Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: silverfox on February 05, 2013, 03:25:54 pm
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If you want to skip the introduction just go to Question:
A funny thing happened on the way to my first build- I continued looking at various schematics until I learned a little and went crazy a little. Now I've started to build my amp.
First off- tubenit- Thanks for all of your work. It has brought me to this place. I stated the Marshumble build and realized I wanted a different tone and that tone was JCM-JMP. I play almost exclusively 70 Hard Rock and Metal.
Further, I'm going to incorporate many of the features from that build into what I'm doing so it was not a waste of time. A great learning experience too studying all those schematics. Thanks again everyone for that initial design work.
Question: Has anyone built sluckey's Dual Marshall Preamp? How does it sound?
Here's the link for the schematic: home.comcast.net/~seluckey/amps/misc/Marshall_Dual_50.pdf
I've started the build now and got the power supply-rectifier circuit done, filaments wired up and power transformer installed. I used 35 watt Iron from the 7686 based amp laying around here. I'll post pics soon for review and advice.
V1a has a 330 uf capacitor connected to the cathode- Is that the correct value? Or should it be 3.3 uf?
Question: Awhile back I posted a tube mixer question. I eventually found what I was looking for. I want to run two preamps off one guitar simultaneously, then mix the outputs prior to sending them onto the active effects loop. I want to be able to use a balance control to favor one channel over the other prior to mix. Will the voicings' clash or will this be an En-harmonic monster?
Silverfox.
Question: How do I mod the output tube section to run at 35 watts. Do I just build it with 35 watts of Iron and that's what I'll get or do I have to change component values?
I'll post some
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cool! perhaps to taunt us with some progress pics?
--pete
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I have not built it exactly as Steve has it laid out, because I already had a Handwired JCM 800 and added the plexi components and also JTM 45 to make a decade switch. 60's 70's and 80's. It is really nice for those into Marshall tones. I tried the same with a JTM 45 and not so good. Needs more plate voltage as I cannot get a clean sound out of it using El34's. I did keep cathode split on v1 and have a plexi in 2 holes and JTM 45 in 2 holes, but it is not the same as it has KT66 tubes.
I used a different MV, a PPMIV. I can assure you it will scream. Not really my style, but sometimes I just have to pull out the Les Paul and play Neal Schoen licks or for that matter, Bad Company. I am not sure, but I think it is running a little better than 50 watts. It can get LOUD. I wish I were playing with a group where I could get some use out of it.
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Here are some first pics. My question here is: I want to put the rectifier board over top of the PT. There is an end bell on both sides as you can see. Not sure if this will induce hum or not but I don't think so. I plan on taking the HV leads from the board over to their connection points.
http://min.us/m3yjGocRAe4Ol (http://min.us/m3yjGocRAe4Ol)
The circuit I'm working off came from sluckey's home page but there are some details over at ax84 relating to one of the channels. Over there it is referred to as an October or November build. In looking into the November build, it appears that went on to become an October- one of the preamp channels. Lots of build info over there.
I put some workup tone stacks onto a prototype board to experiment with if you're wondering what the circuit is in the background.
Silverfox.