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#197771 - 02/24/08 11:30 AM Re: Amplifier Capacitance ? Axiom amp versus my monos [Re: SirQuack]
SirQuack Offline
shareholder in the making

Registered: 01/29/04
Posts: 13311
Loc: Iowa
I also forgot to add after reading the article that JohnK mentionned above, that each of mono's are made up of 8 15,000uF capacitors for a total of 120,000uF each monoblock. The article hints that there are benefits of having more capacitors to make up the total, versus say 4 30,000uF caps.

I'm guessing that Axiom must use 4 35,000 uF caps to make up the total of 140,000uF,at least that is what it appears in the pictues.

Looks like the ripple effect and other specs change based on design.
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#197854 - 02/24/08 10:12 PM Re: Amplifier Capacitance ? Axiom amp versus my mo [Re: fredk]
JohnK Offline
shareholder in the making

Registered: 05/11/02
Posts: 10308
You got it, Fred; there ain't no more.
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#197857 - 02/24/08 10:28 PM Re: Amplifier Capacitance ? Axiom amp versus my mo [Re: JohnK]
fredk Offline
axiomite

Registered: 12/06/07
Posts: 6969
Loc: Canada
Perfect, back to fat dumb and happy for me. Funny, I'm usually the guy who wants to know all the intimate details and geeky stuff.

Now, if I could just sort out those pesky Blu-ray HD audio formats...
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#197864 - 02/24/08 11:55 PM Re: Amplifier Capacitance ? Axiom amp versus my monos [Re: SirQuack]
jakeman Offline
aficionado

Registered: 10/03/05
Posts: 851
Loc: Toronto
Good stuff, Randy. I should also mention that the other factors that determine the size and number of capacitors has to do with powersupply rails and whether or not the amplifier modules are bridged or not. The size and number of caps influence how fast voltage can be drawn from the powerrails and output. A good comparison is to look at two Bryston amps that have identical frequency response, THD, IMD, S/N and other specs.

I used to have a Bryston 14BSST a few years ago, which was the stereo version of the 7BSST monoblocks... the ones Axiom used as a basis for its development of the A-1400-8. Both these Bryston amps used the same components and had similar specs. However they differed somewhat in how the capacitors were arrayed and rail voltage.

The 7BSST monos had 16 x 10,000 mfd small capacitors close to the output section. The 14BSST used 4 x 27,000 mfd large capacitors instead of 16 small ones in the 7BSST. Also the 14BSST have a slightly lower powersuply voltage of 60 volts instead of 65 volts for the 7BSST.

People comparing these two similar amps reported a tighter more responsive sound with the 7BSST or a "softer" sound in the 14BSST, which can be attributed to the use of many small capacitors in the 7BSST and its higher voltage powerrails. Basically the 7BSST was able to respond more quickly to power demands during transients because of these small differences between the two amps.



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#197883 - 02/25/08 07:11 AM Re: Amplifier Capacitance ? Axiom amp versus my monos [Re: SirQuack]
jakeman Offline
aficionado

Registered: 10/03/05
Posts: 851
Loc: Toronto
 Originally Posted By: sirquack

I'm guessing that Axiom must use 4 35,000 uF caps to make up the total of 140,000uF,at least that is what it appears in the pictues.



I should check but I thought the Axiom used an array of different sized caps 4 big ones and 4 smaller ones to get better response time. The number and size of the caps also depends on the amount of voltage in the powerrails. Going by memory, I recall that the A-1400-8s voltage was higher than most amps at around 80-85V. The bottom line is that its a very "fast" responsive amp. It has to provide dynamic power to whatever channel needs it.
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#197890 - 02/25/08 08:46 AM Re: Amplifier Capacitance ? Axiom amp versus my monos [Re: jakeman]
SirQuack Offline
shareholder in the making

Registered: 01/29/04
Posts: 13311
Loc: Iowa
Stop trying to talk me into one. ;\)
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#197897 - 02/25/08 10:14 AM Re: Amplifier Capacitance ? Axiom amp versus my monos [Re: SirQuack]
jakeman Offline
aficionado

Registered: 10/03/05
Posts: 851
Loc: Toronto
Just calling it the way I hear and see it. Wasn't it Joe Friday who used to say "just the facts ma'am." \:\)
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#197931 - 02/25/08 03:50 PM Re: Amplifier Capacitance ? Axiom amp versus my monos [Re: jakeman]
ditcin Offline
old hand

Registered: 05/02/06
Posts: 77
Loc: NY, USA
Jakeman -
How do you think the A1400-8 stacks up against the Sherbourn 7/2100A w/mono blocks? http://www.sherbourn.com/products/7_2100A.php
Would love to know your thoughts on it.
Thanks.
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#197951 - 02/25/08 06:17 PM Re: Amplifier Capacitance ? Axiom amp versus my monos [Re: ditcin]
jakeman Offline
aficionado

Registered: 10/03/05
Posts: 851
Loc: Toronto
Ditcin, some random thoughts. From your link its Scott I believe. \:\)

Firstly let me say the Sherbourn 7/2100a is a fine example of a terrific class AB HT amp. Its the kind of powerful 7 x 200W@8ohm monoblock amp that should form the foundation for any HT, in my opinion. I've always been a fan of monoblock designs and before the A-1400-8, it was the type of amp I would recommend to my friends who were looking for the best HT amplification. I've never owned the 2100/7 but did have a Bryston 9BSST for a while which I really enjoyed, a 5 x 140w monobloc design with gain controls to boot.

To put your question into perspective, the A-1400-8 design embraces the monobloc phylosophy and takes it a step further. If you check out the video on the amp you'll hear Tom and Ian talk about how they set out to replace a stack of 7 monos with one unit that was more dynamic, didn't clip and provided much more power than available with monos.

To get the 2100/7 to output at its max you need to plug both cables into separate outlets otherwise your limited to 1440W total or 205w max over the seven channels. Setting aside the 8th channel and dynamic handling for now, the axiom design will actually output more than the 205w max because of its ability to draw more power out of the line, supposedly up to 285w per channel all driven.

It is rare though that all channels are driven simultaneously at the same power levels and that is where the Axiom really shows its technological advantage. If needed the Axiom can direct over a kilowatt of energy into any channel. It achieves that because of how its switching circuits can route power from its 85v+ powerrails and single massive (over 1600kva !) transformer. With that much power on tap this amp will clip under only the most massive loads and demands. Despite all my attempts one afternoon with no one home, I could not get the 1400-8 to clip. One thing about monos the size of Sherbourne is that they will clip in demanding scenes or in complex musical passages.

Another main difference, aside from the Axiom being half the size and weight and running much cooler, arises from the much faster response time of the a-1400-8. AB designs take longer to ramp up and down whereby a fast switching type D amp will respond much faster to power demands. What helps make it so fast, is the way the 1400-8 has 4 x 33000 mfd caps repowering smaller 4 x 2000 mfd caps as they drain.

Slew rate can be measured several ways but the Axiom weighs in at around 8V/ms while the Sherbourne is a bit over half that rate or 4-5V/ms. I know some folks think that its inconsequential but amp designers sweat for months trying to get amps to respond as quickly as possible since it impacts dynamic presentation and how loud and sharp transients will sound.

Where I believe the Sherbourne and monos in general have an advantage is that there is zero crosstalk associated with them. Any amp with a single transformer will have some level of channel crosstalk though in the Axiom it is well in the inaudible region. Some would argue that there is more crosstalk in the DSP circuits of a processor but the less the better. The other stat I pay close attention to is signal to noise and both amps have great specs.







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#197958 - 02/25/08 06:45 PM Re: Amplifier Capacitance ? Axiom amp versus my monos [Re: jakeman]
St_PatGuy Offline
axiomite

Registered: 03/07/05
Posts: 7373
Loc: Glendale, Arizona
Very informative, John. Thanks for summarizing all that and making it easy for us (me) to understand.
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