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Commercial Gainclone kit- building instructions

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A

AndrewT

R.I.P.
Joined 2004
dasein said:
1) I live in the US and I'm trying to figure out how to safely ground the chassis and everything. I'm building a stereo with one rectifier and transformer. Can any more experienced DIYers in the US suggest what screw size and bolts and gauge wire I should be using to ground things to Safety Earth? Otherwise I was going to emulate P. Daniel's set up at the beginning of this thread to the best of my abilities.
Click to expand...

Bill_P said:
1. I use 14 gauge wire for safety ground crimped into a ring tongue terminal. The screw should be 8-32 or larger and a lockwasher should be used under the nut.
Click to expand...
The Safety Earth has ONE wire going to it. Only 1.
That is the third wire in the mains power input cable.
Once this is permanently fixed to the chassis, nothing else disturbs this permanent fixing.

You can connect the Audio Ground above that permanent nut with two extra nuts. Or you can connect the Audio Ground to a separate point on the chassis.
 
N

northernsky

Member
Joined 2008
Hum, after some months

Hi,

I am a newbie who built two monoblocks based on the LM3875 AUDIOSECTOR premium kit following the instructions of this thread. They are now playing from about 6 months and I am very pleased of the sound.

Some weeks ago one of the monoblock started to produce a hum (low level noise) I could hear directly from the amps and also from the speakers. At first the hum was only occasional, for instance switching off for a couple of minutes was sufficient to cancel the hum when switched on again. But now the noise is becoming more and more frequent.

Have you any idea why? Is it possible a transformer failure?


Thank you

Renato
 
captainobvious

captainobvious

Member
Joined 2008
Very interested after reading this thread in building 2 amplifiers. First would be a 4 channel LM4780 (to power midbass and sub), second would be a 4 channel LM3875 (to power mids and highs).

Do you have a kit for a 4 channel amp of each type or would it just require buying (2) of each kit? Also, can I use a single transformer in each of the two amplifier cases and which size would you recommend?

For reference, I live in the US with standard 120v mains, and the speaker loads will 4ohms.
 
Peter Daniel

Peter Daniel

Member
Joined 2002
audiosector.com
Paid Member
A single LM4780 kit can actually produce 4 separate amplification channels. It's only when you want to go parallel you need two of them.

As for LM3875, each kit is good for two channels. You can request a kit without PS section though.

I would recommend separate transformer per channel: 250-300VA would be a good size.

northernsky said:
started to produce a hum (low level noise) I could hear directly from the amps and also from the speakers.
Click to expand...

Good be a loose ground too.
 
captainobvious

captainobvious

Member
Joined 2008
Peter Daniel said:
A single LM4780 kit can actually produce 4 separate amplification channels. It's only when you want to go parallel you need two of them.

As for LM3875, each kit is good for two channels. You can request a kit without PS section though.

I would recommend separate transformer per channel: 250-300VA would be a good size.
Click to expand...

Thanks for the quick response. So then (2) LM4780 kits would probably be ideal for me then I guess. Since there are 8 total amplification channels (as you said, 4 per kit), are you saying I would require 2 transformers, one for each LM4780 kit or am I misunderstanding you?

Thank you. Looking forward to getting an order in :)
 
W

Wavne

Member
Joined 2007
Hey Everyone;
I'm new here. I just ordered the 4780 Dual Mono Kit from Peter. While hunting for transformers I found these guys..Primrose Audio. Has anyone tried these?

I'm planning on getting One and run the kit in stereo until I can afford a second, then run in dual mono. I have a price of $125 CDN after tax and shipping for a single primary 300vac 22+22 secondaries.

regards,

Wayne
 
E

etoiledusoir

Member
Joined 2009
Wavne said:
Hey Everyone;
I'm new here. I just ordered the 4780 Dual Mono Kit from Peter. While hunting for transformers I found these guys..Primrose Audio. Has anyone tried these?

I'm planning on getting One and run the kit in stereo until I can afford a second, then run in dual mono. I have a price of $125 CDN after tax and shipping for a single primary 300vac 22+22 secondaries.

regards,

Wayne
Click to expand...

You can ask Richard if he have surplus stock. I ordered from him two 300va 22-22 for 40$ each about two month ago. Check also for Antek, for more competitive price.
 
captainobvious

captainobvious

Member
Joined 2008
Regarding isolating the chip from the chassis/chassis mounted heatsink...The kits come with a strip of insualting foil. Do you need to use heatsink thermal compound on both sides of this foil (between foil and chip, and between foil and heatsink) ?

I read through the thread but couldnt find a clear answer on isolating the chip. Thank you.
 
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