AX84 BBS Threads with new messages as of Sat, Feb 28th, 2015 @ 12:19:18 Amp Parts and KitsDoberman Music Products, LLC offers a variety of parts and kits Want Fender Vaporizer Mods!(by Matt Whittingham) Hi guys, I'm modding my guitarist's Fender Vaporizer with new efficient speakers, to try and make it as loud as 12 Watts should be! On it's own this is a great upgrade but whilst I'm waiting for the new tolex to be fitted I'd like to modify the circuit. I have seen countless praise of the BillM mods for Blues Junior amps, and I'd like to try and achieve the same kind of results with the Vaporizer, the only problem is I cannot source a Schematic for it. I'd like to do the tone stack upgrade (Orange Drops) and the Power Supply Stiffening upgrade (bigger). How would I achieve these mods? And do you guys have any suggestions to make the amp sound 'bigger' and louder? :)Sat, 28 Feb 2015 11:01:29 -0500 parallel wire(by JB Angelo) I don't have 600 volt wire for my power amp section, which is running about 475 at the plates. Is there any issue with twisting 2 300volt wires together in parallel? Will that cause an extra magnetic field around the wire which can induce noise? Thank you Fri, 27 Feb 2015 23:11:38 -0500 Two More Questions About 1x12 Cab(by cpsmusic) Hi, Picked up the timber for the 1 x 12 cab yesterday. I have two more questions regarding the plans: 1. The front baffle and rear panels are recessed by 1/4 and 3/16 respectively. Any reason for the recess and also any reason for the difference between the two? 2. The timber I got for the battens is 40mm x 19mm. The carcase timber is 19mm thick. 60mm screws will be too long and I couldn't find any 55mm screws so I ended up getting 50mm ones. My question is, will these be long enough as only 10mm will go into the case? I guess glue will help here? As the cab is going to be covered I was thinking that dowels might be better and stronger? Cheers, ChrisFri, 27 Feb 2015 22:13:33 -0500 Troubleshooting HF oscillations using oscilloscope (by Denny Gracey) Just finished Brian's L2L. Works fine, cleans are nice, but with gain cranked suffering from HF interference (squeal). Had same issue with the SEL after removing the board several times for mods which weakened a few wires at their solder joints. I've likely got a bad solder joint on a wire somewhere, but before i pull the board and resolder, is there a way i could isolate the problem using oscilloscope? Fri, 27 Feb 2015 21:08:43 -0500 Amp Switching Circuit Popping(by 8Len8) I've get a Phaez amp that has 2 individual inputs, one for each channel. I decided instead of using an AB box that I'd install a switching circuit to route a single input to either channel. Originally the amp had each channel's preamp tube connected to its own input jack. I got a Granger optoFET channel select board: <a href=" " target="newwin1425143958">[link]</a> I powered it off a wall-wart and hooked it up like this (all connections via coax): 1 NC - ground 1 Com - clean channel 12AX7 cathode 1 NO and 2 NC - input jack 2 Com - dirty channel 12AX7 cathode 2 NO - ground My only problem is that I hear a slight pop when switching from the clean to dirty channel. I've read that FET based channel select circuits should have quiet switching. Is there a pull-down resistor or something that I'm missing that could be causing the pops?Fri, 27 Feb 2015 18:12:05 -0500 20W PP poweramp(by CRFHX) Hi everyone! I have a few questions here so any help/advice would be greatly appreciated! I recently purchased LINE6 UX1 interface and is really great but gets kind of boring to play through headphones all the time. So one nice tube power amp to hook up with that would be nice. I also have one 8ohm 1x10'' vintage celestion cab for that project too. So my first question is about connecting that interface to my future tube poweramp: can I just hook up line out or headphones out from interface to power amp input through 10k pot, or? I don't need to build preamp, I want to use my interface instead of just tube poweramp is in the plan. My power requirements are low but I want to have some juice hanging there if I need 15 or 20W is OK. Also, I have one big 325-0-325 PT which is enough for that load so I want to use it for this. I'm guessing something like 6V6 or EL84 PP would be for this application but I like EL34 or 6L6 sound more. So general idea is to build low wattage EL34 or 6L6 PP poweramp, but can I reduce output power and primary current just by cathode resistor or grid biasing regardless of plate voltage? Also, do I use standard primary impedances for those tubes on reduced power set-ups? And how would it sound when EL34 is on, say 40% load? I'm not really experienced about biasing and experimenting with power tubes and I don't want to blow new set of those when searching for right load. Is it better to just go on 20W 6V6 set-up just like presented here? Thanks in advance! Fri, 27 Feb 2015 17:58:53 -0500 Westlabs transformer sets(by Henrik Reiersen) Hi all, New member, Henrik from Norway here. A few years back, I bought some transformer kits from a company called WestLabs, run by a person called Dave West. I haven't used them yet, but now I'm thinking of a new build. I tried to connect to the website but it's no longer in existence, and since the transformers didn't come with a wiring diagram, I no longer know how these babies are wired. According to Dave, these were left surplus after the Matchless factory closed the first time around. Did anyone here have the forethought to download the wiring diagrams for the westlabs 30 and 15w transformer kits before they closed shop? I appreciate any help. Kind regards, HenrikFri, 27 Feb 2015 09:58:23 -0500 Appropriate to use these caps for C9 and C14?(by SolarPowerPhil) Hey all, First of all thank you guys with boat loads of experience and understanding for contributing to this forum. Ive learned a ton from your threads and posts and continue to do so every time im here. I have drilled my chasis and installed all of the chasis components, even the unpopulated eyelet board to be sure. I have been studying the circuit and layout for the provided eyelet board and im ready to begin soldering in anticipation of following Mr. Rubys guided startup routine. Here is my issue: I am missing the capacitors for C9, and C14. I would much rather buy something local than have to wait longer for audiophile level components via shipping. This is my first amp build. I just want to get it done and working, then ill worry about whether or not i want to tweak things. The Frys down the street from my house sells Ceramic 100pF (C14)caps, and mylar/film 0.01 uF 630V (C9)caps. Would a mylar/film 0.01 uF 630V cap be ok to use in the tone stack portion of the circuit? Also, would a ceramic disc cap be ok for C14? And what is the purpose of C14 in the circuit exactly? Is it cutting frequencies off the gain into the second stage of preamp? Thanks againFri, 27 Feb 2015 09:23:14 -0500 BIAS supply(by mategenomics) Hello guys. I am recently building a CERIATONE JCM800 2203 amp with non original transformers. I have 350V taps for HT, 6.3V for heating but just 40V available for biasing. Amp from which I took PT had integrated circuits so that is maybe the reason for such atypical voltage. My schematic needs 100V bias supply. Is there any schematic for suitable voltage multiplier for instance? And do I understand correctly that it doesnt matter for which currents is it built as g1 draws current in microvolt-magnitude? Thank you in advance!Fri, 27 Feb 2015 07:24:07 -0500 October vs 18 Watt(by turtle441) I'm only half way through my current project but already starting to plan for my next one. Can anyone with experience playing both the October and a Marshall 18 Watter give a good comparison? I'm looking for a Marshall-ish build, something in the 18-20 watt range. I play mostly blues/rock, as well as some praise and worship stuff at church. Mix of HB's and single coils, probably more HB than single coil. There's plenty of 18 watt demos out there, but not that many of the October. For the few that I've heard, it seems like the 18 watter might sound a little smoother distorted, but I've got to admit some of the October cleans sounded pretty sweet. As a sub-question, what speakers have worked well with October builds (and did you use open or close-backed cab)?Fri, 27 Feb 2015 04:50:43 -0500 Gibson GA-55V build(by Brad Weeks) I found a copy of the Gibson GA-55V (true pitch shift vibrato based on the Wurlitzer circuit) in the Jack Darr (4th edition) guitar amps book. The vibrato mixer/modulator in the GA-55V schematic is different then Gibson's GA-83S vibrato amp and their GAV1 stand alone vibrato. Gibson has been known to have errors in their schematics and was wondering if anyone can confirm the GA-55V drawing as being correct? Thanks, Brad Fri, 27 Feb 2015 01:09:09 -0500 1x12 Speaker Cover(by cpsmusic) Hi, The 1x12 Cab plans don't give any indication of how to construct and attach a speaker cover (other than indicating that the speaker is recessed 1/4 inch). I'd like to protect the speaker with Fender-style cloth. Just wondering how other people have done this? I was thinking of using a wooden panel with a hole cutout for the speaker (in the standard way). I have two questions: 1/4 inch isn't very thick and with the thickness of the cloth (x2 if it wraps around the back) that decreases it further. Also, how should the speaker cover be attached to the speaker baffle? Cheers, ChrisThu, 26 Feb 2015 17:46:40 -0500 Book recommendation (by nonzero) Hey kids (and grownups), I am looking into making some of my own effects pedals to go with all these homemade amps, but I don't know where to start. With the amps, this site and Merlin's books set me on the correct path. Does anyone have suggestions as to what material I should read to start building useful circuits right away? (theory is great, but useful schematics would be even greater).Thu, 26 Feb 2015 12:42:27 -0500 New Faceplate for FF (by Rico Delrosado) Hello, ax84! I've been lurking around here for a while, reading all the Firefly posts, but this is my first post. I just received my custom FF faceplate from Mojotone. I'm very excited. If I wasn't sick, I might be able to start work on it, but at least I'm able to buy parts. :) Anyway, if I can figure out how to post a pic, I will. You may or may not see a pic below. Stand by for lots of questions. RicoThu, 26 Feb 2015 11:04:39 -0500 Does anyone know where to find quick connects?(by Alva Goldbook) I've been having trouble finding these. I'd prefer not to solder onto the giant lugs of this power switch. Thu, 26 Feb 2015 10:14:08 -0500 SEL - one knob(by winghamwill) Hi, I built an SEL a while ago and it died, not sure what happened to it, I tried a few things but haven't got to the bottom of it so it has been sitting alone for a while.... I have recently come across the Big Crunch one knob guitars and this has stirred me up so I thought... New project, get the SEL running as something similar and simple like the one knob. Any one have any ideas of how I could do this, would it be a case of ripping out the tone stages and bypassing the gain pots or a big overhaul? If anyone fancies altering a schematic I would forever be in their debt! Thoughts? Cheers WillWed, 25 Feb 2015 21:16:58 -0500 19 rack ground loop problem(by jack plug) I need some information on how to hook up a 19 inch rack which contains a tube stereo power amp,a tube stereo pre amp and a lexicon reverb to avoid ground loops as the preamp and tube power amp are earthed or grounded via the mains plugs and also through the steel rack mounts. Also commercial jack cables have continuity through the screened portion of the cable. I'm thinking i should make up my on cable sets with one end of the screen disconnected so signal ground goes via the earthed portion of the supply. I'm also trying to work out how i can isolate the 19 rack units from the rack mounts to prevent a ground loop here.Wed, 25 Feb 2015 19:04:48 -0500 Merlin Figure 12.10(by GeoMan) One of the things I've had trouble with is parsing schematics into real layouts. I've gone through the exercise of making a "layout" out of the parallel effects loop in Merlin Figure 12.10. <a href=" " target="newwin1425143958">[link]</a> I understand in broad brush strokes how it works. I know this isn't a proper layout, but if anyone has a minute, and wouldn't mind making sure that I've got all of the right things going to the right places, that would be awesome. Thanks as always. -PLWed, 25 Feb 2015 15:02:05 -0500 BOM and Cutting List(by cpsmusic) Hi Folks, I'm new to the forum so sorry if this question has been answered before (I've done a search but couldn't find anything). Is there a bill of materials and/or a cutting list for the 1x12 cab? Cheers, ChrisTue, 24 Feb 2015 20:33:22 -0500 Using a multi tap iso PS(by MikeT) Hi everybody, I want to build this amp and have some questions about the PS. I like to use recycled parts as most as I can, I mean what I already have on hand.. so the only missing part is actually the PS. Since Hammond transformers are quite expensive where I live, in the hope of saving money, I looked in my junk part box and found a 60VA 120vac/120vac isolation transformer, which has a "multi tap" primary.. Then I though about using it in the "reverse way", I mean by hooking 120vac at the secondary I get exactly 207vac at the primary (com/230 wires). Here it is <a href=" " target="newwin1425143958">[link]</a> The wires are pretty thick at both primary and secondary! Since 2 X 12ax7 and a 12au7 will not draw that much current maybe this isolation transformer would be a good try? Thanks for your advises and comment!Tue, 24 Feb 2015 08:58:55 -0500 Transformer Help(by Jeph88) Any assistance on how this would be wired? Series? <a href=" " target="newwin1425143958">[link]</a> Tue, 24 Feb 2015 00:14:56 -0500 dropping PS voltage(by ColinD) For the sake of experimentation, can I use something like a bias supply circuit as a negative voltage source in order to reduce the HT in an amp? In other words, if the rectified HT is 450v, can I insert a -100v source to bring the HT down to 350v? Or is there going to be a fire?Mon, 23 Feb 2015 21:35:13 -0500 New 10W SE build(by DanGu) Here my new build. It's made only from spare parts I got left from other builds. The only buyed parts are the pots and the case. <a href=" " target="newwin1425143958">[link]</a> <a href=" " target="newwin1425143958">[link]</a> <a href=" " target="newwin1425143958">[link]</a> The layout isn't very neat as I'm used to do. In fact it has some kind of artistic tridimensionality. I was to lazy to design a layout board. The chain is the following: EL34 < tone+master < 6cg7 gain stage < 6cg7+ef86 paralleded gain stage < 12AT7 paralleled gain stage the high/low switch connects the input jack to the 12AT7 to push the ef86+6cg7 into overdrive. If set to low, the 12AT7 is bypassed and input taken directly to ef86+6cg7 for smoother blues sound. This amp is ideal for music that goes from the classic blues to the hard rock and southern. It has a great variety of tonal sounds, and only made with spare parts. Don't expect a real clean tone from it. It's always a single ended without NFB.Mon, 23 Feb 2015 14:13:39 -0500 schematic writing software(by Alva Goldbook) I was curious what programs you guys are using to write out schematics. I've been using Eagle, but it's pretty cumbersome and time consuming. Mon, 23 Feb 2015 10:16:04 -0500 Using Unwanted Circuitry to Build a Mini Guitar Amp (by Robin1) I have the circuitry from a TDK model number NX-4CD-WHDS. I would like to use it as a mini guitar amp. Can anyone advise where I would connect a guitar lead toMon, 23 Feb 2015 06:40:52 -0500