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Old 3rd June 2006, 12:29 AM   #21
lndm is offline lndm  Australia
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A larger transformer is generally a good thing for any amp running in class AB. Besides, a large transformer is a good thing to have where future expansion is considered.
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Old 3rd June 2006, 12:49 AM   #22
dfdye is offline dfdye  United States
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Quote:
Originally posted by lndm
A larger transformer is generally a good thing for any amp running in class AB. Besides, a large transformer is a good thing to have where future expansion is considered.
Both very try comments, but since cost is such a concern in this instance, the minimum requirements often have to be discussed for economic considerations.

To be 100% clear, it is my opinion that if you can get two 160VA transformers for your monoblocks, that would be very nice for all the reasons lndm mentioned, but you should be able to use two 80VA transformers with the audiosector kit if cost is the overriding concern without worrying about underpowering your amplifier.

David
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Old 3rd June 2006, 01:47 AM   #23
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I've had and heard a lot of amps of all flavors up to 18Kclams and the best bang for the lowest bucks is is the Adcom GFA 535 II - You can find one used on e-bay for 100 - 150 bucks. I keep one for a spare and have fooled audiophile friends into thinking it was a 300B amp by hiding it while having my 300b's lit up. The II model is better than the original and worth the extra few bucks. I admit not to ever hearing a chip amp - building one now.
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Old 3rd June 2006, 03:35 AM   #24
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DANG you guys are so helpful! well im in toronto so im goign to see if i can just buy the kit direct from audiosector, it would save on shipping it a couple kilometers away.

a pot for volume would be fine, is there any degrade in signal quality by doing this?

im assuming that any 25v-25v 80VA transformer is fine, and i wont have to worry about toroidal or not?
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Old 3rd June 2006, 03:39 AM   #25
dfdye is offline dfdye  United States
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Quote:
Originally posted by xstephanx
a pot for volume would be fine, is there any degrade in signal quality by doing this?
depends on who you talk to, but the general concensus is yes, a little. Use a quality pot and you should be fine. Do a search and you should find a thread started by Peter about his experiences with input pots.
Quote:
im assuming that any 25v-25v 80VA transformer is fine, and i wont have to worry about toroidal or not?
For each chanel, yes. The benefit of toroids is they contain stray magnetic fields better than traditional transformers. I must admit this is not my area of expertiece, but if you are going to have the transformers within close proximity of the amps, you would be better served by toroids. If they will be far away, there isn't really a difference AFAIK.
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Old 3rd June 2006, 08:01 AM   #26
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Torroids are better from a hum/noise point of view when in the case with the amp, I agree if external it is pretty irrelevant, big torroids (over 300VA) tend to get a little noisy and produce interfering fields, so if you went that way I would put it in a seperate box or shield it.

I did a few experiments with pots a while back, the 10K pots worked by far the best, I tried a 50k and others as well, the 50K pots ruined the sound in my opinion, sorry but I don't have a tech explanation for why, but the difference was obvious. Try 10 or 20K as a max.

With clones I think the most important issue is not the brand of the pot but its value!
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Old 3rd June 2006, 03:09 PM   #27
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Zero One -- A question:

I hope to use an old Hafler chassis/transformer for a stereo LM3875 chip amp. The chassis is the same size as the Hafler DH-120 but has an international transformer to supply 28VDC for the rails.

The transformer is has an IE format and will be about 2-3 inches from each channel's PCB. Will I get hum?

The 3875 is supposed to have good PSRR and I will use shielded twisted pair for the low level input signal and all other wiring will be as short and twisted as possible. Will I get hum?

Thanks.....
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Old 3rd June 2006, 04:02 PM   #28
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The DH-120 transformer supplies +- 54 volts after rectification and filtering. Too much for the 3875.
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Old 4th June 2006, 05:08 PM   #29
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Actually I will use the transformer/chassis/heat sinks from a Hafler PRO 1200. As I stated:

"but has an international transformer to supply 28VDC for the rails."

I will wire the transformer for 220 VAC but use it on 117 VAC, so the rails voltage will be OK. Sorry I was not more explicit.

So, my question still remains. Will I get too much hum from being close to the EI transformer?
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Old 4th June 2006, 05:58 PM   #30
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I don't think hum will be a problem. Look how close the circuitry is to the EI transformer in a Hafler DH series amp. 2-3 inches. Just an opinion though.
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