AX84 BBS

Amp Parts and Kits

Doberman Music Products, LLC offers a variety of parts and kits

RE: Finshed wiring. Please give feedback(by Dave E)

Tue, 16 Mar 2010 20:08:13 -0400

Towards the bottom of this page [link] is a photo of a preamp tube with a good heater wire layout. Both wires are twisted together very tightly right up to pins 4 and 5. Then one of the wires (the purple wire) goes right across the center of the tube to pin 9. (Actually in the photo there are two sets of wires because this tube is in the middle of a daisychain, but you should get the idea.)

RE: Finshed wiring. Please give feedback(by Evil Armada)

Tue, 16 Mar 2010 19:49:25 -0400

Yeah I thought that might be a issue, but that is what the layout suggested. Where would be a better place to place the heater wire?

RE: Someone has to fess up(by spud)

Tue, 16 Mar 2010 19:10:50 -0400

Ingenious, i like how the variac is used to control the voltage to the iron and the temp of the coffee - man, I'm glad I read Merlins web pages and the AX Theory document. And whoever it is shouldn't try to lie to us, that is most certainly not a first build. Spud

RE: Can't get rid of Hum/Buzz on my build could it be my House?(by MadDog)

Tue, 16 Mar 2010 18:27:58 -0400

The two person rule is great - just make sure the second person knows what to do if you start doing the "60 Hertz shuffle", if they just reach out and grab you then your rescuer can turn into the second fatality. In the Navy, they'd tie a nylon rope around your waist and the second person had instructions that if you started taking a buzz they were supposed to jerk you off. ...which, of course, led to all kinds of gallows humor, but you get the idea. Alternatively, the second person can be standing by the breaker or extension cord or whatever so they could immediately de-energize you without actually touching you.

RE: Can't get rid of Hum/Buzz on my build could it be my House?(by LuisG)

Tue, 16 Mar 2010 17:54:57 -0400

the amp hums even when I put one of these on: [link] it has no cable, I do it just to make the connection. I recently re wired the complete input jack, tested the resistor with a DMM, and cutted new shielded wire and had no effect. I have tried 2 brands of preamp tubes andn power amp tubes as well. Still Gain makes things worst, so it has to come before the gain stage, Input Jack, B+ line, Cathode. But I don't know from where :(

RE: Someone has to fess up(by Charlie Cyr)

Tue, 16 Mar 2010 17:34:31 -0400

Great way to capture wasted heat and keep the coffee warm!

RE: Someone has to fess up(by MadDog)

Tue, 16 Mar 2010 17:15:17 -0400

You're right. What was I thinking??

RE: Saw Steve Morse Saturday Night(by BnATX)

Tue, 16 Mar 2010 17:07:12 -0400

Cool! My first exposure to Steve was back in the mid 80's i think it was, he opened for Rush. He is an amazing player. Great show that was.

RE: Tube types and brands for my upcoming Firefly build (by Pete Trippe)

Tue, 16 Mar 2010 17:02:35 -0400

I replaced my 12AU7 with an ECC99 for the power tube, then I put that 12AU7 in the boost stage, and I'm really happy with that. The original configuration had a bit too much gain for my taste.

RE: Can't get rid of Hum/Buzz on my build could it be my House?(by joe kerr)

Tue, 16 Mar 2010 16:25:51 -0400

On 03/16/2010 @ 16:00, LuisG wrote : Here it is, : : 1) Hums with guitar plugged : 2) Hums with cable plugged and no guitar plugged. : 3) Does not hum without guitar cable plugged. : : The hum of 1) and 2) is about the same : : Thanks : Luis --

Well if what your saying is correct then your amp is fine. "3) without guitar cable plugged in does not hum." That means your signal is grounded at the input jack and no noise is being introduced by the amp. If the noise only happens when you plug in a guitar and cable then you need to look at everything external. That could be your input jack, the cable, the guitar, you or the environment.

RE: Output Transformer Question(by headspaz)

Tue, 16 Mar 2010 16:02:21 -0400

If your OT provides a 16 ohm secondary tap, you could hook up an 8 ohm speaker to it, thereby making the primary 2.5K and 3.5K respectively. That'd be ideal for an EL34 if you decide to go that route. But is it a Single Ended transformer?

RE: Can't get rid of Hum/Buzz on my build could it be my House?(by Stubie)

Tue, 16 Mar 2010 16:00:35 -0400

In my case the the amp chassis is a "super solid bonded earth gound" at the ac input to the chassis, I have also a bonded chassis ground to circuit common at the input ( 3/4") from the jack. Both of these are without compromise and I stake my life upon them! The reason for my question is it happens with the les paul and strat in varying degrees dependind on settings of tone filters etc. And increases with volume.

RE: Can't get rid of Hum/Buzz on my build could it be my House?(by LuisG)

Tue, 16 Mar 2010 16:00:30 -0400

Here it is, 1) Hums with guitar plugged 2) Hums with cable plugged and no guitar plugged. 3) Does not hum without guitar cable plugged. The hum of 1) and 2) is about the same Thanks Luis

RE: Can't get rid of Hum/Buzz on my build could it be my House?(by joe kerr)

Tue, 16 Mar 2010 15:38:31 -0400

For the people new to amps reading this I'd like to warn them it's very dangerous to lift the earth wire from the mains IEC to chassis connection. If their is a short in the amp and the chassis is live you could become the path to ground and be killed! Be Very Careful when your disconnecting safety features. Professional rules are 2 people in the room when working on live equipment, this scenario would be a good time to use that rule.

RE: Can't get rid of Hum/Buzz on my build could it be my House?(by ampedup)

Tue, 16 Mar 2010 15:36:17 -0400

does it hum with no guitar or cable plugged in? leaving the cable in with no guitar makes a lot of noise.

RE: Can't get rid of Hum/Buzz on my build could it be my House?(by LuisG)

Tue, 16 Mar 2010 15:23:21 -0400

can't find the nasty little bug!

RE: Can't get rid of Hum/Buzz on my build could it be my House?(by dludwig)

Tue, 16 Mar 2010 15:21:02 -0400

On 03/16/2010 @ 13:01, LuisG wrote : Hello dludwig, : : I gave the 6V DC battery heater test a try yesterday and the hum/buzz still there, so it seems that my heaters are no the culprit :( --

well, guess you're right... keep plugging.

RE: Anodized Chassis(by 3rdof3)

Tue, 16 Mar 2010 15:06:21 -0400

The gunmetal I was suggesting is grey ... ish. Think an Aluminum chassis shot with a light overspray of coal dust. If you do decide to get into it, I'll be the first to order 18" in each Black, Gold and GM.

RE: Output Transformer Question(by rockyo)

Tue, 16 Mar 2010 14:58:09 -0400

Thank you for your time and effort, it really helped.

RE: Can't get rid of Hum/Buzz on my build could it be my House?(by LuisG)

Tue, 16 Mar 2010 14:57:13 -0400

I tried the 10 OHM resistor last night, this is what I did: 1) Disconnected the line going from the AC socket 3rd prong to the chassis. 2) Used aligator clips to connect a resistor 10 OHM in between the 3rd prong and the chassis (I had a pack of asorted resistors, they are low voltage but since its ground that is ok??) 3) I am still using the 6V Energizer battery for the heaters. 4) turn on the amp and the hum still there! #$%@# 5) While on and humming I take one of the aligator clips and remove it from the resistor, NOISE goes like 5 times louder but its the same noise. So I figure that the ground does have a positive impact on the hum :) 6) I connect the alicator clip without the resistor while the amp still live, just to compare hum levels with and without the 10 ohm reistor. 7) So elevating the ground with the 10 ohm resistor and having the chassis grounded directly has the same exact hum levels, so the resistor seems to be taking no effect on lowering the hum. I don't know if I should try a bigger resistor but I figure if it was working at all it would have at least lower the hum a little bit, but its not :( Thanks Luis

RE: Gothic Ring layout?(by Randy Fay)

Tue, 16 Mar 2010 14:49:00 -0400

Good ole Epos ES14's eh? Use to have a pair. Great with small tube amps.

RE: Can't get rid of Hum/Buzz on my build could it be my House?(by LuisG)

Tue, 16 Mar 2010 14:43:53 -0400

On 03/16/2010 @ 14:13, Stubie wrote : Sorry I don't have an answer to your question but I am having similar problems, when I touch my guitar strings the buzz goes away and when I touch the amp chassis !! so,I think my touching the chassis is like adding a large resistive shunt or something I don't think my house ground is clean and must have noise riding on it, maybe that gadget you linked me to will work in my case. Does anyone know what kind of circuit it is? --

Highjacker!!!!!!!! Well regarding the touching of the strings. That sounds like the guitar is not grounded and when you touch the strings you become the ground. open the guitar from the back and make sure the pots are all well soldered you might have a lose solder in there. As for touching the amp chassis, that sounds like the same problem, make sure the circtuit board is grounded to the chassis, and that the chassis is connected to the ground of the AC socket. Buy a ground tester, this is what I have [link] it tells you if the AC lines comming from the wall are reversed, it also tells you if the ground on your wall is actually grounded and not just a phony!

RE: Radial Caps(by headspaz)

Tue, 16 Mar 2010 14:39:17 -0400

If you go that route... you might consider picking up a few of these caps... 47uF x 450V Nichicons $1.00 each [link] 22uF x 350V Nichicons $.45 each [link] I bought some awhile back... the price is right and they are NOT fakes.

RE: Turret / printed circuit board(by Celeste hall)

Tue, 16 Mar 2010 14:31:48 -0400

Stress fracture is pretty common in the leads of components that are above the board. Even large components that are supported on the board fail to frequently if there is not another means of support other then the leads. every Fender Princeton 112, 65, 65 dsp or 650 i have found dead, was caused by broken leads

RE: Tube types and brands for my upcoming Firefly build (by headspaz)

Tue, 16 Mar 2010 14:29:04 -0400

OK. Sounds good to me. I like it when things are easy. Thanks Doug.