Amp Repair - Stereorepair.net

12 Technology Drive, Ste.13   East Setauket, NY 11733

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Should I Send You My Amp For
Repair?
(Our answer may surprise you.)


Repair, Restoration and Top Grade - Three levels of Service


Parts Make a Difference About Resistors and Caps:
The Keys to Tone


"The Tone" What it is, how to get it and some of our thoughts on this  topic
 

"My custom made boutique amp died and as far as I know so did the guy who built it. Help!"
 

 

 

 

 Modifications and De-Modification

Our basic philosophy on modifications


SEVEN SIMPLE RULES FOR MODIFICATION:

1.
Never, never do ANY  modification to a vintage collectable amp that could have a negative effect on it's resale value unless you are really sure about what you are doing.
Although I think it is a bit strange, collectors will pay more for a completely original plexi Marshall that doesn't even work than a well restored and renewed unit (kind of like getting a '63 strat with the original factory string tag on it and then never playing it to "keep it mint" - but perhaps I'm missing something). Anyway, the point is, never do anything you are not willing to accept the long run consequences for. And DO NOT SWAP OUT THE TONE CAPS!
Quite often I am asked about " modding" an amp with half dead tubes, dried out filter caps and a beat speaker. All that really has to be done is to get the amp working the way it should and it can sound great.
 
We do strongly advise that really collectable vintage amps not be extensively modified. In some cases we will decline work that we feel would ruin a piece of vintage equipment.      
 
2.
Be certain that any mod is reversible. At the very least you should be able to get your amp back to where it was before you started.  MAKE A DIAGRAM,  LIST THE PARTS YOU HAVE CHANGED AND KEEP THE ORIGINALS.

3.
Start with the most simple mod first.  Speakers should be the first thing to work on. 
The right speaker will do more for you than any preamp tweak, master volume circuit or tone control rework.  It is very easy to change your own speakers. But often the speaker is the last link in the tone chain that is addressed. The reason is simple: Most really good speakers are expensive. In the long run it is better to go for the largest expense first instead of wasting money bit by bit. Reissue speakers from Jensen ( very good value for the money, sweet sounding speaker), Celestion ( The Alinco Blue and Greenback are very different sounding but excellent speakers , the blue possibly the best guitar speaker of all within  it's power limitations.)  EV makes a reissue of the EVM12, a good "can't go wrong" standby, While Weber, ToneTubby and the very broad and inexpensive Eminence line are also good choices.
Next  are tubes. Easy to change yourself  and there are some very good resources and reviews on this. Google it or try www.tubestore.com.

4.
Stay with simple changes first. For example, "blackfacing" a post CBS Fender is easy and gives very good results. Feedback loop mods, adding a presence control, high cut control, gain/tone profile are simple and effective. Taking a unused input channel and changing to a different circuit will work and is a favorite advanced mod, but be realistic. Just building a VOX or Marshall  preamp stage into a Fender twin  may sound pretty good, but will not make it sound exactly like a VOX or Marshall. Most modern Fenders and Marshalls will sound much better simply by replacing the hard epoxy tone caps with Mallory150's or SoZo Mustard caps.

5.
Know your limitations and those of the person working on your amp. Exotic mods like squish power supplies, staggered bias/mode output stages, triode wiring and tube choking, and power scaling are really getting into "deep voodoo". Not anything for a amateur to get into and only for really experienced technicians. Output tube, transformer and power supply damage is very possible if these mods are not done correctly.

6.
Never get into mods to try to duplicate someone else's sound, you will be disappointed.  Really distinctive players sound like themselves regardless of equipment used. This doesn't  mean you can't admire a tone quality in someone's setup and try to add it to your sound, but touch, phrasing, feeling and ability are unique to every player.

7.
Protect your investment. Amps that sold for  $400.00 ten years ago can go for 2,500.00+ in today's market. It just does not make sense to let a friend, amateur or semi-competent tech get in over their head on a project at the expense of your equipment and hard earned money.


DE-MODIFICATION:

Sometimes this is easy, often a real pain. After  20-30 years or so and several owners a lot of amps have been fiddled and tweaked with until they are not what they started out as at all.  There are two ways back. First is to shotgun the whole deal and just restore it back to stock. The other is to carefully go through the unit, leave any mod the customer may like, possibly improving or correcting a mistake, and putting back to original any ill advised work. This is very time consuming and about the most costly work we do because of the time element involved. We have had many a successful outcome on this type of job, but it was not because of a happy accident. A lot of time and effort was required.
 
We do not routinely change film (tone) caps unless by customer request, are actually defective or have been replaced with improper parts in the past as these are critical to the sound of a vintage amplifier.