Developing the DIY "Champ" for first time builders

[ChrisM]

Check out the Carling Progressive Switch RJ, it does exactly what you want.

[jhaas]

A couple other ideas to shave some off the cost -

Radial Electrolytics, as opposed to Axials
LED pilot instead of a jewel
Inline, interior mounted fuse holder instead of panel mounted. (If you're building an amp for yourself, and the fuse blows, IMO it's not a big deal to remove the chassis, because you'll probably want to get at the guts to investigate why it blew in the first place.

[jhaas]

The switch Chris referred to is AES: P-H520

The down side is you can't switch both PT primary leads which is seen as "best practice" these days.

[RJ Guitars]

The switch Chris referred to is AES: P-H520

The down side is you can't switch both PT primary leads which is seen as "best practice" these days.

thanks guys - this does exactly what we need and the price is decent.

rj

[RJ Guitars]

To address a couple other issues mentioned -

Radial caps - The price on these is killer and I think the function is probably equivalent to Axials for our purposes. It's hard to sort out if my preference for the axial installation is based on my old school prejudice or real. My intended longer term concession is the thought that I will ultimately do phases of this project that would lead to an even simpler and cheaper PCB based amp that would using radials.

We can knock down the overall price a little bit by going to a 22uF filter cap on the first B+ node. and a 10uF on the next two nodes. However I read somewhere (maybe in Gerald Weber's first book) that increasing the filter cap values in a Champ would have a negative impact on the tone. I am a skeptic but would be curious if anybody knows otherwise. This is getting down to the small stuff but if it doesn't torpedo anything it helps the cause.

Comments?

Speakers - Although this is outside of the discussion for making a $100 amp, it is a good discussion to have. We've already desecrated any hopes for keeping to the original Champ specifications so my first thought is that the bigger speakers tend to make better tone. I know that's a deeply flawed statement but buried somewhere in there is a useful trend. Keep the discussions going.

rj

[TheGimp]

As far as the switch goes, I believe a simple on off switch is sufficient. The amp is a practice amp, and as such won't be setting around for protracted periods between sets where a standby position is useful.

As long as the caps are rated for the initial voltage surge before the tubes heat up, there won't be any issue with overvoltage on them.

At this low of a B+ there wont' be an issue with cathode stripping so a standby switch won't help there either.

KISS.

[M Fowler]

I agree you don't need a standby switch.

[Zippy]

As far as the switch goes, I believe a simple on off switch is sufficient.

My blackface Champ just has a slider ON-OFF switch. Still original - no failures. That Carling switch looks much too elegant for a no-frills starter build. I'd rather put the extra couple bucks into, hmm, I don't know what - a nice knob?

[David Root]

Me too. I have a brown Deluxe, it has no standby switch either. It does use a 5AR4 rectifier though.

[TheGimp]

Just don't use those cheap Tiwan switches, I had two of them break in the last week. It seems they have a weakness in the design such that pressure directly on the front of the toggle breaks them.

[selloutrr]

switch - why not use a dp on - off - on switch so the standby and power are one switch.

filter cap values in a champ. i've experimented with this due to parts on hand the correct values are the better sounding moving them does cause stiffness.

speaker - its not the size of the speaker its the effiency how much spl/db at 1watt. keep in mind the champ is very low wattage so a speaker that requires a high amount of wattage to get loud will suck this amp dry.

radial caps.... they are just fine, its more about layout, or cap hieght then fuction or tone at this point. as said --- it's a price point.

[Structo]

Sounds like a neat project.

My 2 cents is, make sure that this amp is something that a person will enjoy playing after the building experience.

I know that is a tough prerequisite because you want to keep it simple enough for beginners but have it sound good enough for a decent guitar player to enjoy playing through it.

So maybe the larger speaker is the key here.

I know the few times I have plugged into an original Champ with the tiny speaker I was left disappointed by the sound.

[Zippy]

speaker - its not the size of the speaker its the effiency how much spl/db at 1watt. keep in mind the champ is very low wattage so a speaker that requires a high amount of wattage to get loud will suck this amp dry.

They won't "suck it dry", they just won't get very loud. On the other hand, a low efficiency speaker may be the way to go if one wants to push the amp yet not get REAL LOUD when playing guitar in their home.

[Zippy]

So maybe the larger speaker is the key here.

I know the few times I have plugged into an original Champ with the tiny speaker I was left disappointed by the sound.

I put a replacement/upgrade Weber in my blackface Champ and it sounds pretty good. A reasonable (ie cheap) upgrade is to add an aux speaker jack. A Champ running into a high efficiency 4-12 cabinet can be pretty nice too!

[selloutrr]

speaker - its not the size of the speaker its the effiency how much spl/db at 1watt. keep in mind the champ is very low wattage so a speaker that requires a high amount of wattage to get loud will suck this amp dry.

They won't "suck it dry", they just won't get very loud. On the other hand, a low efficiency speaker may be the way to go if one wants to push the amp yet not get REAL LOUD when playing guitar in their home.

that's what I meant I guess dry is not the correct term but all the amps output volume/wattage will be used up with little noticable change in precieved volume. Small speakers can sound great. like any speaker it's all about taking the time to break them in.

The champs are not a very loud amp anyway so even pushing them full out they would be IMHO a bedroom amp.

The nice part about the champ circuit is that if you don't like the tone of the amp- voice it with tubes until it's your cup of tea.
I - know from a price point the Solid state rec makes sense. I've never heard a champ solid state rectified so I can't comment possitive or negative on it. but I do know the sag and proper rectifier tube makes or breaks a true champ.