Ok IRFP it is.
My speakers are 2 way speakers with ribbon tweeters. I do not have a big room but I do like my music relatively loud. I currently have F4 monoblocks and the room seems to be handling the heat just fine.
My speakers are 2 way speakers with ribbon tweeters. I do not have a big room but I do like my music relatively loud. I currently have F4 monoblocks and the room seems to be handling the heat just fine.
Are you driving the F4monoblocks from a balanced preamp?
If not, build one, and you will have the 100WPC with the same heat. 🙂
If so, you already have 100WPC Class-A Firstwatt amps. 🙂 🙂 🙂
If not, build one, and you will have the 100WPC with the same heat. 🙂
If so, you already have 100WPC Class-A Firstwatt amps. 🙂 🙂 🙂
I am running them from a balanced preamp, but who says that having 2 amps is a bad thing? I wanted to compare the sonic differences.
I mean you can never have enough amps IMO 😀.
What would be better suited for my needs? V3 or V2?. I think its the V3 but I am not sure what rails to get and what to bias to. I think I should have the standard 32V rails with a 24V 800VA transfromer but I am not sure what to bias everything to. Now if I am reading everything I read correctly I will need 2 sets of boards for 2 pairs of extra output mosfets per channel on the V3.
What would be better suited for my needs? V3 or V2?. I think its the V3 but I am not sure what rails to get and what to bias to. I think I should have the standard 32V rails with a 24V 800VA transfromer but I am not sure what to bias everything to. Now if I am reading everything I read correctly I will need 2 sets of boards for 2 pairs of extra output mosfets per channel on the V3.
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rails voltage is what determinds what power you will get out of your amp. With +/-32VDC rails you get about 50W @ 8ohm. if you want a turbo V3, you need to crank up the rails a bit. to +/-45VDC that will get you to the 100W mark at 8ohm.
bias depends on how long you want the amp to stay in class A. if you want 100W class A, then the bias needs to be 2.5A or higher. or 0.625A pr device (0.3125V over source resistors) with 4 pairs. wich will calculate to around 225W dissipation pr ch + whatever dissipation you will get from the transformer, PSU and FE.
bias depends on how long you want the amp to stay in class A. if you want 100W class A, then the bias needs to be 2.5A or higher. or 0.625A pr device (0.3125V over source resistors) with 4 pairs. wich will calculate to around 225W dissipation pr ch + whatever dissipation you will get from the transformer, PSU and FE.
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just one more Q:
what determines at what bias level the amp "starts" in cold condition
one monoblock starts at approx 150mV and the other at 250mV
best
Leif
what determines at what bias level the amp "starts" in cold condition
one monoblock starts at approx 150mV and the other at 250mV
best
Leif
Why not build a BA3B to drive the F4's in bridged mode, the F4 has virtually no 'sound characteristic' of its own, and the BA3B is very similar to a F5X. Opps, forgot the Pumpkin
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Unless you are building some very large, fan-cooled enclosures, you will run out of heatsink before you run out of bias current...
The easy rule of thumb is bias until you have 65C transistors and 55C heatsinks.
Yes.
any body knows the answer to post # 3547?
also I wonder if I fried the drivers in one of the amps, the one that starts@250mv...very flimsy offset
when testing choke input psu, they got over 40v from psu
even blew a row of outputdevices too 😱
choke input psu for class A amp has been a very bumpy road
definitely in the fire extinguisher league
best
Leif
also I wonder if I fried the drivers in one of the amps, the one that starts@250mv...very flimsy offset
when testing choke input psu, they got over 40v from psu
even blew a row of outputdevices too 😱
choke input psu for class A amp has been a very bumpy road
definitely in the fire extinguisher league
best
Leif
Buy a bunch and match them. Not difficult at all, just takes a little time and a number of excess thermistors.
But, that's not going to do anything about the differences in the rest of the circuit that make the offset wander a bit until everything is up to temperature.
Like I said, If you are concerned, add a switch to the outputs.
But, that's not going to do anything about the differences in the rest of the circuit that make the offset wander a bit until everything is up to temperature.
Like I said, If you are concerned, add a switch to the outputs.
no juice in "matching" them
matching wise - they need to be matched across entire temp. range , and that's Neverland
besides , there is entire bunch of temp. dependable nonlinearities - in Jfets and mosfets
what's needed is exact uniformity in physical layout = meaning how NTCs are mounted to mosfet body
6moon pics of F5 , look no further
matching wise - they need to be matched across entire temp. range , and that's Neverland
besides , there is entire bunch of temp. dependable nonlinearities - in Jfets and mosfets
what's needed is exact uniformity in physical layout = meaning how NTCs are mounted to mosfet body
6moon pics of F5 , look no further
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The V3 is the latest version, I would build that.
The FQP12P20/FQP19N20 are available from www.digikey.com
I have builld many amps with the IRFP9240/IRFP240 and they sound very good.
Have a good one,
John
Thank you. It looks like a 1000VA 32V transformer will work wonderfully here. I think that makes 45V rails. Is it possible to bias the amp to 200W class A at 4ohms?
Why not build a BA3B to drive the F4's in bridged mode, the F4 has virtually no 'sound characteristic' of its own, and the BA3B is very similar to a F5X. Opps, forgot the Pumpkin
Ya I think I will start to work on a BA-3 or impasse soon. is there a difference between the BA3 and BA3B?
I should do just fine with a 4U chassis I believe. With 0.31C/W x2, I should theoretically get about 45C (if my math is correct), so (again if my math is correct) I think it will work just fine.
Thank you. They also seem to be in stock at mouser.
Already done 😱
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45V rails and a 5U will make a hot stereo, or a decent monoblock.
BA-3B is balanced, you need two PCB and such, and tie them together to make a balanced circuit.
(Look into the Impasse for your F4...)
BA-3B is balanced, you need two PCB and such, and tie them together to make a balanced circuit.
(Look into the Impasse for your F4...)
2x35V is needed to reach +/-45 rails under load.
4U 300mm chassis will get too hot. 5U will be needed here.
you want to stay between 25-30c above ambient.
25/225=0.11C/W pr ch. and then there is the thermal resistance of insulators and grease.
With the 4U 300mm chassis you may end up as high as 45c above ambent.
4U 300mm chassis will get too hot. 5U will be needed here.
you want to stay between 25-30c above ambient.
25/225=0.11C/W pr ch. and then there is the thermal resistance of insulators and grease.
With the 4U 300mm chassis you may end up as high as 45c above ambent.
The transformer for a ClassA amplifier is typically 6 to 10 times the maximum output.
For 200W of ClassA output and using the general rule, you end up with 1200VA to 2000VA.
Another way to approach it, is to compare the maximum continuous output current of the transformer + rectifier, with the continuous bias current of the amplifier.