Hi
I wonder if you can clarify the ratings of the toroid transformer please?
I am a newb and cannot see full reference in the thread
Cheers
Wayne
I wonder if you can clarify the ratings of the toroid transformer please?
I am a newb and cannot see full reference in the thread
Cheers
Wayne
For a stereo Modulus-86 amplifier intended for the reproduction of music, I recommend using a 150-200 VA rated transformer that provides 2x22 VAC (or 22-0-22 if it's a center tapped transformer).
Something like an Antek AS-2222 or AN-2222 would work well. The difference between the AS and the AN is that the AS has a built-in electrostatic shield which you connect to ground.
~Tom
Something like an Antek AS-2222 or AN-2222 would work well. The difference between the AS and the AN is that the AS has a built-in electrostatic shield which you connect to ground.
~Tom
Hi Tom
I guess you've sold a few boards; are you aware if anyone has finished building the amp as yet? I would be keen to read some reviews (of the amp) if any owners are out there.
I guess you've sold a few boards; are you aware if anyone has finished building the amp as yet? I would be keen to read some reviews (of the amp) if any owners are out there.
Yep. The Antek transformers will work both for 120 V and 230/240 V. They're pretty international that way.
The feedback I've gotten from the builders has been positive. I know one of the guys who built the amp posted a few of his findings in this thread.
One builder, Mike from Canada, tossed me the following feedback in an email. I did get his permission to quote:
~Tom
Last edited:
Assuming a 10 dB crest factor (i.e. music reproduction) and ±28 V rails, I would go with 160 VA per channel if driving an 8 ohm load. I.e. two Modulus-86 boards, bridged, on one 160 VA transformer.
If using a bridged-parallel configuration (four Modulus-86 boards per channel) to drive a 4 Ω load at ±28 V rails, I'd recommend 300 VA per channel. Again assuming a 10 dB crest factor.
~Tom
If using a bridged-parallel configuration (four Modulus-86 boards per channel) to drive a 4 Ω load at ±28 V rails, I'd recommend 300 VA per channel. Again assuming a 10 dB crest factor.
~Tom
Thanks.
I'd like to be able to handle a 22 dB crest factor... That is the maximum DR that JRiver reports in my collection. I understand that the DR reported by JRiver is this crest factor -- loudest peak in dB above average.
My space is small and the speakers are quite efficient ( about 95 dB/1w/1m subs and low mids, 105 dB/1w/1m horn).
The target application is the horn and/or low mids. General listening levels never really exceed 90 dB. I currently have transformers with 37 VCT @ 185 VA, and want to build monoblocks.
I'd like to be able to handle a 22 dB crest factor... That is the maximum DR that JRiver reports in my collection. I understand that the DR reported by JRiver is this crest factor -- loudest peak in dB above average.
My space is small and the speakers are quite efficient ( about 95 dB/1w/1m subs and low mids, 105 dB/1w/1m horn).
The target application is the horn and/or low mids. General listening levels never really exceed 90 dB. I currently have transformers with 37 VCT @ 185 VA, and want to build monoblocks.
You need to aim for the lowest crest factor. A low crest factor means that the RMS value of the signal is close to the peak value. That's the worst case for power dissipation and power consumption.
If you have the data, I would be interested in the distribution of the crest factors. Or at least, min, max, and average.
~Tom
If you have the data, I would be interested in the distribution of the crest factors. Or at least, min, max, and average.
~Tom
WOW, Jriver exported that nicely.
Average DR reported was 11.22, min 5, max 22 out of 797 songs that have been analyzed for DR.
The R128 DR is average is 8.9 LU, min 0, max 27.4 LU
So it looks like a DR of 10 is a very good estimate!
Average DR reported was 11.22, min 5, max 22 out of 797 songs that have been analyzed for DR.
The R128 DR is average is 8.9 LU, min 0, max 27.4 LU
So it looks like a DR of 10 is a very good estimate!
Very cool. Thanks for the data!
Can you say a little bit more about the music collection that was analyzed? I'm just trying to get a feel for what was measured, that's all. From the numbers it looks like a good sample of everything from heavy metal to classical or vocal music.
~Tom
Can you say a little bit more about the music collection that was analyzed? I'm just trying to get a feel for what was measured, that's all. From the numbers it looks like a good sample of everything from heavy metal to classical or vocal music.
~Tom
I wonder how the crest factors of the signals out of an active crossover relate to the crest factor of the whole music signal?
You can explore that for yourself using Audacity - the version I have (2.0.5) has a new 'contrast analysis' feature which takes the RMS volume of your waveform selection. Using the 'amplify' command finds the peak value (in the indication of the maximum gain before clipping).
You can use the high/low pass filter options to explore different crossover points. Not bad for free software.
I found the contrast analysis feature a bit temperamental - if analysing a stereo track be sure to split it into two mono tracks first.
You can use the high/low pass filter options to explore different crossover points. Not bad for free software.
I found the contrast analysis feature a bit temperamental - if analysing a stereo track be sure to split it into two mono tracks first.
The collection is largely prog (Yes, Genesis), jazz (Hancock, Joni Mitchell, martin medeski wood), avantgarde (Robert Wyatt), ECM recordings, with some classical (HD,24 bit) and classic rock ( Bowie, Roxy Music, pink floyd), folk ( Joan Armatrading, Navarro), little feat, ry cooder. It is quite varied. I did remove one LP that had a DR of 3 before generating stats.
My main concern was to ensure that the amp would not clip.
I suppose if used on the horn, the amp would not even have to be bridged, but the benefit is that the connection to the active crossover becomes balanced, and likely less noisy.
That is EXACTLY what I wanted to do, to attempt to find a lower limit for the power on the horn tweeter. Same for low mid and bass...
Thanks for the tip!