First Gainclone (Hell, first amp...)

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Llamas

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Joined 2003
#1
I am going to build a pair of gainclone monoblocks, each with its own power supply.

I've been working the search function, and prowling the various linked web sites (including Nuuk's FAQ). Rather than start different threads with different questions, I'm going to try to keep everything confined to this thread.

I am very new to this. Please forgive my cranial density.

I've got most of my parts list together, and I'm seeking feedback. The only example parts lists I could find were referecing European suppliers, so I couldn't cheat by simply copying their part numbers. Here's what I've come up with so far:

Part,Supplier,Part Number,Quantity
Blackgate Cap 4.7uf 100V,referenceaudiomods,BG_STD_4P7_100,2
22V 160VA Dual Transformer,Parts Express,122-625,2
Rectifier Bridge 25A 50V,Digikey,GBPC25005-ND,4
Fuse Holder (soldered, panel),Digikey,F005-ND,2
2A Fuse Slow,Digikey,283-2182-ND,5
1000uF Capacitor 50V (Panasonic FC),Digikey,P11263-ND,4
2200uF Capacitor 50V (Panasonic FC),Digikey,P10335-ND,4
10K Carbon Film Resistor (input),Digikey,10KQBK-ND,5
100K Metal Film Resistor (input to signal ground),Digikey,100KXBK-ND,5
22K Metal Film Resistor (pin 8 to signal ground),Digikey,BC22KW-1CT-ND,5
18K Metal Film Resistor (pin 7 to signal ground),Digikey,BC18KW-1CT-ND,5
LM3875 Amplifier (TF isolated?),Digikey,LM3875TF-ND,2
1uF Capacitor 50V (Panasonic FC) (bypass),Digikey,P10312-ND,2
220K Carbon Film Resistor (feedback),Digikey,200KH-ND,5
.20 Wirewound Resistor 3W (output),Digikey,23JR20-ND,2

(Some of the 5 counts are due to minimum quantities. I'm also getting both 1000uF and 2200uF caps to try out, since I've seen schematics using one or the other.)

I still need heatsinks, RCAs, power connectors, etc. I figure I'll make a case out of wood or spam or something.

Any brand recommendations? Warnings about anything I've chosen so far? Can I update the list to make it more readable?

Thanks,

--Mike
 
#3
Thanks for the digikey numbers! Also, for the heads-up that PE is now selling decent toroidals.

I am in just about the same position as you, but I am looking for a great enclosure before I do the circuit. Starting to get impatient, lost a couple of auctions on Ebay for cool old stuff. Might go ahead and breadboard it first out of sheer boredom/impatience!

GnD
 
#4
you guys might wanna email steve at apexjr.com
periodically he has surplus toroids for cheap. i bought from him a 300va 25v 0v 25v toroid for $25 and i am very happy with it. he also carries a variety of inexpensive misc parts like rca's and binding posts...
 
#5
power supply caps

While I'm not typically super picky about parts I would say one drastic improvement worth a shot is BlackGate 1000uF. I built a gc using this schematic (one of a few...) and toyed around with both pan fc's and bg's. I can't tell the difference between resistors, diodes, or even input caps hardly (using bg 22uf only because i have em). I'll tell you what though... I can definitely tell the difference here. It is definitely minute, but the BG is better.

As for the input cap I don't think that needs to be bg. They aren't too expensive though so it may be worth it.

I also didn't hear a difference between isolated and non so I just go with the TF.
 
#6
I got the schematic from the Chip Amp DIY Forum . There are links at the bottom for a few schematics.

I also found another thread here (couldn't find it before I posted) that covers some parts from North American suppliers.

Nuuk's advice in his
beginners' FAQ was the opposite on the BG caps. He recommended BG for the input, and FC for the 1000uF. The more I read the forums, the more I realize that I am going to have to hear things for myself.

I think the isoloated vs. non-isolated chip is just an issue of convenience. If I am not mistaken, you can just bolt the isolated chip to the heat sink, while the non-isolated part required electrical insulation.

I'm going to breadboard mine while I figure out the enclosure. I still think I'll end up fashioning one out of wood. I think the wood makes it that much more different from the plastic and metal of mass produced products.

Thanks for the feedback!

--Mike
 
#7
...and a word of warning: The parts list I submitted above is the work of someone VERY new to the hobby, working from a schematic and general recommendations.

Part of the reason for my post was to get feedback concerning my choice of type of resistors, capacitors, etc. Thanks for your input in this regard, Breguetphile.

I wouldn't want anyone to take my parts list and run, just to find out that I don't know what I'm doing.

Now, onto heatsinks! I've seen plenty of posts in the vein of, "if I bolt the chip to a hamster, will that be good enough?" but I don't think I've heard a specific spec on required heat dissipation. Since I'm just starting to accumulate "junk" for future products, I'll probably just order a couple of heatsinks along with the other parts. How many watts does the heat sink have to dissipate?

Thanks,

--Mike
 
#8
Hi Mike,

I would definitely recommend just knocking one of these amps on a piece of timber to get started. Having it open like that makes it very easy to see what is going on and do a last minute visual check of the circuit.

And if changes need to be made, they can be done quickly and easily.

I have built two GCs now. The first were my small monoblocks and doing any changes to the circuit was a bit of a pain. My second is dual mono built on a plank of wood and I have done it that way while I experiment with buffers etc.

When the amp is finalised, then it can be put into a nice case.
 
#10
Well, I'm back from vacation, I've finished my speaker project (except for the grills), and I'll be assembling my gainclone this weekend.

What I finally ordered (warning: parts picked by new guy):

Code: 
Part						Source		Part Number	Quantity	Price	Extended Price
Blackgate Cap 4.7uf 100V				Parts Connexion	BLKGATE60098	2	2.7	5.4
18V 160VA Dual Transformer				Parts Express	122-610		2	38.79	77.58
Rectifier Bridge 25A 50V				Digikey		GBPC25005-ND	4	3.78	15.12
Fuse Holder (soldered, panel)			Digikey		F005-ND		2	2.45	4.9
2A Fuse Slow					Digikey		283-2182-ND	5	0.718	3.59
1000uF Capacitor 50V (Panasonic FC)			Digikey		P11263-ND		4	3.22	12.88
Riken 10K 1W 1% Resistor (input)			Parts Connexion	RIKEN62161	2	2.7	5.4
50K pot, linear taper, horizontal mount w/ bushing	Digikey		P3R7503-ND	2	1.94	3.88
Riken 22K .5W 1% Resistor (pin 8 to signal ground)	Parts Connexion	RIKEN62103	2	1.8	3.6
Riken 18K .5W 1% Resistor (pin 7 to signal ground)	Parts Connexion	RIKEN62102	2	1.8	3.6
LM3875 Amplifier (TF isolated?)			Digikey		LM3875TF-ND	2	5.81	11.62
1uF Capacitor 50V (Panasonic FC) (bypass) 		Digikey		P10312-ND		2	0.46	0.92
Riken 220K .5W 1% Resistor (feedback)		Parts Connexion	RIKEN62119	2	1.8	3.6
.22 Wirewound Resistor 5W (output)			Parts Express	015-.22		2	0.19	0.38
AC receptacle for PC power cords			Digikey		Q210-ND		10	0.58	5.8
Gold RCA Chassis Jack (pair)			Parts Express	091-1120		1	5.3	5.3
Binding Post					Parts Express	260-314		2	7.95	15.9
					
												179.47

I grabbed a bag of the AC connectors since I have a bunch of cords laying around, and I figure they would prove useful in the future.

I also picked up some breadboard from RS to mount things on. I also grabbed some small heatsinks from RS.

I'll post pictures of what I do this weekend. They will probably be in the vein of "I'm clueless. What's wrong with this picture?" than anything instructive to others.

--Mike
 
#11
Llamas, Great post! I am a "Gainclone" newbee also and its nice to see this

forum so active. I am just starting to gather parts, I have visited the info links

and with luck and standing on the shoulders of people like Peter Daniel,NUUk,

Joe Rasmussen,Planet 10,Dimitri,Kuei Yang Wang, Etc.Etc.Etc.(sorry If I

missed anyone!) I might just pull it off. :nod:
 
#15
Llamas - I noticed you stocked up on bridge rectifiers. I know it's too late to save you the money now, but you can order samples of MUR860 fast recovery soft diodes from On-Semi. Peter Daniel really seems to like them, so I thought I would give them a shot, especially since samples are available. I've got 20 of them, and could mail you some if you like 😉
 
#16
OK, I put together the my first power supply, this afternoon. Nothing caught on fire. Let me know if there are any good practices I should be following. This IS my electronics background.

Here's a picture:

An externally hosted image should be here but it was not working when we last tested it.


and a better one from a lower angle:

An externally hosted image should be here but it was not working when we last tested it.


As can be read from the picture, it's a double 18V 160VA toroid. I'm reading 26.5 VDC output.

I've mounted things to a cutout piece for an 8" speaker driver, and used disconnects in places so that I could take things apart more easily.

I have a neophyte question (I'll hit the FAQ pages, and crack my electronics book to start looking for this...): Where does earth ground tie into the schematic? I don't have a metal chassis to ground...

In any case, I make the amp section in the morning. Once I get one monoblock built in prototype fashion, I'll try to build the other one in a more finished manner.

Thanks,

--Mike
 
#20
Llamas.

A couple of things:

Firstly, I would not rely on Cable Nuts to hold when using flexible cable for your mains connections, and I also see no fuse. This is important, and even more so at the prototyping stage.

Secondly, I see you have linked the two bridges. Where are you getting the psu ground from? In fact, GCs work better running the two grounds from the bridges to the amp psu caps, and joining them there.
 
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