1959 Tweed Bassman – Part IV

Part 4, Final Assembly and testing of the chassis:

NOTE: The ground switch is not connected. Due to the current power grounding schemes in the US, the Ground switch does not do anything to help in getting rid of hum. You will notice that I used one of the ground switch terminals as a connection point only. The proper way to hook up the power input to the Power Transformer is by connecting the white wire to one of the black PT input wires and the black wire (coming in) going thru the fuse and the Power switch before connecting to the other black PT wire. Great Mix Recording

Tip: For minimum hum, keep all wires as short as possible. FinalLeft

Now, a discussion of tubes is in order. Currently there are less than 6 manufactures of audio tubes in the world. Czechoslovakia, China and the former Soviet Union. I prefer the Russian tubes. MojoTone uses JJ tubes in their kits. While these are pretty good, I have my own ideas on tubes. I picked the Sovtek 5AR4 rectifier based on past experience with Sovtek and reviews of great extension and tightness on the bottom end. NOS (new old stock) tubes can provide better handling of the rectification but I feel that the cost is too much for what you get. For power tubes I decided on 5881’s vs 6L6’s. In general 6L6’s have a bit more gain but I’m going for tone. So, 5881’s by the newly reissued TungSol version built by the Russians. The preamp tubes get more interesting as there are a lot more choices and which ones you put in what stage. As you peruse the internet you will find hundreds of opinions on all sorts of combinations. For V1 I am staying with the 12AY for better tone. I have picked the EH (Electro Harmonix) from “Doug’s Tubes”. No reason for balancing or matching the triode’s as ½ the tube is for the normal channel and the other ½ is for the bright channel. Who cares, its 2 different inputs. Viva la difference. V2 goes before the tone circuit, the first ½ increases the voltage and the second ½ matches the impedance for the tone circuit. Here I chose a NOS 12AX by GE, this is where you want to use a great sounding tube. (Does not need to have matched gain or balanced triode’s). Next up is V3, the phase inverter. This tube creates the plus and minus waveforms for each of the 5881’s. Some also call this the “driver”. This is where you want to use a high quality tube and get it with balanced triode’s and matched gain. I used a reissued 12AX TungSol from Doug’s Tubes.

So, fired it up sans tubes, took some voltage measurements and all was good. Put the tubes in and ran some sound thru it, no issues. Took the amp over to my Guitar buddy Kris and we ran it thru a 2-12 cabinet with v30 Celestion’s. Playing his custom late 2000 Strat, he was grinning ear to ear. That sounds X@X@Xing awesome he says. A few adjustments of the gain and tone controls and he’s loving it.

Where’s the 4-10 cabinet he says. That, I say, is for another day and another blog. 🙂

Great Mix Recording

Great Mix Recording

Great Mix Recording


Stay tuned for more to come on this exciting project!

. Record . Mix . Master . Music .

1959 Tweed Bassman – Part |||

Part 3, More Assembly:

Next up is the high voltage filter capacitor board. This is a very important part, so make sure it is done correctly.
Great Mix Recording Notice position of the caps on the board and how the minus side of the caps are tied together.
Great Mix Recording

When done and wired go ahead and mount with “cover” to the chassis running the wires thru the grommet into the chassis. I did add some rubber feet to the bottom of the cap board to take up space under the cover so it does not bounce around and put some sticky pads on the chassis for the caps to sit on. Mount so that the caps sit on the chassis. Great Mix Recording

The main circuit board is pretty involved, so take your time. If you are a “righty” start on the left and work your way to the right. If a “lefty” reverse the procedure. Do the underside tie lines first before mounting components.

Great Mix Recording Double check you work constantly. I found myself making a few mistakes and corrected them by comparing the schematic to the wiring diagram. Pay particular attention to the 2 bias resistors (220k) and the 2 screen resistors (470). These need to match very closely in value in order to get the most out of your matched power tubes.

Great Mix Recording Wire all leads going from the board to the chassis components to the underside, as it will give a cleaner look. I also wrote the values of the orange drop caps on the caps to aid in servicing down the road. Dry fit the board to the chassis and drill 2 holes through both boards to mount directly to the chassis. Make sure you do not hit any wiring or components on the other side of the chassis.

Stay tuned for more to come on this exciting project!

. Record . Mix . Master . Music .

1959 Tweed Bassman – Part ||

Part 2, Assembly:

The chassis is finished off in chrome and for an added bit of protection I cleaned and polished the chassis with automotive chrome cleaner. 1959 Bassman Kit - Great Mix Recording Start by mounting all the hardware pieces to the chassis. The three transformers, pots, jacks, switches, fuse holder and tube sockets.

Start with the transformers, wires should be twisted for minimal hum noise. Next, install the potentiometers in their proper location. TIP! Use a nut driver to tighten the nuts. This will prevent you from scratching the finish. Lock washer on the bottom, regular washer on top then the nut. Sizes for drivers are 1/2”, 7/16” and 11/32”. The power and standby switches only mount one way. Tighten the nut on the backside of the chassis rather than the finish nut. Position the ground switch as seen in the image. Install the tube sockets with the same orientation in each of the locations. TIP! After installing the sockets, mark the pin out on the chassis to help in wiring. The installation manual is pretty loose as to where/how things get mounted and wired. So having experience with electronics is a big plus with this kit. 1959 Bassman Kit - Great Mix Recording I also used images of old Tweed’s to help me with wiring.

The kit does not come with tube hold-downs. I bought some tube covers for the small tubes and Fender style clamp hold-downs for the 2 power tubes and the rectifier. One other addition I did was to use Loctite on the screws for the tube and transformers.
1959 Bassman Kit - Great Mix Recording
1959 Bassman Kit - Great Mix Recording
Stay tuned for more to come on this exciting project!

. Record . Mix . Master . Music .

1959 Tweed Bassman – Part |

Hi boys and girls. I have a new project that I am very excited about. Ever since I have been involved in electronics I never once built an electronic kit of any sorts. Of late I have been dabbling in tube guitar amp repair/modding with my good friend Kris and discovering how great older tube Fender amps can sound. During this time I have discovered that one of the “holy grail” of amps is the 1959 Tweed Bassman.

This type of amp is currently selling in the neighborhood of $4000 so buying/trying one out is a bit prohibited. But, I have found a company that makes a kit that you can build with the same circuit and cabinet design that Fender used all those years ago. My kit has arrived and I am going to blog about the build of a 1959 Tweed Bassman with the 5F6-A circuit and my own idea of what tubes to use.

Part 1, The Kit:

The kit I am using is from MojoTone. ( http://www.mojotone.com/amp-parts/amp-kits-tweed-style/Tweed-Bassman-Style-Amplifier-Kit#.Ug2OfFPsqGo ) I decided that I would use the recommended speakers as they most closely match what would have been used in the original Bassman. I ordered the kit without tubes as I did not agree with Mojotone as to the tubes they recommended. I will elaborate on this in a later post. Suffice to say that I will be using a mixture of new and old tubes to give me the vintage sound that this amp is capable of. The kit shipped complete with the exception of the cabinet as this is made as needed. Which is quite ok as it will take me some time to build and document this project. The cab will ship in about 30 days. After receiving the kit I went through the parts and verified with the included list and found that it did not include tube covers for the pre-amp tubes or hold-downs for the power and rectifier tubes. Bummer! So, back to the internet and ordered some cool colored tube sleeves for the 3 pre-amp tubes and some Fender style clamp units for the power tubes. It was nice that all the small parts came in parts cases with a corresponding list attached to the underside of the lid. Very nice!

A side note: This kit is not recommended for people who barely know how to use a soldering iron and are not familiar with reading a schematic diagram. Tube guitar amps have very high voltages that can KILL you if you do not know what you are doing.

1959 Bassman Kit - Great Mix Recording

Stay tuned for more to come on this exciting project!

. Record . Mix . Master . Music .

Build out a Mixing / Recording room – Part I

Studio Buildout:

From time to time I am hired or asked to provide technical services in the design and construction of recording studio spaces and systems. As a partner with my good friend Kevin Sucher, in a studio, we find ourselves in a situation where we need to do a buildout in a residence on a pretty tight budget. In the following months I will blog about the experience to document and hopefully provide insights and thoughts to help other persons in such an endeavor.
-Jacques Sewrey

The Space:

An unfinished room in a residential basement. Dimensions are roughly 17′ x 29′ x 7’9”. This what we have to work with for better or worse. The better part is that the room is a fairly large space and is rectangular in nature. The worse part is the ratio dimensions are not the preferred kind and the height is a bit on the short side. Preferred height would be a minimum of 10′.

In looking at a space for the monitoring of high quality audio, many considerations need to be taken into account. The size of the room, the type of audio production that will be done in the space, the type of building construction of the bare space, any other adjoining rooms of the space and their use, the neighborhood in which the space is, proximity to any low-frequency generating business’s or sounds, access to electrical and HVAC systems.

The use is going to be production, mixing, vocal over-dub and small acoustic instrument recording. Possible drum recording will be done in the garage.

Our space uses construction block as the type of material that the walls of the space are constructed from. This is a very good thing. Construction block or poured concrete is very good at stopping the transmission of sound from and to the outside. And being below “grade” is also helpful. However, being below grade can be an issue if the space is located near low-frequency generating sources as the low-frequency can pass through the ground and into the studio space then get trapped and reverberate. This is unacceptable!! One of the numbers you may run across is the STC. Sound Transmission Coefficient. Which is the amount of sound that is stopped by the material/construction. A wall, floor, ceiling, sofa etc.. The higher the number the more sound is stopped. The average hollow wall in a normal home is 30-35. Filled block and poured wall construction is 50-55. A double wall separated by airspace with 2 layers of drywall on each side and fiberglass insulation is 55-60.

The biggest issue we face is noise coming from the living room and laundry room above the space. I will talk about this in the next installment of the blog.

The first thing I did was to measure the room dimensions and plot them (to scale) on paper. Do all the nooks and crannies. In doing this you can start to layout your room. Make decisions of equipment locations, speaker placement. Added walls and possible sound treatment. Always try to set up your monitoring position in the first 1/3rd of the longways of the space.

Come up with a budget, something you can do with-in your business plan. The budget for this project is a healthy $8000. This only includes the buildout, no recording equipment. In planning a studio think of everything. The equipment you have or will add. How it will be wired. What cue system you will use. Storage space. Internet. Lighting. How you will incorporate HVAC.

Stay tuned for more to come on this exciting project!

. Record . Mix . Master . Music .

9.9.2013 – Please note – this project has been put on hold. If you have any questions on your Studio Build Out do not hesitate to contact me directly.

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