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-   -   A few questions before buying (http://www.diyaudio.com/forums/audio-sector/187659-few-questions-before-buying.html)

inverseopamp 23rd April 2011 02:05 PM

A few questions before buying
 
Hi,

I am new around here. I was looking for a DIY audio amplifier and I really like the Audio Sector featured amps. But before I order, I have a few questions for Peter. Kindly bear with me, I am a newbie (with some experience of building of 1010 and 4440 amps).

The following question may all sound dumb but I really need to clear my confusions.

1. My source will be a Yamaha CD Player. My room is 10 feet wide.12 feet long and 10 feet high. I have an graphic equalizer that I had built around LB1405 (5L+5R). I would like to keep that between the source and amplifier. Which amplifier should I choose. LM3875 or LM4780?

2. Being in India, I have a few constraints like getting quality speakers and transformers. What speakers work best with these amps? Any recommended brands?

3. If I put a tweeter, can I use a crossover?

4. Do the amps perform best with full range speakers or a woofer - mid-range-tweeter setup can be used?

Now for the amps,

1. Considering I am using the LM 4780 amplifier, do I need 1x LM4780 for both channels or 2xLM4780s for 2 channels?

2. Do I need 2 transformers (dual mono) or can I use one?

3. Do I need to use a 3-pin plug for the primary source? Line+Neutral+Earth? I am just concerned about any humming that might arise.

Thanks in advance!
Basu

Richard Ellis 23rd April 2011 03:33 PM

Let me try to answer this...
1. Both amplifiers will have the same 'line-level' inputs....so your EQ will work with either. The LM3875 has slightly less distortion at full rated power.
2. Either amps will drive just about anything you can hook up to it..beware of extremely low impedence loudspeakers however...they can overtax some amps.
3. ALL tweeters MUST have a crossover... a capacitor to filter out low frequencies.
4. Full-rangers are nice, but expensive...have low SPL outputs(Except large cone....8"+ versions).....but need no crossovers.Multi-ways are relatively complex........This is a whole nuther' topic!
1a. Both amps are on a single circuit-board...The board is then "broken" in half for two seperate boards...each one is one channel.
2a. The power supply is set-up to drive both channels...one transformer.
3a. Yes, you should have a three wire wall current......any deviation here and you invite possible shock hazards.
These kits are straightforward, oddly, they use outboard power supplies...
The heatsinking approaches are using chunks of Aluminum, rather than true heatsinks...
Cheap toroid transformers from Antek can fit the bill for your transformer needs..if you can get them....there are a few more components you will need to complete the PS...but there's not much.

AndrewT 23rd April 2011 04:06 PM

I always recommend that beginners should start with an AC coupled amplifier.
Then learn why this is the safer option (for your speaker), so that informed decisions can be made on whether to adopt a DC coupled amplifier.

Peter Daniel 23rd April 2011 04:17 PM

Quote:

Originally Posted by inverseopamp (Post 2548350)
Hi,
Now for the amps,

1. Considering I am using the LM 4780 amplifier, do I need 1x LM4780 for both channels or 2xLM4780s for 2 channels?

2. Do I need 2 transformers (dual mono) or can I use one?

When using LM4780, for simple stereo setup you will actually need only half of the kit (single LM4780 chip). It is a dual chip and the board allows two separate channels configuration from a single chip: http://www.diyaudio.com/forums/audio...tml#post636565

I usually recommend a single transformer, 300VA, 2 x 22V AC or similar

inverseopamp 24th April 2011 03:12 AM

Quote:

Originally Posted by Richard Ellis (Post 2548411)
Let me try to answer this...
1. Both amplifiers will have the same 'line-level' inputs....so your EQ will work with either. The LM3875 has slightly less distortion at full rated power.
2. Either amps will drive just about anything you can hook up to it..beware of extremely low impedence loudspeakers however...they can overtax some amps.
3. ALL tweeters MUST have a crossover... a capacitor to filter out low frequencies.
4. Full-rangers are nice, but expensive...have low SPL outputs(Except large cone....8"+ versions).....but need no crossovers.Multi-ways are relatively complex........This is a whole nuther' topic!
1a. Both amps are on a single circuit-board...The board is then "broken" in half for two seperate boards...each one is one channel.
2a. The power supply is set-up to drive both channels...one transformer.
3a. Yes, you should have a three wire wall current......any deviation here and you invite possible shock hazards.
These kits are straightforward, oddly, they use outboard power supplies...
The heatsinking approaches are using chunks of Aluminum, rather than true heatsinks...
Cheap toroid transformers from Antek can fit the bill for your transformer needs..if you can get them....there are a few more components you will need to complete the PS...but there's not much.

Thanks!

Quote:

Originally Posted by Peter Daniel (Post 2548455)
When using LM4780, for simple stereo setup you will actually need only half of the kit (single LM4780 chip). It is a dual chip and the board allows two separate channels configuration from a single chip: http://www.diyaudio.com/forums/audio...tml#post636565

I usually recommend a single transformer, 300VA, 2 x 22V AC or similar


I have sent you a message via the website contact form, since I would like to order, please revert when you get time.

inverseopamp 25th April 2011 03:22 PM

I have got a quote from a Toroidal Xformer manufacturer in India. The price looks bit low. Is anything compromised?


__________________________________________________ ___________

TOROIDAL TRANSFORMER

1. PRIMARY : 0---230 V.
OD / HT (in mm) 125 / 60
SECONDARY : 22---0---22 V./ 300 VA.
Rs. 1,545/- ~ 34 USD
Weight App. = 3.15 Kg.

MOUNTING : RESIN CENTER POTTING THROUGH HOLE
WITH FLYING LEADS.





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