# YGM2 mod to bring out the bottom?



## LowWatt (Jun 27, 2007)

A buddy of mine just bought a YGM-2 and loves it, but is worried it does not have enough bottom end for his needs. He's playing indie rock and roll and doesn't need anything too heavy in the bass, but he says it feels light compared to the mids and treble. 

I'm wondering if there's a prescence cap in the power supply that can be clipped like in the YGM-3. I did that to my YGM3 and immediately it brought the presence in check and the bass got all it's power back. So I'm hoping there's a similar simple and non-intruisive mod for the YGM-2. 

Any tips?


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## Wild Bill (May 3, 2006)

Nope! Pete Traynor didn't use a presence cap in this design! In effect, it was "pre-snipped out".

I would go back into the pre-amp stage and rewire that tone stack to be like the typical old Fender. That will give you better bottom.

Wild Bill


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## LowWatt (Jun 27, 2007)

Wild Bill said:


> Nope! Pete Traynor didn't use a presence cap in this design! In effect, it was "pre-snipped out".
> 
> I would go back into the pre-amp stage and rewire that tone stack to be like the typical old Fender. That will give you better bottom.
> 
> Wild Bill


Thanks Bill. Hmm...this is not a guy comfortable with internal part swapping. A simple snip is one thing, but he won't want me playing with circuit values. It's got a Jensen in it and who knows how many hours on ethe tubes (and I haven't heard it yet myself) so I'm hoping strong tubes and possibly a different speaker should be enough.


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## Wild Bill (May 3, 2006)

Tubes won't help. Tubes do not directly affect tone. There is no sound inside a tube. There are no maple or rosewood parts inside a tube. Only electricity! There is no sound inside an amp until the speaker moves air.

When a tube grows weak the overall gain may drop, but it will be across the board - all frequencies at once. You won't get any bottom boost.

The only difference between brands of tubes is overall quality. All 12AX7s or EL34s sound the same!

Changing the speaker certainly CAN make a difference! However, it may make things worse! You see, modern speakers tend to be louder and much better in the mids and highs . Vintage speakers of older days lacked top end, not usually bottom. It's the bottom end that's bothering you here. By all means, try it! Simply plug cabs with different types of speakers into the external speaker jack and take a listen.

I can understand how some follks don't like to make major changes but why do they think Mr. Traynor junked that tone stack circuit in the first place? Why did he use a different one (Baxandal Tone Stack) in the next generation, the YGM-3?

Changing the circuit will almost always make FAR more difference to an amp's tone than dinking around with tubes and even speakers! If changing a tube was all that was needed why is there more than one circuit for all the amps out there?


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## traynor_garnet (Feb 22, 2006)

First thing to try is a different speaker. After that, if the YGM-2 is anything like the YGM-1 I had, the stock "mids" level is insane (like a Marshall with the mid knob permanently cranked)! Changing that value will totally transform the amp. My guess is that the amp doesn't lack bass, it has WAY too much middle.

TG


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## LowWatt (Jun 27, 2007)

Wild Bill said:


> Tubes won't help. Tubes do not directly affect tone. There is no sound inside a tube. There are no maple or rosewood parts inside a tube. Only electricity! There is no sound inside an amp until the speaker moves air.
> 
> When a tube grows weak the overall gain may drop, but it will be across the board - all frequencies at once. You won't get any bottom boost.
> 
> ...


Great info. Thanks Bill, but it's not mine to mod. I'm still waiting to hear the issue myself. Hell, for all I know it could be how he's setting the knobs or an unrealistic expectation. I'll do some listening with it plugged into every cab I have and we can see what we get.


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## LowWatt (Jun 27, 2007)

traynor_garnet said:


> First thing to try is a different speaker. After that, if the YGM-2 is anything like the YGM-1 I had, the stock "mids" level is insane (like a Marshall with the mid knob permanently cranked)! Changing that value will totally transform the amp. My guess is that the amp doesn't lack bass, it has WAY too much middle.
> 
> TG


And that's why I love my YGM-3. When I play a Marshall I always go right to cranking the mids anyway.


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## parkhead (Aug 14, 2009)

its a different amp 

it does not have the cap to remove like the YGM3 

However you should do the following 

#1 you should locate the 12ohm resistor that acts as the choke and replace it with 2 to 5 watt 1k to 2k 
this will prevent output tube failure this is just good insurance 


#2 the phase inverter input is .01, .02 will have more bottom end 

#3 the v1 plate load resistor is 100k, change this to 220k like the ygm3 for more gain & bass at the front end 

#4 the bass cap in the tone stack is .1 change this to .02 do this last ...as this tightens the bottom end, this will be needed once you have the rest fixed up 

use a v30 or similar large magnet speaker 

#5 if the amp has a bright switch locate the .001 cap attached & put a 470k resistor in series with the cap to tame the wild brightness 
if the brightness is pre set do the same mod only you have to find the cap 

#6 if you want still more bass swap the 100k tone stack slope resistor to 56k, 47k or 33k
the lower the value the more bass, if you get to 33k you may want to change the treble cap to 500pf mica (the classic marshall tone stack) 
to add some treble back in 

#7 finally: If you need more headroom locate the 56k step resistor in the power supply and swap this out to 22k or 10k 
this will dramatically increase gain, headroom, clarity and cut as well as bass at the expense of brown lo fi dirt 
the amp will also get much louder and thisis important if you need to get over a loud drummer 


I just re-read all the posts get that JENSEN out of there ! 

and you must do #1 to keep the screens happy with modern el84's 

the non invasive way to do the mods above is to use paralell values for most of the changes 

ie #4 put another .01 in paralell with the stock .01 
#6 put another 100k in paralell with the slope resistor 
#7 put 22k in paralell with the 56k 

the stock parts stay in place & the problems are mostly resolved 

p


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## Wild Bill (May 3, 2006)

I agree with you about screen protection, Parkhead. I hadn't noticed that 12 ohm resistor in the power supply. What do you think about adding a 100 ohm half watt in series with each screen, tied back to that 1k resistor you suggested? I like 100 ohm 1/2 watt for EL-84's because while 1/2 watt is far more than enough for the screen current of these tubes if you get a tube screen short those 1/2 watts will blow open like a fuse, protecting things back up the line.

Also, of course a 220K resistor for the plate of V1 will dramatically increase gain but I don't understand why the gain would be any higher for the bass range than the rest of the spectrum. Could you explain it for this old guy?

Wild Bill


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## parkhead (Aug 14, 2009)

Wild Bill you know this stuff better than I do! I'm just a dumb geetar player...

the sound "browns out" a little with the 220k resistor and give the illusion of more lower mids and bass 

the amp also sounds slightly dirtier ...

to answer your question properly if you do the math 

doubling the plate load, shifts the roll off of the associated coupling cap. 

For example in a ygm3 the plate load is 220k so a .01 cap is the equivalent high pass of a .02 cap with a 100k plate load 

in a YGM3 the stock cap is .1 with the stock 220k the bass starts at 8hz ... with .01 its at 80k 

in the ygm2 the eq network follows the plate load so the scenario is slightly different but 

the bass should increase slightly with the gain boost of the 220k 

since the style of music mentioned was "rock" 220k should put a smile on the players face ...

bottom line, the best way to do the 7 suggested tweaks is with the player present and playing between changes 

once things have gone too far the tech can always back up one step 

or go back to stock 

Warning I have not done the & changes to a ygm 2 ... I have worked on quite a few YGM3's 

the key to adding bass is to add it at the right spot ( the power amp and output section) & tighten it up at the front end 

so the amp still cuts and does not flub or fart ... 

Good to see you back wild bill 

sometimes its best not to spend all of ones time online LOL 

I totally agree with your idea of the extra screen resistors. BTW I stole the 1k screen mod from the Re-issue as soon as I saw it I went "damn no more toasted sovteks !" and it 

sounds better! 


p


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## Wild Bill (May 3, 2006)

Hey Parkhead, you made perfect sense to me! I learned something new!

When it comes to the theory I learned long ago that it is far easier using it to explain rather than predict! Sometimes changes arrived from experience are positive. One can always work out the theory afterwards!

thetubestore.com sells some Russian EL-84 equivalents that are mil-spec and are rugged as hell! I've used them with some old tube eaters. They are much more pricey, however. Like you, I would rather lower the screen voltage with a good value of protection resistor.

A small computer fan does wonders, too! If the customer is willing to pay I will put a small filament transformer backwards and out of phase at the input to the PT, to buck the line voltage down 12 volts or so. Pete's early Traynors often had primaries of the PT more suited to 110-115 volts. This puts everything 10-15 % too high, including filament voltage which of course hurts tube life. It's an easy trick I swiped from a buddy at www.geofex.com.


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