5E3 to 6G3 Conversion

[bcmatt]

I have a 5E3 head that I built a number of years ago that I keep modding over and over because it seems to see the least amount of playing time. It's been a "Herzog" 5E3 with an internal dummy load and line out. It's been modded to "The Edge" specs. Then it was modded again to a form of Tweedle-Dee. I should mention that it has always also had VVR to make it a bit more versatile volume-wise.

After how happy I was with the 6V6 Songwriter (with Blumlein Garter Cathode Biasing) I built out of an old Garnet Stencil amp, I had considered modding this 5E3 into the same thing (because that Songwriter I gave to a friend of mine).
However, I ran across some videos of the Brown Deluxe it it got me curious. I knew one thing I really felt I needed was to convert this into a long-tailed-pair PI, so I wondered if just the bright channel of the 6G3 (with no trem) would work. I decided I also wanted to keep it Cathode Biased because I'm into that sort of thing and I wouldn't need to change the VVR.

To make use of my extra knobs, I also added a Master Volume before the PI that allows a little bit adjustment to the feel of the amp. It is in place of the 15k/100K voltage divider. I used an 82K resister and a 50K pot with a 68k resister across its outside legs making it about a 30K pot. That allows me to bring the volume down to nothing, or up a bit higher than the stock circuit. (I found the 100K pot on it's own with no resisters was only useful in the first 3rd of the wipe, so I'm keeping it to a useable range).

20250403_134546.jpg

I also made use of a back panel knob to give variable NFB control. Stock value is 56K. I used a 33K resister in series with a 100K pot. I measures and installed the knob so that 12 noon is the stock value. This could realistically be a switch with three values (33K, 56k, 100k). Actually, I find myself mostly just going between 33k and 56K depending on whether I want the 33K to help the gain transition come on faster with the guitar volume knob. The challenge is always to try to keep things as simple as possible for the user so that I'm not giving extra features or control ranges that aren't useful.

Anyways, I'm really liking this amp. I do think the Brown era of Fender might actually be my favorite now. I use a 6G15 Reverb unit all the time already, so this would be the era it belongs with historically. I feel like this is also the era of Fender that connects the closest to Trainwreck style amps in my mind.

Anyways, for those considering a 5e3 build, you might want to listen to some clips of the brown deluxe and use the parts for it instead. I find it more user friendly. It did require a couple terminal strip near the tubes in order to still fit the preamp and PI on the board.

I forgot to mention, I'm still using the 5Y3 rectifier since I most often run the VVR under half anyways. It seemed to put all the plate voltages about 20 volts under the 6G3 schematic. With a GZ34 swapped in, it ran about 10 Volts higher than the schematic.
I did tweak the dropping resisters a bit, but I forget where they settled at.

[bcmatt]

I should point out that the 50k pot with the resistor across it really was just replacing a planned 25k pot that didn't seem to fit with my faceplate being slightly too thick.

[B Ingram]

... I'm still using the 5Y3 rectifier ... It seemed to put all the plate voltages about 20 volts under the 6G3 schematic. With a GZ34 swapped in, it ran about 10 Volts higher than the schematic. ...

Perhaps it's worth knowing that "Schematics aren't Gospel."

I own a 1962 Deluxe now, and use to also have a 1963 Deluxe. There were 3 different power transformers used in the 6G3 Deluxe during its short run. My 1962 Deluxe uses the one that probably delivered the lowest voltage (the 125P17A power transformer), and I get a little over 400v at the power tubes with a GZ34 rectifier. This is while sending 117v AC to the power transformer, as that gave 6.3v AC on the heater winding.

The takeaway is that all of the 6G3 Deluxe amps had higher voltage than is shown on the 6G3 Deluxe schematic. Therefore, you don't need to work so hard to duplicate the figures on the schematic.


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If you use Ohm's Law on some of the other figures on the 6G3 Deluxe schematic, you will find some of the numbers don't add up.

[Mark]

The 6G amps did have a few incarnations. I think the Bassman had three versions 6G6, 6G6a, 6G6b, and the Bandmaster had at least two 6G7 and 6G7a, according the the Hoffman site there are two versions the Concert 6G12, 6G12a.

[bcmatt]

Perhaps it's worth knowing that "Schematics aren't Gospel."

I own a 1962 Deluxe now, and use to also have a 1963 Deluxe. There were 3 different power transformers used in the 6G3 Deluxe during its short run. My 1962 Deluxe uses the one that probably delivered the lowest voltage (the 125P17A power transformer), and I get a little over 400v at the power tubes with a GZ34 rectifier. This is while sending 117v AC to the power transformer, as that gave 6.3v AC on the heater winding.

The takeaway is that all of the 6G3 Deluxe amps had higher voltage than is shown on the 6G3 Deluxe schematic. Therefore, you don't need to work so hard to duplicate the figures on the schematic.


___________________________________________

If you use Ohm's Law on some of the other figures on the 6G3 Deluxe schematic, you will find some of the numbers don't add up.

Thanks for weighing in. That's very helpful. I guess you could say my amp is mostly inspired by the 6G3 in general while trying to prove that one could convert their 5E3 mostly into one. Tonewise, I feel like it is totally worth it. People find trying to coax different tones out of a 5e3 rather charming. I feel like the 6g3 is easier to get nicer cleans and nicer distortion out of... Even while only having the bright channel and remaining cathode biased.

Now that I know it is still totally in range of the actual units voltage-wise, I'll try the GZ34 to see if I notice a difference in feel. Although, I imagine it would need an altered cathode resister. Because of my dependence on VVR, I would guess it's not worth the swap... But I should test my assumptions.

[bcmatt]

The 6G amps did have a few incarnations. I think the Bassman had three versions 6G6, 6G6a, 6G6b, and the Bandmaster had at least two 6G7 and 6G7a, according the the Hoffman site there are two versions the Concert 6G12, 6G12a.

Yes, you are right... I think there was even a short-lived EL84 version early on that was too suicidal. I watched a video about someone's that was warranty/factory-converted from that one after issues.
I was just looking at this schematic for mine:

deluxe_6g3_schem.pdf

[B Ingram]

... I guess you could say my amp is mostly inspired by the 6G3 in general while trying to prove that one could convert their 5E3 mostly into one. ... Even while only having the bright channel and remaining cathode biased.

Now that I know it is still totally in range of the actual units voltage-wise, I'll try the GZ34 to see if I notice a difference in feel. Although, I imagine it would need an altered cathode resister. ...

Neither Fish nor Fowl.


Fender raise voltages in the Deluxe up & up & up & up from the early-50s tweed 5B3 to the mid-60s blackface AB763 model. They seemed to want to increase power output, and increased voltages to help get there.

However, eventually the "more Power" goal requires a move to Class AB. The tweed Deluxe is already straying out of Class A into a very hot Class AB, but it can't go far. That's because you cannot cathode-bias far into Class AB.

You're likely to have problems keeping a 12w tube cool enough with cathode bias when converting to other "6G3 stuff," as this is exactly why Fender switched to fixed-bias in the 6G3.

Apart from that, copying some aspects but not others leaves the amp in a middle-ground where it is no longer a 5E3, but isn't quite a 6G3 either.

[bcmatt]

Neither Fish nor Fowl.

Fender raise voltages in the Deluxe up & up & up & up from the early-50s tweed 5B3 to the mid-60s blackface AB763 model. They seemed to want to increase power output, and increased voltages to help get there.

However, eventually the "more Power" goal requires a move to Class AB. The tweed Deluxe is already straying out of Class A into a very hot Class AB, but it can't go far. That's because you cannot cathode-bias far into Class AB.

You're likely to have problems keeping a 12w tube cool enough with cathode bias when converting to other "6G3 stuff," as this is exactly why Fender switched to fixed-bias in the 6G3.

Apart from that, copying some aspects but not others leaves the amp in a middle-ground where it is no longer a 5E3, but isn't quite a 6G3 either.

Ya, I really don't know what happened to the Deluxe between the 5E3 and the 6G3 and if there were any amps imagined or produced, but somewhere in there is the amp that I want. I don't want the extra power of the Brown, but I want the extra gain and that PI. I'm not saying it's my dream amp but it for me it's the most useable Deluxe. I want power tube breakup dialed in anywhere between 2 and 12 watts.
The main thing I consider is whether I want more tone controls or not. This single control is better than I expected, but I wonder if something like a Bass control and a Cut Control like the Songwriter would be more versatile while still keeping things pretty simple and not dumping too much gain.

[maxkracht]

Cool build! I have had a similar journey with my 5e3. First amp I ever built, Mission kit, i've probably rebuilt it 3-4 times at this point. Have you considered adding a toggle or rotary switch for smaller coupling caps on V1 as a bass control? Haven't tried that on my 5e3, but I have built a few similar amps with that setup and liked the results.

[bcmatt]

Cool build! I have had a similar journey with my 5e3. First amp I ever built, Mission kit, i've probably rebuilt it 3-4 times at this point. Have you considered adding a toggle or rotary switch for smaller coupling caps on V1 as a bass control? Haven't tried that on my 5e3, but I have built a few similar amps with that setup and liked the results.

Ya, if I recall correctly the Edge version took the Normal Channel and gave it smaller coupling caps. I think the Tweedle-dee also did that. It wasn't on a selector, but that would also be a good idea.

[maxkracht]

Slight pain to wire up, but rotary with 6 or so cap options makes me not miss a bass knob so much. Can leave the .1 in place and use lower voltage caps in series to make fitting it all on the switch a bit easier.

[bcmatt]

At this point, I'm not finding the bass level to be a problem.
I pulled out the MV put I had added before the PI and put it back to a more stock 6G3 bright channel. The simple Volume and Tone controls seem pretty good, so I went ahead and made a Leather Faceplate with the simpler controls.

20250507_170158.jpg

I kept the NFB knob because I like the idea of being able to change how fast or gradual distortion comes on with the guitar volume knob with the stock value being noon.

I installed the Blumlein Garter Bias today as well. Before changing, the dissipation was in the around 85% with the 250R 25uF single Cathode Resistor.
Using 4x 470R resisters and 220uF in the garter circuit, it only biases at about 82%.
I buttoned it back up for now since I run at much lower plate voltages anyways, but one of these days I'll figure out some more appropriate resistors to hit closer to 100% at full plate voltage...