hi everybody.
I'm a new member here.
happy to join.
i am planning to build a single ended EL34 triode amplifier, can i use an opt rated for 70Hz at full rated power? if i will go with a subwoofer to handle frequencies below 80Hz??
any answer i appreciate
thanks.
I'm a new member here.
happy to join.
i am planning to build a single ended EL34 triode amplifier, can i use an opt rated for 70Hz at full rated power? if i will go with a subwoofer to handle frequencies below 80Hz??
any answer i appreciate
thanks.
P = Urms^2 / Primary impedance
Alternating flux density = Urms / 4.44 * Coresurfacearea * Turns * Frequency
If you get full power x at 70 Hz, you'll get 1/4 power at 35Hz.
Alternating flux density = Urms / 4.44 * Coresurfacearea * Turns * Frequency
If you get full power x at 70 Hz, you'll get 1/4 power at 35Hz.
thanks 50AE.
yes, i think i know about that.
but i mean is it ok to stay with that opt.?, or should i trade it for one that is rated for 30Hz at full rated power like minimum standard opt SE.??
then, what about the core saturation distortion if i connect subwoofer with speaker level input??
yes, i think i know about that.
but i mean is it ok to stay with that opt.?, or should i trade it for one that is rated for 30Hz at full rated power like minimum standard opt SE.??
then, what about the core saturation distortion if i connect subwoofer with speaker level input??
Just consider if the power rating is enough for you. But that would be a vague rating compared to distortion, due to the fact different manufacturers use different core materials and different flux density value at the rated power, which brings all kinds of distortion figures.
If you're looking for THD, the easiest thing might be to measure it yourself. And remember your driving stage is also part of your THD, especially internal resistance.
If you're looking for THD, the easiest thing might be to measure it yourself. And remember your driving stage is also part of your THD, especially internal resistance.
thanks for the answer.
but I'm not satisfied with that yet
let's say the speaker has a lower bound of around 50Hz
and I connected the sub with speaker level, and the distortion is severe at 40Hz and the sub takes the signal from the speaker terminal to pass through the opt , will the distortion be heard clearly on the main speaker whose lowest frequency is 50Hz or will it only be heard on the sub??
maybe both??
but I'm not satisfied with that yet
let's say the speaker has a lower bound of around 50Hz
and I connected the sub with speaker level, and the distortion is severe at 40Hz and the sub takes the signal from the speaker terminal to pass through the opt , will the distortion be heard clearly on the main speaker whose lowest frequency is 50Hz or will it only be heard on the sub??
maybe both??
I found your script a bit hard to understand, but distortion will be apparent on what the transformer feeds, hence the subwoofer.
so the opt can't saturate to 20Hz if i take the sub's signal through the speaker terminal, because the sub will see it.
and if the sub signal is taken before the amplifier the opt option can be smaller and lighter cheaper of course.
Thank you for your help.
and if the sub signal is taken before the amplifier the opt option can be smaller and lighter cheaper of course.
Thank you for your help.
Using a subwoofer
The hard way:
An amplifier that has a limited low frequency response due to inadequate output transformer, and will have low frequency 2nd harmonic distortion and 3rd harmonic distortion . . .
That amplifier should have a high pass filter at its input connector, or internal to that amplifier.
The subwoofer amplifier (subwoofer driver) should get its signal before the low pass filter.
Do not use the limited low frequency bandwidth amplifier output signal to feed the subwoofer amplifier.
That setup requires a volume control to be before both the mid / high frequency amplifier and subwoofer amplifier.
Or . . .
The easy way:
Just use a very good output transformer on the mid / high frequency amplifier (and no high pass filter to / or in that amplifier).
Then take that amplifier output to send signal to the subwoofer amplifier. A dual volume control to both the main amplifier and subwoofer is not required (if the subwoofer has enough gain, and its own fixed level potentiometer).
An amplifier that does not have a high pass filter at the input; and that has output transformer that has limited low frequency bandwidth,
will cause harmonic distortion of the low frequencies, and saturation of the core, and intermodulation distortion of the low frequencies with the mid and high frequencies.
Many high pass filters, and many low pass filters that are used with mid / high frequency amplifiers, and with subwoofers are not real sharp cut off filters. That means some mid frequencies get to the subwoofer, and some low frequencies get to the mid / high frequency amplifier.
Just my opinions.
The hard way:
An amplifier that has a limited low frequency response due to inadequate output transformer, and will have low frequency 2nd harmonic distortion and 3rd harmonic distortion . . .
That amplifier should have a high pass filter at its input connector, or internal to that amplifier.
The subwoofer amplifier (subwoofer driver) should get its signal before the low pass filter.
Do not use the limited low frequency bandwidth amplifier output signal to feed the subwoofer amplifier.
That setup requires a volume control to be before both the mid / high frequency amplifier and subwoofer amplifier.
Or . . .
The easy way:
Just use a very good output transformer on the mid / high frequency amplifier (and no high pass filter to / or in that amplifier).
Then take that amplifier output to send signal to the subwoofer amplifier. A dual volume control to both the main amplifier and subwoofer is not required (if the subwoofer has enough gain, and its own fixed level potentiometer).
An amplifier that does not have a high pass filter at the input; and that has output transformer that has limited low frequency bandwidth,
will cause harmonic distortion of the low frequencies, and saturation of the core, and intermodulation distortion of the low frequencies with the mid and high frequencies.
Many high pass filters, and many low pass filters that are used with mid / high frequency amplifiers, and with subwoofers are not real sharp cut off filters. That means some mid frequencies get to the subwoofer, and some low frequencies get to the mid / high frequency amplifier.
Just my opinions.
It also depends on how you cross it at 70 Hz. For example, if you cross it first order, it will be -3 dB at 70 Hz and -6 dB at 35 Hz. So, specing your transformer for, say, low distortion 10 W at 70 Hz is not enough, as it should be also able to handle 5 W at 35 Hz. Steeper crossover will reduce power requirement at lower frequencies.
First order (6dB/octave) with crossover frequency at 70 Hz (-3 dB) gives -9 dB at 35 Hz, not -6 dB....
@6A3
then I need to get an opt capable of handling 30Hz at full rated power.
feed the sub from the speaker terminals and they work for the same signal and same phase, am i right??
it would be a very expensive opt.
@sser2
isn't it if 10w to 70Hz
then 5w will be 49.5Hz
@daanve
my choice would be first order high pass before amplifier.
oh, if we serialize the second order what will be the fourth order?
then I need to get an opt capable of handling 30Hz at full rated power.
feed the sub from the speaker terminals and they work for the same signal and same phase, am i right??
it would be a very expensive opt.
@sser2
isn't it if 10w to 70Hz
then 5w will be 49.5Hz
@daanve
my choice would be first order high pass before amplifier.
oh, if we serialize the second order what will be the fourth order?
I would use an active crossover and call it a day. Feed a sub amp with the low pass, and the tube amp with the high pass.
I use a Behringer CX2310 in my set up. https://www.behringer.com/product.html?modelCode=P0132
There are also small 12V ones made for car audio that you could hide behind the system.
I use a Behringer CX2310 in my set up. https://www.behringer.com/product.html?modelCode=P0132
There are also small 12V ones made for car audio that you could hide behind the system.
First order high pass is next to useless. Second actually drops the low frequency enough to be useful. And 4th is better if you can properly integrate the sub with it and if it has its own 4th order low pass. A store-bought sub may or may not have its own high pass. They all do, BUT often only through the speaker-level inputs - which you really can’t directly use here. They are designed for lazy consumers - hook it up to the “speakers” or the LFE output (which is already filtered). It is never optimum, but gives people the boomy bass they desire. Active crossover is the way to go if you want to make the most out of your system.
IF the line level input has an adjustable low pass you’re in luck. You just need to high pass the mains - then you effectively have an active crossover. You CAN do this passively if you have to. Those little stand alone pro units are nice - but if you are allergic to op amps they’ll give you hives. On paper, measurement wise, there is absolutely nothing wrong with them. If you build a little complementary high/low pass using op amps - for much less than the $100 street price of a CX3210 - and stick it back there behind the system it will also work. The only problem is that you’ll know it’s there. If that doesn’t bother you the problem is solved and you move on to the next.
If the presence of op amps does bother you, then start by learning to make Sallen-Key filters using tubes. They work just fine. It’s just a lot more work. If NFB is what bothers you (not just the solid state op amp), start looking for inductors - you will need them for passive filters.
IF the line level input has an adjustable low pass you’re in luck. You just need to high pass the mains - then you effectively have an active crossover. You CAN do this passively if you have to. Those little stand alone pro units are nice - but if you are allergic to op amps they’ll give you hives. On paper, measurement wise, there is absolutely nothing wrong with them. If you build a little complementary high/low pass using op amps - for much less than the $100 street price of a CX3210 - and stick it back there behind the system it will also work. The only problem is that you’ll know it’s there. If that doesn’t bother you the problem is solved and you move on to the next.
If the presence of op amps does bother you, then start by learning to make Sallen-Key filters using tubes. They work just fine. It’s just a lot more work. If NFB is what bothers you (not just the solid state op amp), start looking for inductors - you will need them for passive filters.
IMHO, feeding a subwoofer from the amp output is always a bad idea and should be avoided unless there are no other options. Others have pointed out alternate solutions that should work in this particular application. So to that end, I would keep the 70Hz transformers and use a X-over such as Koda is suggesting any day of the week over wasting money on better output transformers, only to end up with a suboptimal overall solution.
Why?
If mid-frequency driver is capable of reproducing bass down to 50-60 Hz, why not crossing it first order at 120 Hz? 70 Hz would be a little too low for such scheme.
Shallow crossovers have well-known advantages. The only reason for not using them is limited bandwidth of drivers.
Summing the electronics to have both flat amplitude at, close below, and close above the crossover frequency, and also be in phase . . . is wonderful.
Just be careful how far apart you place the main speaker(s) from the sub woofer(s).
A 5.4 foot space between a main speaker and a subwoofer is 90 Degrees out of phase, for a 50Hz bass tone (An electric bass guitar's lowest note is 40Hz).
A 10.8 foot space between main and sub . . . cancels the 50Hz bass note!
A single subwoofer is probably most practically placed behind the main speakers; and equally spaced between the left and right main speakers.
Now, back to which layer of the onion are we peeling off: the outer, middle, or inner layer?
Just be careful how far apart you place the main speaker(s) from the sub woofer(s).
A 5.4 foot space between a main speaker and a subwoofer is 90 Degrees out of phase, for a 50Hz bass tone (An electric bass guitar's lowest note is 40Hz).
A 10.8 foot space between main and sub . . . cancels the 50Hz bass note!
A single subwoofer is probably most practically placed behind the main speakers; and equally spaced between the left and right main speakers.
Now, back to which layer of the onion are we peeling off: the outer, middle, or inner layer?
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Why? Because transformer induction will not decrease with frquency but XL will.
The lower the frequency, the worse the XL to R relation becomes, and that translates into distortion. You propable would not want to hear the 7th harmonic of a, still comparable strong, low fundamental. 6db wont cut it, you need 12db/octave at least.
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