Amp'a Pre-amp Out Not working as expected

[Jack_TriPpEr]

I tried to use my Fender Blues Deluxe Reissue (BDRI) Combo amp's Pre-amp out connection as a send to an input on my powered mixer tonight, and the result surprised me in not just one but two disapponting ways:

1) my powered mixer acted as if it was getting zero feed from my BDRI
2) my BDRI continued to emit sound out of its own speaker even though I had no feed into its "Power Amp In" jack.

I ruled out the cable going from the amp to the powered mixer as bad, by using another known good cable and got same result.

I also jumpered the BDRI's Pre-Amp Out directly to it's Power Amp In and verified that (as expected) sound emitted from the amp (meaning that the problem is not a 'dead' Pre-Amp Out jack).

[EDIT: I also verified that the powered mixer's input channel wasn't malfunctioning, by sending the output of the guitar directly to it, and achieved guitar sound out of the powered mixer that way, as expected]

Here is the applicable section of the BDRI's owner's manual - it reads to me like I should be able to send a signal to another amp from the Pre-amp Out jack AND expect to hear zero output from the BDRI (because I have nothing plugged into the BDRI's "Power Amp in":



Am I misunderstanding something about the manual????

 

[dominus]

Re: Amp'a Pre-amp Out Not working as expected

It's a tube amp. There's usually no way to defeat the built in speaker, you HAVE to have a load on the amp. You may be able to use the standby switch, some amps will still let you use the effects loop/preamp out while that's engaged. Whether or not you want to use it for an extended amount of time is a question for the ages.

Were you using a speaker cable or an instrument cable from the preamp out to the mixer?

 

[Jack_TriPpEr]

Re: Amp'a Pre-amp Out Not working as expected

It's a tube amp. There's usually no way to defeat the built in speaker, you HAVE to have a load on the amp. You may be able to use the standby switch, some amps will still let you use the effects loop/preamp out while that's engaged. Whether or not you want to use it for an extended amount of time is a question for the ages.

Were you using a speaker cable or an instrument cable from the preamp out to the mixer?

Instrument cable from the Preamp Out to the powered mixer in.

 

[Jack_TriPpEr]

Re: Amp'a Pre-amp Out Not working as expected

... You may be able to use the standby switch, some amps will still let you use the effects loop/preamp out while that's engaged. ...

Thanks for that tip. Went back this morning, tried that out, but the amp doesn't seem to be designed to support that. No signal that way either. Sucks. Maybe AMT F1, here I come...

 

[Jack_TriPpEr]

Re: Amp'a Pre-amp Out Not working as expected

It's a tube amp. There's usually no way to defeat the built in speaker, you HAVE to have a load on the amp. ...

I sort of forgot that point 1, getting a feed from the Preamp Out jack, is still unexplained at this point. I can deal with the combo amp's speaker emitting sound, but why is the Preamp Out jack acting like it needs the loop to be closed with Power Amp In jack? Referring back to that snapshot of the user's manual in my first post, this behavior/restriction doesn't seem to match what they are saying about being able to drive another unit. Any ideas?

 

[dominus]

Re: Amp'a Pre-amp Out Not working as expected

Try putting an extra cable into the power amp in. Maybe it's only active when there is a cable inserted into both jacks. (Really guessing now. )

 

[zzmoore]

Re: Amp'a Pre-amp Out Not working as expected

1) my powered mixer acted as if it was getting zero feed from my BDRI
2) my BDRI continued to emit sound out of its own speaker even though I had no feed into its "Power Amp In" jack.

I also jumpered the BDRI's Pre-Amp Out directly to it's Power Amp In and verified that (as expected) sound emitted from the amp (meaning that the problem is not a 'dead' Pre-Amp Out jack).

I read a big contradiction here.
To me it means There Is a dead pre-out jack. It does not send anything to the mixer, but it always sends signal to the power amp.
Sounds like the switch on the out jack is bad.

 

[BrianS.]

Re: Amp'a Pre-amp Out Not working as expected

^That'd be my guess, too.

 

[Jack_TriPpEr]

Re: Amp'a Pre-amp Out Not working as expected

Ok, I figured it out. All is working fine, I guess. I just needed to crank the Gain and the Volume on the channel that I am sending into on the powered mixer. Much higher than for any other instrument or signal that I normally send into these mixer channels. I guess the Preamp Out signal from the BDRI is pretty weak. Even w the Gain level at 100%, the red clipping LED on that mixer channel never turns on.

Thanks everyone.

 

[zzmoore]

Re: Amp'a Pre-amp Out Not working as expected

But you still have a problem...and that is why your signal is so week.

2) my BDRI continued to emit sound out of its own speaker even though I had no feed into its "Power Amp In" jack.

Unless this is a parallel loop that you did not mention.....the cable into the out-jack should switch off the feed to the PI.
You should not be hearing music from your speaker, if you are sending the signal out to another device.

 

[Jack_TriPpEr]

Re: Amp'a Pre-amp Out Not working as expected

But you still have a problem...and that is why your signal is so week.

2) my BDRI continued to emit sound out of its own speaker even though I had no feed into its "Power Amp In" jack.

Unless this is a parallel loop that you did not mention.....the cable into the out-jack should switch off the feed to the PI.
You should not be hearing music from your speaker, if you are sending the signal out to another device.

I agree the signal seems a little too weak and I should keep looking into that, but I did verify (by a call to my Fender-authorized tech), that as Dominus reported earlier, this amp is not designed to kill signal to the power section even w the Preamp Out in use. The tube power section still needs to see a load. Maybe higher-end tube amps have a substitute dummy load feature, IDK, but not this one.

 

[zzmoore]

Re: Amp'a Pre-amp Out Not working as expected

I agree the signal seems a little too weak and I should keep looking into that, but I did verify (by a call to my Fender-authorized tech), that as Dominus reported earlier, this amp is not designed to kill signal to the power section even w the Preamp Out in use. The tube power section still needs to see a load. Maybe higher-end tube amps have a substitute dummy load feature, IDK, but not this one.

Seeing a load, and seeing a signal into the Power Tubes is 2 different things.
The power tubes do see a load...the speaker is still connected...that IS the load.
BUT...if Fender says it is normal for the pre-out not to kill the signal to the PI, then so be it.
Seems very atypical to me...but I am NO engineer.
best

 

[BrianS.]

Re: Amp'a Pre-amp Out Not working as expected

http://support.fender.com/schematics/guitar_amplifiers/BluesDeluxe_Reissue_2004_schematic_Rev-A.pdf

It looks to me like this is some form of parallel effects loop, but with no "mix" knob.

You could have a dirty jack or possibly something wrong with the op-amp that is driving the loop. Clean the jack with De-Oxit and see if that helps. If it doesn't, you probably need to take it to a tech.

 

[Jack_TriPpEr]

Re: Amp'a Pre-amp Out Not working as expected

Seeing a load, and seeing a signal into the Power Tubes is 2 different things.
The power tubes do see a load...the speaker is still connected...that IS the load.
BUT...if Fender says it is normal for the pre-out not to kill the signal to the PI, then so be it.
Seems very atypical to me...but I am NO engineer.
best

Ahh, I see what you mean. Definitely worth checking out. I will give Fender a call on Tuesday after the holiday. Thanks!

 

[zzmoore]

Re: Amp'a Pre-amp Out Not working as expected

I should have looked at the schem sooner.
I am NOT good with SS Circuits, but the Out Jack is buffered in some way. I suppose that is to make it pedal friendly (dumbleator).
But those are TRS Jacks. Are you using a TRS cable.?
If not, that would explain why you are still sending signal to the PI...and maybe why your Out Signal is kind of weak.?
Fender will clear all of this up for you. Let us know how that loop works after you talk to them.
best
yeah...let us know what does what.......

 

[Jack_TriPpEr]

Re: Amp'a Pre-amp Out Not working as expected

I will still call Fender, but this link from the Fender forum I just found, might clear some things up. Others have found that the BDRI amp emits sound when the Preamp Out jack is used (suggesting the loop is parallel (?)), and the signal output from the jack is a little weak. One of them came up with a neat trick where plugging a cable into the Poweramp In jack kills *most* of the sound emitting from the speaker. Gonna try this shortly and verify ....

 

[Jack_TriPpEr]

Re: Amp'a Pre-amp Out Not working as expected

I should have looked at the schem sooner.
I am NOT good with SS Circuits, but the Out Jack is buffered in some way. I suppose that is to make it pedal friendly (dumbleator).
This is definitely a Series Loop.
But those are TRS Jacks. Are you using a TRS cable.?
If not, that would explain why you are still sending signal to the PI...and maybe why your Out Signal is kind of weak.?
Fender will clear all of this up for you. Let us know how that loop works after you talk to them.
best

I have been using a mono/TS cable. Will retry with a TRS cable - thanks!

 

[Jack_TriPpEr]

Re: Amp'a Pre-amp Out Not working as expected

I tried the dummy plug into the Power Amp In and that significantly reduced the volume of sound emitting from the BDRI's speaker. The output now is now pretty faint.

Use of a TRS cable into the Preamp Out jack did not make a difference in improving the output signal strength. The weak signal strength from the BDRI hassn't really been an issue since I goosed the mixer input channel's Gain ( and raised the BDRI's Volume know from about people 0.75 to 2. I think I am all set, but I'll still Fender on Tuesday. Thanks zzmoore and BrianS.!