupid question again: has anybody tried chaning the Mosfets irpf240 to bipolars like the TIP3055? The pin-out of the pcb looks like the 3055 can be put in there just like that.
Because of the automatic current control the output stage will put out around 1 Amp just the same. At the 'gate' (base) of the TIP3055 now will be around .7 V (instead of 4V with mosfet). VR1 still can be uses to set-up the midpoint voltage. Correction of the current flowing through Q4 needs a lower value of R9, so change 1k into 150 or so.
Seems this could work just the same.
But .... from earlier attemps to build a 2-stage BJT power-amp I know that it is far more difficult to drive a 3055 with full swing than it is for the mosfet. That's the reason why hybrid amps always put mosfets after the tube stage.
So: anybody a clue if this is going to work (put out enough swing from the 2SK170 to drive the TIP3055 to 5 Watts)?
where it could go wrong ?
simply everywhere - because bjt is demanding "some" current on base ..... that means , you need driver stage biased that much in A class to cover linearly entire current swing , needed for current hungry 2N3055 base
even if you take modern bjt , with much higher beta ( and much lower variation of same , in current domain) there is still considerable current swing , in need to cover
it's doable , but that will be completely different amp
simply everywhere - because bjt is demanding "some" current on base ..... that means , you need driver stage biased that much in A class to cover linearly entire current swing , needed for current hungry 2N3055 base
even if you take modern bjt , with much higher beta ( and much lower variation of same , in current domain) there is still considerable current swing , in need to cover
it's doable , but that will be completely different amp
You're right. Without modification it seems rather useless. For succes you will need a revised amp that's not ACA anymore. That's beyond the scope of this discussion, I agree.
So: this circuit (2-stage, single-ended, 20V blabla) is in some kind of optimal state and includes the use of mosfets as output from it's design principles/constraints. Only fine-tuning is left for experimentation (some more of this, less of that, change one fet for the other etc).
If nobody here denies this claim, this means end of 3055/bjt-trial.
So: this circuit (2-stage, single-ended, 20V blabla) is in some kind of optimal state and includes the use of mosfets as output from it's design principles/constraints. Only fine-tuning is left for experimentation (some more of this, less of that, change one fet for the other etc).
If nobody here denies this claim, this means end of 3055/bjt-trial.
Hi
Gave up searcing,sorry
Whats the DC voltage input range ?
I want to use a 24V/290Ahr.batteri.
Will I need regulation ?
Any other disavantages using a batteri as PSU ?
(Apart from charging)
Jan
BTW.:See this:Copenhagen Suborbitals | Copenhagensuborbitals
Gave up searcing,sorry
Whats the DC voltage input range ?
I want to use a 24V/290Ahr.batteri.
Will I need regulation ?
Any other disavantages using a batteri as PSU ?
(Apart from charging)
Jan
BTW.:See this:Copenhagen Suborbitals | Copenhagensuborbitals
It's always a good idea not to power ON/OFF your pre-amp with the power amp ON unless you have some sort of muting arrangement at the pre-out.
Just plain curious
Can someone post an example or link for the type of battery being discussed? Sounds like one big green spark to me.
Hi
The batteri came from our old boat.
Marine type,sealed.Truck caravane...?
Havnt any clou of the brand,my farther bought them and a heat-exchanger from someone in the marina.
Sold as "ORIGINAL VOLVO PENTA" sparepart.
Back to the point,whats is the voltage range on the ACA ? (Min.-Max.)
Jan
The batteri came from our old boat.
Marine type,sealed.Truck caravane...?
Havnt any clou of the brand,my farther bought them and a heat-exchanger from someone in the marina.
Sold as "ORIGINAL VOLVO PENTA" sparepart.
Back to the point,whats is the voltage range on the ACA ? (Min.-Max.)
Jan
Hi
Thanks Zen
Im used my lab.psu for testing.
Voltage: 22-24v seems to be optional for the ACA."Soundwise."
(driving a pair of alpair 7.3 in pensils).
Then connected a cheap 24V/5A SMP,(measuring 23.8V at 2.77A.2 channels)
The verdict:
If any of you out there are running your ACA on 19V,try 24V for a nice surprice !
Jan
PSlacing and hiding the batteri project will proberly end up in a "thatstotallyoutofquestion" situation and is put on ice at the moment.
Thanks Zen
I know,but where? I couldnt find it again ?
Im used my lab.psu for testing.
Voltage: 22-24v seems to be optional for the ACA."Soundwise."
(driving a pair of alpair 7.3 in pensils).
Then connected a cheap 24V/5A SMP,(measuring 23.8V at 2.77A.2 channels)
The verdict:
If any of you out there are running your ACA on 19V,try 24V for a nice surprice !
Jan
PS
lacing and hiding the batteri project will proberly end up in a "thatstotallyoutofquestion" situation and is put on ice at the moment.Hello guys
I'm an enthusiast and hobbyst of electronics. I already have this amplifier on my breadboard for initial tests. Sounds awesome (tough some refinements have still to be done).
One of these "refinements" regards the current sensing resistor network (R1 to R4).
Indeed I'm running the amp @23 volts and using a single sensing resistor 0R39, setting bias current to ~1.5 amps. Speaker signal is taken after resistor, from Q1's drain.
I was wondering what's the deal of having this resistor network instead of a single resistor.
Does it change sonically speaking?
What do you think?
I'm still learning a lot
I'm an enthusiast and hobbyst of electronics. I already have this amplifier on my breadboard for initial tests. Sounds awesome (tough some refinements have still to be done).
One of these "refinements" regards the current sensing resistor network (R1 to R4).
Indeed I'm running the amp @23 volts and using a single sensing resistor 0R39, setting bias current to ~1.5 amps. Speaker signal is taken after resistor, from Q1's drain.
I was wondering what's the deal of having this resistor network instead of a single resistor.
Does it change sonically speaking?
What do you think?
I'm still learning a lot