Tube Amp Archive

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If you're going to use a nibbler you need one of these. Cut out the corners with a punch also makes life easier.

Try rotating the speaker 90 degrees.

Can a VVR be used to just regulate the screen voltage? My next build may use TV vertical deflection type pentodes. These tube types can accept high voltages on their plates but if screens go over their published limits the tubes fail early. They sound good and are cheap. The 807 transmitter tube can...

Scan through the Gibson service manual and look for Monitor jacks. I've posted links to two different types. The first noted (GA-77RVT) taps the signal from the grid to kathode connection of the PI. http://www.el34world.com/charts/Schematics/files/gibson/GA-77RVT.pdf The second one noted (GA-19RVT) ...

For all Fender or any transformer driven reverb you want an input Z of 8 ohms and an output Z of 500-600 ohms. When you get into higher Z impedance you assume solid state or capacitor driven reveb tanks. The other coded numbers have to do with how many springs and length of delay. Choose those to su...

The part number decodes to: reverb type: two spring small input Z: 150ohm output Z: 2250 ohm decay: short connectors: insulated mounting: horizontal open side up. http://roymal.tripod.com/accutron.htm It seems it would work if you modeled your circuit to the Ampeg type C capacitor driven reverb. It ...

I have a blonde Bandmaster head that a previous owner installed a Twin Reverb output transformer. The two 6L6 amp now wants to see an 8 ohm load.

I plan to install it in a combo cabinet with either a single 8 ohm 15" or two 10" 16 ohms speakers wired in parallel.

Do I need to make the capacitor value larger or smaller to increase useable range on a top cut circuit, (Vox type)? I currently have a 250kl in line with a .0068uf cap. That was the nearest value I had on hand. The Vox AC15 schematic show .005uf for normal/treble models and a .01 for bass models. Th...

Sorry, I don't know how the transformer is wound. If you feel the need to run a 5U4 in one to lower voltage try a 5T4. It has the same specs but only needs 2 amps. Its a metal envelope tube. They're cheap at about $10.00 each from Surplus sales of Nebraska, Fair Radio sales has them used for $3.50 e...

I've tried grounding the grids directly and through a 1M resistor. That didn't fix the issue. I replaced the .1 cap that that ties the plate to the volume control with a new one. Now I get 170 VDC on the plate. This reading is with no other tube installed (except 5Y3). I'm not sure why disconnecting...

Currently the preamp is disconnected from the amp except the power supply. The grids are disconnected and the preamp is disconnected from the amp by disconnecting the circuit at the volume pot input. It is currently just Plate and Kathode. I've tried three different tubes in socket with similar resu...

with a tube inserted in the socket I measure 342 on the B+ node for the preamp. On the 12AX7 plate I measure 63VDC with 2.1VDC at the Kathode. Without any tubes (except 5Y3) I measure 380vdc at the preamp node and 375 vdc at the plate. Zero voltage on the kathode. There is no mesureable AC ripple. T...

I built this amp in a Weber Deluxe chassis. This set many constraints and workarounds. I like this kind of puzzle. The power transformer was cannibalized from an old hifi console. it ran two 6BQ5 tubes a 5Y3 and numerous signal and radio reception tubes. Since the chassis has three octal holes and t...

I just built an 18 watt inspired amp based on Mark Huss' 18 Watt-enstein circuit. The amp sounds very good, no ground loop noises etc. But. When I put a 12AX7 in the preamp slot the approximatly 300vdc drops to about 60vdc. This is with no other tubes except a rectifier. 100k ohm shared plate resist...

Yes. Salvadged wire generally won't be reused in the aircraft because they are all marked to conform with the wire diagrams of the aircraft. Find a local avionics shop and ask nicely, assure them that it won't ever be used on an aircraft again and they will probably give you all you'll ever need.