Recto pre witn 2:100 & speaker configuration

[MRX2099]

Ok I got both pre and power amp used so no manuals, I need to know if I run these together in 2 sets of 8ohm speakers wired series (totaling 4 ohms each set ) can I run stereo of the 2:100, one channel 4 ohm outputs and other channel 4 ohm outputs? or do I have to use both 4 ohm outs on each channel to get the load correct,? in other words can only one 4 ohm out per channel be run or will it hurt the poweramp or speakers..I will be using G12T 75 2 sets of 8 ohms each wired in series to equal 2 sets of 4 ohms 150 watt sets

or will 4) 16 ohms G12T 75 wired - 2 sets parallel to equal 8ohm 75 watt per sets
be enough watts for the 2:100

Jeff

 

[PUBH]

I'm not following your wiring scheme (getting confused, lol)... but I CAN tell you how the 2:100 works...

The 2:100 has TWO channels (each at 100 watts). Each channel has 3 output plugs... one, labeled 8ohm, and two others (which are "paired" together) labeled at 4ohm.

The 8ohm jack must see an 8ohm load. So... whatever wiring scheme you use, this jack must see an overall load of 8ohm connected to it. (This could be a single 8ohm speaker; or two 4ohm speakers in series; or two 16ohm speakers in parallel; there are more possibilities with four speakers, but if I read your post right, I'm sure you are talking about pairs/sets of two speakers.) Also note: The 8ohm jack on the other channel work the same.

Now... for the "paired" 4ohm jacks. Whatever you plug into these jacks... the amp connects these jacks together in parallel internally. So... if you take two 8ohm speakers, connect one into one of the 4ohm jacks, and the other into the other 4ohm jack... the amp will only see a 4ohm load, which is what it wants (cause two 8ohm loads in parallel is 4ohm). As far as I recall, you do not have to load each jack on the paired 4ohm outputs (or at least, I have not heard otherwise, though you may want to check with Mesa directly, I've never tried; but, as far as I know, as long as the amp sees a 4ohm load overall from these two jacks together, you should be fine). So this leaves a lot of options for these jacks... one 8ohm load in one jack, another 8ohm load in the other jack... which amounts to a lot of options, when you consider one of these "8ohm loads" could be two 4ohm speakers connected in series, or two 16ohm speakers in parallel; etc (and more if it is a 4-speaker setup).

Regardless... on a channel... you cannot put a load on both the 8ohm out and the paired 4ohms... you must choose one or the other: 8ohm... or 4ohm (paired).

Also... if you only use one channel; you must put the level at ZERO on the unused channel. If you are using the 2:100 as a "normal" poweramp; turn the presence knob ALL the way up (on the unused channel), and put the level at ZERO (on unused channel). But... if you are using the Recto Pre with it, and using the Pre to control the 2:100 volume, you will need to control this by NOT connecting the Recto Pre to the 2:100 on the channel you do not want to use. So; if you have the Pre's left out going to channel A, and right out going to channel B... if you only want to use channel A, then you need to disconnect the cable connecting the Pre's right out to channel B.

Hopefully this helps. Also, Google Mesa Boogie... their website has all their manuals online in PDF form.

 

[PUBH]

One more note...

The 2:100 is a TUBE amp. This means you need to MATCH your impedance, or you risk damage to your amp (ie, its transformer, etc).

So... if your amp wants 8ohm, GIVE it 8ohms.

But... you CAN safely mismatch impedance on the 2:100 (and many other poweramps). But to do it safely, you need to connect a higher impedance than what the amp wants. So, if your amp wants 8ohm... you can connect a 16ohm (but be warned this risks possible tube damage; which realistically will only result in the tubes not lasting as long as they should). This is because 16 is > than 8ohm. But... if amp wants 8ohm, you CANNOT connect a 4ohm cab/speaker... this WILL result in internal amp damage (even if it is not noticed immediately).

 

[MRX2099]

Ok the main thing I wanna know is use 2 8ohms 75Wspeakers parallel = 75 watts 4ohm into ChA 4 Ohm output

then use 2 8 ohms 75 Watts speakers paired = 75 watts 4ohm into ChB 4 Ohm output
without having to use all (4) 4 ohms outputs

which basically is outputting 100w CHA into 75 watts
then outputting 100W CHB into another 75 Watt

so just one 4x12 cab wired into 2 sets to go stereo for now even thought it will not be 100 watt output per channel , will the 75 each Channel be enough

how does mesa wire their 4 x 12 rectifier cabs what ohm speakers do they use in them, can you use it to go stereo from the 2:100 or do you have to use 2 cabs to get the full stereo

 

[PUBH]

2 8ohms 75Wspeakers parallel = 75 watts 4ohm into ChA 4 Ohm output

If you wire two 8ohms in parallel, you would have a 4ohm load. So yes, you should be able to connect this then to one of the 2:100's 4ohm outputs on ChA. Or, you could wire each speaker; as in, an 8ohm speaker to one of the 4ohm, and another 8ohm speaker to the other 4ohm. Though this would require more output jacks on your cab I assume lol

And of course, you should then be able to do a similar routine for ChB and with two other speakers.

which basically is outputting 100w CHA into 75 watts
then outputting 100W CHB into another 75 Watt

so just one 4x12 cab wired into 2 sets to go stereo for now even thought it will not be 100 watt output per channel , will the 75 each Channel be enough

If you wire 1 set of speakers into each channel (where a set is made of two speakers, rated at 8ohm, that are connected in parallel)... since the amp outputs 100watts per channel... each speaker will technically only see 50watts each. Since the speaker is rated to handle 75watts, and it will only actually see 50watts; you should be fine. (I worked this out by figuring out how much power the amp will push to each speaker; however, I am not sure what the "total" wattage of your "speaker set" would be).

So... if you take 4 speakers, throw them in a cab. Connect two speakers (at 8ohm each) in parallel, and connect these to an output jack (creating an overall load of 4ohm), and do the same for the other two speakers... you should have a single cab with two outputs, that you should be able to hook up to the 2:100.


I would give Mesa a call about the 4ohm paired jacks. Their manuals do not specifically state you can run only off run, but it is implied. And given my circuits knowledge, I don't see why it should be a problem. But to be safe, you may want to check.

 

[myqqy]

If you go to the mesa website, you can download the manual for the 2:100- i just got mine last week and printed out the manual for reference. This particular manual has several pages of diagrams explaining different wiring possibilities for the 2:100, and which load mismatches are safe.