Using a Champion 600 as a preamp?

[Bobby]

I picked up one of those 5 watt Fender Champ 600 amps and, because you can unplug the speaker and have those tiny 5 watts power another cab, I got to wondering if I could use it as a preamp into a Fender Deluxe Reverb by simply running a cord from the speaker jack inside the champ 600 ( by unplugging the Champs speaker) straight into one of the channels on the twin without blowing out all the Fender Champs circuits? Will that keep some load on the Champ or will it fry in minutes because of no driver load?

[Blue Strat]

Probably won't fry it in minutes, but it's definintely not a good idea. You'd need a dummy load of some sort.

[Bobby]

Probably won't fry it in minutes, but it's definintely not a good idea. You'd need a dummy load of some sort.

So how could I create a 'dummy load' (other than asking my wife and geting the ususal response)? Could I attach leads from the Champ 600 driver to a jack and plug in there?

[dk123123dk]

You need to modify the amp with an effects loop. You could then just take the send from the smaller amp and plug that into the return of a larger amp.

But if you just run a wire from the speaker to the input of your amp it will be bad!

dk

[Bobby]

You need to modify the amp with an effects loop. You could then just take the send from the smaller amp and plug that into the return of a larger amp.

But if you just run a wire from the speaker to the input of your amp it will be bad!

dk

hmmmmmm. Time for me to come clean. I'm completely technologically challenged so thought this was the right place to ask this question. Sadly I never understand the response so here's the thing I'm trying to do.

WAAAAAYYYYYY back in the day we could run a wire from the 'out' on the back of a smaller amp (seems every amp had an 'out' in those days) into the input of our Hendrix wannabe Marshall 100 watt heads. So when I got the 5 watt I though " wouldn't it be cool to plug it into the input of the Deluxe Reverb." So things like creating 'a dummy load' and 'effects loops' and what on earth a 'return' is on an amp, I have absolutely no idea what all of this means. So would some kind, and undeniably incredibly patient individual please explain this in terms I could hope to understand? Thanks to those who did reply to this already. I know it seems simple but to me it's all a foreign language.:bkw

[dk123123dk]

No worries mate, some of this stuff seems a lot harder than it is.

Basically every guitar amp has a Preamp, and a Poweramp. To simpfy things, lets say the preamp shapes the signal, and the power amp makes the signal louder (amplify).

An effects loop is basically an in and an output jack between the preamp, and power amp. Possible uses are :

Plugging in an effect. This way your effects can be heard clearer. Delay and reverb work well here. Running the pedal in front of the amp, then shaping the tone, then amplifying it, will sound muddy with any distortion from the amp.

Running a smaller amp or external preamp into a larger amp. You plug into the smaller amp. Then you run a cord from the "send (preamp out)" of the small amp, to the "return (poweramp in)" of the bigger amp. Some people use a nice tube amp as the small amp, and a loud solid state amp. This will get you a lot more tube tone, but won't be the same as an all tube setup.


I think what you are remembering is running a wire from the speaker, or the speaker output, to the larger amps input. This will work, but its bad for both amps. The small amp NEEDS a load on the amp while its running or you could blow the transformers (expensive). Plus you would be running through two preamp sections, and two poweramp sections. This will most likely sound like a big muddy mess, and could damage both amps!

The Dummy load, is something that allows the amp to "think" a speaker is attached. This way it doesn't blow the transformers, but you can still send a signal to the PA or larger amp.

SO, without mods to your amp, or someway to add a dummy load to the champ (attenuator with a line out would be key), you are basically out of luck. If you had an effects loop or line out installed on the champ, you would be in business.

If you like the way the champ sounds, you could always put a mic in front and just run it to the PA!


Good luck, and I hope I can help with any more questions you may have.

dk

[jh45gun]

If the amp does not have an jack for an extension speaker and evidently it does not if you do not want to add one you could put a parallel jack off of the speaker and run a PASSIVE DI box off that jack to an other amp. You would run a guitar cord from the jack off the speaker to the Passive DI HI Z input. Then run a Mic cord from the low Z output with a low z on one end and a quarter inch jack on the other end to the High Z input of the slave amp. The DI box's Transformer will match every thing up so it will work fine. This way the speaker still is providing a safe load for your champ and the parallel jack gives you a place to plug in a cord to the DI box. Just make sure the DI box is PASSIVE and you use the Hi Z input on the slave amp.

[burner]

Why not just build a line out off of the speaker jack.
You'd still have the speaker connected to the champ but you could then line it out into a bigger amp and get the whole sound of the power amp...not just the preamp as you would if you simply built an effects loop.

[Blue Strat]

Burner makes a good point. As long as you don't mind the self contained speaker operating (which you wouldn't hear over the bigger amp you're driving).

There's a circuit for this shown in one of Gerald Weber's books. It's basically a resistor and a pot. Very simple, but I don't know the values off hand.

What DK is recommending is not only too complicated for a novice but won't give you the overdriven power tube tone that you're looking for.

[Blue Strat]

PS, a THD Hotplate is an example of a unit that has a built in Dummy Load.

[jh45gun]

When I suggested the Line out with a couple of resistors and a pot Several others here suggested the Passive DI box as a better method. I tried it and it does work.

[Bobby]

Burner makes a good point. As long as you don't mind the self contained speaker operating (which you wouldn't hear over the bigger amp you're driving).

There's a circuit for this shown in one of Gerald Weber's books. It's basically a resistor and a pot. Very simple, but I don't know the values off hand.


First thank you guys SO much for taking the time to help me with this and being so patient.

So let me try and repeat this back to you in 'duh' (the only technical language I can speak) and see if I'm getting closer to understanding. The simplest thing to do is attach leads to the still connected Champ speaker (so there's still load on the amp, but won't this create a parallel or series connection and change the load on the champ?) then to an output jack. Should it be positive to positive? Then I need that circuit you mentioned (if you ever find it let me know ok? particularly if you find it in coloring book format with pretty big pictures). Is the pot so I can control the output to the Deluxe Reverb? I have no clue what the ' resistor' is. Am I getting warmer?

[Bobby]

When I suggested the Line out with a couple of resistors and a pot Several others here suggested the Passive DI box as a better method. I tried it and it does work.

Would I (a COMPLETE novice) have any chance understanding what a 'Passive DI box' is let alone how to build/use/find one?

[dk123123dk]

Would I (a COMPLETE novice) have any chance understanding what a 'Passive DI box' is let alone how to build/use/find one?

Does a complete novice understand a simple Google search for "Passive DI box" would give you all the answers you need?

dk

[Bobby]

Does a complete novice understand a simple Google search for "Passive DI box" would give you all the answers you need?

dk

Yeah thanks dk I'm all set.

A DI unit or DI box is an electronic device that connects a high impedance (http://en.wikipedia.org/wiki/Electrical_impedance) line level (http://en.wikipedia.org/wiki/Line_level) signal that uses an unbalanced cable with a 1/4" phono plug to a low impedance mic level input that uses a balanced cable and XLR connector (http://en.wikipedia.org/wiki/XLR_connector). For example, one can connect an electric guitar to a DI box which can then be connected to a mixing console (http://en.wikipedia.org/wiki/Mixing_console)'s microphone input. It performs level matching, balancing, and either active buffering (http://en.wikipedia.org/wiki/Buffer_amplifier) or passive impedance bridging (http://en.wikipedia.org/wiki/Impedance_bridging) to minimise noise, distortion, and ground loops (http://en.wikipedia.org/wiki/Ground_loop). (DI units do not perform impedance matching (http://en.wikipedia.org/wiki/Impedance_matching).)
DI is variously claimed to stand for direct input, direct injection or direct interface. DI units are extensively used with professional and semi-professional PA systems (http://en.wikipedia.org/wiki/PA_system) and in sound recording (http://en.wikipedia.org/wiki/Sound_recording) studios.

[burner]

First thank you guys SO much for taking the time to help me with this and being so patient.

So let me try and repeat this back to you in 'duh' (the only technical language I can speak) and see if I'm getting closer to understanding. The simplest thing to do is attach leads to the still connected Champ speaker (so there's still load on the amp, but won't this create a parallel or series connection and change the load on the champ?) then to an output jack. Should it be positive to positive? Then I need that circuit you mentioned (if you ever find it let me know ok? particularly if you find it in coloring book format with pretty big pictures). Is the pot so I can control the output to the Deluxe Reverb? I have no clue what the ' resistor' is. Am I getting warmer?

Yes correct.

[G.Boccasete]

Just add a line out-off the speaker output lead-

there are lots of ideas on the net-

here is one I tried a few years ago-It worked and I didnt even use the same resistor size.

http://www.rru.com/~meo/Guitar/Amps/Kalamazoo/Mods/ezlo.html



If you do this and want to disconnect the speaker then add something like a 10-20 watt resistor the same as the speaker, it will take some of the load and protect the OPT.

Ive tried this and it works quite well, although I was inputting it into a power amp, it will still work with the extra PA just set the second amp up as clean as you can get it.

Gildo

[jh45gun]

NOTE: This is not a pre-amp out! It's a quick and dirty hack taken off the speaker outputs. As such it will not be as good an impedance match, or as clean, as a real line out. But it works.
But keep the speaker plugged in! Otherwise, you may well fry your output transformer and/or the 6BQ5!

taken from that site. I think that is why I asked about this it was suggested that the Passive DI box is a safer and better route to go.

[Bobby]

jh45gun: But the info I got of of Google said:

"(A Passive DI box) performs level matching, balancing, and either active buffering or passive impedance bridging to minimise noise, distortion, and ground loops."

So, again being techno-challenged --don't I WANT 'noise and distortion' to come through and not have it 'minimized' like it says in the description of a Pasive DI box? What I'm trying to do here is have a 5 watt stomp box.

[jh45gun]

Bobby, Here is what John Phillips said about this at another thread and about using the Line out that was suggested using a resistor or two he says not to do it but use the DI box instead. Instead of you searching for the link and reading through it all I will post it here for you.

It might 'work', but it could cause serious problems...

It's totally unknown what voltage will reach the desk input. With just a pot and a resistor on the speaker output, the final voltage seen by the desk's input stage will be dependent on its input impedance - and actually, for a typical 10K or so input, a series resistor of only 220 ohms is nowhere near enough... depending on where the pot is set, the desk could still see up to almost of the full output voltage of the amp, which is plenty high enough to damage input transistors or ICs.

It will also probably cause a ground loop between the amp and the desk.

Do NOT do this. If you want to DI an amp into a desk, it the very least it must have a proper voltage divider before the level control (and whose values depend on the power of the amp), and preferably ground isolation. It will also sound pretty poor without speaker emulation, or possibly powerful EQ (you can use a three-band EQ with a sweepable mid to approximate a speaker curve reasonably well usually).

Please don't take advice about how 'things were done in the good old days and worked OK' (especially from people who appear to have little technical knowledge). Some things did work, some things didn't... and some things caused expensive damage.

The best solution, by far, is the Red Box, Palmer or Behringer type of speaker-emulating, ground-isolating DI box. It does not involve any mod to the amp, is totally safe for the desk, avoids a ground loop and sounds good all at once.
______
I would like to add my two cents. A direct box requires no modding to the amp itself adn allows you to still use the amp the way it was intended without undoing anything.
Is it a passive, transformer-balanced DI box? (I can't remember about this model - but the 'high frequency attenuation' sounds like it should be passive.) If you're not sure: does it need a battery? If yes, it's active. If still unsure, open it up and look inside - if it's a passive transformer box that's all there will be in there.

If it is a passive transformer type, you can use it very simply: connect the 1/4" high impedance jack to the first amp's speaker output, and then get a mic cable with a 1/4" plug on the 'amp' end (old-fashioned now, but still available) and connect that between the XLR output and into the second amp. The transformer will drop the signal level to a safe range for the second amp and also eliminate any potential ground loops. (Yes, I know the output side is in theory low-impedance, but it still works, with the higher input signal level.)

You can't do this with a normal active DI box because the level at the speaker jack will be too high for the box's input circuitry and will make it distort badly even if it doesn't damage it.

If you're intending to reamplify the signal through another amp and back into a guitar cabinet, you specifically don't want a speaker-emulating type or it will sound muffled.

Originally Posted by jh45gun http://img.thegearpage.net/board/images/buttons/viewpost.gif (http://www.thegearpage.net/board/showthread.php?p=3490206#post3490206)
So John just to be clear on this you keep the speaker hooked up to the normal speaker jack so the speaker runs and gives the amp a load and then run the box through the parrallel speaker jack to send the signal out to the box into an other amp or mixer right?

Yes. But not to a low-impedance balanced input, since you will then overload it. The trick only works if you deliberately connect the low-impedance output to a high impedance input.


Quote:
so how does the transformer work better than the resistor idea? Just wondering to broaden my knowledge of the issue.
Because it totally breaks the signal path between the two amps, including the ground. No ground loops and reduced noise transfer. From the point of view of the second amp, the transformer is the signal source, just like a guitar pickup.

The reason it works is because by converting the high-impedance signal to low-impedance, it also drops the signal voltage level. For balanced applications, it also greatly increases the current capability so it will drive very long cable runs with minimal loss, which is the normal reason to use one - here it doesn't matter since if you feed it into a normal high-impedance input you throw away the high current capability anyway... but you retain the lower signal voltage.

Ideally you want a DI box with a pad switch as well, but those - at least passive ones - are now rare, so you'll have to hope it will be about right. With a low-powered amp as the source, it should be.

I've used an old DOD passive DI box like this occasionally.

The Silvertone 1391 does not have an external speaker jack and the speaker is hardwired without a jack. I assume I need to add an external jack in order to connect to the DI Box. I am not sure how to accomplish that and still have a speaker load on the 1391 amp? Thanks for your time and help with this. The simplest way is to get a short cheap guitar cable, cut one end off, and solder the wires directly to the speaker terminals - making sure the shield goes to the one that is grounded at the amp. Plug that into the DI box. Of course you must be careful that when you're not using it, the loose end of the cable doesn't touch anything else on the amp chassis, but if it's a typical combo amp you can leave it in the bottom of the cabinet with no harm - or tape over the tip of the plug to be sure.__________________
Here is the link Bobby if you want to read the whole thread:

http://www.thegearpage.net/board/showthread.php?t=197704&highlight=Passive

__________________

[jh45gun]

Just remember it has to be the passive transformer type and not an active or speaker emulating kind. Pretty simple and easy once you read the info. Mine is a Peavey and it works fine. Others were listed above like Behringer and Red Box and Palmer. I am sure there are others as well. Just remember it has to be the passive transformer type and not the active kind and you hook it up from the low z out to the Hi z in on your slave amp.

[Bobby]

Thanks jh45. I read through the other post you linked to. Very informative as well and thanks a lot for that. Sooo many questions..... I think I have about a 1 watt understanding at this point.

I checked out the DOD web site (http://www.dod.com/accessories/accessories.htm) and came across the DOD AC265 Stagehand direct box and checked out the manual which was simple enough but hard to understand all the same (some talk of 'balanced' vs 'unbalanced' which I don't really get at this point). Seems like there are 3 plugs to use not just two. Is that normal?

[jh45gun]

Well my Peavey has a Line in Hi Z in a Hi Z Line out that has a line showing them connected so I suspect that the two jacks are in parallel so you can run a line out to some thing else with out going through the transformer and a Low Z out which would make it three jacks. A Low Z input or output is considered balanced and is a 3 wire cord like a microphone cord that has the three wires with the connectors to match. An unbalanced cord would be like a standard two wire guitar cord. Of course then for patching capabilities you have mic cords for the Hi Z mikes that have a low Z connector on one end and for the mic and a Hi Z on the other end so you can plug it into a guitar amp or a older PA head that does not have the low Z inputs. Of course they make adaptors that has a transformer to make a Low Z mic cord into a Hi Z on one end. FYI the Z mentioned stands for Impedance.

[Bobby]

I'm getting REALLY confused with the back and forth impedance levels so let me try and say what I think I need and, if you don't mind you correct me where I'm wrong ok?

Champ 600 speaker speaker terminals (attach jack positive to positive = high impedance unbalanced output) > Passive DI box HI impedance input > Passive DI box low impedance unbalanced output > Deluxe Reverp input jack? Am I close?

I'm finding most DI boxes seem to have a BALANCED (three wire = microphone right?) output rather than an unbalanced output

[Bobby]

So I'm still wondering if my above post would be correct to use a Champ 600 into a Deluxe Reverb. Anyone? Did I get it right?:messedup

[jh45gun]

Yea Bobby you got it. Yes that low z out uses a standard low z microphone cord so for what you want to do is, you either need a mic cord for a high Z mic which is the low z jack that plugs into the mic one end that fits into the DI and a standard quarter inch jack on the other end for plugging into the amp input or use a standard low Z mic cord and get a hi z adaptor which they sell for those that need to plug a mic into an amp or an older PA that does not have low Z inputs. Just remember that if the amp your using as a slave amp has a hi z input and a normal input use the first input which is the hi z one.