Gnome

MOD
Garnet Gnome - extra gain stage

      Source circuit:     1959 Fender 5E3 Tweed Deluxe
                   Style:     2-channel cathode-biased 2 x 6V6GT amp
                    Built:    October 2001 - February 2002
Source Schematic:    5E3 Schematic
Source Layout:          5E3 Component Layout
My build Schematic:  Sean's 5E3 Tweed Deluxe - version R3 (Now with Voltage measurements)

--- Design Comments: 

The Fender 5E3 Deluxe is one of the most popular tube amps of the late 50's and is coveted for it's low volume clean tone by some guitarists, but most relish it's outrageous tube overdrive capabilities. The cathode-biased dual 6V6GT output stage coupled with a 5Y3GT rectifier tube provide lots of compression and the amp can sing and sustain beautifully when turned up. 

Beside this, why built the 5E3? I listen to a lot of blues music much of which was and is recorded with tube amplifiers built in the 50's. I didn't own such an amp but wanted to recreate some of those tones, and some of my own. At the same time, Bruce Collins of Mission Amps was starting to offer kits with all the parts necessary to build the 5E3 and also created some support documentation to aid in the construction.

This is my first homebrew amp but I've been modifying my own tube amps for a few years. I know that I will build more now that this one is complete...it's a very satisfying activity. 

Below you'll find construction details, parts selections, and sound samples.

Visit the 5E3 Deluxe Q&A Forum hosted by Ampage for ongoing discussion on building 5E3 style amps.
 

---- Parts: 

Some notes on the parts I selected...

A critical part of any tube amp is the output transformer (OT). Next to the speaker, many builders feel this is the most important (and sometimes most expensive) aspect to consider when looking for a particular tone. Indeed, there is a trend to replace the OT in Fender and Marshall reissue amps with hand-made boutique units. 

For my amp I selected the MojoTone reproduction of a Tweed Deluxe OT which is an interleaved paper bobbin transformer designed to perform like a vintage Fender unit. I also used the MojoTone Tweed Deluxe power transformer (PT) which actually has a Fender label on it and provides the correct voltage levels.

I bought a WeberVST 5E3 chassis and partially populated circuit card from a friend who had an extra (thanks Bill!). I also ordered a WeberVST P12Q speaker directly from Weber and bought another circuit card because I wanted to use some different components. The original Fender Deluxe came with either a Jensen P12R or P12Q both of which are AlNiCo blue-bell speakers. I selected the P12Q because it can handle slightly more power than the other.

Part-Is-Parts is operated by John Sprung who is the co-author of the Fender Amp Book (highly recommended for Fender amp fanatics). He had the authentic Fender-style smooth blond tolex and oxblood grillcloth I wanted for this project.

Finally, I sent Bruce Collins a list of the remaining parts I needed to build the circuit and he graciously picked out exactly what I needed...one of these, two of these, etc...

Here are some references for the parts I used: 

    WeberVST - chrome 5E3 chassis and eyelet board, P12Q speaker
    MojoTone - power transformer, output transformer, tubes, misc hardware
    Bruce Collins/Mission Amps - circuit components
    Parts-Is-Parts - tolex and grillcloth

Here is the worksheet I used to determine the parts I needed and record the prices. It's somewhat incomplete because I didn't include the complete list of components necessary to complete the amp, but does include the part numbers for most of the main parts (PT, OT, speaker, etc). 

Vacuum Tubes: I installed matched NOS Mazda (French Millitary) 6V6GT output tubes, an NOS Sylvania JAN 12AX7A, an NOS GE 12AY7 in the first pre-amp stage, and an NOS Philips JAN 5Y3GT rectifier.
 

---- Circuit Board: 

The first step in constructing the amp was to install the resistors and capacitors in the circuit card. This style of material is called a fiber eyelet board which I find easier to use than a turret board. All electrolytic capacitors are Sprague and the coupling caps are Mallory 150 series. All flying leads were installed at this time as well. Some leads go under the board (these are the dashed lines on the layout diagram) and these are sandwiched between with the bottom card..

The layout I used was suggested by Bruce Collins and based on the original 5E3 Deluxe and with some improvements. I also substituted parts in a couple of places (see my schematic - link above). For example, I used 25uF cathode caps instead of 22uF and have since replaced the 5W 6V6 250R cathode resistor with a 10W to enable use of 6L6GT output tubes (that's the 5W in the pic above).

I added a modification that allows me to switch in a negative feedback loop. Check the build schematic for details...this reduces overall volume and tightens up the sound a little bit. I prefer it disabled actually.

Tip: I circled each "eyelet" on a printed copy of the layout as I completed all connections to that point. This made it easy to track progress and confirm that all parts were in their correct orientation and position. It's worth the time to triple check the layout before installing it in the chassis.

Completion of the board took approximately 4 hours.
 

---- Chassis Construction: 

Laying out and installing the parts in the chassis was a challenging and rewarding part of the process. Again, the classic Fender layout was followed with some improvisation when required. I used 1/2" stand-offs for mounting the circuit board to the chassis and screws with lock washers for mounting the transformers.

Here is an image of the chassis using my flatbed scanner. At right is a photo of the installed chassis and Weber speaker....

Completion of the chassis required approximately 12 hours.

After completing assembly, I triple checked every connection then powered it up without any tubes installed to verify the correct voltages were being produced by the PT. This is a rough method because the tubes are not drawing current so the voltages will be higher than normal. Voltages checked out ok so I installed the rectifier tubes, power tubes, and preamp tubes - checking voltages after each type of tube was installed. 

Part way through this process I found that I neglected to solder the ground on the cathode resistor but after this was fixed the amp worked perfectly. I hooked the amp up to a speaker cab and tested it thoroughly at various control settings and was satisfied everything was cool. 

Here are some more detailed shots of the completed chassis. The third pic shows the push-pull switch on the Channel 1 volume control being used for a negative feedback modification (see schem for details).:

---- Cabinet Construction: 

I chose to build the cabinet myself instead of buying from one of the many companies making reproductions to reduce overall costs and because I really enjoy woodworking. I based the design on the rough dimensions of the original late 50's Deluxe and the style of a particular Caesar Diaz amp I liked. Here's my sketch:

Note the offset speaker hole in the baffle. This is to offset the weight of the PT for a better carrying balance, and to provide clearance for the speaker under the chassis. 

For materials I tried to stay close to Leo Fender's woods of choice: Pine for the frame and plywood for the speaker baffle. For simplicity, I used simply butt joints plus braces instead of finger or dovetail joints. I sealed the assembled frame with Verathane Professional Clear finish and primed and painted the baffle black (this is so it blends with the black speaker cone behind the grill cloth).

The frame is clear Eastern Pine, the baffle cleats are Western Maple, and the baffle is Baltic Birch ply. Note that I'm in Canada and these are the common names for these woods, wood identification might vary depending on the region you are in.

Here are some pics of construction in progress...

(Left) the frame glued and screwed, and cleats cut and ready. (Mid) my brilliantly conceived baffle cutting jig in action! (3" x 1" board mounted to bottom of plunge router with a hole for the bit to pass through). (Right) detail of the inside corner showing baffle and rear panel cleats, and a corner brace

Using MS Word, I made up a Tube Chart and pasted it inside the cabinet.
 

---- Finish details...: 

I wanted something different from the "tweed" for my Deluxe so I chose smooth blond tolex and oxblood grillcloth. Fender used this briefly in the early 60's and I like the contrast of the light/dark colours. There is lots of advice on which adhesive to use for tolex but I just went with Weldbond white glue. It holds well but does not set immediately so I needed lots of clamping and drying time. Worked out well in the end I think.

Completion of the cabinet, including applying tolex and grillcloth, took approximately 35-40 hours. I don't have any pics of the tolex process because it was too time-consuming to want to remember in graphic detail!! Check out the "Casey4s" tutorial on applying tolex (there is a link on the WeberVST Enclosures board).

Just for kicks, here's a shot of my workbench: 
 

---- Sounds ! : 

These samples were recorded using 1 Shure SM57 right on the speaker grill and another several feet back for ambiance. These were patched into a cheapo Realistic mixing board then directly into my PC soundcard.

These are MP3 files at 64Kbps 22KHz and vary in size from 100-400KB.
 

  * This is a full hollowbody with 2 P-90 style pickups. The "Junior Watson" guitar.
** For details on the homebrew strat with Fralin pickups, go here: Daphne Strat.
 

---- Final comments: 

I love this thing! I've played it at a few blues jams and it cuts through nicely with a thick rich tone. Clean headroom is impossible with a 5-piece band and full PA, but for the kind of blues I play it works very nicely. As tonal reference points, with a Les Paul and the amp volume cranked it's possible to get close to Clapton's Bluesbreaker tone, while a Strat can cop convincing Anson Funderburg tone. Haven't tried for the Neil Young thing yet... :)

I'm not convinced the P12Q speaker is the best match yet so I might do some experimenting here. It sounds quite good but I may prefer a speaker that doesn't break up as much.

Thanks to Bruce Collins and contributors to the 5E3 and Ampage boards for assistance and encouragement!

Cheers,
Sean  (Email)

--- JANUARY 2003 UPDATE:

I've continued to play this amp at local blues jams and often get compliments on the tone. It's a great rig!

I found I never used the feedback enable/disable switch, so I've removed it and use the switch to toggle the value of the 2nd stage cathode capacitor: either 25uF (stock value) or 0.68uF (less bass, brighter overall tone). This would be effective for reducing the woofiness of a humbucker for example.

I also reduced the value of the coupling cap on the bright channel from 0.1uF to 0.022uF to brighten it up a little bit and to increase the difference in tone between the two channels.

Next up, I performed the "Paul C" mod which DC-biases the phase inverter. The result is a slightly smoother breakup at higher volumes and slight increase in headroom (though not much). Nice! Here's a before and after example of the mod:

And here's a pic of the modified circuit board:

These changes are reflected in R3 of the schematic available at the top.

Cheers,
Sean  (Email)

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            Amp:     1978 Garnet Gnome G-15T
             Mod:     add full-bypass switchable extra gain stage

The Garnet Gnome G15-T has one 6V6 output tube,  two 12AX7 preamp tubes, and an 8" Marsland speaker. The circuit design is almost exactly the same as the Fender Vibro Champ. Front panel controls are Input, Bright Input, Volume, Treble, Bass, Speed, Depth, Footswitch (for tremolo on/off).

The tremolo uses only half of the 2nd 12AX7 so I decided to use the unused half as a boost circuit. I wanted to retain the original tone of the amp so used the "bright" input as a location for the 3PDT toggle switch. The boost circuit is based on the Ken Fisher - Trainwreck pages idea in Gerald Weber's first book.

Here are the schematics I traced out:
               Original1978 Garnet Gnome  (GIF format, 21KB)
               1978 Garnet Gnome Boost Mod  (GIF format, 15KB)

I recorded the following sample with an SM57 pointed at the cone 12" away. Guitar was an Epiphone '56 Les Paul GoldTop with P90 pickups. Bridge pickup direct into the amp with volume on 10 and boost engaged...

                Sound sample of the boost engaged.   (MP3 format, 300KB)

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                   Amp:     197x United Amp (built by Garnet)
     Source circuits:    1959 Fender 5E3 Tweed Deluxe, 1959 Fender 5F4 Super
                   Style:     single-channel fixed-biased 2 x 6L6 amp
                    Built:     June 2002
United amp schematic:  United Amp Schematic
Source Schematics:      5E3 Schematic, 5F4 Schematic
By build Schematic:      Sean's Super-Deluxe Amp

The United brand of tube amplifiers were built by the Garnet company in Winnipeg, Manitoba, in Canada. They are what is referred to by Garnet fans as a "stencil" brand and often represent a Garnet model in United clothing, so to speak. This particular amp is the same circuit as a Garnet Rebel II Deluxe which is a 2 x 6L6 amp with a Baxandall tone stack and tremolo.

My amp needed some work anyway, so I decided on a rebuild instead which included new filter caps, pots, and several discrete components. It was a platform for a couple of experiments but currently it is my "Super Deluxe" which is essentially a single-channel 5E3 Tweed Deluxe preamp with a master volume followed by the fixed bias output stage of a 5F4 Tweed Super.

Controls are as follows: Volume, Tone, Master Volume, Presence.

The master volume is a pre-phase-inverter type and allows some overdrive at lower volumes, but there isn't enough gain in the pre-amp to really create much distortion unless you're using humbuckers and a boost pedal. The 120pF cap helps retain some highs at lower master settings.

The sound is pretty good actually and I'm happy with the results. See the build schematic for the final revision (so far) which the result of some time with Paint Shop Pro to merge the schematics together.

I am ordering parts to add reverb to the circuit so stay tuned...

I recorded this sample with an SM57 pointed at the cone of a WeberVST C15CA 15" California speaker... Guitar was an Squire Tele with Fralin pickups and I provided a variety of the tones the amp can produce. The tubes are a mix of old stuff of unknown history and certainly need replacing, but for now this is what I've got..

                Sound sample of the final circuit  (MP3 format, 480KB) 

      Source circuit:     1959 Fender 5E7 Tweed Bandmaster
                   Style:     1-channel fixed-bias 2 x 6L6GC amp
                    Built:    December 2002 - January 2003
Source Schematic:    5E7 Schematic
Source Layout:          5E7 Component Layout
My build Schematic:  Sean's 5E7++ Bandmaster - version R3 (Jan 18, 2003)
                            

--- Design Comments: 

Having built the 5E3 Deluxe, a 15 Watt cathode-biased 6V6 amp, the next logical step was one of the 35 Watt tweed Fender designs. The 1959 5E7 Bandmaster, 5F4 Super, and 5E5-A Pro circuits are almost exactly the same with only a couple of component changes between them, specifically the feedback resistor around the second stage and the output transformer secondary. All three share the same fixed-bias dual 6L6 output stage with a 5U4GB rectifier tube.

The 1959 5E7 Bandmaster has three 10" AlNiCo 8-ohm speakers wired in parallel and shares the same 4 ohm OT as the Super amp. I was thinking about building this design when a friend set me up with the chassis and helped me locate the Victoria Amp Co. cabinet I ended up using.

---- Modifications to the original 5E7 circuit: 

I called my amp the 5E7++ because I made some additions to the circuit to make it a little more versatile, while maintaining the original signal path and tone. When I modify or build classes circuits, I like to have any mods integrated via switches so I can maintain the original tone of the design, then switch in other options.

I made the following changes:

1. Grounded power cord - for safety of course!

2. Single channel design with different value for the "bright cap". I found the stock 100pF cap to be TOO bright so I lowered this to two Silver Mica 47pF in series resulting in an effective 23.5pF. This results in a *slight* boost in the highs at lower volumes.

3. "Paul C" phase inverter mod to DC-bias the phase inverter. See details in the 5E3 section above.

4. Pre-PI Master volume. This allows me to dial in some crunchier tones at lower volumes and works very well with the next mod...

5. Fully-bypassable gain boost stage. This is an independent tube gain stage that takes the place of the 2nd channel that would normally exist in a 5E7 amp. I modeled this partially on 1/2 of a Dumble overdrive circuit found in some of his amps. This is engaged via a DPDT toggle switch in place of one of the input jacks. The input and output level potentiometers are also installed where 2 input jacks would normally reside. The 1M trim pot is set to approximately 600K.

6. Variable bias using a 10K bias pot.

Chassis-top controls are (left to right):

     Drive
     Drive Volume
     Drive Switch
     Input
     Master Volume
     5E7 Volume
     Treble
     Bass
     Presence
     Standby
     On/Off

---- Parts: 

---- Circuit Board: 

---- Chassis Construction: 

     

---- Victoria Amp Co. 35310 3 x 10 cabinet: 

The cabinet I used is an original 1995 Victoria Model 35310-T cabinet with tweed covering. This is a pine cabinet with thin plywood baffle that resonates very well. The person I bought this from had no idea where the original chassis went, and Mark Baier of Victoria couldn't tell me either. These pics below are of my chassis installed in the cabinet:

Here's a link to the Model 35310-T description on the Victoria site.

There are interesting markings on the inside of the cab (see pic). MB = Mark Baier of Victoria and he stated that the MW was a reference to Muddy Waters. The serial number is 0019 so this was the 19th 35310 built.

---- Final Comments: 

Cheers,
Sean  (Email)

** NEW 5E7 SOUNDS**  ---- UPDATE Feb 19, 2005:

These 5E7++ samples were recorded using a ribbon mic connected to a portable DAT recorder. The DAT samples were recorded into a PC through a regular soundcard. There is a little bit of post-processing reverb. Some are MP3s, others are WAV files. The playing and recording were executed by my friend Bill.

File sizes vary in size from 100-400KB.

      Source circuit:     1950s Fender 5E5 Tweed Pro, and 6G15 Reverb
                   Style:     single-channel cathode/fixed-bias 2 x 6L6GC amp with reverb
                    Built:    (currently in design stage)
Source Schematics:  5E5 Schematic , 6G15 Schematic
Source Layout:          TBD
My build Schematic:  Sean's 5E5 Pro + Reverb - version D3 (Nov 03, 2004)