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5E3 "Tweed" Deluxe

This is my interpretation of the 5E3 Deluxe made by Fender® in the mid to late 1950s. I met a gentleman online who wanted to build an amp but didn't have any electronics experience. He is a woodworker, and built me the beautiful solid oak cabinet. In exchange for the cabinet, I built him a fully stuffed circuit board, and punched and drilled the chassis for him.

I had a blast building the project and it is the first complete amp I've done. It sounds very good too. It is a bit bass heavy, but some tweaking of the coupling caps should eliminate some of the boomy bass. I recently hooked up a Tech21 Double Drive pedal to the amp and got some amazing singing compressed lead tones.

	This shot is of the front of the cabinet. My friend originally used a 1/4" thick piece of mahogany plywood for the speaker baffle. I've since replaced it with a 1/2" piece of birch plywood. The grill is held on by 4 #8-32 brass machine screws, brass finishing washers and #8-32 T-nuts. I used a piece of 1/2" MDF covered in oxblood grill cloth, for the grill. I cut both circles in the speaker baffle and grill cloth board using a plunge base router and a circle cutting jig. It was my first experience using a circle cutting jig and both holes came out perfectly.
	The handle is leather. Originally, I used brass screws to hold on the brackets for the handles, but unfortunately one of the screw heads twisted off. (Always pre-drill holes in oak) I ended up getting the screw out (without a screw extractor) but damaged the cabinet. I drilled out a 1/2" hole and plugged it using an oak dowel. I found some steel screws that were a gold-like color, and they worked better than the solid brass screws and matched the brackets.
	Here is a shot of the back of the amp showing the back panels. They are made of 1/4" oak.
	Here is another shot showing the controls. From left to right, they are: pilot light, on/off, standby, tone, volume for channel 2, volume for channels 1 & 2 in parallel, input for channel 2, and input for channels 1 & 2 in parallel. I departed from the original design by pre-jumpering channels 1 & 2, putting them in parallel. This gives a little thicker tone than just using either channel by itself. I also only used one input jack per channel, unlike the original 5E3's two per channel.
	The electronics are housed in a Hammond 1441-18 steel chassis measuring 13.5" x 5" x 2". It was a challenge getting all the parts fitted to the chassis. The rectifier and power tubes are a little closer than I'd normally put them, but the amp is very quiet. I'd never worked with steel, as I preferred to use aluminum. It proved easier than I thought. I used a Unibit to drill all the holes and it cut through the steel like butter.
	Here is a close up of the circuit board and chassis. I used orange drop caps for all the coupling caps. The cathode bias resistor caps are 10µF for the pre amp tubes. I used mostly carbon film resistors in the pre amp. There are a few metal oxide resistors in the power amp and the power supply. Tone caps are silver mica. Notice the Mojotone MP12R alnico speaker.
	This picture is of one of the mounting brackets. I used one on either side of the chassis to secure it to the cabinet. I got them at Lowe's. Since the chassis was not long enough, I couldn't mount it through the top by the control cutout like on the original.
	Here is a close up of the two pre amp tubes. The tube on the right is a NOS GE 6072, which is a low noise industrial equivalent to the 12AY7. The tube on the left is an Eico labeled Mullard 12AX7.
	The tubes the the right are the power tubes, JAN Raytheon 6V6GTYs. They were pulls that I got at a hamfest. The tube on the left is a GE 5V4GA rectifier tube. I tried a NOS 5Y3GT tube in circuit as in the original, but the plate voltage was too low. The 5V4 has less voltage drop so the plate voltage is a tad higher.
	The output transformer is a Hammond 125E. I have it set for 8k2:8 ohms. I used an NOS Thermidor power transformer. It is rated for 600vct @135mA. Originally, I had planned to use an aluminum chassis to save on cost, but due to the size of the Thermidor, I used a steel chassis instead. The aluminum would have been too flimsy.
Update: 10/23/05	I this spent the afternoon converting my 5E3 clone for use with 6K6GT tubes. Before the conversion, the amp had a GE 5V4GA rectifier tube, two Raytheon JAN-CRP 6V6GTY power tubes, a Mullard 12AX7 and a GE 6072 as listed above. The voltages were lower than a stock 5E3 so I figured a conversion to use 6K6GT tubes was in order. The OT is a Hammond 125E, which is fortunate as it can be configured for multiple primary impedences: Hammond 125E Hookup Data The 5E3 circuit sounds boomy to me even with single coils, so I swapped out two of the .1µF caps with .022µF caps. I left the two .1µF caps in the phase inverter intact. I planned to replace all the .1µF caps with .047s, but I didn't have any in my parts bins. That seemed to cut down on some of the boominess enough. Before converting the amp to use 6K6s, I measured the voltages with three different rectifiers. With 6V6s and a GE 5V4GA rectifier tube, the plate voltage of the amp was 350v, cathode to ground voltage was 21.37 and the cathode bias resistor was 270O. 21.37/270=.079A x 350v = 27.70 or each tube dissipating 13.93 watts. I tried a 5Y3 rectifier as well and got: plate voltage: 317v, cathode to ground: 18.92v, 270 ohm cathode bias resistor. 18.92/270 = .070A x 22.21 watts dissipated for both tubes or 11.105 watts each tube. Finally I tried a Groove Tubes "5U4" SS replacement rectifier. I put 5U4 in quotes as it doesn't drop anywhere near as much voltage as a 5U4 tube. It also doesn't have any slow start up characteristics. Plate voltage: 375v, cathode to ground: 22.96v, 270 ohm cathode bias resistor. 22.96/270 = .085A. 375 x .085 = 31.89 watts dissipation for both tubes, or 15.945 watts each tube, over the 14 watt limit. I got the 6K6GT data here: http://www.nj7p.org/Tube1.php?tube=6k6gt Class A Amplifier Plate Voltage: 315V Grid No. 2 Voltage: 250V Grid No. 1 Voltage: -21V Peak Grid No. 1 Voltage: 21V Plate Resistance (approx): 110K ohm Plate Current (Zero Signal): 25.5mA Plate Current (Maximum Signal): 28mA Grid No. 2 Current (Zero Signal): 4mA Grid No. 2 Current (Maximum Signal): 9mA Load Resistance: 9K ohm Power Output (approx): 4.5W Total Harmonic Distortion: 15% I swapped out the 270 ohm resistor for a 470 ohm. I then changed the the secondary taps on the 125E from 5 & 2 (8.2k ohm) to 1 & 4 (11.6k ohm ) as the data sheet specified anywhere from 9k to 12k depending on the voltages. I had four 6K6GT tubes, two were in RCA boxes, although one of them was labeled GE, it was identical to the RCA-labeled RCA tube. I also have a GE and an older RCA. I reinstalled the 5Y3 rectifier to cut down on the plate voltage. Here are the voltages I got: 332v plate to cathode, 23.36 cathode to ground, and 470 ohm cathode bias resistor. 23.36/470 = .049A x 332 = 16.5 watts for both tubes or 8.25 watts each tube, pretty close to the 8.5w Design Center Maximum Value. I checked the screen voltage as well: 265v, under the 285v limit. The 470 ohm cathode bias resistor was a lucky guess. I fired up the amp and played my Warmoth parts guitar with Bill Lawrence 280 pickups through it. It struck me that it was mechanically more noisy. I don't know if it was the tubes, or not but the the amp seemed lots quieter with the 6V6s in it. In terms of acoustical loudness, the amp was a lot less loud with the 6K6GTs in it than the 6V6GTYs. I have the front end configured so that one input is both channels in parallel and the other channel is one triode of the 6072 tube. The amp still breaks up on about 3 or 4 on the volume knob, but only gets so loud. It would probably not be loud enough for gigging with a loud drummer unless miked. According to the specs, this amp should be putting out about 4.5 watts which seems reasonable. It is less loud than my SE Tweed Princeton with an upgraded PS, OT and a GT KT66HP tube. I plan on trying the other set of 6K6GTs in the amp and mixing and matching to see if that improves the mechanical noise. I also swapped out the Mojotone alnico speaker with a Carvin G12-75-8 ceramic speaker. The Carvin still sounds a little thin, but it is still brand new and not broken in yet.

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