Parallel adds the current, voltage stays the same.
Series adds the voltage, current stays the same.
Connect 35-0-35 - 35-0-35 and the 35 - 35 junction is your centre tap. Note however that this will give you almost 100V DC. No offence but given your current apparant knowledge that's too much power and voltage to be messing around with. Build a smaller amp first
Series adds the voltage, current stays the same.
Connect 35-0-35 - 35-0-35 and the 35 - 35 junction is your centre tap. Note however that this will give you almost 100V DC. No offence but given your current apparant knowledge that's too much power and voltage to be messing around with. Build a smaller amp first
Ahmad_tbp said:again ...
sorry
it may seems a silly question
You need to run them in parallel with this module. Make sure that the transformers are exactly the same otherwise there will be problems.
35 0 35 volts AC will give you about +/- 49 volts DC for your rails.
This equates to a power output of around 100 watts into 8 ohms, and around 180 watts into 4 ohms.
The maximum transformer voltage I would recommend for your amp is 50 0 50 volts AC.
As far as the FETs being fake goes, it depends on who made made them. I have used IRFP450s made by other manufacturers besides International Rectifier but it doesn't mean they are fake. I would not worry about the effect on the sound. Hexfets were primarily designed to be used in switching applications (power supplies, motor control etc.) so I doubt you will hear much difference (probably nothing) between different brands of FETs.
Cheers
Cheers
lol yup sure ,, i donno why they makin such a cheap devices ..
the seller told me that most of transistors in Iran s stores r fake and all made in china ! lol ...
and another awefull truth is the price of fakes r almost s the same as originals ! ... lol ..
i saw the price of the irp450 in the net s bout 2-3 dollars ,,, and the fake irp450 price is 2-3 dollars here too ! ... lol ..
Nobody is in the business of intentionally making cheap devices. The IRF devices are cheap not because of poor performance but because of their large scale.
A lot of the genuine devices today are manufactured in China, and it is in the interest of the fake ones to behave like the genuine ones, even on prices. Otherwise, you would be able to tell them apart easily.
A lot of the genuine devices today are manufactured in China, and it is in the interest of the fake ones to behave like the genuine ones, even on prices. Otherwise, you would be able to tell them apart easily.
Plastic Box.
You could put it in a plastic box without problems but there could be a small (very small) noise issue if the box is located near other electronic equipment. However for your application as a bass amp it should not be a problem.
Have you thought about building it into your bass cabinet with a nice front panel etc.
Cheers
Ahmad_tbp said:
You could put it in a plastic box without problems but there could be a small (very small) noise issue if the box is located near other electronic equipment. However for your application as a bass amp it should not be a problem.
Have you thought about building it into your bass cabinet with a nice front panel etc.
Cheers
Ahmad_tbp said:the box was built but ..... the sound s really bad
i bought two rcf full range 12" speakers and built a 4x12" cab w 2 subs and 2 rcfs w the help of simon , but the subs r realllllyyyyyyyyy s**** in a little high volume
Hi man,
You're still around and didn't say a little hello to me?
I'm a bit frustrated that your box sounds like ****. Did you use a 2nd order crossover highpass on the RCF woofers and also a 2nd order crossover lowpass on the Sony woofers? If yes, I guess you have a severe air leak, or those RCFs are ****. Even a small air leak can DESTROY the sound. Maybe you have some resonance issues. Are you sure the carpenter followed exactly what you and I designed?
The very loud noise you're talking about seems like the RCFs are bottoming out, you may have already damaged them. The crossover should have protected them so I don't understand. That's why I suspect a air leak that would increase the displacement alot. The two chambers MUST be totally isolated.
Maybe you could show pictures of the finished cabinet, inside pictures too.
You could also try sealing the port on the subwoofer part of the cabinet.
Good luck!
Sorry for being off-topic...
Nelson Pass said:
Hi Nelson,
I have been researching and doing calculations to compare "net" Ciss to compare number of parallel output pair devices choices vs using a single output pair device. There is one school of thinking that for mid range or tweeter amplifiers that the ideal device configuration is to use just a single pair of output devices. So far the opinion for woofer amplifiers is parallel pairs of output devices is best. I seem to recall, but my memory is not certain, reading online somewhere that parallel devices are better for woofers vis a vie damping factor. I do not recall where online I read this. I have been doing extensive reading and research which seems to differ to your very respectable knowledge and experience. I suspect from my questions to follow that you will enlighten me about why my research above has been >95% of the opinions.
My questions would be as follows when considering LF range <= 150-200Hz, MF 150-200Hz to 2-3KHz, and HF >= 2-3KHz :
1) What differences in are there in MF and HF using single VS parallel devices?
2) Is damping factor affected by number of parallel devices? If so, generally the general trend of difference.
3) Is it fair to assume that output device having a single output device Ciss of 2600pf is the same as using two output devices having a Ciss of 1300pf assuming perfectly match devices and identical devices in all other respects? I know such identical devices do not exist, I just set the context to limit the scope of the question.
4) Generally what aspects of the amplifier design that affects if a single device or the ideal number of parallel devices should be used? Is the answer generally speaking different based on amplifier class, i.e. A, or AB.
5) Generally from experience how does one determine the ideal number of devices for a given design?
6) Does the bias level chosen or designed affect any of the above questions answers?
I am not design savvy, but I can handle a little bit of technical amplifier design detail. I can handle math most of time even if I do not understand the theory of how the math models things. I am assuming the nature of my questions will only make use of basic math and application theory.
Regards,
John L. Males
Willowdale, Ontario
Canada
28 June 2005 00:12
28 June 2005 00:16 Correct typo errors.
Re: Relevance ?
Quasi,
A few questions:
1) Is there an easy way to determine looking at a design if it has a low impedance output driver stage?
2) Visually on the scope with 10KHz square wave what will one see to indicate a well vs marginal or poor driver stage design?
3) Does one scope at the output of the driver stage or driver stage output to observe the 10KHz square wave test signal?
4) Can using a square wave test signal >10KHz to < 25KHz demonstrate a well vs marginal/poor driver stage design any better or seperate well design ed driver stages subtle differences more?
5) Can you expand what you mean by "swamp" in you comment of "... will swamp out any variations in capacitance."?
Regards,
John L. Males
Willowdale, Ontario
Canada
28 June 2005 00:37
28 June 2005 00:43 Corrected typo errors
quasi said:With a well designed and low impedance output driver stage the effects of gate capacitance can be minimised to a negligible (non-audible) level. A low impedance drive will swamp out any variations in capacitance.
Visually this can be observed with a 10Khz full rail swinging square wave where with a well designed driver stage the effects observed are quite small. (IMO).
Cheers
Quasi,
A few questions:
1) Is there an easy way to determine looking at a design if it has a low impedance output driver stage?
2) Visually on the scope with 10KHz square wave what will one see to indicate a well vs marginal or poor driver stage design?
3) Does one scope at the output of the driver stage or driver stage output to observe the 10KHz square wave test signal?
4) Can using a square wave test signal >10KHz to < 25KHz demonstrate a well vs marginal/poor driver stage design any better or seperate well design ed driver stages subtle differences more?
5) Can you expand what you mean by "swamp" in you comment of "... will swamp out any variations in capacitance."?
Regards,
John L. Males
Willowdale, Ontario
Canada
28 June 2005 00:37
28 June 2005 00:43 Corrected typo errors
keypunch,
Paralleling device is not really anything much to do with your first round of points, it simply comes down to the power handling of the devices and how much power you need to dissipate. Damping factor may be slightly lower with more devices.
Regarding the second round of questions, the impedance of the driver stage can be given a knowledgeable eye and a rough guess as to ballpark high/low impedance can be judged. This is based on transistor configuration (emitter/collector driving), standing current and to some extent the resistor values.
Looking on a scope poor results could come from any one of the stages in an amp and really you need to scope at several points (LTP, VAS, drivers and output) to see where the problem lies.
Going up in frequency of square wave may start to bring in effects due to amplifier bandwidth more. These could be a little misleading as the harmonic content of square waves is very high, so for it to be replayed properly you need orders of magnitude more bandwidth than the square wave fundamental.
To swamp something out means that e.g. the resistor applied close to the gate of a MOSFET swamps out or dominates over the track inductance thereby rendering it not a problem.
Paralleling device is not really anything much to do with your first round of points, it simply comes down to the power handling of the devices and how much power you need to dissipate. Damping factor may be slightly lower with more devices.
Regarding the second round of questions, the impedance of the driver stage can be given a knowledgeable eye and a rough guess as to ballpark high/low impedance can be judged. This is based on transistor configuration (emitter/collector driving), standing current and to some extent the resistor values.
Looking on a scope poor results could come from any one of the stages in an amp and really you need to scope at several points (LTP, VAS, drivers and output) to see where the problem lies.
Going up in frequency of square wave may start to bring in effects due to amplifier bandwidth more. These could be a little misleading as the harmonic content of square waves is very high, so for it to be replayed properly you need orders of magnitude more bandwidth than the square wave fundamental.
To swamp something out means that e.g. the resistor applied close to the gate of a MOSFET swamps out or dominates over the track inductance thereby rendering it not a problem.
Yep ...what richie00boy said.
The easiest drive impedance indicator (indicator only) is to look at the value of the gate to rail / gate to line resistor.
If the FET requires 4 volts to turn and 6 volts for maximum load current and the resistor is 100 ohms then 40mA to 60mA will run through the driver stage. This gives you an indicator of the drive capability.
Of course if the gate to rail resistor is 10 ohms then 400mA will flow.....but things (driver transistors) then start to get very hot.
Cheers
The easiest drive impedance indicator (indicator only) is to look at the value of the gate to rail / gate to line resistor.
If the FET requires 4 volts to turn and 6 volts for maximum load current and the resistor is 100 ohms then 40mA to 60mA will run through the driver stage. This gives you an indicator of the drive capability.
Of course if the gate to rail resistor is 10 ohms then 400mA will flow.....but things (driver transistors) then start to get very hot.
Cheers
What Mosfets to use?
I have a question related to Mosfets.
A few years ago I bought 5 pairs of TO3 Mosfets, 2SJ50/2SK135 which
I haven't used. At the time they cost me $4.00 each as opposed to $15
they cost now.
I'm planning to build an amplifier that uses 2SJ162/2SK1058, about
150W per channel.
Are both devices compatible so I can use the 50/135 instead of these
new ones?
As far as I know they both lateral Mosfets, but I'm not sure, perhaps
you guys could enlight me.
I'd appreciate.
I have a question related to Mosfets.
A few years ago I bought 5 pairs of TO3 Mosfets, 2SJ50/2SK135 which
I haven't used. At the time they cost me $4.00 each as opposed to $15
they cost now.
I'm planning to build an amplifier that uses 2SJ162/2SK1058, about
150W per channel.
Are both devices compatible so I can use the 50/135 instead of these
new ones?
As far as I know they both lateral Mosfets, but I'm not sure, perhaps
you guys could enlight me.
I'd appreciate.
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