Music Electronics Forum - Guitar Amps http://music-electronics-forum.com/ General discussion about amps en Tue, 21 May 2013 09:38:18 GMT vBulletin 60 http://music-electronics-forum.com/images/misc/rss.png Music Electronics Forum - Guitar Amps http://music-electronics-forum.com/ Replace OT on a Laney GH50L? http://music-electronics-forum.com/t33162/ Mon, 20 May 2013 03:30:21 GMT An amp tech told me the reason my Laney is so hummy is because of the output transformer. Not that it's malfunctioning, it's the design. It's one of those sort of donut shaped ones wrapped in clearish plastic. I was wondering if a new transformer might help and possibly improve the sound overall. If so, can you recommend one?

Thank you,

TA ]]> Guitar Amps Thee Abomination http://music-electronics-forum.com/t33162/ <![CDATA[SVT-CL: No "balanced" line out, but otherwise works fine]]> http://music-electronics-forum.com/t33069/ Thu, 09 May 2013 20:42:00 GMT I've got an SVT-CL in my shop that works fine, except there's virtually no signal at all at the XLR "balanced" out. This model (the later version, I believe) has the [line] transformer (as opposed to the [earlier] version that is driven by op-amps). Even before the transformer, there is barely any signal coming from the preamp, yet the speaker out is still putting out full power! Damn, this bugger is driving me batty! Has anyone out there run into this scenario? ]]> Guitar Amps mac1amps http://music-electronics-forum.com/t33069/ Roland JC-120 Chorus amp http://music-electronics-forum.com/t33041/ Tue, 07 May 2013 16:30:57 GMT Hello, I have owned 2 of these awesome amps. This is my second one. For some reason the amp cut-out at one of my shows on the weekend. After doing a... Hello, I have owned 2 of these awesome amps. This is my second one. For some reason the amp cut-out at one of my shows on the weekend. After doing a bit of trial and error, it appears to be the guitar input jack on the amp. The jack is intermittent. Is this something I can fix or is it better to take to a tech? Is the amp difficult to take apart? Has anyone else experienced this problem? What would the most likely cause of this be?
Thanks ]]> Guitar Amps kpinks http://music-electronics-forum.com/t33041/ Your Best Vintage Finds http://music-electronics-forum.com/t33040/ Tue, 07 May 2013 16:00:27 GMT I was just finishing some yard work and housework for a friends grandmother, we start talking and get on the subject of guitars and amps and mentions... I was just finishing some yard work and housework for a friends grandmother, we start talking and get on the subject of guitars and amps and mentions there is an old amp in the basement I coulp have if I wanted. So, I start looking through the basement and it's found, a Magnatone Custom 260!!! Get home and start cleaning it up a bit, plug in, let it warm up, and jam..... It a beast, everything works and sounds amazing, going to bring many years of joy until I'm too old to play and trade it for some yard work too hahaha
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]]> Guitar Amps duffalluff http://music-electronics-forum.com/t33040/ what happens to tube amp if powered on without cabinet. how and why http://music-electronics-forum.com/t33030/ Mon, 06 May 2013 14:37:04 GMT I would like to understand more as to why the impedance selection on an amplifier is crucial and how a cabinet affects it. Thanks I would like to understand more as to why the impedance selection on an amplifier is crucial and how a cabinet affects it. Thanks ]]> Guitar Amps hesamadman http://music-electronics-forum.com/t33030/ <![CDATA[Marshall 18watt, el34's]]> http://music-electronics-forum.com/t33009/ Sun, 05 May 2013 04:09:46 GMT Hey guys. I built a Marshall single channel 18watt clone, but I built it with el 84's. Now I found Transformers that should work. The OT works fine, and I'm pretty goldarn sure of the power transformer. Anyway, I built it just like the el84 version otherwise, but I only got 30W out of it, and it didn't even sound as good. But the problem is that I had a Bridge Rectifier (not sure of part # or whatever) but it worked great. The problem with that is that the power tubes would redplate, and that the preamp would distort really bad the the voltages were so high. So I replaced the bridge rectifier with two in4007's and it worked for a while but it was only 30w... So I went to put in a real bias supply, and I have a 100V winding on my PT. I used two in5400 diodes (big guys) and I KNOW I put the components in correctly, but I'm barely getting any negative voltage. All I'm getting is -2, and for some reason, I actually got upwards of +50VAC after the diodes. I can't figure that out. So anyway, the circuit I tried is like this. Winding/both sides connected to reverse diodes/filter cap (also reversed, +to ground)/at the junction of the cap and diodes there is the top lug of a 25kb pot/ then the wiper of that pot goes to the two 220k resistors which connect to the grid stoppers. the bottom of the pot goes to ground. I didn't use a dropping resistor since I drew too much current through the 2W I had used (which blew up) when I tried drawing the voltage from right before the normal rectifier, which is two in4007's running in parallel which works fine. But this amp has always had that problem of drawing WAY too much current through the rectifier. I had THREE 1k 9W resistors in parallel for about 300ohms and 27w capability because the bridge rectifier (i had at the time...) had too much V. But it blow those resistors, and once they got SO hot that the solder holding them in place was as wet as if I had held the soldering iron there. But now it resides with the funny bias supply and two in4007 diodes. as the two rectifiers in the amp. Something that just came to mind is that the bias winding on teh PT does NOT have a Center tap, so I'm wondering if it needs one to function, since I only was getting -2Volts, which I Think were basically "ghost" volts. If I got a center tap would that work? (although you can't really "get" a CT) but would fashioning a "fake" CT with two 100k resistors to ground work? Like many filaments do?
Also, I read that to prevent redplating on the power tubes you can just raise or lower the cathode resistor (when running in cathode bias mode) is that true? Could it be possible for me to run the I believe around 450V through EL34's as long as the cathode resistor is +or-'ed and as long as the screen voltage is lower than the plate voltage of course? Hope these ramblings made enough sense for someone to help me. I need the help. I really want to get this to work. ]]> Guitar Amps isaac http://music-electronics-forum.com/t33009/ Wanna trade? http://music-electronics-forum.com/t33005/ Sat, 04 May 2013 15:23:21 GMT I was thinking... A lot of folks here have been through the speaker selection process and ended up with a few (or a lot) of speakers that they... I was thinking... A lot of folks here have been through the speaker selection process and ended up with a few (or a lot) of speakers that they haven't used or sold just sitting in boxes. I thought we could all benefit from an organized trade program to save the expense of buying speakers every time one wants to try a different model. Example:

I currently have a pair of Emi 16 ohm Red White and Blue's and a pair of old (but still good) Celestion 16 ohm G12M70's. The RW&B's are supposedly Emi's version of an EV type speaker. The RW&B's sound too boxy to me. I've read that Andy Fuchs really likes them. If you have an amp that is too boomy and fizzy they could be just the thing. The G12M70's are a sort of "love 'em or hate 'em" model. Malcolm and Angus used them for a little while and did some recordings with them. I like the G12M70's with Marshall amps.

I'd like to try an Emi Wizard (8 ohm)

If we had a forum sub category just for trading (things like speakers) I think we could all expand our options and save some money. ]]> Guitar Amps Chuck H http://music-electronics-forum.com/t33005/ HELP my ampeg!!!! http://music-electronics-forum.com/t32995/ Fri, 03 May 2013 12:56:11 GMT i was pretty much GIVEN a 1969 ampeg v-22 2x12 combo amp. same as a V-4 head. great looking amp on the outside and no visual signs of mods other... i was pretty much GIVEN a 1969 ampeg v-22 2x12 combo amp. same as a V-4 head.

great looking amp on the outside and no visual signs of mods other than a pair of carvin vintage speakers.

so, i get it home, check to make sure the tubes [all 400 of them] are all in their sockets, plug it in, hit the switch and a HUGE, LOUD LOW END HMMMMMMMMMMMM comes blasting out!! tubes are not lit when this happens and it appears no power is getting to them.

i know there could be a zillion reasons for something like this and i am no tech.

any suggestions where to start? i will be taking it in unless its something relatively easy enough for me to do.

i have been playing for almost 40 years and FULLY realize the dangers of these big 'ol glass monsters and will not attempt anything i havnt done before. i have some electronics experiance, no degree, but a gigging, [poor] musician with all the practical knowledge it entails like tube changing, caps and resisitors. light stuff.

but it appears NO power is getting to the tubes when this huge low hum comes out INSTANTLY when the switch is engaged. ]]> Guitar Amps Orgazmo http://music-electronics-forum.com/t32995/ <![CDATA[Quik'n'Dirty way to fix tiny tear in Fender grille cloth?]]> http://music-electronics-forum.com/t32966/ Wed, 01 May 2013 07:44:11 GMT This is a 1999 Fender Champ 30 with a tiny tear that is contained within a 1/2" square. It is over the speaker cutout so there is good access to both sides. I am more concerned about it unraveling and getting worse than the cosmetic aspect. I was thinking of gluing something on the back of the tear- perhaps some kind of finely woven cloth? (I used to use fiberglass bus screen for all sorts of repairs but I am fresh out of it.)
Any other ideas?

Thanks!

Steve Ahola ]]> Guitar Amps Steve A. http://music-electronics-forum.com/t32966/