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Topic: Session 400. effects loop? |
Richard Mitcham
From:
Ocklawaha, Florida
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Posted 27 Jul 2007 8:29 am |
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Could an effects loop be built into these old 1970's Session 400 amps?
If not can I use my Nashville 1000 amp useing it for my effects loop and patch into my Session amp and get the sound I want from the Session 400?
Thank You |
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Ken Fox
From:
Nashville GA USA
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Posted 27 Jul 2007 5:13 pm
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Yes it can be accomplished. The preamp plugs onto the power amp board with a Molex connector. It can be removed from there to break the preamp to power amp circuit. This would be a peramp level signal and may be too strong for some effects units (1 volt RMS I believe).
Two jacks are needed, a Switchcraft #11 jack for the preamp out and a Switchcraft #12A for the power amp input. The preamp out is connector to the tip of the #11 jack and to the contact on the #12A jack. The tip of the #12 jack is connected to the power amp input.
Requires shield cable, jacks and chassis drilling.
One could use the #2 input jack hole and abandon the old 12A jack used there. The signal would route to there first and then to the back of the amp. There you could disconnect the booster jack (seldom used output for a power amp, lime level signal). There you would put in the #12A jack and wire the front jack back to it. From that jack wire to the power amp input.
A lot of potential for hum and ground loops. You need to understand how to "telescope" shields on the signal cable to avoid this problem.
Best left to a good tech to do! |
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Richard Mitcham
From:
Ocklawaha, Florida
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Posted 27 Jul 2007 7:44 pm
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OK, I can't do it for sure. Would this be somthing you guys would or would not recommend to do to this amp?
My Nashville 1000 is quite going through the effects loop. couldn't this be a good thing to do to this old Session 400? I like the way these old Sessions sound if I could just make it a little more useable for my 6 string with all the effects I use with it. My steel is ok as I only use very little delay with it. Nobody around here could do it that I know of "NW PA". I doubt peavey would since it wasn't a factory option. Any takers or should I forget it and move on as a bad idea? |
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Ken Fox
From:
Nashville GA USA
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Posted 28 Jul 2007 5:09 am
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I could do it. But if you have to ship it this far to do just that you might consider the Brad Sarno mod that I do as well. That will get the amp all new filter caps, film coupling caps and a lot more. Just a thought.
There must be someone on the Forum close to you that does amp work?? If you just want to add the effects loop you might post to see if there is a tech around your area.
If you want me to do it I would be glad to take it on. I have the Molex pins and Molex extraction and crimp tools needed to add new, longer cables to the old Molex connectors at the preamp board and the power amp board. That would allow proper routing to avoid any hum issues. |
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Colby Tipton
From:
Crosby, Texas, USA
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Posted 28 Jul 2007 5:41 am
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Ken,
Could you route these changes to the switch and booster jacks on the back of the amp?
That way you wouldn't have to drill any holes in the original chassis. |
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Ken Fox
From:
Nashville GA USA
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Posted 28 Jul 2007 5:58 am
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The power on/off switch? I would not do that. Plus that area has the potential to induce hum in the signal cable.
If you use the the #2 input jack and the booster jack no holes are needed.
If it were mine to do I would look at the possibility of drilling a hole beside the booster jack and putting a printed label on there for proper identification of each jack's function.. |
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Mike Wheeler
From:
Delaware, Ohio, USA
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Posted 28 Jul 2007 6:10 am
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Ken, I think Colby might have meant the footswitch jack.
_________________
Best regards,
Mike |
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Ken Fox
From:
Nashville GA USA
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Posted 28 Jul 2007 6:51 am
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Ah! Good choice. Yes, that can be done. Both these jacks are rarely used.
Great idea, Colby! |
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Colby Tipton
From:
Crosby, Texas, USA
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Posted 28 Jul 2007 7:09 am
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Good deal Ken.
I'll get up with you about doing a Session 400 for me shortly.
2 more questions.
1. Can you use the #2 speaker jack and the #2 instrument jack too? That way you could have 2 effects loops. 1 for a passive volume pedal and 1 for effects.
2. Can you do anything like that with a Fender tube amp.? |
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Ken Fox
From:
Nashville GA USA
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Posted 28 Jul 2007 7:11 am
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I would not attempt two effects loops myself on the Session 400.
Never done one on a Fender. Brad Sarno has more expertise on that subject! |
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Colby Tipton
From:
Crosby, Texas, USA
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Posted 28 Jul 2007 7:20 am
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Well, one on a session is better than none.
It's funny that this thread came up on the session effects loop, I was thinking about this the other day.
I know that Peavey didn't do the effects loop in the session days because people just didn't use all of the stomp box stuff back at the time. |
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Ken Fox
From:
Nashville GA USA
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Posted 28 Jul 2007 7:58 am
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I still would be cautious of doing it, as the 1 volt RMS potential signal might be to much for the effects pedals! They are designed for instrument level. In the case of a MPX100 and other rack unit really designed for PA use it would be OK.
Most of the effect loops in amps are picked up in the circuit well before the preamp output. |
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Ken Fox
From:
Nashville GA USA
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Posted 28 Jul 2007 8:40 am
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for example:
A Boss Compressor pedal wants a nominal signal of -20dBu (.077Volts RMS) at a 1 meg input impedance. max signal with 20 db of head room would be 0 dBu or .775 volts RMS.
A Nashville 400 preamp out (similar I am sure to the Session 400) is a nominal 0 dBu or .775 RMS and can max at +18 dBu, 8 volts RMS
The preamp output would distort a typical guitar pedal!
Would be a nice signal to a rack processor for PA use.
The patch jacks on a Nashville 400 are more in line with pedals:
output -14dBu, .2V RMS at 1K ohms
input -14dBu, .2V volts at 220K
This is a loop using opamps to send the signal and receive it (buffers the signal) |
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Richard Mitcham
From:
Ocklawaha, Florida
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Posted 28 Jul 2007 8:42 am
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Ken, I emailed you also.
What I would like to run through the loop would be a Boss DD-3, RV-5, DS-1, and a Chorus. All stomp boxes. Would I be good to go with all that going through it? |
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Ken Fox
From:
Nashville GA USA
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Posted 28 Jul 2007 8:58 am
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Judging by the nominal input level of these pedals (-20dBu) I would not do it with the Session 400.
The pedals are designed for a guitar level, not a line level. You would get distortion or at best poor signal to noise ratio.
I can not see why anyone would use an effects loop for guitar pedals. The pedals are designed for use with a guitar signal and best used that way.
An effects loop would be much better suited to rack mount processors designed for these levels, such as a Lexicon MPX-1. MPX-100, MPX-500. These processors do not work well with a guitar plugged into them, they need a stronger signal from an effects loop. They work with a guitar but do not get their optimum signal to noise ratio as they are not getting their nominal input signal. |
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Richard Mitcham
From:
Ocklawaha, Florida
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Posted 28 Jul 2007 9:23 am
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| I don't doubt you one bit Ken, your the man when it comes to this stuff. I do know though, that my Nashville 1000 is super quite with all these effects pedals going through the effects loop and all seem to work better that way also. Go figure? Could it be that amp is designed to except the stomp pedals? Yes, I could go with the processers, but I need to make changes on the fly sometimes when we jump quickly into one song to another. Being the old fart I am I get lost on those processers these days. |
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Ken Fox
From:
Nashville GA USA
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Posted 28 Jul 2007 9:34 am
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Well, the signal levels seem to be close to what a stomp box wants to see in those loops on the N-400. I can see where they would work OK.
I still would rather run my guitar thru them and into the amp. That is what I have done for years with my pedal board for 6 string and steel.
Like you, I like to get my hands on the individual controls so I do not use a processor at all for guitar.
Still to put a proper loop in the Session 400 would require some surgery into the signal path way before the final preamp output.
Next time I get one on the bench I will run a nominal input signal thru it with a signal generator and scope around a bit to see what might be possible. |
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Colby Tipton
From:
Crosby, Texas, USA
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Posted 28 Jul 2007 9:42 am
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Oh well, back to the drawing board.
It was just a dream anyway.  |
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Richard Mitcham
From:
Ocklawaha, Florida
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Posted 28 Jul 2007 8:29 pm
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Ken,
I want to thank you for your input on this it has been very nice conversing with you. I can live with the amp the way it is on the job. Recording, thats another story but I'm not doing much of that these days either. To old, slow, and can't think quick enough.
Thank You again for your help in helping me understand what all is involved. |
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