EVH 5150 III: 50 vs 100 watt

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Ruben
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Re: EVH 5150 III: 50 vs 100 watt

Post by Ruben » Thu Jun 07, 2012 5:52 am

Those Blix (PM sent) clips sound awesome. My 100 watter certainly didn't sound like that!
I thought the 100 watt was to 'nasal' sounding and sold it. Now I'm leaning towards the EVH III 50 watt....

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Re: EVH 5150 III: 50 vs 100 watt

Post by evh0u812 » Thu Jun 07, 2012 7:49 am

My 50 watter is a great amp, but there was something that just didnt sit right with me. Ive spent the last 2 nights tinkering under the hood and Im loving the mods Ive come up with. Green channel is now at unity gain with the blue. The jump in volume was unacceptable, not sure why Fender let it out this way. Green channel also does a fair JTM45 impersonation with the gain maxed. The blue channel has less top end fizz and sounds much closer to my ideal cascaded plexi sound. The red channel now has a much more useable range of gain. Stock sounded good, but from 2 on the gain to max, there was no change in gain structure, just more compression and background noise. Also the clipping diodes are gone, its now all tube goodness! Ive still no idea why they were there with 5 gain stages, a localised positive feedback stage and a cathode follower. Gain control maxed now sounds close to the stock circuit did at 12-1pm, but now I have dozens of tonal options as you roll down the gain.

Gotta love the smell of solder fumes!!! LOL.

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Re: EVH 5150 III: 50 vs 100 watt

Post by allenc5150 » Thu Jun 07, 2012 8:38 am

evh0u812 wrote:My 50 watter is a great amp, but there was something that just didnt sit right with me. Ive spent the last 2 nights tinkering under the hood and Im loving the mods Ive come up with.
Hi, could you detail the mods you did? Very curious about specifics if you don't mind getting into it.

Thanks,

Craig
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Re: EVH 5150 III: 50 vs 100 watt

Post by evh0u812 » Thu Jun 07, 2012 5:04 pm

Sure.
Green/Blue channel-
10k voltage divider to 42k
This raises the clean level and increase gain slightly.

250pf mica on the 100k plate of the second triode.
Smoothes out top end on the blue channel.

Red channel -
Removed the 2 1uf cathode bypass caps C16 and C30.
Lowers the gain and makes the gain pot more useable across the range.

Replace 47pf on the PI with 100pf.

Still looking at the power supply filtering, but thats it for now.
Last edited by evh0u812 on Sun Jan 20, 2013 5:39 am, edited 2 times in total.

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Re: EVH 5150 III: 50 vs 100 watt

Post by evh0u812 » Sat Jun 09, 2012 6:44 am

Thought a re tolex job might be in order while she's apart.
I could only get the ivory colour when I bought it and I hated the look.
At least my corners are better than the job they did when it was assembled in Vietnam, haha.


Almost done.

Image

Image

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Re: EVH 5150 III: 50 vs 100 watt

Post by allenc5150 » Wed Jun 13, 2012 9:47 am

evh0u812 wrote:Sure.
Green/Blue channel-
10k voltage divider to 42k
This raises the clean level and increase gain slightly.

250pf mica on the 100k plate of the second triode.
Smoothes out top end on the blue channel.

Red channel -
Remove 16.5 v zenners Z1 and Z2. Replace with 680k resistor.
Takes away the diode fizz and l the voltage divider lowers gain slightly making the gain pot useable.

Replace 47pf on the PI with 100pf.

Still looking at the power supply filtering, but thats it for now.
Very cool, thanks. I am tinkering with the idea of getting this amp again. I had it on order when it first came out but it was backordered and delayed for so long I eventually cancelled.
"It is man's sympathy with all creatures that first makes him truly a man." - Albert Schweitzer

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Re: EVH 5150 III: 50 vs 100 watt

Post by Ruben » Wed Jun 13, 2012 5:48 pm

Bought a EVH III 50 watt last saturday. Man this thing sounds waaaaayyyyyyy better than it's big brother. No nasal sounds!
Awesome amp. Plexi sound? Dime volume channel II all the way and adjust and gain according to taste.

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Re: EVH 5150 III: 50 vs 100 watt

Post by MrBeasty » Wed Jun 13, 2012 6:10 pm

Mods???! Yeaaaah!

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Re: EVH 5150 III: 50 vs 100 watt

Post by Ruben » Fri Jun 15, 2012 9:48 am

Is it possible to replace the two 6L6's with EL34's?

Would be intresting to hear what it sounds like

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Re: EVH 5150 III: 50 vs 100 watt

Post by mpmusic » Fri Jun 15, 2012 12:15 pm

Hoi Ruben Helaas, dat wilde ik ook...gaat niet

Not possible for two reasons -

1) The filament current is too high for the power supply design, 0.6 A higher on each tube.

2) The EL34 has a separate G3 grid connection on pin 1 of the tube. The 6L6 has an internal G3 gird connection to the cathode, pin 8. Pin 1 is not connected on the PCB of the head, so it would have to be jumped to pin 8.
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Interesting thread about the 50 Watt amp: http://www.thegearpage.net/board/showth ... 59&page=40

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Re: EVH 5150 III: 50 vs 100 watt

Post by Blix » Fri Jun 15, 2012 12:18 pm

Ruben wrote:Is it possible to replace the two 6L6's with EL34's?

Would be intresting to hear what it sounds like
From EVH/Fender's Howard Kaplan:

"Not possible for two reasons -

1) The filament current is too high for the power supply design, 0.6 A higher on each tube.

2) The EL34 has a separate G3 grid connection on pin 1 of the tube. The 6L6 has an internal G3 gird connection to the cathode, pin 8. Pin 1 is not connected on the PCB of the head, so it would have to be jumped to pin 8."

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Re: EVH 5150 III: 50 vs 100 watt

Post by Blix » Fri Jun 15, 2012 12:22 pm

Duh, you beat me to it. :)

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Re: EVH 5150 III: 50 vs 100 watt

Post by xhennex » Thu Jan 17, 2013 4:39 am

evh0u812 wrote:Sure.
Green/Blue channel-
10k voltage divider to 42k
This raises the clean level and increase gain slightly.
Hi,
I purchased the 50Watt Version last year, one of the early Vietnam productions.
It is one of the most versatile and best sounding amps for rock and metal nowadays
and I really can tell that after having checked out almost every amp on this planet.
I bought it despite the well known volume-jump issue but now I have to switch to cleans frequently and this really pi!?§%es me off.
Are you talking about replacing R79 by a 42k Resistor based on this schematics ?
http://ebookbrowse.com/evh-5150iii-50w- ... d385660508" onclick="window.open(this.href);return false;

I`m really interested in modding my head, probably you could mark or name the devices you modified and upload the schematics ?

Regards,
Henne

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Re: EVH 5150 III: 50 vs 100 watt

Post by MXR117 » Sat Jan 19, 2013 7:02 pm

I´m looking for good mods too.

I can´t stand the volume jump between Ch1/ch2. Next thing I dislike is too much gain...

I asked howard kaplan and he replied that changing r79 did not work out....

I think that the best way would be a second (or third) master volume, switchable by a relais via channel switching).

Anybody more experienced could have a look on the schmematic?

What is the function of the zeners in channel three?


Thanks!!

MXR

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Re: EVH 5150 III: 50 vs 100 watt

Post by evh0u812 » Sun Jan 20, 2013 5:41 am

Leave the zenners alone, theyre for FET protection. Mods amended above.

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