Fender Champ Modifications

[th3sku11]

A few months ago I bought and built the ampmaker champ kit (http://www.ampmaker.com/wf-55-4w-tweed-style-amp-830-0.html). I'm pretty pleased with how it went and was wondering if anyone knew of any mods that could be done? It sounds great cranked but at more modest volumes its a little too dark for my tastes.

So if there are any mods out there that could brighten it up and possibly add some more gain at lower volumes that the various amp experts on here know of I'd appreciate being pointed in the right direction!

Thanks!

Ken

[WezV]

have you asked barry? 

[th3sku11]

You know, that didn't even occur to me! D'oh! I'll drop him an email.

Cheers

Ken

[BigB]

So if there are any mods out there that could brighten it up and possibly add some more gain at lower volumes

Err... What about a treble boost ;)

[HTH AMPS]

assuming its this schematic... http://www.ampmaker.com/images/ak00kit/ak00sc2.jpg

try these...

* add a 25uF capacitor in parallel with R4 (the 1.5k cathode resistor on the first gain stage), this will add more gain.
* add a 100pF capacitor between lugs 1 and 2 on the volume pot, this will give a small treble lift (bright cap).
* remove R7 (22k), this is the negative feedback and is not strictly needed - you'll get less clean headroom and a slightly 'rawer' tone.

what I would do if you want lots of gain is to add another ECC83 (assuming the PT can take it), then you have four gain stages to play with - could make a mini-JCM800, complete with master volume.

[th3sku11]

So if there are any mods out there that could brighten it up and possibly add some more gain at lower volumes

Err... What about a treble boost ;)

Its an option for sure - i'd rather see what I can do with the amp itself being the big cheapskate that I am! ;)

[th3sku11]

assuming its this schematic... http://www.ampmaker.com/images/ak00kit/ak00sc2.jpg

try these...

* add a 25uF capacitor in parallel with R4 (the 1.5k cathode resistor on the first gain stage), this will add more gain.
* add a 100pF capacitor between lugs 1 and 2 on the volume pot, this will give a small treble lift (bright cap).
* remove R7 (22k), this is the negative feedback and is not strictly needed - you'll get less clean headroom and a slightly 'rawer' tone.

what I would do if you want lots of gain is to add another ECC83 (assuming the PT can take it), then you have four gain stages to play with - could make a mini-JCM800, complete with master volume.

Thanks HTH - exactly what I was looking for. I'll order some parts and give this a try. Will let you know how it turns out.

[HTH AMPS]

assuming its this schematic... http://www.ampmaker.com/images/ak00kit/ak00sc2.jpg

try these...

* add a 25uF capacitor in parallel with R4 (the 1.5k cathode resistor on the first gain stage), this will add more gain.
* add a 100pF capacitor between lugs 1 and 2 on the volume pot, this will give a small treble lift (bright cap).
* remove R7 (22k), this is the negative feedback and is not strictly needed - you'll get less clean headroom and a slightly 'rawer' tone.

what I would do if you want lots of gain is to add another ECC83 (assuming the PT can take it), then you have four gain stages to play with - could make a mini-JCM800, complete with master volume.

Thanks HTH - exactly what I was looking for. I'll order some parts and give this a try. Will let you know how it turns out.

no probs, glad to help.

[th3sku11]

Hi

Just thought I'd update this just in case anyone was interested. Shortly after posting the above I found this linked from the ampmaker site:

http://www.ampmaker.com/forum/viewtopic.php?f=21&t=32

It overlaps with the info which HTH kindly provided to some extent. I ordered some parts and have spent the evening tinkering. I have to say its been hugely enjoyable!

I really liked the fullness of the stock amp - cranked through my 4x10 it was great (I hope my poor neighbours agreed!). I really wanted it a bit gainier with more bite though at lower volumes and I think I managed to get it to where I wanted it to be.

I started off with 470nF caps across R4 and R6 - this straight away gave me the gain I was looking for and a nice top-end lift. I liked it but it did lose some of the bottom end. I put a 25uF cap across R6 instead and this thickened things back up a bit. I added the bright cap in the name of experimentation and this made the top end much more consistent across the range of the volume knob. I tried removing the feedback loop and putting it back which was interesting - a 'rawer' sound as HTH said and a bit of a volume boost.

Finally I tried a JJ ECC803s instead of the ECC83. This has quite a full but kind of 'grainy' mid range to my ears that I like but its never sat well in other amps. With the feedback loop removed though it sounded really great with my MQ loaded tokai love rock. Actually, I just had another wee go with it there and for ACDC type crunch its spot on. It doesn't really do anything else but I'm really pleased with it.

Anyway, enough of my yakking - hopefully this will be of interest to anyone thinking about trying one of these kits!