| DragonMaster |
Hi,
I'm planning to build "Tube Gainclone for DIY Buffs", but after losing a lot of time with P2P wiring of an other GC (Never finished, I'm starting over), I decided to build a PCB.
I have not marked the resistors and caps, and there are some that are going to be mounted on-chip, so they aren't there. But I'm not going to silkscreen the PCB and what I'm not sure of is mainly ground, in and out position, and if there are some components poorly positioned. |
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| dfdye |
It looks like you have the wrong package for a LM3875. I got tipped off when I saw the mute pin (which isn't on the LM3875), but I started looking at the other pins and it looks like you have something goofy going on there. I checked to make sure you weren't using the LM3886, but that didn't make much sense either. Double check your pinouts on your chip for starters. Also, I would put the bypass caps as close to the power pins as you can. That should at least get you started.
David |
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| DragonMaster |
Well, I'm using LM3886 with the tube scheme for 3875.
The Mute pin seems to have no place to go, but that's because I'm not sure if I'll use it or not. (If I do, the circuit will be on the PSU)
BTW, the PSU is going to be regulated, so, for the caps, I could use only 1000µF, or an other option instead of my original 10000µF plan. |
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| DragonMaster |
An other attempt, cleaned things a bit.
The hole going nowhere next to the output pin is for the part with 10k 100r 10k part that's going to be mounted off-board:
http://www.customanalogue.com/diytubegainclone/ps.htm
Also, for the pre and regulator, should they be on the same board? |
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| DragonMaster |
| Oops! Here's the file. |
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| phn |
| Antoine, have you tried Mick Feuerbacher's web site? You have the address already, but HERE it is. |
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| DragonMaster |
Yes, but I'm not as good in µsoldering as Mick. The Orange Drop I intended to use for the GC schematic I wanted to build first was kinda hard to solder...
I'll get the components first and see if it's easy to do something with them.
So, the PCB is a maybe??, but I think I'm going to use one anyways. |
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| Greg Erskine |
hi DragonMaster,
I think you need to look closely at the schematic and the LM3886 data sheet. There seems to be a few things wrong. For example, V+ should go to 2 pins and the mute resistor goes to V- not earth. It's a little hard to comment further without the proper schematic. ;)
regards |
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| DragonMaster |
| quote: | | For example, V+ should go to 2 pins and the mute resistor goes to V- not earth. |
Looked at a couple of designs and they never use both V+ pins...
It's not a mute resistor, but a resistor from Vin+ to GND. Mute is the pin next to it. I'll try to work on it a bit to make it easier to read... |
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| Greg Erskine |
| quote: | Originally posted by DragonMaster
Looked at a couple of designs and they never use both V+ pins...
It's not a mute resistor, but a resistor from Vin+ to GND. Mute is the pin next to it. |
We must be looking at different designs. :D The ones I look at always have pin1 and pin 5 connected to V+.
I've got my glasses on now - I can see its not the mute resistor now. ;)
regards |
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| dfdye |
What size output resistor are you planning on using? The pin spacing looks a little tight for a high wattage resistor that you would want.
David |
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| DragonMaster |
| I have no idea. All I know is that it should be 0.22ohm |
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| dfdye |
| quote: | Originally posted by DragonMaster
I have no idea. All I know is that it should be 0.22ohm |
I would recommend using a 5W resistor there (at least). All of the power output of the amp will be running through that resistor, and you don't want it to be strained in any way! If that makes your board unaccepatbly large, you can always mount it on the speaker output terminal.
David |
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| phn |
Antoine, I was actually thinking PCB. The 47 Labs PCB was to say it doesn't need to be fancy and that you can have components on both sides (like the FB resistor) even if the PCB is single-sided. A nice layout is helpful if you have dozens of components, but irrelevant here. I would recommend using one of those pre-printed PCBs. In this case one of those that has three holes connected. (I don't know the names for that stuff.) This would allow you to combine PCB and P2P soldering. Think short signal-path.
David, I will not argue. I have nothing to stand on. But are you sure 5W? I would think 1/4W is enough for the FB loop. And anything over 1W elsewhere would be excessive. I can be wrong. |
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| dfdye |
| quote: | Originally posted by phn
David, I will not argue. I have nothing to stand on. But are you sure 5W? I would think 1/4W is enough for the FB loop. And anything over 1W elsewhere would be excessive. I can be wrong. |
You are correct that for the FB resistor, 1/4W will be great, but I was talking about the output resistor needing to be larger. That one should have a higher rating since you don't want it being challenged when flowing high currents in the signal path.
David |
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| DragonMaster |
| OK, I've applied "components on both sides" more this time, it reduces the size a lot. The in capacitor is going nowhere for now : I think I'll put the tube stage on the PCB. |
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| DragonMaster |
| Now I need to draw a 9-pin tube socket custom component in ExpressPCB... I just don't know the good size... |
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