The Amp Garage

I'm working on a schematic for a new project, push pull EL84 power section with fixed bias. I expect the transformer I'm using to be in the range of 360-370v B+ and I want plate voltage to be more like 320-330v. This is a non center tapped PT that I will be using with a solid state bridge rectifier....

I just bought an old Columbia (sony) C-690 TR reel to reel cheap on craigslist and I am looking for some advice on converting it to use as a guitar amp. This tape deck uses one 12ax7 and one 12BH7 with a grid leak biased input and one half of the 12BH7 in a single ended power stage. Here's a schemat...

I just realized I never got around to posting the sound clip I promised!

Here is my (very) rough demo... only 2 months late:

https://soundcloud.com/user-545789156/tods-demo-hb-1

I had a little more time to play the amp and I'm happy to report it is actually very quiet with humbuckers, so it seems it was more the guitar than the amp that was at noisy the first time I tired it out. I do have plans to record some sound clips, but I'm going to take some time to get to know the ...

I too like your cabinet. Looking forward to any sound clips you may have. Where did you get those knobs? Mike I found them on Amazon at some point when I was stocking up on parts for pedal builds. They were inexpensive and look nice, but they ended up being slightly too small for standard solid sha...

Well, I built it and it works! I ended up using a set of the winged C russian "6BM8" tubes and they sound good. Here are some pictures of the finished product: IMG_20170919_004908 (1).jpg IMG_20170926_141826.jpg IMG_20170922_004006.jpg The only issue I had was having to change the power tube cathode...

Does anyone have experience with the Svetlana, winged C 6BM8/6F3P tubes? I'm shopping around for a set of Power/PI tubes for this build. NOS US or British 6BM8s on ebay are a little pricier than I had hoped for and I have heard mixed reviews on the current production EHX tubes. I keep seeing winged ...

Here is a layout of the schematic in my last post: Tweed ODS micro layout.png It is intended to be mounted marshall style, on the bottom of a head cabinet, but with the input/preamp side on the left when you are facing the control panel. I've gone ahead and ordered a blank chassis, Edcor transformer...

Double post...

Another revision, with the clean level removed, PPIMV implemented, and the screen and OD triode nodes seperated again. I thought about the power supply design some more and it did seem like combining the screen node with the node for that triode was asking for trouble, especially in a high gain desi...

Regarding a choke or not, .......... just a personal preference in tone and I don't necessarily seeing one approach "better" then the other. I'd probably use a choke IF I had room, but if not I'd just use a resistor and enjoy the amp that way. I think your Edcor trannie with 210-0-210 and 120ma wil...

Ok, here's an updated schematic: Tweed overdrive micro Schem rev 2 6bm8.png I've updated the Power section and PI values for 6BM8 tubes, moved the choke so its between the Plate and screen power nodes, combined the Pi and V2b power nodes to simplify the power supply, and recalculated the power suppl...

I'm reworking my schematic for 6bm8 tubes etc right now. Putting a choke inline between the plate node and screen node, and I notice that I have roughly the same voltage for the screens that I need for the v2b triode in the overdrive section of the preamp. Would it be a problem to supply the screens...

The 6BM8 is still in production. It's one of my favorite tubes. It has a great bass tone for a low wattage tube. I'd aim for around 310v or less on the plates IF I was attempting this idea. I'd also use a 5751 instead of the 12AX7 in V1. And I'd eliminate some of the components between the DPDT swi...

Musical Power Supplies has an PT with 190-0-190 and 120ma. So 190 X 1.4 (solid state rectification) will be maybe 265 volts or so? That might work OK? I think you'd have to experiment a little with dropping resistors on the B+ rail to make sure V1 is getting the plate voltage that you'd want. (140 ...