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Topic: Post-repair Session 400's? |
Ernie Renn
From:
Brainerd, Minnesota USA
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Posted 17 Sep 2017 10:08 am |
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I have several Peavey Session 400's that have been repaired by various tech's over the years. Some I had done and some before I acquired them.
What I'm wondering is: Why, when they use parts with the same specs, do the tonal characteristics change SO drastically after repair? Where I normally set my Presence on 7 and my Treble on 6.5, post repair I can barely stand the highs at 2 and 1.5.
I'd think it was a one off, but I have multiple amps with the same problem. Two Session 400's and a Session 500.
The 500 also has another weird quirk. After you use the built in phase shifter and turn it off again some of the phased tone stays and you can't shut it off. I used to use it for outside gigs because it has the power, but the tone issues made me rethink that.
Any ideas?
Thanks!
_________________
My best,
Ernie
www.BuddyEmmons.com |
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Jack Stoner
From:
Kansas City, MO
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Posted 17 Sep 2017 10:38 am
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If the correct components were not used in repairs, there can be differences in the tone. e.g. if a capacitor was replaced by a different value or even a different type it can have an affect on tone. Same way a resistor. In the original model Session 400's which were discrete components (e.g. transistors) if one of those were changed with a different transistor it can cause sound changes. On the later reissued Session 400's IC Op Amps were used in the preamp section. As has been done with the Ken Fox chip mods on some models such as the Nashville 112 and 1000, a different Op-Amp can make a dramatic change in overall amp sound.
On the Session 500 (I had one of the original "small cabinet" models). This could be a problem with the switch (and it will need replaced). |
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Ernie Renn
From:
Brainerd, Minnesota USA
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Posted 18 Sep 2017 12:03 am
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Thanks for your reply, Jack!
My question becomes, Why would a repair technician use parts that are different than intended? Discontinued parts and they're using the suggested replacement? I suppose I have to go thru the whole amp and check that the parts are what they call for... (Above me head after so many years of not keeping the tricity thing going...)
[A while back I had an MXR pedal worked on. Post repair I didn't work anything like it originally did. I sent it to a friend in TX who had dealt with that problem before. He said that while the part was what was suggested to be the replacement for the part, it operated differently. Luckily he had some old parts to use and thanks to him, it's back in the chain...]
500: Would spraying the switch with DeOxIt help?
I had a short one, too. They said they made 25 short cabinet ones. The made them taller because with the shorter model to get the speaker out you had to remove the amp, as well.
_________________
My best,
Ernie
www.BuddyEmmons.com |
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Jack Stoner
From:
Kansas City, MO
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Posted 18 Sep 2017 2:02 am
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A replacement part such as a capacitor may have a different tolerance (plus/minus the mean value) and cause a response difference. This is often the case in old Fender tube amps. The original components in many Fender amps were poor at best in many cases and replacing with modern day components can have a dramatic change. Some capacitors in old Fenders had a plus/minus 80 to 100% tolerance and replacing with a modern 10% or 20% tolerance cap can make a big difference. Resistors are another example, a 20% tolerance resistor is replaced by a 5% and it can make a big difference.
OTOH someone didn't have the exact value component and used something "close". |
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Ernie Renn
From:
Brainerd, Minnesota USA
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Posted 18 Sep 2017 5:17 am
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In light of these facts, how can you ever get an amp repaired and have it retain the originally sweet tone?
_________________
My best,
Ernie
www.BuddyEmmons.com |
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Jack Stoner
From:
Kansas City, MO
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Posted 18 Sep 2017 6:06 am
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It can be done, in most cases. Just depends on the amp tech or company. For a Peavey, I would send it to the factory repair. A hassle to remove it from the cabinet, pack up and ship but the best option to get it properly repaired.
Old Fender's with the "poor quality" parts that were used however, are candidates for sounding different after repair as many of the original parts are either no longer made or not available. Its actually amazing that the old Fender's sounded as good as they do(did).
I did amp repair (I was the tech at Little Roy Wiggin's "Music City" store on lower Broadway in the early 70's). I strived to replace parts with either exact OEM replacements or equivalent type/value replacements. I didn't "modify" devices. In fact, if someone brought me an amp to repair and it had been modified I would refuse to work on it. |
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Ernie Renn
From:
Brainerd, Minnesota USA
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Posted 18 Sep 2017 11:06 pm
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Saving up to send an amp(s) to Peavey.
Some old Fender amps sound great, some don't. This could be the cause.
I understand. You wouldn't know what you were getting into...
Thanks for sharing your experience and knowledge. I appreciate it!
_________________
My best,
Ernie
www.BuddyEmmons.com |
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