What was interesting when looking at the current draw from the PSU was that when the amp delivered close to full output the current dropped to about 1.1 A or so. If an unregulated PSU is used this will cause the voltage to raise. How much depends of the internal impedans in trafo etc. I will use a 300 VA trafo pr channel. It will keep a very constant output voltage and will not vary much with load. It was a reason to use such an over dimensioned transformer. For the test I used a regulated lab PSU.
Maybe some can comment on the current drop at full output.....if it is real or my amp has a problem...….
Maybe some can comment on the current drop at full output.....if it is real or my amp has a problem...….
Could it be that the meter is "fooled" so it can't show a correct RMS value at frequencies much higher than 100 Hz (have to check that)?
If the test frequency is e.g. 1 kHz at full output then there will be an AC current. It requires a true RMS A-meter.....so maybe I saw something that was not real. It is my theory…..
If the test frequency is e.g. 1 kHz at full output then there will be an AC current. It requires a true RMS A-meter.....so maybe I saw something that was not real. It is my theory…..
Ok.....I am quite sure now that the A-meters in the lap supply is not true RMS.....so they are good for DC only (maybe 50 Hz also). I need some more advanced to measure RMS current when it is AC.
At low frequencies (< 20 Hz) it also showed strange results…….I now know why…...
When you design the PSU it is good to use the Duncan PSU designer II which is a free download program:
PSUD2
It is used much by "tube nerds".....the voltage drops over chokes etc. is not that easy to predict. The program can take parameters for the transformer, diodes in bridge etc. When the simulation is in place it is easy to e.g. change the load and see what happens….or change a capacitor…..or resistor.
Re-posting from the ACA 1.6 thread as I haven't had a reply there and maybe owners with OB's can address my question:
Will the ACA have enough power to drive my parallel dual woofers on my open baffles ? The drivers in use are:
- 1 x 5" full range @ 92 dB 6.3 Ohms (Tang Band W5-2143)
- 2 x 15" woofers @ 100 dB 2.94 Ohms wired in parallel (Eminence Alpha 15's)
The XO varies from 100 - 225 using miniDSP HD but I plan to switch that out pending the Pass active XO kit being released.
Thanks !
Will the ACA have enough power to drive my parallel dual woofers on my open baffles ? The drivers in use are:
- 1 x 5" full range @ 92 dB 6.3 Ohms (Tang Band W5-2143)
- 2 x 15" woofers @ 100 dB 2.94 Ohms wired in parallel (Eminence Alpha 15's)
The XO varies from 100 - 225 using miniDSP HD but I plan to switch that out pending the Pass active XO kit being released.
Thanks !
I think your woofers impedance is way too low for most amplifiers, not just ACA.
Maybe try to use one only as a woofer, or wire them in series, you have plenty of dBs there.
My best bet is you'll need a different amplifier.
I run an ACA with a 8 ohms 2 way, 10 inch FR plus a tweeter at 2kHz in an aperiodic box (total SPL approx. 94dB) and at times the bass control is a bit lacking.
Still nothing stops you from trying it.
Or thinking a bit further, you'll definitely benefit from bi-amping.
ACA for the top, your full range, and something like F4 or BA-1/2 or M2 for the bottom.
Others may have other and better ideas.
Or for a bit more grunt, a pair of bridged ACAs on the FRs and your favorite flavor of ballsy power for the woofers. For Schitts and giggles I just might try to get Dave to try a Hypex UcD180 in his WAW system once the rest of parts for ACA amp chassis arrive. (XLRs for balanced operations, and different binding posts)
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I trialled an 8W SET A amp powering the parallel woofers and I thought it was ok but had nothing to compare against but it sounds like the ACA might not be what I need (was hoping for). But ... I am fortunate in that the woofers are wired with two pairs in parallel so that means I can just decouple one pair from the speaker plugs which would be 94 dB 5.88 Ohms for single woofer. Of course that goes against the original design of parallel woofers with a near matched full range driver to get a better lower end - but let's see what the ears say ! I can also do in series and would join the -ve of the one pair to the +ve of the other pair at the speaker plug and then use the opposing +ve and -ve leads to the speaker plug to the amp to get them in series which would be 94 dB 11.76 Ohms. That would be an easier load but then I have a steep drop off after 80 Hz with a significant spike around 120-125 Hz.
Look forward to your + Dave's results if you are able to do that as it would give me more insight into doing the same myself. I looked at the Hypex's and as a put together kit with no soldering they are appealing, but they only have the mono 400 which needing two would blow my budget for bi-amping.
I have FW ACA and F4 and already tried out this combination biamping/active XO for my OB speakers. 15'' Eminence beta sub and SAL 8'' for FR.
I had best sonic results for driving F4 for Sub and ACA on FR. I tried it the other way around and the sonic was bad if ACA for sub and F4 for FR. Hope it helps
Regards,
TD
I had best sonic results for driving F4 for Sub and ACA on FR. I tried it the other way around and the sonic was bad if ACA for sub and F4 for FR. Hope it helps
Regards,
TD
Yes that is correct jklow888. I used to have 2 x 15'' per side running in // but I did not have good bass response. later i changed to using H-frame with only 1 x 15'' beta per side and I had great bass since then I only used 1 x 15'' beta per side.
Regards,
Tom
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oooh! I recognize those images. I have that 'scope' as well.
What did you do to get that particular data to show? Probably best to PM me, so as not to clutter up the thread. Thanks in advance!
