I have a plate amp that is rated at 110w RMS @8ohm and 156w RMS @4ohm. The power supply section of this amp looked a bit chinsy to me so I decided to upgrade with some old parts of another amp I had laying around. It allready had two 6800mfd 63v caps and I added two more 10,000mfd caps,a 500VA transformer and and a 50 amp rectifier. Overkill? I hope so.......lol. MY question regards the voltage of new transformer and how much wattage is actually gained. The original transformer supplied +-48v and the new one supplies +-63v. It doesn't run much hotter and seems to be stable but I would just like to know someones best guess on the gain or way to figure out an estimate without having to test the amp. Thanks in advance for any replies
.
.a simple estimate is circa 190W into 8 ohms
and a lot more into 4 ohms.
However if the sub amplifier has well designed SOA (safe
operating area) circuitry and was designed to run near its
limits you will get barely more power.
Its possible the extra rail voltages would kick in the SOA
circuitry earlier so you'd get less power !
Or it could have no SOA circuitry, so the first estimate applies,
but your circuit board is more likely to perfunctorally expire.
As a general guideline upgrade current and smoothing
capability of a power supply, changing the output voltage
of an amplifier power supply is generally not a good idea.
sreten.
and a lot more into 4 ohms.
However if the sub amplifier has well designed SOA (safe
operating area) circuitry and was designed to run near its
limits you will get barely more power.
Its possible the extra rail voltages would kick in the SOA
circuitry earlier so you'd get less power !
Or it could have no SOA circuitry, so the first estimate applies,
but your circuit board is more likely to perfunctorally expire.
As a general guideline upgrade current and smoothing
capability of a power supply, changing the output voltage
of an amplifier power supply is generally not a good idea.
sreten.By my calcualtions:
Going from +/-48 VDC rails to +/- 63 vdc rails (ignoring all other factors)
will result in an amplifier that is 2.2 dB louder. Not much. That is a best case calculation.
Will this greater voltage put your amplifier's components at risk? Hard to say. I speculate that if your expertise is at the level that you had to ask your initial question, you probably cannot answer this question on your own.
HOWEVER......
If you wanted to improve the sound of you amplifier and make it "sound louder" consider adding voltage regulation to your amplifier's power supply. Regulate the power supply down to about the original rail voltage.
Do not be surprised when it really sings.
Good luck,
Aud_Mot
Going from +/-48 VDC rails to +/- 63 vdc rails (ignoring all other factors)
will result in an amplifier that is 2.2 dB louder. Not much. That is a best case calculation.
Will this greater voltage put your amplifier's components at risk? Hard to say. I speculate that if your expertise is at the level that you had to ask your initial question, you probably cannot answer this question on your own.
HOWEVER......
If you wanted to improve the sound of you amplifier and make it "sound louder" consider adding voltage regulation to your amplifier's power supply. Regulate the power supply down to about the original rail voltage.
Do not be surprised when it really sings.
Good luck,
Aud_Mot
Thank you for your reply sreten. This is not a well built amp, lol. So I doubt there is any type of limiting circuitry. It has been running in this new config for awhile now and it hasn't burnt itself up yet. I did the"upgrades" because I was bored and had the pieces and didn't really care if I broke it or not.
My post was assuming that he already installed the overkill transformer. So what to do now? Wait for the mod to blow up his amp? My suggestion would do two things 1) return his amp to using applied voltages that should be safe 2) give him the sonic advantages of a regulated power supply.
I do not understand the point of the over specced transformer. Since I recommended a lowering of rail voltage, the only penalties of a "too big" transformer are physical size (taken care of) and expense.
Aud_Mot
I do not understand the point of the over specced transformer. Since I recommended a lowering of rail voltage, the only penalties of a "too big" transformer are physical size (taken care of) and expense.
Aud_Mot
Sorry,
we are talking about 2 different things, at crossed purposes.
If the transformer is overspecced, VA wise then adding
regulation or a multiplier is poor engineering, due to it
being overspecced VA wise it will have good regulation.
You are perfectly correct that adding regulation to reduce
rail voltage to the original value is the sensible option,
and IMO the best option for similar VA transformers.
Boils down to why you are adding the regulation.
If the amplifier works at the higher rail voltages then
everything thing is fine, adding regulation will lose power.
If it doesn't, then regulation is required to drop rail voltages
and the overspecced VA rating of the transformer doesn't
matter.
sreten.
we are talking about 2 different things, at crossed purposes.
If the transformer is overspecced, VA wise then adding
regulation or a multiplier is poor engineering, due to it
being overspecced VA wise it will have good regulation.
You are perfectly correct that adding regulation to reduce
rail voltage to the original value is the sensible option,
and IMO the best option for similar VA transformers.
Boils down to why you are adding the regulation.
If the amplifier works at the higher rail voltages then
everything thing is fine, adding regulation will lose power.
If it doesn't, then regulation is required to drop rail voltages
and the overspecced VA rating of the transformer doesn't
matter.
sreten.
This increase in supply rails may be reliable as long as loads below 8 ohm are no longer used
To be fully reliable it would also require all transistors in the circuit to have enough blocking and thermal capabilities and biasing schemes good enougn to not come into runaway with higher supply rails
From the point of view of dissipation and SOA of the output devices, running them with +-63V and 8 ohms load isn't much worse than running them with +-35V and 4 ohms [except if they are old 100V Vce devices like TIP35/36C]
To be fully reliable it would also require all transistors in the circuit to have enough blocking and thermal capabilities and biasing schemes good enougn to not come into runaway with higher supply rails
From the point of view of dissipation and SOA of the output devices, running them with +-63V and 8 ohms load isn't much worse than running them with +-35V and 4 ohms [except if they are old 100V Vce devices like TIP35/36C]
Hi Anonymous,
This is a long-shot, but is your plate amp by any chance the RCM Acustik Detonator DT-110 (or something like that!)?
If so, then it's the same as mine. I added 40,000uf to the PSU with no apparent problems. It sounds more gutsy, but still isn't going to use my Tempest driver to the full...
This is a long-shot, but is your plate amp by any chance the RCM Acustik Detonator DT-110 (or something like that!)?
If so, then it's the same as mine. I added 40,000uf to the PSU with no apparent problems. It sounds more gutsy, but still isn't going to use my Tempest driver to the full...
No, mine is the no name "Part Number 300-792" that they sell at parts express. I really appreciate every bodies input here, but the first answer probably suites my question the best. Like I said before, I'm not having any problems with the amp after the modifications I did. Its been running a 12" 4ohm sub for quite some time now with no ill effects. I was really just interested in what the average gains of such a change would be. Oh, and I dont know how much it helps the amp but I used heat sink epoxy to glue little heat sinks on every last transistor on the pcb.
theAnonymous1 said:MY question regards the voltage of new transformer and how much wattage is actually gained.
The original transformer supplied +-48v and the new one supplies +-63v.
It doesn't run much hotter and seems to be stable
but I would just like to know someones best guess on the gain
or way to figure out an estimate without having to test the amp.
Thanks in advance for any replies
well, this is plain mathematics
Data we need:
1. impedance of your speakers, lowest value (like 5 Ohm maybe, for one 8 Ohm speaker)
2. the voltage of your supply
as you say +- 63 VDC
but under heavy load this may sink a little bit (even for 500VA trafo)
----------------------
let's say max 55 +-Volt DC
this is the peak value
the RMS value is 0.7 of that ~40 Volt RMS
If your output tansistors can deliver:
40Volt / 5Ohm RMS = 8 Ampere average output
then we get max power output of something like:
U(voltRMS) x U(voltRMS) / R(speaker Ohm) = P (power)
into 5 Ohm max peak power = 40x40/5 = 320 Watt rms
into 8 Ohm nominally = 40x40/8 = 200 Watt rms
Now, the limiting factor is Your Amplifier .. not your supply ...
If amp is built to deliver 320/200 Watt
you may get it ... otherwise bad things will happen
Lineup - The Mathematical Wizard from Sweden
I hate to butt in on this one , but I have the schematics for a lot
of MCM /PE plate amps(I owned one) and they DO NOT derate
the components like in our beloved DIY world!
In most commercial amps (I observed today 22v with 25v caps
)
if you see 45Vdc (like your original),they will use a 50V or 63V cap
(hopefully).
saves them money. $$
So ,this mod might work for a while ,but I would check all the caps
in the amp (rail to ground)make them 80V/100V, and check all
trannies(drivers ,output), make sure Vceo is above new supply
voltages.(160V and up)
I have 3 150+ watt DIY amps running at +-60VDC , I use
100V caps exclusively and 200+V Vceo all trannies, they'll
run 10 years+.
Wish you luck with your mod, OS.
P.S... The amp is a dayton 300-792 sub amp.
don't push it too hard.
of MCM /PE plate amps(I owned one) and they DO NOT derate
the components like in our beloved DIY world!
In most commercial amps (I observed today 22v with 25v caps
)if you see 45Vdc (like your original),they will use a 50V or 63V cap
(hopefully).
saves them money. $$So ,this mod might work for a while ,but I would check all the caps
in the amp (rail to ground)make them 80V/100V, and check all
trannies(drivers ,output), make sure Vceo is above new supply
voltages.(160V and up)
I have 3 150+ watt DIY amps running at +-60VDC , I use
100V caps exclusively and 200+V Vceo all trannies, they'll
run 10 years+.
Wish you luck with your mod, OS.
P.S... The amp is a dayton 300-792 sub amp.
don't push it too hard.
An externally hosted image should be here but it was not working when we last tested it.
Is that your amp?
300-792 Manual
By the looks of it ,small heatsink... might be a bridged
IC amp (STK/TDA-XXX)? Hard to believe to-3p or to-247.
(Dayton 240W amp is where they start braggin' up the
discrete outputs.)
many of these can take +- 80 or more,
cant find schema YET.
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