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Hoffman Amps Forum image Author Topic: Wiring questions.  (Read 3539 times)

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Offline tinker

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Wiring questions.
« on: May 16, 2010, 09:40:06 am »
I'm starting on a guitar amp and I was wondering whether to try and use a turret board or go point to point. As far as I know this is an original design circuit. I'm not sure about boards as to where or not they can be generically used. If I go point to point can I put the preamp tubes in front over the pots? I found the circuit at Yahoo Groups / Files /Wes Final Amp.   I hear a lot about input filter chokes also but I don't see them in every circuit I look at on Schematic Heaven.. Any input would be appreciated.          http://f1.grp.yahoofs.com/v1/YPrvSxuQZwY-mfNco-ZKk6KmkVGm3VLIIWjKaVRuxGtKfSlYZ2IFQQXOFH5kOb-vcuBzu2oLsV4T7SV4UYLg2Uurww-sEaj1jg/WesAmpFinal.pdf     Tim

Offline supro66

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Re: Wiring questions.
« Reply #1 on: May 16, 2010, 10:03:18 am »
look in my site and you will see some point to point Supro 6420 Thunderbout 35 Watts
http://fatbasterdamps.com/

Offline HotBluePlates

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Re: Wiring questions.
« Reply #2 on: May 16, 2010, 01:08:15 pm »
I couldn't view the amp schematic, but it doesn't really matter.

Whether or not you use a board is a matter of preference. A strict definition of point-to-point wiring is where the leads of the components use form most of the wiring of the amp, and could look messy if not executed well. A board gives a stable and orderly platform to mount the components, with perhaps more wiring between the components and tubes sockets and controls.

A generic board might be one with 2 parallel rows of eyelets, turrets or terminal lugs, between which all components are mounted. From these mounting points, wiring is run for ground, power and signal in/out.

I'm guessing what you'd like is a worked out layout for the amp you want to build. Several folks here could probably draw that up quickly. Layout isn't rocket-science, mostly we use an approach that we've seen work on other designs.

Offline sluckey

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Re: Wiring questions.
« Reply #3 on: May 16, 2010, 01:51:00 pm »
The amp is basically a JCM-800 2204 switchable high gain preamp into a basic LTP driving 6V6s without NFB. Layout will be more critical due to the high gain. I suggest following one of the many proven board layouts available rather than true point to point.

Here's the schematic...
A schematic, layout, and hi-rez pics are very useful for troubleshooting your amp. Don't wait to be asked. JUST DO IT!

Offline HotBluePlates

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Re: Wiring questions.
« Reply #4 on: May 17, 2010, 12:47:13 am »
Layout will be more critical due to the high gain. I suggest following one of the many proven board layouts available rather than true point to point.

I agree completely.

Despite how the schematic is drawn, the two 12AY7 sections, U7 and U8 must physically be swapped when built. What I mean is U7 must be closest to the input jack and be the first thing the signal hits, with U8 coming second. If you build with all tubes in a row towards the back edge of the chassis, this won't matter too much, since both sections are part of the same tube.

This is a case where I'd build Matchless-style, if space allowed. What I mean is the old Marshall amps were like the Fender amps, and had the tubes in a row on the chassis, nearest the back panel. But on some models, Matchless positioned the input tube closer to the front panel. It makes for a longer reach to swap that tube when the chassis is in the cabinet, but it shortens the wiring to/from the input jack and front panel controls. If you had space available between the front panel and controls and where the edge of the circuit board is, I'd put that input tube up there between the board and front panel. The wiring to and from the switch to activate U8 is critical. It short be short and probably shielded wire for everything from the input jack to the grid of U6.

Offline jojokeo

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Re: Wiring questions.
« Reply #5 on: May 17, 2010, 02:57:01 pm »
I just used good layout w/ shielded wire and no issues. The tubes are all lined up along the back, ala Fender. I would suggest you look at the values used for the pi and pa parts. I see a couple of issues w/ those. Those values are for EL84s not 6V6s.
To steal ideas from one person is plagiarism. To steal from many is research.

 


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