active speakers - 4x myref per channel
Gents,
I'm planning to build up to activate my speakers using Myref amps. The system has 2x 170 alu subs, 2x 130 alu mids and 1x ceramic tweeter. My plan is to spend each sub an amp, one for both mid speakers and one for the highs. In total 4 amps per channel. My question is what is the required trafo power? I will use a 2x 25V type. Is 300VA enough to be really on the save side?
Thx
Peter
Gents,
I'm planning to build up to activate my speakers using Myref amps. The system has 2x 170 alu subs, 2x 130 alu mids and 1x ceramic tweeter. My plan is to spend each sub an amp, one for both mid speakers and one for the highs. In total 4 amps per channel. My question is what is the required trafo power? I will use a 2x 25V type. Is 300VA enough to be really on the save side?
Thx
Peter
25Vac will give you about 60W per channel.
4 chipamps fed from this will give a maximum of ~240W .
Normally We would recommend that a transformer between 240VA and 480VA would do this duty, but all four amplifiers will rarely if ever be producing maximum power at the same instant. You could de-rate the transformer slightly, maybe 180VA to 350VA.
Your chosen 300VA is towards the top end of this range. You will find it very difficult to get any improvement in your speaker performance by putting in a bigger transformer.
BTW,
are the loads for the four amplifiers all 8ohm? i.e two 8ohm bass drivers, two 4ohm mid range drivers and one 8ohm treble driver. Two 16ohm mid range drivers will have the same 8ohm impedance as the two 4ohm drivers.
I am curious if there would be a sonic advantage/change to building two seperate amps . I know there would be an extra AC in the system but I have read often that placing a power amp close to the drivers is preferred over longer speaker cables. A lot of high-end studio monitors even place the amp inside the enclosure.
Bob M.
Bob M.
Checked out the M1. That is very interesting.
www.meridian-audio.com/w_paper/DSP_speakers_scr.pdf
When I get my Ref-Cs completed (hopefully by week's end) I will have two Twisted Pear V1.2 and two Linuxguru Premium amps. I own a dbx-234 crossover that can be configured as 2, 3 or 4 way operation. Although they were not designed for bi or tri amping, I just completed a pair of "The Sunflowers" by Paul Carmody.
Sunflowers - undefinition
Should be very interesting to see what the combination will produce. If the results are good there may be a new path to follow - DIY electronic crossovers.
www.meridian-audio.com/w_paper/DSP_speakers_scr.pdf
When I get my Ref-Cs completed (hopefully by week's end) I will have two Twisted Pear V1.2 and two Linuxguru Premium amps. I own a dbx-234 crossover that can be configured as 2, 3 or 4 way operation. Although they were not designed for bi or tri amping, I just completed a pair of "The Sunflowers" by Paul Carmody.
Sunflowers - undefinition
Should be very interesting to see what the combination will produce. If the results are good there may be a new path to follow - DIY electronic crossovers.
Some more coupling cap substitutions
Hi All,
After all of the dire warnings about runing the amp without coupling caps I thought I'd better try a few more to see if my first impressions of removing the coupling cap were correct. So I modified things to let me easily swap coupling caps and did a trial. I tried the obbligatto 2.2 uF that came with the kit again, I still didn't like what it did to the sound, it seemed to make the sound stage a bit smaller and vocals a little acerbic, not too bad, but something bugs me about the sound. Next I tried a large 1.2 uF 1200 V GE metalized PP that I had lying around, because it was closer to Mauro's original spec, not so good, worse than the obbligatto, thinner sounding. Lastly I tried a 2 uF audiocap theta, much better, clear and warm, sounds very realistic on vocals. No cap still sounds really good with more detail, but the audio cap is really close to it.
PJN
Hi All,
After all of the dire warnings about runing the amp without coupling caps I thought I'd better try a few more to see if my first impressions of removing the coupling cap were correct. So I modified things to let me easily swap coupling caps and did a trial. I tried the obbligatto 2.2 uF that came with the kit again, I still didn't like what it did to the sound, it seemed to make the sound stage a bit smaller and vocals a little acerbic, not too bad, but something bugs me about the sound. Next I tried a large 1.2 uF 1200 V GE metalized PP that I had lying around, because it was closer to Mauro's original spec, not so good, worse than the obbligatto, thinner sounding. Lastly I tried a 2 uF audiocap theta, much better, clear and warm, sounds very realistic on vocals. No cap still sounds really good with more detail, but the audio cap is really close to it.
PJN
Hi everyone.
I am looking for the approximate input sensitivity of the MyRef v1.2, using Peter's kits and a 25-0-25 160VA transformer.
My speakers claim to handle 160W so I'm not worried about blowing them with the MyRef, however I'd like to know how much I can feed the amp without asking too much of it. I understand that the LM chip goes to crap once the SPIKE protection kicks in so i thought it diligent to structure the input levels such that this never (or very rarely) happens.
I have a true RMS multimeter and means of generating tone signals. If this can be used to accurately determine the sensitivity I'd love to be schooled on how to do this correctly.
Regards,
Tani.
I am looking for the approximate input sensitivity of the MyRef v1.2, using Peter's kits and a 25-0-25 160VA transformer.
My speakers claim to handle 160W so I'm not worried about blowing them with the MyRef, however I'd like to know how much I can feed the amp without asking too much of it. I understand that the LM chip goes to crap once the SPIKE protection kicks in so i thought it diligent to structure the input levels such that this never (or very rarely) happens.
I have a true RMS multimeter and means of generating tone signals. If this can be used to accurately determine the sensitivity I'd love to be schooled on how to do this correctly.
Regards,
Tani.
look at the schematic and find the Global FeedBack loop.The two resistors in there define the gain of the amplifier. The sensitivity is the output divided by the gain.
eg.
47k and 1k5 in the NFB gives gain = 47/1.5 + 1 = 32.33
sensitivity for 1Vac output is 1/32.33 = 30.9mVac
sensitivity for 1W/8ohm output is 2.83/32.33 = 87.5mVac
sensitivity for 50W/8ohm output is 20/32.33 = 619mVac
eg.
47k and 1k5 in the NFB gives gain = 47/1.5 + 1 = 32.33
sensitivity for 1Vac output is 1/32.33 = 30.9mVac
sensitivity for 1W/8ohm output is 2.83/32.33 = 87.5mVac
sensitivity for 50W/8ohm output is 20/32.33 = 619mVac
Myref-C Problem
I completed my two MyRef-C Twisted Pear version 1.2 amps (red board) today and both have the same fault. The music comes through clear and undistorted for about 2 to 3 seconds. Then a sustained .5 second duration click, click, click sound appears. With my limited knowledge I would describe it as what a capacitor unloading would sound like. I have M-Cap 250V +/_ 5% 1.00uF in C13. The amps respond to volume changes and there is no audible distortion when the click starts. Does anyone have experience with or suggestions about this condition.
Thanks, Bob M.
I completed my two MyRef-C Twisted Pear version 1.2 amps (red board) today and both have the same fault. The music comes through clear and undistorted for about 2 to 3 seconds. Then a sustained .5 second duration click, click, click sound appears. With my limited knowledge I would describe it as what a capacitor unloading would sound like. I have M-Cap 250V +/_ 5% 1.00uF in C13. The amps respond to volume changes and there is no audible distortion when the click starts. Does anyone have experience with or suggestions about this condition.
Thanks, Bob M.
To me sounds like LM3886 SPIKE protection being triggered...
First of all: are you using a heatsink? It's big enough?
If it's so then check voltages on LM318 (should be +-12V) and LM3886 (should be around +-36V).
LM3886 rail voltages of +/- 32V are better for overall sonics as well as to avoid triggering the Spike protection. However, during normal operation at comfortable listening volumes, it shouldn't usually trigger the Spike protection. Is the Speaker 8 ohms impedance or higher? Is it a difficult load, i.e. a capacitive electrostatic speaker? Try it with an 8-ohms full-range driver and see if the symptoms continue.
Hi Bob,
the heatsink seems adequate.
Did you take care of the small heatsink for R3 so that it don't touch anything?