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DIY amplifier

post #1 of 73
Thread Starter 
I'm thinking of building a DIY amplifier such as http://ampslab.com/c200.htm

Does anyone know the relative cost of building some thing like this, and could post a link to a transformer for it?
Edited by WagBoss - 1/26/13 at 11:59am
post #2 of 73
Thread Starter 
also, for resistors and capacitors, is it ok to use resistors and capacitors rated HIGHER than it says on the parts list? Such as a 1000uF at 35V instead of 1000uF at 6.3V. or a 1W resistor instead of a 1/4W resistor? I know for safety it is fine, but will it affect the sound of the amplifier at all?

and does anyone know a website better than ebay for buying 1-5 transistors/capacitors/resistors?
Edited by WagBoss - 1/26/13 at 12:30pm
post #3 of 73
Mouser

Getting parts rated for more power or voltage is okay assuming they're equivalent. For example, replacing a 6.3V 1000uF low ESR electrolytic cap with a 35V 1000uF electrolytic is not a good substitution. I'd be pretty surprised if you couldn't find the right parts at Mouser and needed to make substitutions.
post #4 of 73
Hi Wag,

Here are some links to transformers that will work.

Signal 320va from Digi-Key
Hammond 320va from Mouser

I will second Stereodudes recommendation of Mouser for parts, and also add Digi-Key. Those are my two main suppliers. I would avoid eBay, as you can't tell what you will really get.

Generally, I avoid using parts that are over-specifications. A 1-watt resistor is likely to be wire-wound, whereas an 1/8 watt would not be. That means that the 1-watt would have a lot more inductance than the 1/8 watt, which may or may not effect the circuit performance.

I try to design with surface-mount components, preferring 0603 packages, because of the lower stray inductance and capacitance. It may not make a difference in that amplifier design, but it doesn't hurt, and I find it easier to build with surface-mount. It also allows for smaller PCBs, which are also cheaper.
post #5 of 73
Unless you really want to source all the parts, solder them on the PCB, and learn - why not buy a module/transformer/box and assemble one?

http://classdaudio.com/

I've got a couple of their modules I used for testing if you are interested.

JP
post #6 of 73
Thread Starter 
Quote:
Originally Posted by Stereodude View Post

Mouser

Getting parts rated for more power or voltage is okay assuming they're equivalent. For example, replacing a 6.3V 1000uF low ESR electrolytic cap with a 35V 1000uF electrolytic is not a good substitution. I'd be pretty surprised if you couldn't find the right parts at Mouser and needed to make substitutions.

I'm confused, you say rated for more power or voltage is okay if they're equivalent, but then you say I can't? Could you replace a 6.3V 1000uF electrolytic with a 35V 1000uF electrolytic?
post #7 of 73
Thread Starter 
On mousers, what type of capacitor category is the same as "polyester", "multilayer" and "polystyrene" for capacitors? The parts-list for the c200 says these types but they aren't the same as the ones on the website. It also uses silver mica and e-cap but I found those.
post #8 of 73
i would just build a gain clone http://chipamp.com/order/ its pretty easy to build only problem is idk where u could get the transformer from anymore the cheap chinese transformers that worked greats warehouse burnt down recently
post #9 of 73
Thread Starter 
Quote:
Originally Posted by zora View Post

Unless you really want to source all the parts, solder them on the PCB, and learn - why not buy a module/transformer/box and assemble one?

http://classdaudio.com/

I've got a couple of their modules I used for testing if you are interested.

JP

I'm just interested in the whole design/building part, as I am in electrical engineering wink.gif I just want a project to work on.
post #10 of 73
Quote:
Originally Posted by WagBoss View Post

Could you replace a 6.3V 1000uF electrolytic with a 35V 1000uF electrolytic?
You may, the question is why? It won't work any better. The only justification is if you have a pile of components lying about.
post #11 of 73
Thread Starter 
oh, also any suggestions on what to use for RCA inputs, and speaker terminal outputs?
post #12 of 73
you also need to take into account lead spacing for caps and resistors
post #13 of 73
Thread Starter 
Quote:
Originally Posted by Bill Fitzmaurice View Post

You may, the question is why? It won't work any better. The only justification is if you have a pile of components lying about.

Ok, yeah I have stuff lying around. I just wanted to make sure it does not negatively affect the sound.
post #14 of 73
Thread Starter 
Quote:
Originally Posted by cookieattk View Post

you also need to take into account lead spacing for caps and resistors

what spacing should i get for the capacitors for the c200 amplifier? or what is just the general spacing that works the best
post #15 of 73
Quote:
Originally Posted by WagBoss View Post

Quote:
Originally Posted by Stereodude View Post

Mouser

Getting parts rated for more power or voltage is okay assuming they're equivalent. For example, replacing a 6.3V 1000uF low ESR electrolytic cap with a 35V 1000uF electrolytic is not a good substitution. I'd be pretty surprised if you couldn't find the right parts at Mouser and needed to make substitutions.

I'm confused, you say rated for more power or voltage is okay if they're equivalent, but then you say I can't? Could you replace a 6.3V 1000uF electrolytic with a 35V 1000uF electrolytic?


There are a lot of parameters to a capacitor besides voltage and capacitance. I believe Stereodude's capacitor comment refers to the fact that a 35v 1000uF electrolytic would have too high an ESR compared to a 6.3v, so it would not be equivalent.
post #16 of 73
Quote:
Originally Posted by WagBoss View Post

I'm confused, you say rated for more power or voltage is okay if they're equivalent, but then you say I can't? Could you replace a 6.3V 1000uF electrolytic with a 35V 1000uF electrolytic?
Because my example was of non equivalent parts. You shouldn't replace a low ESR electrolytic cap with a standard electrolytic.
post #17 of 73
Thread Starter 
can anybody give some advice on a heat sink for this amp? I assume it needs one, but where/how would I attach it and to what? I don't see any info in the schematics for a heat sink.
post #18 of 73
Quote:
Originally Posted by WagBoss View Post

can anybody give some advice on a heat sink for this amp? I assume it needs one, but where/how would I attach it and to what? I don't see any info in the schematics for a heat sink.
On the link you posted you can see an image of an assembled amp. In the picture it looks like they have 4 heatsinks on 4 transistors. Most likely the output stage. That is why most of those transistors have that little metal tabs with a hole in it, for attaching heatsinks.
post #19 of 73
Thread Starter 
Quote:
Originally Posted by Bushi View Post

On the link you posted you can see an image of an assembled amp. In the picture it looks like they have 4 heatsinks on 4 transistors. Most likely the output stage. That is why most of those transistors have that little metal tabs with a hole in it, for attaching heatsinks.

so tiny hard to see anything on it lol.. Are the heatsinks like surrounding the transistors on 3 sides? Have any links for a good heat sink to use for that?

I think theres 2 of these http://ca.mouser.com/Search/ProductDetail.aspx?R=MJ15003Gvirtualkey58410000virtualkey863-MJ15003G and two of these http://ca.mouser.com/Search/ProductDetail.aspx?R=MJ15004Gvirtualkey58410000virtualkey863-MJ15004G as output transistors, so I need a heat sink that fits TO-204-2 (TO-3), any recommendations off mouser? there's like 60 different ones that size lol

what do you guys think of four of these? http://ca.mouser.com/ProductDetail/Wakefield/690-3B/?qs=sGAEpiMZZMttgyDkZ5WiumXnBK4AuqYZBAr28HNuGv8%3d
Edited by WagBoss - 1/27/13 at 12:47pm
post #20 of 73
Hi Wag,

To do it right, you need a single heat-sink that will hold five transistors: Not just the four power transistors Q11, Q12, Q13 and Q14, but also Q6, as it needs to track the temperature of the four power transistors.

Also, the heat-sink in that last Mouser link looks pretty anemic for a 200 watt amplifier, but I can't say for sure. My suggestion would be to use a Wakefield 435AAAA, which can hold all four TO-3 transistors. You may need to drill an extra hole for Q6.

Here is the datasheet.
Here is a source.
post #21 of 73
Thread Starter 
Quote:
Originally Posted by MarkHotchkiss View Post

Hi Wag,

To do it right, you need a single heat-sink that will hold five transistors: Not just the four power transistors Q11, Q12, Q13 and Q14, but also Q6, as it needs to track the temperature of the four power transistors.

Also, the heat-sink in that last Mouser link looks pretty anemic for a 200 watt amplifier, but I can't say for sure. My suggestion would be to use a Wakefield 435AAAA, which can hold all four TO-3 transistors. You may need to drill an extra hole for Q6.

Here is the datasheet.
Here is a source.

In the picture on the c200 website, is there a reason they don't have Q6 in a heatsink?

How exactly can the Q6 transistor track the temperature of the power transistors? I'm not sure how that would work exactly.

is there any heat sink solution you could suggest from mouser? If I ordered that heatsink you linked it's $40.00 shipping to canada :S
Edited by WagBoss - 1/27/13 at 4:31pm
post #22 of 73
try ebay
post #23 of 73
Thread Starter 
post #24 of 73
Quote:
Originally Posted by WagBoss View Post

How exactly can the Q6 transistor track the temperature of the power transistors? I'm not sure how that would work exactly.
That's a good question. I was simply echoing what the author said on page 2, under "Vbe Multiplier".

In general, junction voltages drop with increasing temperature in bipolar transistors. So it looks to me that, as Q6 is heated by the power transistors, it's lowered junction voltage reduces the bias voltage to the driver transistors, compensating for the power transistor's reduced junction voltage. That's just what it seems at first glance, and I would need to run a spice simulation to know for sure.

As far a those eBay links, I'm really surprised at such a large selection for some great prices. I will have to stop bashing eBay now. I also noticed the lack of hard data, but when you need to fit four TO-3s on a heat-sink, it gets large enough to not worry too much.
That looks like the winner to me. I would use the center spot for Q6.
post #25 of 73
Thread Starter 
Quote:
Originally Posted by MarkHotchkiss View Post

That's a good question. I was simply echoing what the author said on page 2, under "Vbe Multiplier".

In general, junction voltages drop with increasing temperature in bipolar transistors. So it looks to me that, as Q6 is heated by the power transistors, it's lowered junction voltage reduces the bias voltage to the driver transistors, compensating for the power transistor's reduced junction voltage. That's just what it seems at first glance, and I would need to run a spice simulation to know for sure.

As far a those eBay links, I'm really surprised at such a large selection for some great prices. I will have to stop bashing eBay now. I also noticed the lack of hard data, but when you need to fit four TO-3s on a heat-sink, it gets large enough to not worry too much.
That looks like the winner to me. I would use the center spot for Q6.

Ok, Thanks.

Another couple questions if you don't mind.. I was looking on this page http://ampslab.com/c200_3.htm and noticed the Power supply circuit. I need to build this too, right? I'm just confused as they are not on the parts list on the previous page...

For C1, what voltage? It just says 4700 pF X2
for C2 and C3, would these be better http://www.ebay.ca/itm/JAPAN-2PCS-Elna-Lao-10000uF-63V-For-Audio-Electrolytic-Capacitor-New-TOP-HiFi-/190758098340?pt=LH_DefaultDomain_0&hash=item2c6a1195a4&_uhb=1#ht_1536wt_1163 than these http://www.digikey.ca/product-detail/en/ECO-S1JA103EA/P7492-ND/411750 or does it not matter?
What exactly is B1, the bridge rectifier? I can't find any info on what diodes it uses.
For F1, what fuse should I use off of mouser? Again, no info from what I can see.

I assume SW1 is just connected to the main power switch?
Edited by WagBoss - 1/27/13 at 7:13pm
post #26 of 73
Hi Wag,
Quote:
Originally Posted by WagBoss View Post

Ok, Thanks.
Another couple questions if you don't mind..
You're welcome.
I don't mind at all.

Quote:
I was looking on this page http://ampslab.com/c200_3.htm and noticed the Power supply circuit. I need to build this too, right?
Right.

If you are building a single amp, like for a sub, then what is shown is what you need. However, if you are building multiple amps, like for a stereo or surround system, then a larger, single power-supply would be more cost-effective. I suspect that is why he has the power-supply separated from the amp.
Quote:
For C1, what voltage? It just says 4700 pF X2
If you are running on 117 volts AC, then I would use at least a 200 volt cap. If you need to also run up to 240 volts, then I would use a 400 volt cap.
Quote:
. . . for C2 and C3, would these be better or does it not matter?
I doubt that they are any better. If they were close to the same price, then I might consider the "audio" versions just to impress the layman. But price would be my main criteria.
Quote:
What exactly is B1, the bridge rectifier? I can't find any info on what diodes it uses.
Do you mean BR1? yes, it's a bridge. The rating should be at least 60 volts and 10 amps
Quote:
For F1, what fuse should I use off of mouser? Again, no info from what I can see.
I would use a circuit-breaker, myself. 250va divided by 110 volts would say a minimum of 2.3 amps. Probably a 2.5 amp slo-blo would be best. A fast-blow fuse would probably blow on power-up with the surge that fills the filter-caps.
Quote:
I assume SW1 is just connected to the main power switch?
SW1 is the main power switch.
post #27 of 73
Thread Starter 
Quote:
Originally Posted by MarkHotchkiss View Post

Hi Wag,
You're welcome.
I don't mind at all.
Right.

If you are building a single amp, like for a sub, then what is shown is what you need. However, if you are building multiple amps, like for a stereo or surround system, then a larger, single power-supply would be more cost-effective. I suspect that is why he has the power-supply separated from the amp.
If you are running on 117 volts AC, then I would use at least a 200 volt cap. If you need to also run up to 240 volts, then I would use a 400 volt cap.
I doubt that they are any better. If they were close to the same price, then I might consider the "audio" versions just to impress the layman. But price would be my main criteria.
Do you mean BR1? yes, it's a bridge. The rating should be at least 60 volts and 10 amps
I would use a circuit-breaker, myself. 250va divided by 110 volts would say a minimum of 2.3 amps. Probably a 2.5 amp slo-blo would be best. A fast-blow fuse would probably blow on power-up with the surge that fills the filter-caps.
SW1 is the main power switch.

I'm just going with single channel, mainly doing this to learn some practical knowledge.

For the BR1, I need just 4 diodes, right? does the forward continuous current, forward voltage drop, or recovery time matter? do i want a switching diode or general purpose? would four of these work? http://ca.mouser.com/ProductDetail/NXP-Semiconductors/BAS31215/?qs=sGAEpiMZZMtvcUztdGSumHqLbuom3z1b206Gz6j9hC8%3d

for circuit breakers, how long is "slow blow"? I'm actually using a 320va so would I need 2.9A circuit breaker or 3A? could you select one that work best from here please http://ca.mouser.com/Electromechanical/Circuit-Breakers/_/N-6g7n7/

Thanks again
Edited by WagBoss - 1/27/13 at 9:52pm
post #28 of 73
Yes, you can go with four diodes, but a bridge would be simpler and cheaper. Something like this.

You don't need switching diodes. Switching diodes respond in nanoseconds, whereas a power-supply rectifier can respond over milliseconds. The important specs are only the current and voltage.


The fact that the transformer is capable of 320va is not as relevant as the amount of power that the amplifier will actually draw, which would still be only 250va. It means that it wouldn't hurt to use a 3 amp fuse, but a 2.5 amp would also work.

I don't really know how long "slo-blo" is. I just know that fuses are listed as fast or slow. A circuit breaker is typically better, as it is slow for currents marginally above the trip-point, and fast for direct shorts. Personally, I like combining the switch with the breaker, something like this.
post #29 of 73
Just out of curiosity, how hard is it to build one of these DIY amps? I would love to be able to build my own amps, or have the knowledge to tweak and/or modify various components. Can any of you guys recommend a book or place to start learning about this stuff?
post #30 of 73
Thread Starter 
Quote:
Originally Posted by MarkHotchkiss View Post

Yes, you can go with four diodes, but a bridge would be simpler and cheaper. Something like this.

You don't need switching diodes. Switching diodes respond in nanoseconds, whereas a power-supply rectifier can respond over milliseconds. The important specs are only the current and voltage.


The fact that the transformer is capable of 320va is not as relevant as the amount of power that the amplifier will actually draw, which would still be only 250va. It means that it wouldn't hurt to use a 3 amp fuse, but a 2.5 amp would also work.

I don't really know how long "slo-blo" is. I just know that fuses are listed as fast or slow. A circuit breaker is typically better, as it is slow for currents marginally above the trip-point, and fast for direct shorts. Personally, I like combining the switch with the breaker, something like this.

If I go with http://ca.mouser.com/ProductDetail/Schurter/CFTWF030C0/?qs=sGAEpiMZZMsVdjGoHXLeS6l175K4vmU2gVu6BQNIpe0%3D , then I'd put the 4700 pF capacitor in parallel with this switch, and this would be the main on/off switch of the amplifier as well?
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