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  1. Replies
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    Unfortunately there is no non-destructive way...

    Unfortunately there is no non-destructive way that I know of.

    Most pros will ID the speaker based on models they've known before, magnet size, cone type and so on.
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    You were luckier than my client. To Voodoo Labs'...

    You were luckier than my client. To Voodoo Labs' credit, he did play it for a while at 220V before it blew up.

    To try to protect the circuit you can use a 250mA fuse. It's twice the maximum...
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    For the 230VAC model a 250mA mains fuse will do....

    For the 230VAC model a 250mA mains fuse will do. Note that the aux power outlet is not fused, it's a direct tap from mains.

    Was your transformer good after you removed the blown fuse?
  4. Thread: Choke experiment

    by jmaf
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    644

    With an 18k resistor feeding the screens you'll...

    With an 18k resistor feeding the screens you'll get some interesting compression on the output tubes. I don't know if that's your intention because the amplifier will feel more creamy and not "hard"...
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    You shouldn't have to solder brass/copper and...

    You shouldn't have to solder brass/copper and aluminum.

    The main point here is that the transformer will always induce some tiny current on a steel chassis but not on aluminum or brass.

    The...
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    Most amplifier chassis are made out of steel. My...

    Most amplifier chassis are made out of steel. My experiment was an attempt to improve on that.

    The above amplifier is dead quiet which is what I wanted to achieve.
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    Can't praise Morgan Jones' books enough. The...

    Can't praise Morgan Jones' books enough.

    The other volume, about tube amp theory, is probably one of the best tube amp texts you can buy.

    Because of this particular book I started building my...
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    PIV = the last preamp tube before the power...

    PIV = the last preamp tube before the power tubes. (Phase inverter). The effects return should inject signal there. If you have an external preamp (pedal/boost/whatever) you can inject your guitar...
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    If you inject some signal directly to the PIV...

    If you inject some signal directly to the PIV does it come out the speakers?

    I used to have one of those pedals that record guitar playing, I'd have a cable with a 600V capacitor on the other tip...
  10. Since the last post I got my mind set on one of...

    Since the last post I got my mind set on one of these:

    53136

    I'd drill the test tube sockets holes to each side of it on the chassis. The needle would point to the hotter tube. A perfectly...
  11. Filtering: it depends on what you want to spend...

    Filtering: it depends on what you want to spend on the project. If you've got the components and $ then there's no reason not to build a hard PS. Remember : testing with class A bias will set the...
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    IC5 and IC6 are both LM317

    IC5 and IC6 are both LM317
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    I'd surely tell my clients to mod these and add a...

    I'd surely tell my clients to mod these and add a mains fuse. Could use an axial wired fuse holder, from the mains socket, without having to drill the case.
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    Sorry, overlooked that it's a CF. You're right.

    Sorry, overlooked that it's a CF. You're right.
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    I was browsing my "regional ebay" and found a...

    I was browsing my "regional ebay" and found a mint state box of Tungsram PNP resistors for $10.

    This one https://www.etsy.com/hk-en/listing/583992907/2x-ac128k-electrically-matched-pair

    I...
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    Sure but if whoever modded this wanted a full...

    Sure but if whoever modded this wanted a full band NFB why didn't they just use a resistor and make it a divider with the vol pot?
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    visualdistortion asked if he could test the fuse...

    visualdistortion asked if he could test the fuse like he'd test a regular fuse, I hurriedly said yes ["you can test as"] regular fuse.

    That's all, I was just trying to help. I know where this is...
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    Makes sense. The 4 rectifiers are right to the...

    Makes sense. The 4 rectifiers are right to the left on the photo. If it's a SMPS then there's a small transformer right after that. That'd be an isolating transformer, which is what I wondered about...
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    I posted 9 schematics and a few silly comments....

    I posted 9 schematics and a few silly comments. No insult at all.
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    Sure looks like NFB but it's tuned to 0.2 hz...

    Sure looks like NFB but it's tuned to 0.2 hz which is why I thought it was strange.
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    I didn't say Brazil produced these transistors. I...

    I didn't say Brazil produced these transistors. I referred to market conditions in the 1970's.

    So, what I said is impossible? You sure Juan Manuel? Let's take a look.

    Here's a little amplifier...
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    I thought he said that cable came straight from...

    I thought he said that cable came straight from mains (type C EU plug)?
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    Seems pretty intuitive that pins 1 and 4 are...

    Seems pretty intuitive that pins 1 and 4 are mains, the other two look disconnected.

    I hope there's an isolating transformer in there somewhere. From your 1st photo looks like the wires go...
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    Unless I'm missing something terribly obvious,...

    Unless I'm missing something terribly obvious, the top one looks like a typical CF.

    I have no idea what the 3.3 meg resistor and 220nf capacitor are doing there. There has to be more to that...
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    That jumper would kill all audio. It also cannot...

    That jumper would kill all audio. It also cannot go from the plate straight to the grid. The only correct connection for the jumper is as in drawing 1, from plate of tube 1 to grid in tube 2. Also...
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    How come most transformers in consumer devices...

    How come most transformers in consumer devices don't have a thermal fuse then?



    I've never seen a guitar pedal catch fire.

    These things need a fuse to save the complex and expensive...
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    These things need to be redesigned with smaller...

    These things need to be redesigned with smaller fuses not hidden in the transformer.
  28. I'm planning on starting a open-source tube...

    I'm planning on starting a open-source tube matcher project which I'd share here, but I don't have the time right now. I do have it on my to-do list though.
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