The secret EVH amp part

[awangotango]

Phillips Miniwatt is a tube I've not tried, unless it's same as a rebranded amperex bugle? the tele in v3 must be helping keep things juicy.

[N3m0 7h3 Fi5h]

Is this the secret evh amp part ..?
http://forum.metroamp.com/viewtopic.php ... 35#p434917

[spaceace76]

not likely, unfortunately. see my new post in that thread

[rgorke]

Ralle, you were the reason I decided to stick with higher NFB (27k). While the majority of members were following the "DF spec" (low NFB, fat caps etc) you were the only one on the right track. Thanks man!

I have 27k/16ohm on my 12XXX and my JTMP 50. I really like it. For some reason, anything closer to 100k/4 ohm makes the presence howl.

Nice clips stef!!! Jimi described it spot on, comparing the open chords with single note leads. It has the whole package.

[Roe]

Love the ATBL tone Stef!

I have a 100k NFB resistor on the 4 ohm tap on my Metro 12,000 kit head (w/ virtual variac). If I move the tap wire to the 8- ohm, then the 16-ohm, without changing my 100k resistor, will this effectively increase NFB? According to this sticky, my theory makes sense...

Starting with the ubiquitous 100k/4ohm tap, this yields -7.5db if NFB, then extending to different values to achieve the same result:
-7.5db can be 100k/4ohm tap
-7.5db can be 150k/8ohm tap
-7.5db can be 212k/16ohm tap
These are all equivalent... and very loose

Tighter (more FB):
-10db can be 64k/4ohm tap
-10db can be 92k/8ohm tap


-10db can be 134k/16ohm tap

Tighter still (yet more FB):
-12db can be 45k/4ohm tap
-12db can be 66k/8ohm tap
-12db can be 95k/16ohm tap

100k@4=200k@16=141k@8

[Ralle]

Stef, I would like to suggest you try the 47k/16ohm setup... it's about the same amount of NFB, but it drops from a slightly different point in the circut comparerd with 27k/8ohm; the fact that the whole OT is used for the NFB makes it save a bit more harmonics, highs if you will... plus you will keep a bigger sound ( but it might not be what you want, of cours )... I kinda stuck on that value...
Remembering back in the day, I allways came back to 16 ohm... I could work with the resistor, but I allways keept it at 16 ohm... every time I had 8 ohm, it got "thin"... if you know what I mean...
If it gets to "fat" with any higher value than 27k, it's more likely that there's something else that needs attention...

[neikeel]

Stef, I would like to suggest you try the 47k/16ohm setup... it's about the same amount of NFB, but it drops from a slightly different point in the circut comparerd with 27k/8ohm; the fact that the whole OT is used for the NFB makes it save a bit more harmonics, highs if you will... plus you will keep a bigger sound ( but it might not be what you want, of cours )... I kinda stuck on that value...
Remembering back in the day, I allways came back to 16 ohm... I could work with the resistor, but I allways keept it at 16 ohm... every time I had 8 ohm, it got "thin"... if you know what I mean...
If it gets to "fat" with any higher value than 27k, it's more likely that there's something else that needs attention...

Suggestion: a 150k pot in series ( I made mine with a 250k pot with a 390k across it, IIRC) after the NFB resistor (suggest 27k for the resistor) ie between the resistor and the chosen OT tap (I used the speaker jack for 16ohm). I wired mine back to front so that with the pot all the way down it represents low NFB and at 0 on the dial you get approx 180k at 16 which is almost the same as 100k/4ohm and with it turned up fully you get 27k/16ohm. I found the sweet spot at just backed off for maximum (ie between 47k and 27k on 16ohm. You can compare in real time without soldering, flipping the amp etc.
Definitely something for my next project amp too

[stef]

Flipping the amp, soldering etc is no trouble at all, but my amp has a PCB!
Anyhow, today I changed the NFB resistor, 47k/16... and took out one extra secret cap - a 22nf across 22nf at the PI input, now it's stock 1959 spec
I'll try to make a clip and post it in a new thread...

[Ralle]

he he... one step at the time...

[Roe]

Stef, I would like to suggest you try the 47k/16ohm setup... it's about the same amount of NFB, but it drops from a slightly different point in the circut comparerd with 27k/8ohm; the fact that the whole OT is used for the NFB makes it save a bit more harmonics, highs if you will... plus you will keep a bigger sound ( but it might not be what you want, of cours )... I kinda stuck on that value...
Remembering back in the day, I allways came back to 16 ohm... I could work with the resistor, but I allways keept it at 16 ohm... every time I had 8 ohm, it got "thin"... if you know what I mean...
If it gets to "fat" with any higher value than 27k, it's more likely that there's something else that needs attention...

Suggestion: a 150k pot in series ( I made mine with a 250k pot with a 390k across it, IIRC) after the NFB resistor (suggest 27k for the resistor) ie between the resistor and the chosen OT tap (I used the speaker jack for 16ohm). I wired mine back to front so that with the pot all the way down it represents low NFB and at 0 on the dial you get approx 180k at 16 which is almost the same as 100k/4ohm and with it turned up fully you get 27k/16ohm. I found the sweet spot at just backed off for maximum (ie between 47k and 27k on 16ohm. You can compare in real time without soldering, flipping the amp etc.
Definitely something for my next project amp too

22k resistor in series with 220k pot into 16 ohms secondary

[neikeel]

22k resistor in series with 220k pot into 16 ohms secondary

I did that first but at the extreme of low NFB I got instabilty and motorboating with certain PPIMV and presence settings and I actually preferred the higher NFB tones so it seemed sensible to focus it in the usable range.

[Maverick]

You just gotta play the thing ike you stole it! Your not gonna sound ike eddie, even eddie don't sound like eddie no more