Hello Everyone,
I built a 5F1 champ clone and it sounds good but I think it could sound better. I am looking for ways in which to tweak the circuit in order to get better distortion sound.
The main problem I have with the current sound is that the distortion does not seem that pleasing or smooth… the clean is beautiful, but when pushed, it seems to give a kind of harsh distortion sound, most noticeable with chords. Soloing sounds pretty darn good, but even so, it lacks the dynamics, crunch and definition I imagine it could have.
Since this is my first build, I am wondering if I am doing something wrong, like running the tube at a bad operating point? I assume this is possible. I wouldn’t know how to change it. I just copied the vintage 5F1 circuit and used carbon film resistors, Zoso coupling caps, Sprauge cathode bypass caps, Sprauge Atom filter caps and Hammond transformers. This all goes to a Jensen 10” alnico reissue speaker. I tested with a Les Paul and a Stratocaster.
I notice my plate voltage on the 6V6 is 380 volts. This seems high to me. Is it possible that this is contributing to a harsh sound? I think this voltage is higher than what the actual vintage amps were used to seeing back in the days in which they were made. I know that some people use Variacs to lower voltage… evidently this gives a different, often described as more desirable tone. But this would also lower filament voltage.
I am wondering if there is an easy way for me to lower the plate voltage (and screen too?) in order to simulate that Variac lowered “brown” tone that many speak of. Can I just merely insert a resistor in series with the plate supply?... and screen supply? If so, I am kind of confused about how to go about calculating the value needed to drop say 20 volts at the plate? Would it even make a difference?
I have also considered that the Jensen speaker might be the culprit. Unfortunately, it’s the only one I have right now. I am thinking Celestion or Weber might be better for distortion?
Also, there is barely 20 hours worth of playing time so far – do I need to wait for caps and speaker to settle in?
Any help or advice in regards to any of this would be greatly appreciated.
Thanks !!
I built a 5F1 champ clone and it sounds good but I think it could sound better. I am looking for ways in which to tweak the circuit in order to get better distortion sound.
The main problem I have with the current sound is that the distortion does not seem that pleasing or smooth… the clean is beautiful, but when pushed, it seems to give a kind of harsh distortion sound, most noticeable with chords. Soloing sounds pretty darn good, but even so, it lacks the dynamics, crunch and definition I imagine it could have.
Since this is my first build, I am wondering if I am doing something wrong, like running the tube at a bad operating point? I assume this is possible. I wouldn’t know how to change it. I just copied the vintage 5F1 circuit and used carbon film resistors, Zoso coupling caps, Sprauge cathode bypass caps, Sprauge Atom filter caps and Hammond transformers. This all goes to a Jensen 10” alnico reissue speaker. I tested with a Les Paul and a Stratocaster.
I notice my plate voltage on the 6V6 is 380 volts. This seems high to me. Is it possible that this is contributing to a harsh sound? I think this voltage is higher than what the actual vintage amps were used to seeing back in the days in which they were made. I know that some people use Variacs to lower voltage… evidently this gives a different, often described as more desirable tone. But this would also lower filament voltage.
I am wondering if there is an easy way for me to lower the plate voltage (and screen too?) in order to simulate that Variac lowered “brown” tone that many speak of. Can I just merely insert a resistor in series with the plate supply?... and screen supply? If so, I am kind of confused about how to go about calculating the value needed to drop say 20 volts at the plate? Would it even make a difference?
I have also considered that the Jensen speaker might be the culprit. Unfortunately, it’s the only one I have right now. I am thinking Celestion or Weber might be better for distortion?
Also, there is barely 20 hours worth of playing time so far – do I need to wait for caps and speaker to settle in?
Any help or advice in regards to any of this would be greatly appreciated.
Thanks !!
Hi mjf,
5F1:
http://www.schematicheaven.com/fenderamps/champ_5f1_schem.pdf
Hi WRyan,
The 5F1 has got to be the ultimate in simplicity... there's just too little to go wrong with the circuit. Assuming you followed the schematic exactly...
1) What is your speaker?
2) What brand tubes are you using? Some are naturally crunchy.
3) Is this from a kit, ready made or full DIY?
380V is a wee high, but it's what I run my 18W designs at and they live.
Cheers!
5F1:
http://www.schematicheaven.com/fenderamps/champ_5f1_schem.pdf
Hi WRyan,
The 5F1 has got to be the ultimate in simplicity... there's just too little to go wrong with the circuit. Assuming you followed the schematic exactly...
1) What is your speaker?
2) What brand tubes are you using? Some are naturally crunchy.
3) Is this from a kit, ready made or full DIY?
380V is a wee high, but it's what I run my 18W designs at and they live.
Cheers!
Thanks for the responses!
The speaker is a brand new Jensen 10" 25 watt alnico model P10R Vintage Series.
Tubes are:
1 12AX7A -C5 Ruby Tube
1 JJ Electronic 6V6 Spiral Filiment
1 5Y3GT Sovtek
This is a full DIY, not a kit.
I do not have another 5F1 to compare nor have I ever played one in real life. The closest I've had was a blackface Vibro Champ which I think I remember also being a bit harsh when cranked. It is very possible that I might be expecting this amp to do something it is not supposed to.
The only reason I feel like it ought to be different is because most of the time when I read descriptions of the characteristics of this amp, it is "creamy", "smooth", "lots of 2nd order harmonics"... and this seems to be true at lower volume levels. It is very sweet and has lots of chime, however, the harshness I hear when cranked seems to indicate more 3rd and 5th harmonics (I am definitely guessing on this), which I understand is what contributes to "harshness".
If I can figure out how to calculate and interpret the load line (I am still learning this), than I will be able to see if I am running it in a linear region or if I am way off. But then again, I don't know enough yet to know how changing these operating points affect the actual sound and feel.
This is what got me thinking about lowering the plate and screen voltage just to hear what it sounded like.
I drew in the voltages and posted. I only have a needle type reader, not digital, so the readings are not 100% accurate but they should be close. I really need to get myself a digital meter!
Again, any and all help is greatly appreciated.
Thanks so much guys!!
The speaker is a brand new Jensen 10" 25 watt alnico model P10R Vintage Series.
Tubes are:
1 12AX7A -C5 Ruby Tube
1 JJ Electronic 6V6 Spiral Filiment
1 5Y3GT Sovtek
This is a full DIY, not a kit.
I do not have another 5F1 to compare nor have I ever played one in real life. The closest I've had was a blackface Vibro Champ which I think I remember also being a bit harsh when cranked. It is very possible that I might be expecting this amp to do something it is not supposed to.
The only reason I feel like it ought to be different is because most of the time when I read descriptions of the characteristics of this amp, it is "creamy", "smooth", "lots of 2nd order harmonics"... and this seems to be true at lower volume levels. It is very sweet and has lots of chime, however, the harshness I hear when cranked seems to indicate more 3rd and 5th harmonics (I am definitely guessing on this), which I understand is what contributes to "harshness".
If I can figure out how to calculate and interpret the load line (I am still learning this), than I will be able to see if I am running it in a linear region or if I am way off. But then again, I don't know enough yet to know how changing these operating points affect the actual sound and feel.
This is what got me thinking about lowering the plate and screen voltage just to hear what it sounded like.
I drew in the voltages and posted. I only have a needle type reader, not digital, so the readings are not 100% accurate but they should be close. I really need to get myself a digital meter!
Again, any and all help is greatly appreciated.
Thanks so much guys!!
WRyan-
Great project!
As has been mentioned already, I wouldn't get too worried about load lines and much technical detail. You should be OK with the voltages you have, or you could try changing the dropping resistor(s) to get the 340/295/150 as per the original specs. However, these were +/- quite a few %, so you are definitely 'in the ballpark' where you are.
Quality of components- ie audiophile stuff- is generally wasted in a guitar amp, IMO. Just as long as you have fresh caps that aren't leaky and decent resistors, it should sound good.
Just double-check your wiring to make sure you have it right- sometimes guitar amps will perform with wiring errors or wrong components.
1) Speaker- this can make a big difference in the overdriven sound, but the Jensen should work OK. If you can rig up something with some cable adapters to just play music through your amp (from a tuner/walkman/ipod, etc) you can just put it in a closet somewhere (don't block the back or it will overheat) or lay it face down on a blanket and let it play for a few days. That will get rid of questions about 'break-in'.
2) Adjusting relative position of guitar and amp controls will affect the tone/breakup, as you know.
3) Tubes- You might be happier with a different preamp tube with lower gain- 12AU7,12AY7, etc will give different tone and 'breakup'.Good discussion of preamp tubes in a more complex amp will give you some ideas about possibilities for the V1 position in your amp.
Cheers
John
Great project!
As has been mentioned already, I wouldn't get too worried about load lines and much technical detail. You should be OK with the voltages you have, or you could try changing the dropping resistor(s) to get the 340/295/150 as per the original specs. However, these were +/- quite a few %, so you are definitely 'in the ballpark' where you are.
Quality of components- ie audiophile stuff- is generally wasted in a guitar amp, IMO. Just as long as you have fresh caps that aren't leaky and decent resistors, it should sound good.
Just double-check your wiring to make sure you have it right- sometimes guitar amps will perform with wiring errors or wrong components.
1) Speaker- this can make a big difference in the overdriven sound, but the Jensen should work OK. If you can rig up something with some cable adapters to just play music through your amp (from a tuner/walkman/ipod, etc) you can just put it in a closet somewhere (don't block the back or it will overheat) or lay it face down on a blanket and let it play for a few days. That will get rid of questions about 'break-in'.
2) Adjusting relative position of guitar and amp controls will affect the tone/breakup, as you know.
3) Tubes- You might be happier with a different preamp tube with lower gain- 12AU7,12AY7, etc will give different tone and 'breakup'.Good discussion of preamp tubes in a more complex amp will give you some ideas about possibilities for the V1 position in your amp.
Cheers
John
1) Change the rectifier to any NOS and don't use Sovtek. Their 5y3's are not made to correct specs and provide voltage that is high.
2) Add a bypass cap to the 1st stage's cathode, as used on the 5E1 (not 5F1.) I use a 1u to favor the high end since my homebrew was a little dark. Use a 25u to keep the same "EQ" while increasing crunch and compression potential.
3) Increase the cathode resistor on the 6v6. Even with stock voltages, the design idles the 6v6 way too hot. Although the JJs are known to stand up to this abuse. I think I'm using 740ohm.
4) Disconnect the NFB resistor if you still want more crunch. I have mine switched but always leave it off.
Here's mine cranked at various guitar volume settings. It's my favorite amp as far as its tone:
http://www.geocities.com/jjsant/champo_sm58.mp3
2) Add a bypass cap to the 1st stage's cathode, as used on the 5E1 (not 5F1.) I use a 1u to favor the high end since my homebrew was a little dark. Use a 25u to keep the same "EQ" while increasing crunch and compression potential.
3) Increase the cathode resistor on the 6v6. Even with stock voltages, the design idles the 6v6 way too hot. Although the JJs are known to stand up to this abuse. I think I'm using 740ohm.
4) Disconnect the NFB resistor if you still want more crunch. I have mine switched but always leave it off.
Here's mine cranked at various guitar volume settings. It's my favorite amp as far as its tone:
http://www.geocities.com/jjsant/champo_sm58.mp3
Looks like you're in good hands here 
You can also try "rolling" V1 for tone... different brands of 12AX7 as well as 5751 and 12AT7 for a little less gain and a different tone.
The OPT can also have an effect on performance.... 8K load is fair smooth and the de-facto standard for 6V6. Or, you could use as low as 6.6K for hard drivin' rock and roll crunch.
Nice speaker choice, BTW
Cheers!
You can also try "rolling" V1 for tone... different brands of 12AX7 as well as 5751 and 12AT7 for a little less gain and a different tone.
The OPT can also have an effect on performance.... 8K load is fair smooth and the de-facto standard for 6V6. Or, you could use as low as 6.6K for hard drivin' rock and roll crunch.
Nice speaker choice, BTW
Cheers!
WRyan said:
This is exactly the type of behaviour I'd expect from that design. It includes gNFB (and it looks like a lot of it: B= 0.064 here) and that always makes clipping behaviour that much worse, and more like the clip behaviour of a solid state amp.
First order of business: make sure that feedback really is negative feedback, if you haven't done so already.
Next, you might want to try tailoring the gNFB to your preferences. My guess is that the way you built it is exactly how it was meant to sound (or very close to it, depending on VT differences).
Thanks Everyone for your responses!!
I added a Sprauge 25uf bypass cap on the first stage cathode resistor... made a neat difference, more gain. I like it.
I added an additional 470 ohm resistor in series to the existing 470 on the 6V6 cathode, giving a total resistance of 960 ohms. This seems to smooth out some of the harshness. I like this mod too.
I removed gNFB and found that although the gain increased, the low end suffered by getting pretty loose for my tastes. I ended up putting it back. Feels tighter to me at higher volumes with gNFB.
Overall, I am pretty sure now that my amp generally sounds as it should. I think its strong points are clean sounds and light overdrive.
Modern style distortion is not the best part of its vocabulary. I find the more I push it, the less articulate it is... gets pretty muddy for chords. I am thinking it will be fabulous for Stones type of work... classic country, classic rock and blues for sure!
Also, I have a feeling that with less than 20 hours on the speaker, I should really give it some more time to break in. I hear that its normal for speakers to loosen up after break in.
I may also experiment with different manufacturers of tubes and tube types.
What kind of modifications are involved in making this amp support an el84?
Thanks again everyone!!
I added a Sprauge 25uf bypass cap on the first stage cathode resistor... made a neat difference, more gain. I like it.
I added an additional 470 ohm resistor in series to the existing 470 on the 6V6 cathode, giving a total resistance of 960 ohms. This seems to smooth out some of the harshness. I like this mod too.
I removed gNFB and found that although the gain increased, the low end suffered by getting pretty loose for my tastes. I ended up putting it back. Feels tighter to me at higher volumes with gNFB.
Overall, I am pretty sure now that my amp generally sounds as it should. I think its strong points are clean sounds and light overdrive.
Modern style distortion is not the best part of its vocabulary. I find the more I push it, the less articulate it is... gets pretty muddy for chords. I am thinking it will be fabulous for Stones type of work... classic country, classic rock and blues for sure!
Also, I have a feeling that with less than 20 hours on the speaker, I should really give it some more time to break in. I hear that its normal for speakers to loosen up after break in.
I may also experiment with different manufacturers of tubes and tube types.
What kind of modifications are involved in making this amp support an el84?
Thanks again everyone!!
Thanks Miles for the tip about gNFB!
One question – how do I tell the difference between positive feedback and negative feedback? I ask because this was a source of confusion when building the amp. I originally (erroneously) connected the feedback wire to the negative side of the speaker terminal. When I powered up the amp, it oscillated like crazy. Remembering a troubleshooting tip I read before about this, I disconnected the feedback wire from the speaker output and the oscillation stopped. I used the amp for a while and then became curious… I reconnected the feedback wire, but this time to the positive leg of the speaker jack. The amp did not oscillate and it also tightened up in regards to tone; gave more headroom and was generally cleaner… a little quieter too; all the things I hear feedback provides.
Upon reviewing the schematic, I figured out that I originally connected the feedback wire to the wrong side (negative) and now it is correct (positive).
But then your suggestion to verify that it is really negative feedback makes me wonder. How do I verify this?
Thanks Miles!!
One question – how do I tell the difference between positive feedback and negative feedback? I ask because this was a source of confusion when building the amp. I originally (erroneously) connected the feedback wire to the negative side of the speaker terminal. When I powered up the amp, it oscillated like crazy. Remembering a troubleshooting tip I read before about this, I disconnected the feedback wire from the speaker output and the oscillation stopped. I used the amp for a while and then became curious… I reconnected the feedback wire, but this time to the positive leg of the speaker jack. The amp did not oscillate and it also tightened up in regards to tone; gave more headroom and was generally cleaner… a little quieter too; all the things I hear feedback provides.
Upon reviewing the schematic, I figured out that I originally connected the feedback wire to the wrong side (negative) and now it is correct (positive).
But then your suggestion to verify that it is really negative feedback makes me wonder. How do I verify this?
Thanks Miles!!
WRyan said:
You basically do what you did: see if it oscillates, which it will do if you have positive feedback. My preference is to use a test resistor and an o'scope when first connecting the gNFB. Mr. Murphy guarantees that your connection will probably be wrong, and that you just made a big Royer oscillator. The resulting square waves will show up on the o'scope screen without putting your speeks at risk. Max power at ~20Hz into the speeks is not a good thing.
Hi WRyan,
first to say a guitar amp is a totally different thing vs an HiFI amp. The guitar amp and the guitar itself is part of the sound what a musician want. Every component incl. the speaker has a widely affect on the sound.
I recently build an guitar amp similar to what you build. I had problems with the sound which was harsh and dull while being overdriven. At small level with undistorted sound it was ok.
I use the fundamental circuit of the Fender Champ similar like yours, but I adding a overdrive stage to it.
To find out what the trouble was I fiddled with the first stage bias and kathode C. That will change a lot but give not the satisfiying result.
The relative high +B for this Amp is ok, I assumed that pinpoint was the output valve bias. I using the 6V6gc and the opt has a primary of 8k. My amp run with 400V and sounds now ok.
The data sheet of the output tube say a different settings as they are contrary to the established in the original Fender circuit. So I didn´t relied to the specs and start my own experiences.
But before I reach the aim of a satisfying sound I set the bias in a more practical way. I unsolder the kathode R of the output valve and replaced it against a variabel resistor of 1k . Now a friend of mine ( who becomes the owner of this amp) played the gutar and I setting the bias to the best sound. The result was amazing . I replaced the varaible R to a fixed one.
After this procedure I play a bit with the nfb. I did it in the same way like I did with the bias The best value for the nfb resistor is for my amp 5.6 k . You see in the drawing a value of 2.7k which was the original value.
The speaker in my amp is a 12" no name China import, I bought several of them at a local scrapyard. They look like old Fane chassis but they are definitely made in China , but the sound fair in my amp.
I suggest you to try the biasing and the nfb setting in the way I did.
here the schematic with all voltages and a pic of the wiring of my amp :
My conclusion is , that an amp as simple as this can´t be´satisfing al the wishes. But it is a good amp for rehearsal and small club gigs . This ampreally reflexes the sound of the 50/60ies.
good luck !
excuse me for possible mistake in writing/ grammar I´m not native english!
regards
Wolfgang
DF6ZC
first to say a guitar amp is a totally different thing vs an HiFI amp. The guitar amp and the guitar itself is part of the sound what a musician want. Every component incl. the speaker has a widely affect on the sound.
I recently build an guitar amp similar to what you build. I had problems with the sound which was harsh and dull while being overdriven. At small level with undistorted sound it was ok.
I use the fundamental circuit of the Fender Champ similar like yours, but I adding a overdrive stage to it.
To find out what the trouble was I fiddled with the first stage bias and kathode C. That will change a lot but give not the satisfiying result.
The relative high +B for this Amp is ok, I assumed that pinpoint was the output valve bias. I using the 6V6gc and the opt has a primary of 8k. My amp run with 400V and sounds now ok.
The data sheet of the output tube say a different settings as they are contrary to the established in the original Fender circuit. So I didn´t relied to the specs and start my own experiences.
But before I reach the aim of a satisfying sound I set the bias in a more practical way. I unsolder the kathode R of the output valve and replaced it against a variabel resistor of 1k . Now a friend of mine ( who becomes the owner of this amp) played the gutar and I setting the bias to the best sound. The result was amazing . I replaced the varaible R to a fixed one.
After this procedure I play a bit with the nfb. I did it in the same way like I did with the bias The best value for the nfb resistor is for my amp 5.6 k . You see in the drawing a value of 2.7k which was the original value.
The speaker in my amp is a 12" no name China import, I bought several of them at a local scrapyard. They look like old Fane chassis but they are definitely made in China , but the sound fair in my amp.
I suggest you to try the biasing and the nfb setting in the way I did.
here the schematic with all voltages and a pic of the wiring of my amp :
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
My conclusion is , that an amp as simple as this can´t be´satisfing al the wishes. But it is a good amp for rehearsal and small club gigs . This ampreally reflexes the sound of the 50/60ies.
good luck !
excuse me for possible mistake in writing/ grammar I´m not native english!
regards
Wolfgang
DF6ZC
Thanks Funker.
Great ideas!
I will replace the power tube cathode resistor (which is 940 ohms) with a 1K potentiometer. I am anxious to hear how different it sounds as I sweep the range.
Also, I disconnected the gNFB and now I like it... sweeping the range will be a good idea for that too.
Thanks again!!
Great ideas!
I will replace the power tube cathode resistor (which is 940 ohms) with a 1K potentiometer. I am anxious to hear how different it sounds as I sweep the range.
Also, I disconnected the gNFB and now I like it... sweeping the range will be a good idea for that too.
Thanks again!!
Thanks Trout!
I will keep this in mind.
How does one calculate current for that resistor? Sorry, I am still learning much. I did indeed use 1W for that one (was 470, now I have two 1W 470s in series for 940 ohm total). Would this eventually fail?
I know the formulas for ohms law, but I get hung up on which values to apply the formula to... for instance, when calculating the current for that cathode resistor, what voltage do I plug into the formula? I assume once I know that, I just divide that by the cathode resistor value and I will know the current at that point in the circuit? Or do I need to consider other resistances in the circuit to calculate the current at that point? These are the things that confuse me.
If I were to guess, I would say that I read about 20 volts at the cathode, my cathode resistor is 940 ohms... does that mean I have 21 milliamps across that resistor? 20/940=.021
If that is so, then Watts = V*I or 20*.021=.42 does that mean there is almost 1/2 watt across that resistor?
I appreciate any and all help!!
Thanks so much!!
I will keep this in mind.
How does one calculate current for that resistor? Sorry, I am still learning much. I did indeed use 1W for that one (was 470, now I have two 1W 470s in series for 940 ohm total). Would this eventually fail?
I know the formulas for ohms law, but I get hung up on which values to apply the formula to... for instance, when calculating the current for that cathode resistor, what voltage do I plug into the formula? I assume once I know that, I just divide that by the cathode resistor value and I will know the current at that point in the circuit? Or do I need to consider other resistances in the circuit to calculate the current at that point? These are the things that confuse me.
If I were to guess, I would say that I read about 20 volts at the cathode, my cathode resistor is 940 ohms... does that mean I have 21 milliamps across that resistor? 20/940=.021
If that is so, then Watts = V*I or 20*.021=.42 does that mean there is almost 1/2 watt across that resistor?
I appreciate any and all help!!
Thanks so much!!
Hi WRyan,
I just forget to say that what the member Trout just done for me. I used a 10W ceramic wire wound potmeter for my experiences. The potmeter should handle at least 100mA . I do not recommend a carbon type potmeter for this task.
And last not least keep an eye to the max. permissible plate dissipation power , which is 12W.
The plate dissipation power is U plate - U kath * I plate.
For example: With 380V supply, assume 30V loss at the opt and approximately 15V at the kath R, so there are 335V between the plate and kathode , this voltage divided by the maximum permissible dissipation power of the 6V6 will be 36mA plate current which you shall not exceed.
If you find the final value of your choice , calculat the power for the resistor. The formula for the power is P= U² / R .But if you use a 2W wirewound you will be alway on certain terrain.
regards
Wolfgang
DF6ZC
I just forget to say that what the member Trout just done for me. I used a 10W ceramic wire wound potmeter for my experiences. The potmeter should handle at least 100mA . I do not recommend a carbon type potmeter for this task.
And last not least keep an eye to the max. permissible plate dissipation power , which is 12W.
The plate dissipation power is U plate - U kath * I plate.
For example: With 380V supply, assume 30V loss at the opt and approximately 15V at the kath R, so there are 335V between the plate and kathode , this voltage divided by the maximum permissible dissipation power of the 6V6 will be 36mA plate current which you shall not exceed.
If you find the final value of your choice , calculat the power for the resistor. The formula for the power is P= U² / R .But if you use a 2W wirewound you will be alway on certain terrain.
regards
Wolfgang
DF6ZC
WRyan said:
WRyan-
There are several ways of getting to the answer for the power rating of the cathode resistor (or pot in the case discussed above).
I think I've got this right...
I usually follow Funker's advice/method and calculate the max current I want to have flowing through the tube (and the cathode resistor)- in this case 36mA.
Then you can use P=I^2 R to get the power dissipated by the resistor. P= (.036)(.036)(940) or about 1.2 watts. I generally double that number to get the working power rating for the resistor.
BTW, remember that that resistor will be warm/hot, so pay attention to any caps in the area as they generally don't like to be overheated.
Cheers
John
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