Deciding between a Plexi 45 or 50

gitman59 · Post by **gitman59** » Sat Sep 05, 2009 2:26 pm

I am going to order a kit before the 10% Labor Day special is over. I check the posting but could not find any information on how clean the 45 or 50 Plexi's are.

I do like the EL34 sound and this is why I am leaning toward the Plexi 50. Can anyone comment on the cleans of both amps. Also I think I will do the MV mod as I do need to control the volume with our band.
Thanks,
Guy

neikeel · Post by **neikeel** » Sat Sep 05, 2009 3:39 pm

I'd buy a 50watter personally, get both bass and lead specs and dabble

gitman59 · Post by **gitman59** » Sat Sep 05, 2009 4:01 pm

neikeel wrote:I'd buy a 50watter personally, get both bass and lead specs and dabble

Is one spec (Bass or Lead) cleaner?

Post by **VelvetGeorge** » Sat Sep 05, 2009 8:21 pm

Bass spec has less gain. Bass is also more balanced from low to mid to high. While Lead specs roll off the lows and are emphasized in the upper mid-range.

george

flemingmras · Post by **flemingmras** » Sat Sep 05, 2009 11:13 pm

Why not go 100? Could always pull the two outer or two inner tubes and make it a 50 watt (only a 3dB difference in volume anyway).

neikeel · Post by **neikeel** » Sun Sep 06, 2009 1:56 pm

You could with a PPIMV but to be honest most of us can only just make use of a 50watt for most gigs, even then slightly attenuated.

I enjoy using the '68 but is like a chained animal most of the time

flemingmras · Post by **flemingmras** » Sun Sep 06, 2009 2:07 pm

neikeel wrote:You could with a PPIMV but to be honest most of us can only just make use of a 50watt for most gigs, even then slightly attenuated.

I enjoy using the '68 but is like a chained animal most of the time

I ran the Marshall Power Brake on a 100 watt plexi about 6-7 clicks up without any volume issues. Again the volume difference between 50 and 100 watts is only 3dB...hardly discernable.

Speaking as a sound engineer...you'll find that if you EQ your tone very sparingly with the frequencies that the human ear is more sensitive to (i.e. Presence and Highs), you can crank louder than you're used to cranking without being too loud. That's the whole trick...use your EQ to "play tricks" on the people's ears and you'll find you can push your amp harder, crank louder, and your highs will end up coming up with volume rather than trying to boost them before you've had a chance to add volume and gain.

As mentioned before...the beauty of 100 watters is that you can run them as either or (50 or 100). Whereas with a 50 you can only run it as a 50.

syscokid · Post by **syscokid** » Sun Sep 06, 2009 3:35 pm

neikeel wrote:I'd buy a 50watter personally, get both bass and lead specs and dabble

If you're going to go with the experience of building one of these, then it would take just a few minutes, and few different components to switch from one spec to the other. I went with the Lead specs, and can get some very nice and very loud clean tones with vintage style single coils. Also did the Lar/Mar PPIMV. One of these days, I'm going to have to try the Bass specs.

gitman59 · Post by **gitman59** » Sun Sep 06, 2009 3:57 pm

Thanks guys. I just pulled the trigger and ordered the Plexi 50, with the MV mod. I have also decided to use my Headbone for switching between my 66 Bandmaster for cleans and use the Plexi for my cranked tone. I will run both through the 66 Bandmaster 2x12 cab loaded with 25w Greenbacks, it is wired at 4 ohms as that is the only output for the Bandmaster. I love the cleans on the BM and know I will not get the same from the Plexi.

This will be my first amp build and I am really looking forward to it. I look forward to the support of this forum.

Arclight · Post by **Arclight** » Mon Sep 07, 2009 3:40 pm

gitman59 wrote:Thanks guys. I just pulled the trigger and ordered the Plexi 50, with the MV mod. I have also decided to use my Headbone for switching between my 66 Bandmaster for cleans and use the Plexi for my cranked tone. I will run both through the 66 Bandmaster 2x12 cab loaded with 25w Greenbacks, it is wired at 4 ohms as that is the only output for the Bandmaster. I love the cleans on the BM and know I will not get the same from the Plexi.

This will be my first amp build and I am really looking forward to it. I look forward to the support of this forum.

There is a very strong possibility your 25W Greenbacks won't stand up to the 50watt plexi fully cranked.YMMV-but MY 2 Greenbacks DIDN'T

gitman59 · Post by **gitman59** » Mon Sep 07, 2009 8:12 pm

Arclight wrote:
gitman59 wrote:Thanks guys. I just pulled the trigger and ordered the Plexi 50, with the MV mod. I have also decided to use my Headbone for switching between my 66 Bandmaster for cleans and use the Plexi for my cranked tone. I will run both through the 66 Bandmaster 2x12 cab loaded with 25w Greenbacks, it is wired at 4 ohms as that is the only output for the Bandmaster. I love the cleans on the BM and know I will not get the same from the Plexi.

This will be my first amp build and I am really looking forward to it. I look forward to the support of this forum.
There is a very strong possibility your 25W Greenbacks won't stand up to the 50watt plexi fully cranked.YMMV-but MY 2 Greenbacks DIDN'T

I haven't thought of that. Can anyone else confirm that 2x12 25 watt Greenback are not enough speaker for the Plexi 50. I have them wired to 4 ohms due to my Bandmaster.

flemingmras · Post by **flemingmras** » Mon Sep 07, 2009 9:22 pm

gitman59 wrote:
Arclight wrote:
gitman59 wrote:Thanks guys. I just pulled the trigger and ordered the Plexi 50, with the MV mod. I have also decided to use my Headbone for switching between my 66 Bandmaster for cleans and use the Plexi for my cranked tone. I will run both through the 66 Bandmaster 2x12 cab loaded with 25w Greenbacks, it is wired at 4 ohms as that is the only output for the Bandmaster. I love the cleans on the BM and know I will not get the same from the Plexi.

This will be my first amp build and I am really looking forward to it. I look forward to the support of this forum.
There is a very strong possibility your 25W Greenbacks won't stand up to the 50watt plexi fully cranked.YMMV-but MY 2 Greenbacks DIDN'T
I haven't thought of that. Can anyone else confirm that 2x12 25 watt Greenback are not enough speaker for the Plexi 50. I have them wired to 4 ohms due to my Bandmaster.

If you plan to run a master volume and not overdrive the output section itself...

Or if you plan to use an attenuator such as the Marshall Power Brake or the THD Hotplate...

You should be fine.

The problem comes in when you start clipping the output section unattenuated. The "50 watt" rating is the theoretical "clean power" rating of the amplifier (i.e. the amount of power the amp will max out at BEFORE the output section goes into clipping). Once the power section goes into clipping, they'll put out a bit more than that and that's when you'll need to worry.

Clipped power is worse than clean power. This is because while the signal is in the clipped region, it's sending DC current through the speakers. This constant current overheats the coils. On top of that, during the time that DC current is going through the coils, speaker movement stops, which reduces cooling to the coil.

One of the benefits of running a 100 watter (more headroom = more clean power before clip).

gitman59 · Post by **gitman59** » Mon Sep 07, 2009 10:31 pm

There is a very strong possibility your 25W Greenbacks won't stand up to the 50watt plexi fully cranked.YMMV-but MY 2 Greenbacks DIDN'T

[/quote]

I haven't thought of that. Can anyone else confirm that 2x12 25 watt Greenback are not enough speaker for the Plexi 50. I have them wired to 4 ohms due to my Bandmaster.[/quote]

If you plan to run a master volume and not overdrive the output section itself...

Or if you plan to use an attenuator such as the Marshall Power Brake or the THD Hotplate...

You should be fine.

The problem comes in when you start clipping the output section unattenuated. The "50 watt" rating is the theoretical "clean power" rating of the amplifier (i.e. the amount of power the amp will max out at BEFORE the output section goes into clipping). Once the power section goes into clipping, they'll put out a bit more than that and that's when you'll need to worry.

Clipped power is worse than clean power. This is because while the signal is in the clipped region, it's sending DC current through the speakers. This constant current overheats the coils. On top of that, during the time that DC current is going through the coils, speaker movement stops, which reduces cooling to the coil.

One of the benefits of running a 100 watter (more headroom = more clean power before clip).[/quote]

Gitman wrote:
I will use the MV as a cranked Plexi is way too much for what we do. I do want the tones of a cranked Plexi but at lower volumes.

flemingmras · Post by **flemingmras** » Mon Sep 07, 2009 11:18 pm

gitman59 wrote: I will use the MV as a cranked Plexi is way too much for what we do. I do want the tones of a cranked Plexi but at lower volumes.

Then you have two options -

1) Get a power soak, such as a THD Hotplate (Marshall Power Brake is only advertised to work with 8 and 16 ohm loads). The power soak will allow you to run the power section at full crank but at a much lower volume.

2) Install the post phase inverter master volume. This one will get you a tone that is almost virtually identical to a cranked plexi at a much lower volume without taxing your output tubes.

Either way you go, it won't matter whether you get the 50 or 100 watt amplifier. Power has nothing to do with volume (you only gain 3dB of acoustic power everytime you double the amplifier output power, and it takes 10 times the power to get a 10dB increase in acoustic volume. 10dB is what the human ear perceives as "twice louder"). The difference between 50 and 100 watts is more of a "tone" thing as the 100 watt won't break up as much as a 50 watt amp will with the same guitar.

Also, the 50 watt and the 100 watt both run the same preamp and since your "cranked" tone will actually be coming from the preamp, it won't matter whether you have a 50 or 100 watt amp. The beauty of having more power than you need is that you can always turn it down.

Since you'll be running at low volumes your 25 watt speakers will be just fine.

neikeel · Post by **neikeel** » Tue Sep 08, 2009 4:11 am

I like 100watters (I have 4 of them) but for a first time builder playing most gigs (and with a 2x12) a 50 watter is fine. You only have 2 output valves to replace, bias etc and the build troubleshhoting is more straightforward.

The PPIMV and preamp is the same as flemingras says and this is where you get your drive tone.

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