Ampeg Preamp into another Amplifier's In

Discussion in 'Amps [BG]' started by Tim_the_Stoner, Jan 13, 2014.


  1. Tim_the_Stoner

    Tim_the_Stoner

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    Heya,


    So, I've got a V4BH and I'm thinking about chaining the preamp out on it into another amplifier (one by Marshall, IBS200) through the in as it has no dedicated in-section for a preamp.

    Would going from a Ampeg preamp into a Marshall that I'm not quite sure if it has a preamp at all, hurt in any way? I have used preamp pedals into amplifiers In set on clean a lot of times and it didn't sound bad, but maybe I'm in for trouble here. I also have to consider the Phase...
     
  2. Bassmec

    Bassmec

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    I have been using preamplifier outputs into other amplifiers inputs for many years with few problems, in the case of phase concerns most of the problems are polarity issues with things like the labelling of the loudspeakers the amplifiers are driving.

    For instance if you combine a cabinet with JBL drivers with a cabinet
    containing Celestion drivers and the red terminals are connected to the Jack tips, as is the convention. The cabinets will be out of polarity.
    Best to check using a 9 volt battery on the speaker cables and watching the cones offset direction.

    Just as you would if you where God forbid! Connecting dissimilar cabinets to the same amplifier:bawl::spit::D:hiding.
    Anyhoo if the amp you wish to slave is of a similar topology? there should not be a phase differential, beyond the usual issues with active EQ systems introducing phase differential.

    As part of my Job in studio is reamping dry tracks recorded at home by musicians using amp simulation software, sent to me and reamped in studio via the ubiquitous little labs phase tools and Waves phase analysis software tools and driving a variety of tube amplifiers and even some SS ones simultainiously. The audio rulz are there are no rulz! apart from what sounds good to you.

    The physics rules are that, you dissimilar amplifier unit users, henceforth shall be described a slavers, and for that matter others that you may know, that use more than one single coil pickup per string:confused:, being found guilty of gross distortion and phase differential, shall be taken from this place to a gallows and hung by the neck until you are dead.:help::bassist::bag:

    PS If the amp being driven from the other preamp has an active bass attenuator switch, that might be a better choice of input, but I vote experiment.:oops:
    PPS Sometimes you can have earth loop noise issues, but I use the "Lehle Dual" or "P Split", transformer based signal splitter if there are any hum issues in studio.
     
  3. beans-on-toast

    beans-on-toast Supporting Member

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    The purpose of the preamp out and power amp in is exactly for what you want to do. Since your amps doesn't have a power amp in, you could try using an instrument cable to connect the pre-out on the Ampeg to the effects return on the IBS 200.

    In general, it is also possible to chain two pre-amps together. The pre-amp out on the Ampeg would be connected to the instrument input of the second amp. Again, use an instrument cable. You have to be careful of the gain levels. If the Ampeg's level is too high it will cause the second amp's input to be overloaded and you get distortion. Start with the levels off and slowly bring them up using your ears to judge where they should be set.
     
  4. Tim_the_Stoner

    Tim_the_Stoner

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    I had completely forgotten the IBS200 had an effects loop...


    Thanks, guys! Just for you curious, the rig will be:

    Bass > Tuner > Ampeg V4BH Input > SVT-410HE
    Ampeg V4BH Preamp Out > Marshall IBS200 (In or FX Loop, depends on sound) > SVT410HLF

    All STACKED for MAXIMUM thumb.
     
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  6. beans-on-toast

    beans-on-toast Supporting Member

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    Let us know how it sounds.
     
  7. Tim_the_Stoner

    Tim_the_Stoner

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    PS: Does anyone know if a SVT410HE can be stacked on a SVT410HLF comfortably?
     
  8. Bassmec

    Bassmec

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    It will stack fine, the only issue I can think of is that there is no volume control on the Marshall return socket, so it might be better to use the Marshall input to operate that as a separate level control even if you don't use the EQ.:bassist:
     
  9. beans-on-toast

    beans-on-toast Supporting Member

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    You can also try connecting the amps by running an instrument cable from the -15db input on the V4BH to the input of the IBS 200. Plug your instrument into the V4BH.
     
  10. Tim_the_Stoner

    Tim_the_Stoner

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    Ah, yes. That's right, there isn't a "master" volume on the IBS200. I would have to plug it straight in.

    What benefit is there over the preamp out and the -15db out?


    AND ONE MORE THING: What value are the pots in a V4BH? I need to replace one and it's a PITA to open the amp...

    ALSO: Instead of a second 410, would a 115HE be a bad idea? They have independent EQ and Volume settings, so I don't see why not... :D
     
  11. beans-on-toast

    beans-on-toast Supporting Member

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    I'm a bit confused, what model is the Marshall. Is it a 3520 IBS 200W head?

    The V4B pots have different values. Which one are you needing to change? Have you tried using some Deoxit on the pot to see if it can be cleaned? Better to do that than to have to change a pot.

    By going from the -15db into the instrument input of another amp you are using the preamps of both amps. You can have different tone settings on each amp. Basically you are Y splitting the instrument input signal. When you take the pre-amp out and connect that into the power amp of another amp, you are using one preamp and two power amps. So you are Y splitting the pre-amp signal.
     
  12. Tim_the_Stoner

    Tim_the_Stoner

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    Thanks, Beans. That cleared it up a lot. I'm going to run the V4BH from either the Preamp Out or the -15db into the IN of the Marshall IBS200 3520 (yes, it's that one) and hook the Marshall to my SVT410HLF and the Ampeg to a 115HE or a 410HE (need to get that one first)

    I'm looking to change the Gain knob on the Ampeg, the one that adjusts preamp clipping.
     
  13. beans-on-toast

    beans-on-toast Supporting Member

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    The gain pot (P1) is 1 Meg ohms, audio taper. You might be able to buy the exact replacement part from Loud. If you contact them, they should be able to supply you with a copy of the schematic. Good to have on hand in case your tech doesn't have one.

    By the way, the V4BH pre-amp is the same circuit as the SVT CL.

    I'd try connecting the amps both ways and see what works best.
     
  14. Bassmec

    Bassmec

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    You are risking being excommunicated from the church of pure physics
    here.
    I had the temerity to build a 8X10 + 2x15 dual 200 watt tube amp rig with an Ampeg SVT IIP pre amp feeding the pre amps of the amps via a Lehle Dual as a clean dirty rig. Which I utterly love the sound of.:ninja:
    People now cross to the other side of the street as I approach and I don't get Christmas cards anymore.
    Dead Crows are sometimes nailed to my front door, are you quite sure you want to risk hordes of music tech students ear holing you after every gig to tell you all the pure physics reasons for not doing this?.
    Be afraid be very afraid lest ye and all thy progeny shall not now enter the kingdom of physics heaven for this proposed herasy.:eek::bawl::D:bag:
     
  15. Tim_the_Stoner

    Tim_the_Stoner

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    Man, sometimes I wish I was a bass player and not a guitar player... This rig is what I'm building for my brother to use in our band, but I still like it BIG.

    So, all in favor? First time? Second...? Sold.

    I've got my eyes on a 115HE for around 300€, which is think is alright and then I'll just say goodbye to my money for fixing the car, lol.
     
  16. Bassmec

    Bassmec

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    Guitarist eh! well as I am already damned, so I am prepared to come straight out and freely admit that I have been seen playing guitar in public as well.
    This is Nick Johnson using my clean dirty rig in Devilment, Danni Filth's newest project band. rehearsing in the drum room.:bassist:
    [​IMG]
    :D
     
  17. Tim_the_Stoner

    Tim_the_Stoner

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    Nice rig! I see one 810 and two 410 (I think) but I can onlymake out the head on the top to be... Hiwatt? What is the rest?

    Also, does anyone know the exact replacement pot for the Gain pot? I got 1Meg Audio, but no size or brand.
     
  18. beans-on-toast

    beans-on-toast Supporting Member

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    It is a PCB mounted pot. Best to contact parts@loudtechinc.com (or technicalsupport@loudtechinc.com) for a part number and a replacement.
     
  19. Tim_the_Stoner

    Tim_the_Stoner

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    Is it difficult to get around to replace the PCB mounted pot? Or should I send it to a tech?
     
  20. beans-on-toast

    beans-on-toast Supporting Member

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    It depends how comfortable you are doing this sort of work.

    Replacing the pot requires taking the amp apart which is half the battle with some of these jobs. There is some disassembly inside the amp to get the part out. Once all that is done, changing the part takes minutes. It is important when working with circuit boards that you don't use too much heat. It can lift the traces on the board.

    Sending the amp away will get expensive fast. Finding someone locally that can do the repair would be better. If you have the part in advance, it helps with turn around time. Otherwise you take it in, the amp sits there while they wait for the part to come in. At least now you might be able to use it.

    As I said earlier, if the issue is that the pot is scratchy, you might be able to fix the problem with some deoxit. It cleans and lubricates the inside of the pot. This is the first step. It could avoid the expense of changing the pot. If on the other hand, the shaft is broken or doesn't turn, then you need to replace the pot.

    A tech, after having looked at the amp, would be able to tell you what it needs. There are other basic maintenance tasks that should be performed on an older amp. I know more money....
     
  21. Tim_the_Stoner

    Tim_the_Stoner

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    Money's not a problem (not trying to brag, I just don't care what good equipment costs as long as it works) but I rather change it all together as I think it's broken rather than dirty. I'll have to order the piece first... Meanwhile I've got the IBS200 to play around with.
     

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