The Dyno Tweed Amp
The Dyno Tweed continues the low-volume guitar amp theme. It has a 12AX7 preamp and phase invertor, 6X4 rectifier, and a pair of 6AK6 power tubes, which should be about 2 watts. I like to turn it up to 10 to get that open tube sound, which is loud enough for a bedroom! The Dyno was originally a Dynovox amp, hence the name.
Here's a photo of the tweed cabinet. It currently has a 10" Emminence Redcoat speaker.
The eyelet board is made out of red G3 fiberglass.
The power and output transformers were from the Dynavox amp, which someone had painted gold.
The controls are pretty simple: Volume & On/Off, Treble, and Bass. I plan on adding a pilot light (there's a small hole to the left of the knobs).
Finger joints take a lot of work to get right, but it's worth the effort!
I've cut those rear stringers so they are only 1" wide. Originally they were 2", which is the width of the chassis, but it looked odd and wasn't going to make it any more stable.
Here are some sound samples recorded with a Boss BR8 and a Samick Les Paul with DiMarzio Tone Zone and PAF Pro pickups. I start with the neck pickup in single-coil, switch to double-coil, and end with the bridge pickup. The guitar is connected directly to the amp without effects.
These are sounds with 6AK6 power tubes, which is about 2 watts.
- DynaMite6AK6_1.mp3 Volume on 7 for blues clean and crunch
- DynaMite6AK6_2.mp3 Volume on 10 for distortion
These are sounds with 6AQ5 power tubes, which is about 5 watts.
- DynaMite1.mp3 Volume on 7 for blues clean and crunch
- DynaMite2.mp3 Volume on 10 for distortion
I really like this amp because it sounds cool and is really fun to play on 10, which gets that awesome tone. With the 6AK6's you can do that without family members complaining.
Some notes.
The output transformer is stamped 52407, the power transformer is OP-12. Both were from the Dynovox amp. For current production transformers, Antique has the P-T291 Output Transformer, 8W, 4-9K and P-T292 Power Transformer, 120V primary, 140/28/10.5 V secondary.
The layout is based on the Fender Bassman 5F6. The 6AK6, however, has no free pins for the resistor. Initial builds mounted them on the board, which caused inter-stage coupling problems. The wires to these resistors on the 5F6 are underneath the board. My solution was to add a grounded braid shielding and move those resistors near the output tubes. Coupling issues cause a feedback note on top of the main note, which you can see on a scope or hear as a sort of low-frequency bark underneath the played note.
Here's a schematic