Quieting Down a DIY 5F1 Champ(First my Son's Champ, now mine!)

[Platefire]

I build an 5F1 Champ for my Son about 10 years ago when I first started building amps. He is wanting to use it more but wants to get some of the normal champ hum out to use it also for recording.

He sent me a link to Marsh Amplification "Reducing Noise in Tweed 5F1" at the link as follows:
http://www.marshamps.com/5f1noise

It's main focus is twisted heater wires and installing an virtual center tap if needed, using sheilded input wires from input up to the second stage preamp and also increasing the filter cap values on the first and second stage of filtering(OT and Screens)

OK-It already has the twisted heater wires and has a heater center tap-check. I can change the hookup wire out to shielded as they recomend-check.

On the filter caps they recomend for diode rectifier first main filter 100uf/500v(improve low end tightness), 40uf/450(no real change in tone) for screen supply and no change on the preamp filtering 8uf/450V. So my question is does this sound right on the filtering? My son does have a plug in SS rectifier he uses sometimes but mostly uses a 5Y3. IMHO 40uf/40uf or 40uf/20uf would be less a drastic change? Has anybody had any experiance with this? Platefire   

[PRR]

Increasing the existing caps is brute-force with poor leverage.

Humongious first-caps still have a lot of ripple.

+Add+ an R-C section in front. First-cap reasonably-large (not gigantic). Then the added 250 and now-second 40uFd will knock-down first-cap ripple another 14:1 before it goes to the OT/6V6. Net result is 35 times (31dB) less buzz at OT/6V6... from "some" to "none". The screen is reasonably well filtered already (due to large 10K resistor) but with today's cap-prices you may as well round-up from 8 to 20uFd. Voltage ratings similar to the voltages you measure now plus a margin for high wall-voltages in studios or other dives.

[Platefire]

Hello PRR

One thing I noticed about you and I---we seem to do our posting late-late 

Thanks for the nice schematic and explination. My problem with that plan is finding the space for the extra cap and resistor. Not saying it's imposible, just will have to get real inventive. The noise reduction you indicated looks sizeable and desirable as long as it don't hinder the normal champ tone response much. I see you did leave the last 8uf stage intact. I'll talk this over with my Son. Thanks, Bob

[stratele52]

Before put more filtering , how did you build this amp ?

Good  wiring and component installation  it a must. Resistor, capacitor and wire going to tube's grid must be very short. if not they act like antenna.,

Did you use shorting jack for guitar input ?

Can you send us some photo of your wiring , inside the amp

[Platefire]

  Well I admit this amp was done early in my amp building experiance. I learned a lot since then. So re-checking the lead dress and grounding will be one thing I do. I did do it under the direction of a very knowlegable and experianced Casey4s. In fact he hand built the kit himself for me and I just put it together and he was advising me through the whole process. So I think its pretty much assembled OK.
   I don't have my Son's amp presently in my possesion. We have been talking about it by phone. He's also talking about replaceing the coupeling caps with sozo--so we are trying to get all the needed mods figured out so I can do it all at one time when he brings the amp down. Attached is a Flicker link to that project photos that does have some not so good pictures of the circuit. Platefire
  http://www.flickr.com/photos/12623503@N04/sets/72157601870694030/with/1328143458/

[stratele52]

Sorry photos can't help , Poor resolution and no close-up.

[Platefire]

Har! He must of read this post because he sent some new pixs. Here they are:

[woolly]

Yeah! In 2002 I also learned board building from Caseys4 tutorial available at the time.

 is he still here?  thanks.

[tonewood]

+Add+ an R-C section in front. First-cap reasonably-large (not gigantic). Then the added 250 and now-second 40uFd will knock-down first-cap ripple another 14:1 before it goes to the OT/6V6.

Thanks for the drawing, I'm going to try it with mine. I'm calculating that the 220-330 ohm only needs to be a 2 watt. Am I miscalculating? (I'm short on 5W space).
Thanks.

[Platefire]

I think if I mounted a terminal strip between the brass ground plate and the end of the board, I could mount the extra 40uf cap on the terminal strip and run the 250 Ohm/5 watt resistor from terminal strip cap + to existing 16uf location. Of course the 16uf and next 8uf would be changed out to 40uf and 20uf. I believe I can make that work! Attached is a rough sketch of the plan. Platefire  

Woolly: I exchanged e-mails with Casey4s about a year ago. He was doing alright then best I could tell. He was testing effects pedals for some company and doing reviews for them. Great
Guy! Platefire

[PRR]

> only needs to be a 2 watt

At start-up, the first cap comes to (say) 400V very quickly due to high current available from PT, the second cap starts from zero and charges through (say) 250 ohms.

So at that first instant the power dissipation is 640 Watts !! (400V in 250 ohms.)

The second cap will be largely charged-up within 0.01 seconds. That's actually fast enough to shave the apparent 640 Watts, but the math is tedious. There's also PT resistance.

Duncan PSU shows:

Peak of 293V 1.33A or 390 Watts near 0.05 seconds after turn-on.

RMS-averaged over first 0.1 seconds, 86V 0.34A RMS or 29 Watts. Over first second, 4.6 Watts. Over first 10 seconds, 2.15 Watts.

Yes, resistors will take short-term overloads. But the spec is usually 10X, not 390/2 or 200X.

If you ever had these filter resistors blow "for no reason?", that's why. Smack a 2W with 390 Watts for an instant, it doesn't smoke, but it gets micro-cracks. Do it 2 or 20 or 200 times, the crack goes right through and it quits.

_39W_ is the for-sure safe size. However we know from experience that the 10X spec is conservative. Basically we don't turn-on as often as some industrial punch which might apply thousands of overloads an hour 9-5 M-F.

Even long-term you have 1.9 Watts. A 2W part is going to fail.

[stratele52]

Sorry but there is a poor lead dress.
Easy to understand you have some noise.

Wires going to the small preamp tube are like an antenna.

And  many other wire are un-properly dress.  Some shielded wire will help.

Don't spend money on other cap until you fix that first.

[Willabe]

Can't we use a small value R, like 10 or 20 ohms at 5w as the first thing in the B+ PSU to knock/slow down the inrush current a little and then be able to use a lower wattage for the 250R safely?

Would this give a little extra margin of safety/longer life to the 250R at 5w listed value in PRR's reply #1?

                    Brad        

[Platefire]

Well my Son(Greg) wants to proceed with PRR plan. I will also be installing sheilded wiring in the input/preamp section, addressing lead dress issues and installing a couple of sozo .022 coupeling caps.


On another note----This amp presently has a Weber 10F150T speaker that has a ribbed cone for extra treble. This is a little to bright for him. He's looking for a 10" that will compliment the champ tone with a little more thickness and a little less harsh highs. Weber Silver Bell had been a consideration but not tried yet. Any suggestions on what might fill the bill? Platefire

[PRR]

> 10 or 20 ohms at 5w as the first thing

How does that help?

[Willabe]

How does that help?

to knock/slow down the inrush current a little and then be able to use a lower wattage for the 250R safely?

 
               Brad      

         

[HotBluePlates]

What PRR's really getting at is you already have a comparable amount of resistance in the PT secondary winding (even more if you add the PT primary resistance, referred to the secondary).

So you're not doing much by adding the 10-20Ω resistor except adding something else throwing heat in the chassis.

[Willabe]

OK, thanks. Just a thought.


              Brad     

[Platefire]

Regarding these mods on installing sheilded wire. I've had some experiance installing shielded but not a whole lot! So I understand that you only ground one end. So far when I have installed sheilded wire on an input its has always been in a case where the wire went straight from input jack to the preamp tube attached directly to the grid stopper resistor that was connected directly to the tube socket pin #2.

In this case we go from jack to board turret--68K grid stopper resistor--board turret to tube pin #2. It almost seems like your defeating your purpose with the exposed resistor on the board right in the middle of your run to the 1st stage preamp? Is that Ok, or should I bypass the board and go staight to the tube with my sheilded and 68 K R to tube socket?

So the rest of the sheilded run from #1 Plate to board turret-coupeling cap-board turret to volume control/tone stack. Same situation here only exposed turrets and cap on the board?

Also should the sheilding continue from volume/tone stack to second stage preamp?

Just trying to get my ducks in a row before I do this. Thanks, Platefire
 

[stratele52]

Regarding these mods on installing sheilded wire. I've had some experiance installing shielded but not a whole lot! So I understand that you only ground one end. 

ANSWER ; YES

 .. or should I bypass the board and go staight to the tube with my sheilded and 68 K R to tube socket?

ANSWER ; DO LIKE THAT

So the rest of the sheilded run from #1 Plate to board turret-coupeling cap-board turret to volume control/tone stack. Same situation here only exposed turrets and cap on the board?

Also should the sheilding continue from volume/tone stack to second stage preamp?  ANSWER ; YES


Just trying to get my ducks in a row before I do this. Thanks, Platefire
 

Keep the "center " wire of your shield wire as short as possible 1/4 inches. 

[Platefire]

Getting Preped to work on this Saturday. I was wondering on installing sheilded cable on the input to the first preamp stage, I'm thinking of doing away with the second input jack and that way it would be direct with no other connections from the jack to 68K R(maybe 33K better?) connected directly to V1. Run the sheilded right accross the top of the board by the existing abandoned in place 68K Resistors to its destination. Please take a look at the previous pixs and see if you agree. Thanks, Platefire

[stratele52]

On your photos I see that you don't use shorting jacks with 1 meg resistor to ground , you must use it to kill noise.

[HotBluePlates]

Save time, just add the extra C-R filter.

I'll bet $100 the hum goes down. Others on this board have made the same exact change and reduced hum.

[Platefire]

Well I guess your going to have to spell it out for me--not reading C-R Filter? Capacitor-Resistor?
I am planning on adding an additional Filter Caps and resistor more or less like PRR proposed.

So your saying the champ humm is coming from the old under-filtered situation accociated to the tweed champ?

The plan is still in accordance with this pitiful sketch:

[John]

Platefire, I think that yes, he means the extra cap and resistor that PRR inserted in that schem from his post. That extra cap should reduce your hum quite a bit.

[sluckey]

Don't forget to move the red wire from the standby switch. Move from the board to the junction of the 250 ohm resistor and the new cap. Leave the OT connected to the board. You probably knew this. Your pic was not obvious to me.

[Platefire]

Yeah, Thanks sluckey! One of the hardest parts of doing this will be un-doing my inexperiance in those days with multiple wraps of component leads around turrets, globs of solder, poor lead dress and about everything else you can think of a green horn does. I've got my solder sucker, solder wix, iron ready and will need a big dose of patience. Platefire

[Stankfut]

Just to jump in....i used a four section cap can when I rebuilt my kay 703. I used a similar cap and resistor setup as prr mentioned and connected the ot to the second node.....amp is really hum free. I always add extra filtering to se amps fwiw

[HotBluePlates]

So your saying the champ humm is coming from the old under-filtered situation accociated to the tweed champ?

Well, yeah. That, and this was a student-level amp to play with your new Fender Champ lap steel...

First, it's a single-ended amp; there's no cancellation of power supply hum in the output transformer, as there is with push-pull. And the more expensive push-pull amps were targeted at gigging musicians and professionals, and had such expensive frills as a choke to reduce the ripple at the screen node (a BIG ripple here can introduce hum into the output section).

But hum was also mitigated in the original Champ with a 6" or 8" speaker and a tiny cabinet, which didn't really have good bass response down to 120Hz. So overall, it didn't seem to bad, especially in comparison with other similar entry-grade amps.

But we now want to crank up Champs and give them nice 10" or 12" speakers (some people even play a Champ through a 4x12" with surprising volume). The better speakers and larger cabinets start to reveal the extra hum, especially if you're accustomed to higher-quality designs with less hum.

So while you're paying more for all the other upgraded bits, you really have to add another capacitor and resistor ahead of the plate node to knock the hum down to acceptable levels.

[jojokeo]

So while you're paying more for all the other upgraded bits, you really have to add another capacitor and resistor ahead of the plate node to knock the hum down to acceptable levels.

This is THE standard "power supply design 101 for SE amps" as we know it. Fender (& other makers of the day) saved money by their design method, the slight hum/noise trade-off wasn't nearly as big a deal as were the $$ savings. Most know how frugal Leo was. Filter caps weren't cheap back in Fender's day - and still aren't today! Modern SE amps' power section should not be designed how Leo did it and should be as PPR's schem shows. BUT, that's not all as far as Leo's methods that were less than ideal. His heater wiring, component layouts, lead dress, grounding, etc. all had flaws but he worked though these challenges to accomplish his goals and yet he still made great amps that performed well. It also proves that there's not just one way to build a nice amp.

[Platefire]

Yeah, I'm beginning to think that abandoning the two 68K's input grid stoppers on the board and installing a sheilded cable from the main input jack to the maybe a 33k soldered direct to the #2 grid pin may be a waist of time(Like HBP said). I probably should just install the new caps and 250/5 watt resistor first and see if that does what is needed. Platefire

[jojokeo]

Plate - I rarely ever plug into the 68k input if an amp has one and I always design/build everything running the shielded cable to 33k resistor soldered directly to socket - standard way of doing things. Sometimes this is lowered to 22k or 15k depending on amp/tube in V1.

[smackoj]

I just changed my SE Supro Super Six to include PRR's C and R mod. It worked great and the amp can now even handle noisy fender single coil pups that like to buzz and hum. Here is the Supro (Valco) Super Six schem. if anyone wants to try this one?  The Triodestore.com has a reproduction OT for this exact amp made by Mag Components. I like it and it doesn't break the bank.

Have a blessed Sunday.  Jack D

    

[Platefire]

We also did the mod this weekend, busy now will talk and post pictures later. Plate

[Platefire]

We did the mod this last weekend. My son Greg brought the amp down Friday night and we demo-ed old filter caps and installed the new caps/resistor that night. He was looking over my shoulder and lending a hand when needed. The funny thing that happened was after we got the filter caps and 250 Ohm resistor installed we decided to do a test. We hooked it up to the speaker cab with nothing plugged in and flipped it off of standby---nothing! My heart kind of sank becasue I was looking for smoke or what I may have hooked up wrong. Greg got a cord, plugged it in and touched the opposite end with his thum--and buzzz--that was a relief! So he grabbed a guitar and plugged it in and it was working fine--only without noise. Even full volume with only a hint of noise. Needless to say Gregg was very happy.

We installed the Sozo caps next morning tested again got a short scare when we couldn't get it to work but a speaker lead had fell off. Everthing was find after attaching the speaker lead. Couldn't tell a lot of difference between the orange drops and the Sozo. I was then ready to install the sheilded input wire but he chose not to do that. Can always install it latter if needed. Thanks very much PRR for supplying the plans. Platefire

[HotBluePlates]

So I'm guessing you're a believer in the extra filter cap ahead of the plate now? 

[Platefire]

Well I haven't done it to my DIY Champ yet. I played on Greg's quit a bit before he took it home. He liked the SS rectifier in it. He was going for getting the biggest loudest sound out of his champ he could and was shooting for little cleaner headroom. We tried several tubes--JJ 6V6, EH 6L6 and Tung Sol 5881. On preamps a EH 12AX7 and GE 5751. He left the GE 5751, Tung Sol 5881 and Weber SS rectifier in there.

I hate to make judgements on a bedroom test. To me a band situation forces you into another situation where its got to compete with a drummer, bass amoung other things which and I didn't do. In my test if felt a little stiff at about 1/3 volume and loosened up a little better at 1/2 vol. I like a nice response at pretty low volume. The champ hum is not that big of issue with me but I do enjoy a quiet amp. It's something to consider! I'll be interested in hearing Greg's opinion when he works it with his band. Platefire  

[kagliostro]

Sorry for the intrusion

a guy that I know has the same noise problem with his 5F1 clone

I would like to use the PRR mod adding the extra capacitor and resistor

What about the max value of the first capacitor in reference with the used rectifier tube ?

Which is the tube used before of the SS rectify ?

as from datasheet 5Y3 max first cap value is in order of 20uF, a change of rectifier tube is a must as to use the PRR mod ?

Thanks

K

[sluckey]

I'd stay with the 5Y3 if using a 6V6. Unless you just want to run a higher B+. If you do want higher B+ use a 5AR4.

Adding another 20uF and a 250Ω will still give much hum reduction. BTW, I've used a 33uF with 5Y3 in many of my builds with no problems.

[kagliostro]

Hi Steve

Many thanks for sharing your experience

I'll go with a 33uF 

K

[Platefire]

I got my DIY Champ out last night I built in 2001 and gave it a good listen. Its noise floor is just not bad enough to me to warrent the cap change. Very slight hum but not bad and it don't get louder as I turn the amp up. So for now I will leave it as is.

One thing I did notice is the JJ 6V6S I had in there was extremly bright. I don't know if it just me but it seems every JJ power tube I've tried lately seems way to bright?? Why am I just now noticing that? I tried a old GE 6V6 that sounded great but it started red plating. Also an EH 6L6 that was pretty good. The best that I left in there was a vintage RCA 6L6GT---real nice. I really would like to find a new 6V6
that isn't way bright like the jj. Any suggestions? Platefire

[PRR]

> it don't get louder as I turn the amp up

Then the hum in the output stage is greater than the maximum hum in the preamp. You could do better. Of course if it is acceptable, then don't.

[Platefire]

PRR---Your statement "You could do better" reminds me of a term we used in Government Contracts for inspection using the "Performance Requirements Summary"(what the contractor could get away with before corrective measures were taken) which specifies a "Acceptable Level of Deviation". I guess for my purposes the champ noise floor is my "Acceptable Level of Deviation".  

One of my all time favorite Government terms is "Overcome by Events"  

[xm52]

I'm wondering if you are seeing any flash over in the rectifier tube when you first turn on the amp and the PS caps are discharged. You see if as a brighter flash when you turn on the amp. If yes, it can harm the tube. This can happen when larger capacitors are in place than what the tube rectifier can cope with. This can usually be fixed by adding two diodes (1N4007 is fine) in line with the plates of the rectifier tube. You can see an example of how they did this in the reissue '57 Fender Deluxe (http://support.fender.com/schematics/guitar_amplifiers/57_Deluxe_Fender_57_schematic.pdf). The diodes serve to protect the rectifier tube. Not a bad idea to install them.

[Platefire]

Well we are discussing two DIY champs here practically identical originally. My son's champ that we moded was using a Weber SS rectifier in his. So if there any feedback of electrical current to the rectifier there wouldn't be no obvious flash and of course in my champ is all original cap set up like tweed era amp complete will classic champ hum;>/ which is "My Acceptable Level of Deviation"  Thank you Leo.  

[Platefire]

Talked to my Son Greg today. He said he tried his modified Champ out with his band. Looks like it didn't quiet cut the mustard in getting enough clean headroom to compete with his drummer. He said the amp sounds great but the clean stuff he plays is a little too distorted when he turns it up loud enough to get over the drummer. This is un-miked and would probably work that way with the support of a good PA man--which he don't always have. Platefire

[Ed_Chambley]

Well my Son(Greg) wants to proceed with PRR plan. I will also be installing sheilded wiring in the input/preamp section, addressing lead dress issues and installing a couple of sozo .022 coupeling caps.


On another note----This amp presently has a Weber 10F150T speaker that has a ribbed cone for extra treble. This is a little to bright for him. He's looking for a 10" that will compliment the champ tone with a little more thickness and a little less harsh highs. Weber Silver Bell had been a consideration but not tried yet. Any suggestions on what might fill the bill? Platefire

The Weber Silver Bell by itself is very midrange limited.  I have a champ with a celestion blue and it sounds very close to the 12 and it is not harsh at all.  The silver bell 10 is sort of flabby.

[Willabe]

Looks like it didn't quiet cut the mustard in getting enough clean headroom to compete with his drummer. He said the amp sounds great but the clean stuff he plays is a little too distorted when he turns it up loud enough to get over the drummer.

It's a Champ, not built to have clean headroom over a drummer. It was a student model amp.

Drives me crazy, big, loud amp needs to be quiter and small quite amp needs to be louder.

Need a bigger pay load then he needs a bigger truck.


              Brad     

[Platefire]

That's why I hang on the my Pignose G40V that I moded from a 10" speaker to a 12". It's smaller than my DIY Champ and has 40 watts of good fender(5f6A/MV) sounding get up and go. If I need a little power in a small package, that's what I grab.

On Greg's amp, I told him we have stretched the champ circuit about as far as you can go without changing it to something else. Any more milage would have to be accomplished maybe by more efficent speaker as Ed suggested. Platefire

[dinkotom]

I'm wondering if you are seeing any flash over in the rectifier tube when you first turn on the amp and the PS caps are discharged. You see if as a brighter flash when you turn on the amp. If yes, it can harm the tube. This can happen when larger capacitors are in place than what the tube rectifier can cope with. This can usually be fixed by adding two diodes (1N4007 is fine) in line with the plates of the rectifier tube. You can see an example of how they did this in the reissue '57 Fender Deluxe (http://support.fender.com/schematics/guitar_amplifiers/57_Deluxe_Fender_57_schematic.pdf). The diodes serve to protect the rectifier tube. Not a bad idea to install them.

I may be wrong, but aren't the diodes connected differently on the first page schematic (which seems correct to me), than on the other pages (SERVICE MANUAL DOCUMENT  5/31/07), which seems backwards?