AX84 BBS Threads with new messages as of Mon, Nov 24th, 2014 @ 04:17:45 http://ax84.com Amp Parts and KitsDoberman Music Products, LLC offers a variety of parts and kitshttp://shop.dobermanamps.com merlins serial/parallel looop(by arjepsen) I just put together an october club, and implemented the parallel/seriel loop with a mix pot, as Merlin describes in page 220 in the book second edition of his book. It works well at the pure serial and parallel settings, but when I dial between those two outer settings, the volume decrease to around the middle, and then increase again. I'd love to use this loop and be able to dial in the exact amount of fx I want, but right now that doesn't really work well enough. Any good way to avoid that, so the level would be the same at every setting of the mix pot? Regards AndersMon, 24 Nov 2014 04:14:37 -0500 http://ax84.com/bbs/dm.php?id=487535 What to do with a broken Champ...(by JHarris) Hey all, I messed up and damaged my Silverface Champ's OT. These amps use an RCA connection to the speaker and with corrosion + use, they wear out and can lose connection. If you've been away from tube amps for a while you may keep playing, wondering why no sound is coming out... Rather than checking the speaker right away... Oops. Anyways, I have some options at this point (and some related questions). I'd appreciate any input you can offer. 1. Spend $45 on a Fender or Hammond SE OT plus maybe a new 6V6, and fix it. 2. Fix OT, and replace the rectifier with a 6SN7 to get some more gain, which I would like. 2a. Can the heater and HT windings handle an added 6SN7? What about a different preamp tube that draws only 300ma for the heater? 3. Transistor alternative for more gain... I am not superstitious about a non-clipping transistor ruining the tone, but I think tubes are cool, so if the PT can handle it I'd prefer glass. 4. Spend $35 on a Hammond 125 and rewire everything for a 6SN7 PP output stage plus interesting preamp stuff. Bigger project, maybe high component costs when it's all done. 5. Dig out an ancient PT and OT I have lying around, drop $$$ on a chassis + caps, and build an 85w+ PP EL34 amp that eats EL34s for breakfast lunch and dinner. If I'm going to spend time and money on a build, might as well go big. But, the 2W PP 6SN7 might be better for my apartment. 5a. I had this monster assembled in a sketchy test chassis a couple years ago and got some gross distortion, that I think was blocking distortion. My bias was really low at that point. Like, 10w at idle. I think the B+ was around 600v, if I turned bias up higher is it possible to prevent blocking distortion in EL34s at that voltage? I know I will go through tubes, and I'm willing to push them a little harder because I've already accepted that fact. Don't worry, I don't mess around with NOS tubes in this, I do my part to economically support the Russian new-production industry. Thanks for any advice you can offer! Sun, 23 Nov 2014 16:29:14 -0500 http://ax84.com/bbs/dm.php?id=487534 favorite tone stack(by The Tone Surgeon) Hi im fairly new around here and I was just wondering which tone stacks are your favorite. personally iv always liked the simple tmb controld of my p.o.s. solid state Marshall. but I really don't have alot of experience in the matter.Sun, 23 Nov 2014 15:20:49 -0500 http://ax84.com/bbs/dm.php?id=487508 What should I do with my Peavey Classic 30?(by Darren Porter) I have a Peavey Classic 30 that I used from time to time but I was never totally thrilled with the sound. The clean is just OK and the overdrive makes me cringe. Just not my thing. Now that I have built a few amps I really can't see myself using this amp much anymore because I like everything I've built sooo much better. So I'm trying to decide if I should sell this thing and partially finance another build or gut it and convert it into something I actually like. I don't really see a lot of these on the used market so I don't even know what it's worth. I've had it for about 12 to 15 years but it's in pretty-much perfect condition cosmetically and functionally. Anyone have any experiences converting these to something else using the existing chassis and transformers? Sun, 23 Nov 2014 13:54:40 -0500 http://ax84.com/bbs/dm.php?id=487460 mic preamp hum(by DanGu) Hi. i've finished a tube mic preamp for a friend who has to record some tracks. But testing it we noticed that the mic inputs have to much hum for recording purpose. Here the schematic of the input grounding: <a href="http://postimg.org/image/5tuka6b7x/ " target="newwin1416820665">[link]</a> This has about 60dB of gain. The instrument input is after the signal transformer(hammond 140NEX), has about 50dB of gain and it's not so noise. The amp chain is Ham_140NEX->12AU7->12AU7->ecc88->CF ecc88 We tryed to connect the pin 1 gnd directly to the case or lift it without success The heater supply is 12.6VDC and elevated at about 60VDC Power supply transformer is an hammond 370ax, and used a choke 155G for filtering the power supply I'm wondring what else I can do to make it quieter. I'm starting to think I my have bought the wrong input transformer Here a pic by the way <a href="http://postimg.org/image/t3rolqz3n/ " target="newwin1416820665">[link]</a> Waiting for inputsSun, 23 Nov 2014 05:59:03 -0500 http://ax84.com/bbs/dm.php?id=487390 LEDs for Blues Pre(by DutchMarco) I'm ooking to order bits for my Blues Pre + 20W SE + VVR. I wanted to order bits from here: <a href="http://www.okaphone.com/artikelen.asp?groep=423 " target="newwin1416820665">[link]</a> (because that'll allow me to get the IRF820 for the VVR, too, in one shipment). As you might make out (from the Dutch site), there are several options for red and green LEDs, with a voltage drop of &#8804; 2V and a current of &#8804; 20mA. Are those appropriate?Sun, 23 Nov 2014 05:07:21 -0500 http://ax84.com/bbs/dm.php?id=487528 trouble shooting some unwanted distortion(by cameron nicklaus) man oh man I'm stumped. this is a straight up PR clone...It sounded fine except for when I record it I hear a bit of distortion even at relatively low volumes. I almost can't detect it when just listening in the room but it's pretty obvious through a mic. This may end up being a bunch of questions in one... first off, does anyone have any tips for trouble shooting distortion with a scope? I have a decent one but I'm a bit inexperienced at using it. I can dial in a wave on the screen and can put a sine wave through the amp and see when the wave begins to change shape but I can't recreate the type of distortion I'm hearing with a sine wave...it seems to stay normal way beyond the volume I hear distortion with a guitar at. to try to figure out where it's coming from I bypassed all the gain stages and took the line running into the first gain stage and ran it straight into the phase inverter. so basically; guitar-input jack-gain stage that precedes the cathodyne PI. one really curious thing (that may have nothing to do with anything); at one point the tone stack and the triode after the tone stack was bypassed but I still saw signal on the plate of that triode....so nothing wired to the grid of the triode but still saw AC signal on the plate...how is that possible? would the grid pick up enough just through the air? I had guitar signal coming out of the amp...I thought that, if I disconnected the wire going from the volume pot into that second triode, it would kill the signal? any thoughts or suggestions of things to try would really help!!! Sun, 23 Nov 2014 04:46:57 -0500 http://ax84.com/bbs/dm.php?id=487517 Tube rectifier in a SE amp?(by sajyho) Hi guys, I've recently got interested in 6V6 overdrive tone and I'm gathering information to build a SE amp based on the '59 Supro or maybe a champ. I'm just curious; is there any advantage in using a tube rectifier in a SE amp? I mean since there will not be any voltage sag in a class A amp, so is there any other reason that why should I use a tube rectifier? Regards SajadSat, 22 Nov 2014 23:17:29 -0500 http://ax84.com/bbs/dm.php?id=487462 Dual Concentric 1 meg Pots?(by The Ballzz) Hi All, This is my first post, so please be gentle. I have searched for 1 meg dual concentric pots and found them to generally be made of "UNOBTAINIUM", however, I have finally found a source to have them manufactured in reasonable quantity at a fair price. I'm wondering if anyone, besides me, sees or understands the potential use(s) for such a pot? I have not yet placed my order and am exploring interest in any of these at a reasonable cost. This is not intended as a "for sale" post simply seeing if anyone would want a few of these if I were to acquire100 or so of these. If no interest, I will likely not make the investment. Thanks In Advance, Gene Sat, 22 Nov 2014 22:38:07 -0500 http://ax84.com/bbs/dm.php?id=485969 3 Speakers - What to do?(by David E) Hi folks, been a long time. What might I do with three speakers salvaged from an old (solid state) organ? Probably 8 ohms impedance each. I kinda want to build a tweed deluxe, but I haven't built anything for a looong time. <a href="https://www.flickr.com/photos/eggend_houston/15666849580/" target="newwin1416820665">[link]</a> Sat, 22 Nov 2014 12:32:54 -0500 http://ax84.com/bbs/dm.php?id=487512 High pitched oscillation problem(by Kursad K) It's confirmed, I have one: <a href="http://en.wikipedia.org/wiki/Tinnitus " target="newwin1416820665">[link]</a> together with roughly 10dB hearing loss in the bass and treble range. KursadSat, 22 Nov 2014 12:09:46 -0500 http://ax84.com/bbs/dm.php?id=487469 Tube wah (Eric Barbour/Peter Belov)(by Jimbo) Ok total newbie here, forgive me if my lack of knowledge alarms you or makes you fear for mine and others safety :) but.... I am looking at the schematic for the Tube Wah/Fuzz, and thinking I would love to build it but I have a number of questions - can anyone help me please? 1/ UK line voltage is 230/240 (depending how fast the mouse runs), the power transformer spec'd has dual primaries at 120, one is connected to the mains via the 0.5 Amp fuse the other is used to carry the plate voltages off (around 140AC after fluctuations) here is my first problem as I dont want to run the plates hotter (dual primary 230 volt trans would generate 230+ AC?) could I step down and up as in the MCTube schematic to get my B+ ? The other thing that confuses me is the PIV rating of the Bridge Rectifiers is this the same thing as the V(RRM) values quoted in my parts catalogue ie 800PIV is 800V(RRM)... Help me please? Its late and I've bored you all - I'll post my remaining please another day :) JamesSat, 22 Nov 2014 11:50:59 -0500 http://ax84.com/bbs/dm.php?id=99577 Added Merlin's "Scale Control" to my Simple/20WPP(by Darren Porter) I wired-up a 50kB pot as shown in his "Figure 9.16A" method. For some reason, this really made this amp come alive. It doesn't quite get down volume-wise as much as I'd hoped but man it sure has a MUCH more pleasing overdriven tone. I'm wondering how such a change would take this from an amp that was pretty much only good for clean tones (very good that is) to a _very_ nice sounding overdrive. So much nicer in fact that I think my 18 Watt Lite IIb just got replaced as my favorite for overdrive. The circuit used is the Simple Preamp into the 20W Push Pull, both without any changes except I removed the standby switch to make room for the Scale pot on the front panel and I replaced the R23 470R with the scale pot. It was such a simple change (mainly because I didn't have to drill anything) that I recommend trying it out.Sat, 22 Nov 2014 09:57:48 -0500 http://ax84.com/bbs/dm.php?id=487311 rhythm/lead switch question(by Denny Gracey) Installed the rhythm/lead switch in my SEL - seems to work as expected with one nuance- when in 'clean' mode (bypass gain stage 3), the gain 2 knob must be at zero otherwise the signal attenuates as i turn up gain 2. From the schematic it would seem that gain 2 knob is completely bypassed. Is this normal or do I have something wired wrong? Here's the way I wired it: * pole 1 to V4 pin 1 * pole 2 to V3 pin 2 * pole 3 to V3 pin 6 comments anyone? Sat, 22 Nov 2014 09:55:41 -0500 http://ax84.com/bbs/dm.php?id=487362 legacy preamp questions(by The Tone Surgeon) hi.. this question is way out of my league so as your answering just know that you don't have to be worried about some newb attempting this. it's purely to settle my own curiosity/ maybe teach me about how in-depth this hobby can get I'm looking at a schematic I stumbled apon for a 1st generation carvin legacy. which got me thinking how hard would it be too take this preamp and pair it with a 20w push/ pull power amp. the amp is normally 100w I guess my main question is how much would someone have ti change the preamp schematic. or if this would even be a realistic project. not for me at my present experience but a few years from now perhapsFri, 21 Nov 2014 13:56:27 -0500 http://ax84.com/bbs/dm.php?id=487389 Best way to wire the heaters?(by Henrik Lidbjrk) Next step for me is to solder the heater wiring, and I'm deciding whether to use the PT heater center tap or instead solder 100 ohm resistors between heaters and ground. For example, on EL34World.com, it says "I actually prefer the two 100 ohm resistor method because they act like fuses if a power tube plate wire ever shorts out from pin 3 over to pin 2. Pin 2 is one of the heater wires and is a direct short to ground for the high voltage that is found on pin 3. This happens all the time and you can save your power transformer by having the pair of 100 ohm resistors instead of a transformer center tap. The 100 ohm resistors will melt in half if the plate wires ever short out to pin 2. This is way cheaper than replacing a power transformer." What do you folks think about this? It sounds like a good idea, but it feels stupid to not use the PT center tap when it has one. If I decide to use the resistors, exactly where at ground should I connect them? (I'm using a bus ground system.) And I suppose I ain't supposed to use BOTH the resistors and the PT center tap?Fri, 21 Nov 2014 06:26:20 -0500 http://ax84.com/bbs/dm.php?id=487370 HO Wanted(by brownie772000) Looking for a Big Bottle HO working chassis. Please contact me if you have one for sale. brownieqq3@hotmail.comFri, 21 Nov 2014 03:51:06 -0500 http://ax84.com/bbs/dm.php?id=487456 parts for amps build.(by Elbert Elrod) Need help! would an early 60's Lowrey organ be a good source of parts for a tube amp build? I found one that is in working condition for $50, with internal speakers. Fri, 21 Nov 2014 03:10:53 -0500 http://ax84.com/bbs/dm.php?id=487448 New High Pitch Squeal-Help!(by Eric Nelson) I stored my Firefly in the attic while out of town for about two months this summer and when I got it down and played through it it had a high pitched squeal that I've never heard before. The amp is 4 years old now and has always worked fine. I'm sure the amp didn't get wet or anything like that but it does get pretty hot in attics in southern Arizona in the summer. I tried different tubes in all three locations, tried different guitar and speaker cables, and tried different guitars..with no effect on the squeal. It does not happen when I have the boost switch off...I can turn that gain knob all the way up with no squeal. However, when I switch on the boost it starts to squeal when both gains get up to about 50%. I've checked what I could on the board and tightened up all the connections with no luck. Can anyone help troubleshoot this fine little amp? Thanks much <a href="http://s906.photobucket.com/user/rexarsenal/media/FireFly/IMG_1726.jpg.html " target="newwin1416820665">[link]</a> <a href="http://s906.photobucket.com/user/rexarsenal/media/FireFly/IMG_1727.jpg.html" target="newwin1416820665">[link]</a> Thu, 20 Nov 2014 18:54:37 -0500 http://ax84.com/bbs/dm.php?id=487429 Anybody still using leaded solder?(by Kursad K) <a href="http://en.wikipedia.org/wiki/Lead_poisoning " target="newwin1416820665">[link]</a> "No safe threshold for lead exposure has been discovered—that is, there is no known sufficiently small amount of lead that will not cause harm to the body." (quoted from the above) KursadThu, 20 Nov 2014 13:07:32 -0500 http://ax84.com/bbs/dm.php?id=486826 b9a Prototyping board(by Chris Hurley) Merlin was gracious enough to allow me to have some of his awesome 9-pin prototyping boards made. They have arrived and if anyone in the USA is interested in getting one or more, let me know. These are very unusual and very interesting. If you aren't aware of them, check them out: <a href="http://www.valvewizard.co.uk/developmentboard.html " target="newwin1416820665">[link]</a> I was immediately intrigued. Drop me a line if you're interested in these as I am. -Chris Thu, 20 Nov 2014 10:32:22 -0500 http://ax84.com/bbs/dm.php?id=487443 FS: Rocker Switch Sets(by Chris Hurley) I've got about eight sets of rectangular rocker switches- each set has a black one and a green lamped one. Perfect for power and standby. Anybody interested in getting a few of them? Shipping will be about $6.00, so it doesn't really make sense to sell singles. Email me if you are interested... chrish at this site. Thu, 20 Nov 2014 10:27:42 -0500 http://ax84.com/bbs/dm.php?id=480838 Duck Cloth as covering(by juice) Has anyone used duck cloth as a tweed substitute? It's pretty thick, durable, multiple colors, and cheap as hell. I think the black looks pretty good. Locally I can get duck cloth for 6.99/yd at joanne fabrics. They also have a super thick fabric backed vinyl for 14.99/yd, and a thinner version for 9.99 a yardThu, 20 Nov 2014 04:06:30 -0500 http://ax84.com/bbs/dm.php?id=323283 Pre instability?(by hyp3rv1p3r) Hi all, yesterday I was showing a friend how quite is my P1-eX without any guitar connected and, surprisingly, with all master up and gain at 3/4 a sort of feedback (larsen?) started. After some testing I think that the problem is related to the first stage and if I remove C16 it disappears. Also it is absent when a guitar is plugged. I have tried to change C16 with a smaller and larger value cap but the problem persists. Any idea? What am I missing? Should it be related to cathode bias resistor? Thank in advance for your help. Ant p.s. Without C16, as expected, I have a low gain.Wed, 19 Nov 2014 23:37:31 -0500 http://ax84.com/bbs/dm.php?id=487326 Mods for more gain?(by Caprotesta) Hi all, I recently converted my P1 to a Hi-Octane. I'm a high gain guy, and the difference in gain is quite noticeable. This small conversion project got me to thinking about trying to get more gain out of a couple of other amps I have laying around. Does anybody have any good resources for reading up on different techniques to do this? I've read the theory documents for the P1 and Hi-Octane on the gain, but the other amps I want to mod out aren't as simple and don't have the same configuration. Both already have two 12AX7s. I think adding another preamp tube might be overkill. I would think that there should be a way to get more gain out of what I already have. Does anybody have any suggestions? Wed, 19 Nov 2014 18:19:07 -0500 http://ax84.com/bbs/dm.php?id=487384