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Old 30th June 2003, 04:32 AM   #1
S.C is offline S.C  United States
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Question GC Noob

I decided to build a Gainclone after I had read this froum for a few days. However, I had trouble on gathering parts in US, but I found an answer in a thread.
Code:
Qty	Description			Part #			Supplier			Cost (US$)	Total
2	Cond 4.7uF, 50V BlackGate N		BLKGATE- 60186 		partsconnexion.com		$2.50 		$5.00 
4	1000uF, 50V Panasonic FC		P10333-ND (or P11263-ND)	digikey.com		2.37		$9.48 
2	10K Ohm .75W Caddock:MK132		CADDOCK- 51201 		partsconnexion.com		3.95		$7.90 
2	220K Ohm .75W Caddock:MK132		CADDOCK- 62290 		partsconnexion.com		4.5		$9.00 
8	MUR860 Diodes			MUR860-ND			digikey.com		0.76		$6.08 
2	LM3875 Op-Amp			LM3875TF-ND		digikey.com		5.81		$11.62 
												total	$49.08 
1	Transformer (range 20-40)		Surplus?						$0.00 
1	50K Stereo pot	Radio shack?	Radio shack?					$0.00
Originally posted by rammsteinme

The real question was in the transformer part.

What transformer should I use?

Did the shape of the transformer affect (Square, circle ?_?I hope to make it as thin and as small as possible)

What value of Dual potentiometer ( where to connect? input or output )and Power Port should I use?

How can I build this amp with gain control?

How can I build a Gainclone with stereo in (I mean something like
headphone pot.)and RCA in, RCA out and stereo out?

My budget : $100

My Sources: Toshiba 5205-S505 Laptop / a Deatop / even a
system I don't know (My Laptop will be my first
concern.)

My Speaker: Aiwa Speaker System SC-51
Music Power 35W
Normal Power 25W
Impedance 8 Ohm

P.s Feel free correcting my English.
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Old 30th June 2003, 05:59 AM   #2
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I dont understand your post but would like to help if i can...can you maybe rephrase your quiery?


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Old 30th June 2003, 06:45 AM   #3
S.C is offline S.C  United States
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Default Re: GC Noob

I decided to build a Gainclone under the following part list by rammsteinme
Code:
Qty	Description			Part #			Supplier			Cost (US$)	Total
2	Cond 4.7uF, 50V BlackGate N		BLKGATE- 60186 		partsconnexion.com		$2.50 		$5.00 
4	1000uF, 50V Panasonic FC		P10333-ND (or P11263-ND)	digikey.com		2.37		$9.48 
2	10K Ohm .75W Caddock:MK132		CADDOCK- 51201 		partsconnexion.com		3.95		$7.90 
2	220K Ohm .75W Caddock:MK132		CADDOCK- 62290 		partsconnexion.com		4.5		$9.00 
8	MUR860 Diodes			MUR860-ND			digikey.com		0.76		$6.08 
2	LM3875 Op-Amp			LM3875TF-ND		digikey.com		5.81		$11.62 
												total	$49.08 
1	Transformer (range 20-40)		Surplus?						$0.00 
1	50K Stereo pot	Radio shack?	Radio shack?					$0.00
My questions are:

What kind of transformer should I use? (I want to make it as thin & small as possible.)

What value of resistance Dual potentiometer do I use?
( Volume Control ) ( where do I connect it ? On the input or output )

How can I build this amp with gain control?

How can I build a Gainclone with two kind of input and output (headphone kind of pot, and RCA pot or I/O pot

My budget : $100

My Sources: Toshiba 5205-S505 Laptop / a Deatop / even a
system I don't know (My Laptop will be my first
concern.)

My Speaker: Aiwa Speaker System SC-51
Music Power 35W
Normal Power 25W
Impedance 8 Ohm

P.s Feel free to correct my English. [/B][/QUOTE]


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Old 30th June 2003, 09:19 AM   #4
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Hi S.C, I'll try and answer some of your questions.

A torroidal type if transformer is probably your best bet. Unfortunately, if miniturisation is the goal, the transfomrer will be the limiting factor, ie they just don't make very small ones capable of powering a power amplifier.

You will need a transformer with 110 volt primary windings and secondaries of 18-0-18 and rated at 120VA or higher (if you use just one).

If you are building the basic inverted version of the GC, I suggest using the stepped attenuator described on my

FAQ page

The volume control is connected on the input of the GC as shown in many of the schematics posted on this and other chip amp forums.

Why do you want to control the gain? There is no need if you are controlling the volume with a pot of attenuator.

You can build a simple device with resitors to enable you to connect headphones through the speaker terminals. A design was mentioned in another thread but I can't remember where. Try a search.

To use the amp with different inputs, you will need to build a preamp with a selector switch and multiple input sockets. Again, refer to the relevant sections of Decibel Dungeon for more information.

Realistically, your budget of $100 is a bit tight but it depends how much you can pick up at surplus prices and whether you buy, or build your case.

Good luck, it may all seem a bit confusing at first but if you study all the information available and then take things in easy steps, it is possible to build a good sounding GC!
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Old 30th June 2003, 04:35 PM   #5
S.C is offline S.C  United States
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Good info, thx !

I currently had a Panasonic EVJY10 Series Dual potentiometer, is it connect it like the following picture is ok for this amp? Click the image to open in full size.from Headwize
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Old 30th June 2003, 06:21 PM   #6
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Quote:
I currently had a Panasonic EVJY10 Series Dual potentiometer, is it connect it like the following picture is ok for this amp?
Yes, that looks OK to me! What value is that pot?
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Old 30th June 2003, 11:28 PM   #7
S.C is offline S.C  United States
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Panasonic 10K, vertical (EVJ-Y10)
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Old 1st July 2003, 08:43 AM   #8
Nuuk is offline Nuuk  United Kingdom
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Quote:
Panasonic 10K, vertical (EVJ-Y10)
That will be fine to get you going.
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Old 2nd July 2003, 04:57 PM   #9
S.C is offline S.C  United States
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Ok, then I should start ordering parts now. Thx a lot!

Btw, what transformer is Peter Daniel using all the time? Like thisClick the image to open in full size.
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Old 4th July 2003, 12:13 AM   #10
S.C is offline S.C  United States
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After I read some of the transformer suggestion, I had a question.
How come ppl in USA can use transformer input up to 2xx VAC, isn't US Wall supply only have 120VAC?

I'm confused by these transformer stuff now, and what else do I need if I had LM3875 from samples, that make the digikey parts total around $18. Then I need to pay for the $5 handling, unless I make the total cost at $25. In the partsconnexion side also had the same problem.
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