Fender Champ 600 talk

Mark · Post by **Mark** » Thu Dec 11, 2014 11:17 am

Previous post links.

http://ampgarage.com/forum/viewtopic.ph ... =champ+600

http://ampgarage.com/forum/viewtopic.php?t=21601

I've bought a second hand Champ 600. My initial reaction was it's okay but could need work. I have a Kendrick Roughneck which I turned into an 5F1 clone (to my ear the amp sounds nicer as a 5F1 with a mercury fat stack output transformer and Gerard's mods didn't work for me). The 5F1 clone also has a Weber ceramic Silver Ten speaker.

The 5F1 clone was louder and fatter sounding than the 600, Next I wanted to hear the 5F1 with the smaller 6" speaker, it was evident then that the poor distortion was due to the awful speaker break up. The 6" speaker was also quieter that the Weber Silver Ten.

The next step was to lose the Chinese tubes and try the Weber Silver Ten, to my surprise the amp sounded pretty good. This is a surprise as the transformers in this amp are tiny and the power transformer runs very hot after several hours use.

I had thought of putting the Mercury kit through the amp, but the speaker change has made such a difference, the tragedy is that I can't see how the Silver Ten could be fitted to this amp.

I'm keen to hear of other efforts with these amps.

Stevem · Post by **Stevem** » Thu Dec 11, 2014 11:32 am

Yes, speakers and tubes can make a big difference even with a tiny output transformer!
I have a early 60s single ended amp that was made by Philco radio that was of the type as many cheapos where back then and had no power transformer and ran right off the AC line !
I rebuilt it with a fairly big power transformer and and different tubes to take advantage of that and even with it's still tiny output transformer that put out all of 3 watts it sounds great, not much below 100 hz on the low end but real nice thru its Freeby 8 inch Atlas duel cone PA speaker!

Mark · Post by **Mark** » Thu Dec 11, 2014 12:10 pm

I had thought there might be some charm having a decent output transformer and the tiny speaker.

So far for these sort of amps the Weber Silver Ten seems ideally suited as it has such a good bass response for a 10" speaker.

I do have a spare Champ power transformer and a regular Champ transformer which is larger than the one in the Champ 600.

I will have to take photos on the weekend.

rp · Post by rp » Thu Dec 11, 2014 1:22 pm

Champ 600 = 5C1 = 6SJ7, maybe rebuild with EF86? Try the grid leak input, you already got a 5F1 right? Real ran much lower voltage than 5F1 don't know about reissue, but if lower expect less vim no matter what mods.

Stevem · Post by **Stevem** » Fri Dec 12, 2014 12:36 pm

I would go for a 6SJ7 set up and use a N O S tube, new EF86 tubes seem to have a life span of weeks in a combo amp and if you want one that will last then it's big big N O S bucks, where as the SJ7 is far less green and sounds better for guitar use to boot!

Blackburn · Post by **Blackburn** » Fri Dec 12, 2014 7:36 pm

Ooh haven't talked 600s in a while. I love these things, but when I switched to Weber's AlNiCo 6", I found that the cab resonates pretty bad. Not an issue with the stock Jensen (Which sucks by comparison). So much louder with the Weber as well. I actually changed mine up and put a rotary switch on the front for NF, less NF, zero NF and a bypass cap. I ended up selling the more recent one to a friend who plays harp. I like the idea of using the 6SJ7 as in the original. If I get my hands in another one, I may just do that.

Mark · Post by **Mark** » Sun Dec 14, 2014 2:02 am

I was wondering what the efficiency of the 6" Weber speaker was, my Weber Silver Ten is 95 to 96 dB SPL and I've compared it to my 12" Celestion blue which is 100 dB SPL and difference in volume is very noticeable.

Has anyone tried the Mercury kit in there amp?

The output transformer looks significantly larger which would help the bass response.

I suspect the other mods consist of getting rid of the negative feedback. I suspect the negative feedback network might be better than the circuit that is in the 5F1 as the second stage has more gain thus there can be greater control.

Mark · Post by **Mark** » Fri Dec 19, 2014 7:08 am

Post deleted due to moved links. No real useful content removed.

Blackburn · Post by **Blackburn** » Sat Dec 20, 2014 12:24 am

Mark, I clipped out the resistors that could be reused and tossed the boards.

I don't mind the stock trannies. They're there already and it's not a bad thing to reuse them. I'm sure changing the OT would have some desirable results, but I didn't want to put any more money into them, other than a straight up rebuild, plus the speaker and tubes. Very fun amps, but that cab has been a problem for me personally. I'll keep looking into ways to quell the resonance. Maybe an OT swap would be a good thing in my case.

I'm looking forward to seeing your progress with it.

Mark · Post by **Mark** » Sat Dec 20, 2014 12:27 am

Any pictures of your rebuild?

I'd be interested to see that.

Blackburn · Post by **Blackburn** » Sat Dec 20, 2014 12:50 am

One of the links in your OP is my thread, but I'll post some new shots with the rotary switch and maybe a new clip with better fidelity. The second amp in that thread is the one I sold to a friend that blows harp and it's the neater build of the two. I also put an spdt in that one for the same basic effect that my rotary switch does in mine. I just have an extra position for more NF.

Mark · Post by **Mark** » Sat Dec 20, 2014 4:37 am

Here are some of the Mercury pictures from their website. This gives an insight into their mods.

[img:730:548]http://www.mercurymagnetics.com/pages/n ... can045.jpg[/img]
The first cap has been changed from 22uF to 10uF. Notice the 10K power supply dropping resistor is now 4.7K ohms. The tone stack is gone, the 10K grid stoppers on the 12AX7 have been removed. The 470 ohm screen grid resistor has been removed. There is a 270pF silver mica cap across the output valve. The negative feedback circuit has been removed. There is a shot where the tracks have been cut with a Dremel.
[img:730:548]http://www.mercurymagnetics.com/pages/n ... can069.jpg[/img]
I'm surprised the filter caps are all the same given there is a choke inserted in the power supply. I'm not sure if the power supply transformer would handle it, but the first filter cap could be changed to 100uF and this would make short work of the power supply ripple.

Mark · Post by **Mark** » Sun Mar 15, 2015 9:41 am

I did decide to get the Mercury kit, it is expensive, but Mercury are usually a quality product so that is of some consolation.

The speaker is the ceramic Weber Signature series. The Weber is on the left and the stock Eminence is on the right. The stock speaker sounds dreadful when pushed, the Weber doesn't have this problem and is an immediate improvement (mind you there is always someone who disagrees.

)

[img

766]http://i149.photobucket.com/albums/s69/ ... ri1olv.jpg[/img]
[img

766]http://i149.photobucket.com/albums/s69/ ... 09nnab.jpg[/img]
The next difference is the output transformer, it's a no brainer that there will a world of difference between these two transformers.

[img

766]http://i149.photobucket.com/albums/s69/ ... sftbid.jpg[/img]
The immediate effect was the amp was noticeably louder and there was much more bass and mids, I think the highs were a bit better too, but I was quite happy with the highs from the stock transformer.
[img

766]http://i149.photobucket.com/albums/s69/ ... vkt3zl.jpg[/img]
[img

766]http://i149.photobucket.com/albums/s69/ ... cvzzyw.jpg[/img]
This is where I am up to. I haven't put the choke in or done any of the mods. I'm actually a little suspicious of the mods and I think transformers and speaker are doing the heavy lifting with regard to mods to this amp. This is why I've decided to first try the speaker then the output transformer. The transformers and choke will go in before I carry out the mods and these will be done one at a time to evaluate each mod.

I'm more interested in the learning experience rather than do it all in one hit and listen. At this point in time I'd be happy with the speaker and the output transformer, but time will tell.

Mark · Post by **Mark** » Sun Mar 15, 2015 8:33 pm

delete.

Mark · Post by **Mark** » Sun Mar 15, 2015 9:33 pm

Deleted. I tried to edit the missing pictures in a previous post and unfortunately I created a new post. Sorry for the inconvenience. I'm wondering why when I edit the photos the platform creates a new post?

For reference sake here are the pictures comparing the stock Champ 600 transformer set to a stock Champ 5F1 set.

[img

766]http://i149.photobucket.com/albums/s69/ ... cf2fa4.jpg[/img]

[img

766]http://i149.photobucket.com/albums/s69/ ... cd732d.jpg[/img]

[img

766]http://i149.photobucket.com/albums/s69/ ... fa31d8.jpg[/img]

Stock board

[img

766]http://i149.photobucket.com/albums/s69/ ... jyvfto.jpg[/img]

[img

766]http://i149.photobucket.com/albums/s69/ ... d9e260.jpg[/img]