jnorem
180 posts
Apr 30, 2014
4:51 PM
|
I recently had my amp worked on by a brilliant technician who made it loud with little feedback. Great!
So I decided to record myself playing through it, in different channels with a variety of settings. And no matter what I dialed up, the sound was clear and strong. Impressive. This thing could stand up to a guitar player.
But the problem now is that it's clear, loud and clean as a whistle. I couldn't get it to distort. It sounds like a loud-as-hell harmonica.
I will take it back to the shop, but I know there are some very astute amp experts here, so to them I put the question: given the situation, what would you do to give my amp a a little added crunch?
----------
Call me J
Last Edited by jnorem on Apr 30, 2014 5:00 PM
|
Barley Nectar
370 posts
Apr 30, 2014
6:34 PM
|
What year is your SR. Does it have master volume? What did the tech do?
SR's are a clean machine by nature. Yes, they are loud as Hell when healthy. You may not be able to drive it into distortion without feedback depending on the room you are in. Set it out in the back yard and push it. See if it breaks up then. The tone controls make a big difference on those amps. Crank them up some if you have them low. Looks like you tried this already.
As for suggestions, you can reduce the voltage to V1 to brown it up some. You can bias the power tubes cold. You can also use the ground switch to shut off the negative feedback circuit. This will open the amp up and give power tube distortion at a lower volume level. If you have low gain preamp tubes in there this may be the reason the amp stays clean. Put in a couple of smooth cone speaker that break up early. Weber 10F125-O comes to mind, or the Alinco equivalent. You could leave it alone and use a Lone Wolf Harp Attack/Harp Break.
I personally prefer a clean, loud amp. Don't like mud. You may just need to give it some time so you can get used to it. My guess is that the amp is now healthy and you were used to an amp that was not. Good Luck...BN
|
jnorem
181 posts
Apr 30, 2014
7:20 PM
|
Thanks, Barley.
----------
Call me J
|
cliffy
79 posts
May 01, 2014
4:46 AM
|
The absolute cheapest way is to get a pedal. I have used a pedal called the "Blue Tube" (it's actually a bass pedal)in the past. Barley Nectar mentioned the two Lone Wolf pedals... either of them would be fantastic. The advantage of this is that you can now get a good crunchy amplified tone at much lower volumes as well.
I have found that using the Blue Tube pedal makes my rig extremely feedback resistant as well. I spent lots of money having my amp (Bassman RI) modded extensively for harp, but the Blue Tube is what I use on lower volume gigs where I still want the sound to be dirty and crunchy.
|
5F6H
1775 posts
May 01, 2014
7:18 AM
|
Put a 12AX7 in the phase inverter & bias cool (~10mA).
The 12AX7 in the PI seems counter intuitive because it increases gain over the 12AT7 in there before, but you'll get better crunch with a tight signal hitting the power tubes from the PI, lower mu tubes are better for a sweeter, singing tone.
Oh and keep the treble low on the Vibrato channel & push up the middle - even flat out, the SR only ha a middle pot half the size of a tweed bassman.
If you only use one channel, remove the preamp tube for the channel you are not using, this rebiases the remaining preamp tube for more grind (V1, farthest right looking at the back of the amp, is the Normal channel preamp tube, V2 is the Vibrato channel preamp tube).
----------
www.myspace.com/markburness
Last Edited by 5F6H on May 01, 2014 7:19 AM
|
barbequebob
2538 posts
May 01, 2014
10:38 AM
|
What year is is, first of all?? Why?? Because they definitely DO sound different from different years as I used to own a real '65 Super Reverb from a guy who had bought brand new in '65 and things like what brand of tubes being used, from not only the preamp tubes, but the rectifier tube being used as well, and even the output and power transformers can be totally different.
The most harp friendly channel of the two is the one without any effects in it, but I used the one with effects (mainly for the reverb and the old tanks are far better sounding than the newer ones). I had it back in the day when what's now known as NOS tubes were always what you bought back then and the best tube matches for every black faced Fenders were always made by GE in the US (and those were the stock tubes they came with), and most other brands tended to make them too trebly and feedback prone.
One of the first things to remember with the black faced amps is make sure that the bright switch is always in the off position and the bass is never lower than 5 or 6, never let the treble go beyond 3 and find a middle setting you're comfortable with.
They had a variety of different speakers fro different manufacturers over the years from Jensen C10Q's, CTS, and several other manufacturers as well.
Another thing is finding a true 12AX7 tube and the difference between 12AX7's and 12AX7A/7025's is the fact that a real 12AX7 will have less treble and more middle than a 12AX7A/7025 and of the current production being made, the closest to that is either a reissue Mullard or reissue Tung Sol 12AX7.
Certain 6L6's are gonna also be more trebly than others and finding one that's as close to an old GE 6L6 is what I'd try to find like either one made by Groove Tubes or TAD, as far as newer production goes because those are more like 5881's, where there is more middle and less treble.
Every black faced pre CBS SR I've either played thru or on all had 5AR4/GZ34 rectifier tubes and those sounded best to my ears (and that's what was on the one I once owned.)
----------
Sincerely,
Barbeque Bob Maglinte
Boston, MA
http://www.barbequebob.com
CD available at http://www.cdbaby.com/cd/bbmaglinte
|
jnorem
182 posts
May 01, 2014
10:39 AM
|
"What microphone are you using?"
It's a JT30VC that I got in 1995.
----------
Call me J
Last Edited by jnorem on May 01, 2014 10:40 AM
|
harpwrench
836 posts
May 01, 2014
11:06 AM
|
Just an idea but maybe the crystal is weak, or doesn't like the input load. The lone wolf pedals present a higher impedance load to the mic, and have volume level boost, plus the effect. If it were me I'd try the harp octave. Or if you know someone with a hot CM mic have em come over.
----------
www.spiersharmonicas.com
High performance harmonicas.
|
jnorem
183 posts
May 01, 2014
1:02 PM
|
Thanks, Joe. I have been considering a new mic.
Bob, it's a 1968 silver face with the aluminum trim around the grill. I've been told that has the same circuitry as the blackface amps. I'll pass your recommendations along to my tech, thanks.
----------
Call me J
Last Edited by jnorem on May 01, 2014 1:03 PM
|
barbequebob
2539 posts
May 01, 2014
1:15 PM
|
Some of those from that year don't have the 5AR4/GZ34 rectifier.
If you use a JT30 with a crystal, you usually have to get the hottest one you can find and often Green Bullet mikes with either a CR or CM cartridge tend to have a better impedance match with those amps as well as with an old Shure 545 or 565, and I used a JT30 (older one with a screw on connector) that had a fairly hot crystal with the one I had.
From most players I know who have those early silver faced SR's, they're either big hit or big miss for harp.
----------
Sincerely,
Barbeque Bob Maglinte
Boston, MA
http://www.barbequebob.com
CD available at http://www.cdbaby.com/cd/bbmaglinte
|
1847
1748 posts
May 01, 2014
1:52 PM
|
sorry you said super reverb
deleted post
----------
i get a lot of request when i play my harmonica
"but i play it anyway"
|
Barley Nectar
376 posts
May 02, 2014
3:37 PM
|
Crystal mics want to see a high input impedence to get there best bass response. I believe 3M ohm is minimum. If your mic has a VC, this is in parallel with the input resistor at the jack. Replaceing your 68K input R with 5-8M R will help a crystal element on the low end...BN
Last Edited by Barley Nectar on May 02, 2014 3:39 PM
|
HawkeyeKane
2499 posts
May 02, 2014
4:14 PM
|
Goose, could one rig up a box with a higher impedance resistor to go inline before the amp input so one didn't have to hack into the amp?
----------
Hawkeye Kane - Hipbone Sam
|
Barley Nectar
377 posts
May 02, 2014
6:13 PM
|
I don't see why not but it would still be in parallel with the pot and the original R in the amp. Resistors in parallel reduce the total. 1/1/r1+r2+r3 ect. There was a thing that some fellows were using called a J-phat. Search the Lone Wolf forum. I never built one but they were said to be good. 5F6H should remember these...G
|
rockmonkeyguitars
69 posts
May 03, 2014
3:14 AM
|
If you swap the rectifier valve for a 5U4 that will lower voltage and give you earlier breakup. If you need to take it a step further you might want to think about using 6V6 valves instead of 6L6. This will lower the output by about 5 or 6db and breakup will happen much sooner (I haven't done the math so 5 or 6 db is an estimate). 6V6 valves operate at a lower voltage than 6L6 valves so it is important that you swap rectifiers before you swap power valves so that the overall voltage of the amp is lower. Also, it's important to use 6V6 valves that are designed to work at higher voltages that vintage 6V6 valves. I have found that JJ 6V6 valves work really well in a super reverb using a 5U4 rectifier.
You could also disconnect 1 (and only 1) of your four speakers to decrease volume a bit. It creates a slight impedance mismatch making the amp less efficient and therefore quieter and it also means their is less air being moved by the speakers which reduces volume.
These are all things I have done with great success on my own super reverb.
|
atty1chgo
913 posts
May 03, 2014
6:21 AM
|
Perhaps more hand effects and alterations in embouchure is in order. Just sayin'.
|
Barley Nectar
378 posts
May 03, 2014
6:44 AM
|
Rockmonkey, That SR may already be running the 5U4 stock. I think Leo made that tube swap due to cost factors. I put 6L6GB's in mine and biased accordingly. Also implemented a triode/pentode switch. T/P does knock down the output considerably but there is a loss of shimmer and cut also. Don't really care for this. I feel that voltage reduction across the entire amp may be the way to go as you alluded to with the rectifier swap.
|
walterharp
1369 posts
May 03, 2014
8:38 AM
|
another possibility would be to use an attenuator so you can push the amp hard enough to get it to crunch before it gets too loud
i have had ok experience with the weber mass attenuator, but the cables then sent with it were junk.....
|
