[First Build] Sluckey AC4 - Warning! Real noob questions.

[rockaffe]

I admit that I'm a little embarrassed to open this discussion, given the high level of knowledge that exists in this forum, but I have to start somewhere...
Even though I don't have an academic background in electronics, for a few years I've been experimenting with building guitar effects and some small, well-known amplifiers (ruby, little jem...)
As per the title, for my first build I chose, after a very long evaluation period, the Vox Ac-4 and I found the layout attached.

I have more or less everything clear, but since both the schematic and the layout don't specify some values ​​(which will surely be obvious) and there are a couple of components that I've never seen, I prefer to ask rather than make mistakes.

So here are my questions:

Is it okay to use 1W and 3W resistors for the slightly larger ones on the layout?

Are the film capacitors okay at 600v?

What voltage do the 3 25uf capacitors have?

And finally two questions about two components: what is that yellow-orange bar on the far right of the layout?
And what is the circular component on the bottom left circled in blue?

I thank anyone who finds time to help me in this first experience of mine.

Hi!

[moosetone]

Some of your questions are answered by looking at the original schematic (attached as a PDF).

The round blue object at lower left is a 32uF/32uF can capacitor. The resistor on it is 1K 5W.

The yellow-orange bar at right is shielded cable. Note that the shield is attached to ground only at the shield of the input jack.

600V film caps are fine. The 25uF electrolytics are listed at 12V on the schematic. 25V or 50V would be fine (I use MOD 25uF/50V caps).

Lastly, it doesn't hurt to increase the size of the resistors, just don't go lower.

[rockaffe]

Some of your questions are answered by looking at the original schematic (attached as a PDF).

The round blue object at lower left is a 32uF/32uF can capacitor. The resistor on it is 1K 5W.

The yellow-orange bar at right is shielded cable. Note that the shield is attached to ground only at the shield of the input jack.

600V film caps are fine. The 25uF electrolytics are listed at 12V on the schematic. 25V or 50V would be fine (I use MOD 25uF/50V caps).

Lastly, it doesn't hurt to increase the size of the resistors, just don't go lower.

Thank you, your answers are really helpful!

[sluckey]

You may want to use the schematic that's included in my VAC-4.pdf. It contains notes about my FWB rectifier and the optional INTENSITY control.

[rockaffe]

You may want to use the schematic that's included in my VAC-4.pdf. It contains notes about my FWB rectifier and the optional INTENSITY control.

That's exactly the one I'm using, so a double thanks for you!
Even though I doubt it, I hope I won't need any more help, otherwise I'll abuse your kindness again.

Ciao!

[sluckey]

You may want to use the schematic that's included in my VAC-4.pdf. It contains notes about my FWB rectifier and the optional INTENSITY control.

That's exactly the one I'm using, so a double thanks for you!
Even though I doubt it, I hope I won't need any more help, otherwise I'll abuse your kindness again.

Ciao!

I should mention that I have not built this. You may be the first. I'm very interested to see how it turns out, especially if you decide to install an Intensity pot since it's not proven but works on paper. I would also like to see some pics of the completed project.

[rockaffe]

You may want to use the schematic that's included in my VAC-4.pdf. It contains notes about my FWB rectifier and the optional INTENSITY control.

That's exactly the one I'm using, so a double thanks for you!
Even though I doubt it, I hope I won't need any more help, otherwise I'll abuse your kindness again.

Ciao!

I should mention that I have not built this. You may be the first. I'm very interested to see how it turns out, especially if you decide to install an Intensity pot since it's not proven but works on paper. I would also like to see some pics of the completed project.

Of course I'll post the completed project and yes, I've decided to install the Intensity pot.
Probably this project will takes a long time, mainly because I'm struggling finding sites (in Europe) to buy the parts I need and also because being at my first build I have to understand what some components on the layout actually are and how to mount them.
And now, some more noob questions:

1) Waiting for the material for the eyelet board I drew the board on eagle. Is it ok to use an etched board or is it better (or mandatory) to use the eylelet board?

2) In the schematic there's a 1M resistor after the 100k input resistor, but in the layout it's placed before. Is it ok?

3) What's the component in the image?

Thank you to whoever will answer :)

[nholme]

Hi, I have just spotted this thread and so have joined the forum.

I built an AC4 a year ago but was never quite happy with it so shelved it and built a few other valve amps that turned out much better. I have just had a look at my AC4 and find on measuring the voltages that they are way too low. There may also be other issues.

If you are interested I will post photos and will happily make changes if this will help. I'm also likely to try the intensity mod as I found the vibrato to be too aggressive.

[tubeswell]

You may want to use the schematic that's included in my VAC-4.pdf. It contains notes about my FWB rectifier and the optional INTENSITY control.

That's exactly the one I'm using, so a double thanks for you!
Even though I doubt it, I hope I won't need any more help, otherwise I'll abuse your kindness again.

Ciao!

I should mention that I have not built this. You may be the first. I'm very interested to see how it turns out, especially if you decide to install an Intensity pot since it's not proven but works on paper. I would also like to see some pics of the completed project.

Of course I'll post the completed project and yes, I've decided to install the Intensity pot.
Probably this project will takes a long time, mainly because I'm struggling finding sites (in Europe) to buy the parts I need and also because being at my first build I have to understand what some components on the layout actually are and how to mount them.
And now, some more noob questions:

1) Waiting for the material for the eyelet board I drew the board on eagle. Is it ok to use an etched board or is it better (or mandatory) to use the eylelet board?

2) In the schematic there's a 1M resistor after the 100k input resistor, but in the layout it's placed before. Is it ok?

3) What's the component in the image?

Thank you to whoever will answer :)

I suggest plagiarising a Vox AC4 layout, which is ‘proven’ and less likely to result in unwanted/parasitic signal coupling. Keep the input away from the high VAC parts of the circuit etc.

[shooter]

here's a couple of plagiarized pdfs to help that along

[sluckey]

1) Waiting for the material for the eyelet board I drew the board on eagle. Is it ok to use an etched board or is it better (or mandatory) to use the eylelet board?

2) In the schematic there's a 1M resistor after the 100k input resistor, but in the layout it's placed before. Is it ok?

3) What's the component in the image?

1) Your choice. I prefer eyelets because they are more rugged and easier to change components.

2) I was just copying the original schematic. The layout is preferred because it will deliver 100% of the guitar signal to the grid. The schematic shows a voltage divider that will only deliver 90% of the guitar signal to the tube.

3) The third pic shows the input jack with the 1M resistor. The fourth pic shows an insulated standoff turret with a ground lug. They are attached to the chassis with a screw and kep nut. You could use a simple terminal strip. The attached pic shows such a standoff turret...

[sluckey]

here's a couple of plagiarized pdfs to help that along

Both of those schematics are very different from the original Vox AC-4. Neither use an EF86.

[shooter]

 
yep, hence the label;

plagiarized

did work on one, the owner thought it was great, I thought it was a money maker for someone

[tubeswell]

Some interesting information on this page


http://www.voxshowroom.com/uk/amp/ac4_hood.html

[Kesi from Hungary]

I built the ac4 by reusing the PT and choke from an old tube tape recorder. For the rest, Sluckey's layout was used as a guideline, including the intensity control. And it works well. I can adjust it nicely to my liking.