Hello all,
I recently built a BYOC 15watt 5F1 Champ 6L6 and housed it into a Deluxe pine cab w/a 12" WGS G12 C/S for a friend.
What an absolute beast!
So, for my next build, I'm collecting parts for the Tweedle Dee Champ circuit but with the 15watt/6L6 option.
The Tweedle Dee Champ uses 20uf/20uf/20uf electrolytics.
My question is: Would it be okay to try either a 30uf/16uf/8uf or 30uf/8uf/8uf?
My thought was that based on what I've read, a 30uf in the 1st position would reduce hum and tighten the low end without being too large of a value, 16uf or 8uf in 2nd position would either add or roll off bass and a stock 8uf in the 3rd position would preserve pick attack/touch sensitivity.
Thanks in advance.
Don't forget to ride the glide.
You can do anything you'd like with respect to filtering, and you'll know if it's filtered enough or not, but the bigger issue is that some of the tone of the tweedle dee amps is that he intentionally over filtered them to get it a bit cleaner overall. The original champ used 16/8/8, but he liked the 20/20/20 for really clean power supply to the nodes. I think there are other benefits.
You make the call. I don't think it costs a ton more for the 20 vs the 8 caps, so it seems worth it to me.
Phil,
Thank you for the speedy reply and helpful info!
I have not been able or source the Sprague 20uf 450vdc but was able to find some F&T 22uf 500vdc from Hoffman amps.
Hopefully, these will be sufficient for now.
Also, I'm trying to find where R8 (4th turret, 270k resistor) is grounded. Any ideas?
Looking through the really long original thread they have on page 13 a post of pics of a champ. It has a jumper shown there from that ground of the 270k and the cathode section of teh power tube over to the next power supply filter.
Thank you for digging that photo out.
I wasn't sure what to make of the schematic because there are a few ways to secure a ground from there. Run a bus wire, go underneath with a insulated wire, etc. Given that the transformer wires are grounded on the left side lugs, and the filter cap bus wire is split off, it looks like one of the the general themes with the Dumble 5f1 is to get the signal ground wires as far away from the power grounds as possible. The use of a brass plate is curious to me as well.
That's standard for fenders. He's just using what was there. yeah he was pretty serious about decoupling grounding from different stages. On the dumble ODS I built it has 5 different grounding points to keep each area well decoupled. One for input, one for PI, one for Power tubes and power filtering, one for the relays, one for the CT of the HT, if I recall. Something like that basically the higher current devices close to the transformer and the earth, and the more sensitive lower current stuff farther away.
Just finished the build the other day. Thanks for all of your help pompeiisneaks.
First off, the amp idles very quiet. Any hiss is barely detectable. Much quieter than the last 5f1 I built.
I played it through a 12" sealed pine extension cab with a an Eminence Red White & Blue. I find this speaker to be well balanced and generally full range.
However, I did make some mods:
-Several of the signal wires are grounded coax.
-I skipped the brass plate and created a solder ground all the way down to the right side wall which I used to ground B+2, B+3 and used the input jacks to ground R4/C7 as found on the original circuit.
-As an experiment, I relocated the fuse receptacle to the left sidewall and mounted a standby switch in the original hole so that the volume knob controls only the signal. I think separating the power from the signal leads helped to reduce noise.
-Bright cap across the volume lugs. I will likely continue to tweak this value with time and possibly put it on its own switch.
-NFB switch a-la Robinette mod. Currently just on/off but I'll likely put in a 3-way when I find the R values I like in addition to the Dumble 27.4k resistor.
-3-way Bias Capacitor DPDT switch: (down= 2.7k w/.68uf, center= 2.7k/3.3k in parallel, up= 2.7k/3.3k in parallel w/ 25uf) So, I'm getting both the 2.7k and roughly 1.5k R values off of one switch. There is a pop but it's not too loud. There really isn't enough space to fit a rotary make-before-break switch unless I remove an input jack but I like having the hi/lo input options.
So, in all, I really like the flexibility of tones achieved with the mods.
Last edited by Ridetheglide on Tue Aug 14, 2018 11:57 pm, edited 1 time in total.
Attached are a few gut shots.
Try not to laugh at my PTP bias/capacitor arrangement! This is just to get everything working.
I suppose a small auxiliary turret board mounted on the side wall would probably be a more permanent solution considering the vibration in a combo. I'll try to get some audio in front of a good mic when I finish the cabinet. I built a Champ with the same guts for a friend (minus the Dumble mods) who is recording with. So, at some point, I'll have a reference for comparison.
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Yeah, I agree.
I feel like I've paid my dues with building a couple of these now. Working inside such a small chassis is a tight operation.
I would enjoy more real estate to work with next time,
Otherwise, I'm contemplating the removal of the standby switch to just a basic on/off. From what I've read, it seems it's not needed.
Ridetheglide wrote: ↑Sun Aug 19, 2018 12:59 pm
Yeah, I agree.
I feel like I've paid my dues with building a couple of these now. Working inside such a small chassis is a tight operation.
I would enjoy more real estate to work with next time,
Otherwise, I'm contemplating the removal of the standby switch to just a basic on/off. From what I've read, it seems it's not needed.
Their only true function is as a mute, but you can install a mute switch that just grounds the signal path somewhere that accomplishes the same thing, and doesn't need to be a big mains connected clunking switch. The only thing standby switches can do, if implemented incorrectly is damage amp components
Why not use the Tweed Princeton chassis instead, there is more room and you get a tone control.
I don't think a single 6L6 can deliver 15 watts, I suspect the 15 watts is the rating of the output transformer. I use to use an output transformer with a 5K primary and I got 10 watts from it and the power transformer was hotter than the output valve. The volume difference between the stock circuit and 10 watts wasn't all that great and the 6V6's sound pretty cool.
The power supply, the filtering comes into its own when the screen grid conducts, a smaller filter cap means the rail drops providing some compression. HAD is trying to avoid compression.
The output transformer makes the biggest difference to these little amps. I would want to know if HAD used bigger iron?
Re:chassis.
Indeed, this build deserves bigger but it was a kit from BYOC that was on sale at the time so I grabbed it.
As I commenced the build, my imagination took over and I started adding extra features. I ended up with a 3-way bright switch, 3-way NFB switch and 3-way boost switch. I'll have to plan my next build on paper to see how much chassis real estate I may need.
The caps and resistors on the boost switch really deserve their own tag board. So, if I'm going to do that again, I'll likely seek out a rotary make/break dial and add in a few more combinations. (A-la Matchless). Maybe the same thing for the bright caps and NFB values. I really like having this sort of tonal flexibility in such a raw sounding amp. Not to mention, I'm still a beginner so I think the 5F1 simplicity helps me understand the differences of what I'm hearing.
By the time I'm done, I'll be the first dude to have built a Champ into a Twin Reverb chassis.!!
I would be interested in finding out what different transformer combinations would yield. I don't know that the 15watt transformers are much louder but I liked the option of using 6L6 or 6V6 tubes.
check out my Tweedle Dee build. I built into a great chassis from Mike at Modulus amplification. He posts world wide and carries everything you need component wise too.
Building into a head only was great, lots of room and I've fitted a the NFB 3 way switch too and changed one of the channels to high plate dumble values for a different flavour.
It's actually a very versatile amp. I've put 6L6's in.
