Ask Amp Tech Expert Skip Simmons

Hi Skip,

I have a HarpKing 4X10 since 2003. Its been gigged generally twice a week with no issues. I have been using matched Svetlana KT88s as power tubes. I live in Europe and now cannot get Svetlana KT88s from my usual suppliers. I was wondering if you could recommend an alternative KT88 for the Harpking.  Also could 6L6s be substituted for the KT88s without two much effort. 

I'm planning to order two new power tubes for another amp and while I was at it thought I'd include a spare EL84 for my Kalamazoo Model One. My guess is the Raytheon 6BQ5 tube now in the amp is original or close to it. That would make it almost 50 years old though hard to say how much use it's actually seen. My question is, even though a power tube is working fine, no microphonics or other issues, do they gradually wear out and should regular replacement be a general part of amp maintenance? continue reading...

Hi Skip, my danelectro 272   amp is makes a crackling sound when first turn it on amp , then after it warms up it goes away.  I was thinking it might be a resistor ?  Is there a way to test the resistors to pin point the one that's bad?  

Skip,

I have been benefitting from lurking and want to say thanks for sharing your expertise.  It would take me decades to amass as much and even then would be hard pressed to be able to express things as clearly as you have and do.  

I am in the market for my first practice amp.  After reading here and viewing viedeos, I was looking for an excelsior or a fender champ xd.  I came across a 1955 Silvertone.  In terms of sound, tone etc., is this amp in the same league as the other two I was looking at getting, the fender champ xd and the excelsior? continue reading...

Hi Skip, i was wondering what the value of the big dog bone looking resistor  between the power tubes in the ga6 amp is , in the schematic it just says 200. I wanted to change it it looks like it's turning into sand.  Also are all the resistors assumed to be 1/2w cause the schematic doesn't say anything.  I have a mcgohan mg 20 amp and the photo fact schematic for it and that schem is really detailed , the ga6 one is the original manual that came with amp and hand drawn. 

Hi Skip, i wanted to put  a external speaker jack in a  Gibson Ga-6  i have so i can try different speakers and not have to pull the original p12r speaker everytime. I have a swithchcraft 12A closed circuit jack.  Do I connect the wires from OT pos to tip and neg to ground ring,  then from the internal speaker run pos wire to switch terminal and neg wire to the ground ring with the wire from OT?  This should let me switch from internal speaker to extention cab (8 ohm) safely correct? So with it wired like this the amp will always have a load on it right?

Hi, Skip,

Other than the Megatone model, I never see speaker cabinets or amps with both a 10" and 12" speaker in one cab. It seems like it would be a great idea, and I know David likes his. Are there any drawbacks to such an arrangement?

And would it be much more complicated than it seems like it should, to build a cabinet with both a 10 and 12, with a control to either switch from one speaker to the other or to both, or to "balance" the two depending on the situation? I am thinking of impedance issues, but surely this has been done. Any thoughts? continue reading...

Hi Skip , I just finished making a extention cab and was thinking about wiring 2 jacks in series so I could run 2 cabs daisy chain style. I'm not to sure on how to do it , is it ok to use a metal jack dish?  

Hi, 

I have a Kalamzoo model 2 and I understand that the rectifier tube in that one is 6X4. In the "all you need to know about amps" video David talks recommends the 5U4GB recitifier tube. Can that be used instaed of the 6X4 in the Kalamzoo model 2?

Bst regards

Fredrik

If you would like a chance to bring your mike and play through a whole bunch of vintage amps, go to a vintage guitar show in your area.  Visit my booth at the Bay Area show in San Rafael on January 11th and 12th, 2014, and ask a question or two, or bring a repair for me.  Here's a link:

http://www.texasguitarshows.com/NewBayJan.htm

Vintage Guitar Magazine is a great source for information on shows around the country.

Skip Simmons

Vintage Amp Repair