Heartbreaker mods

[burnt fingers]

Hello all,
My 1st post here. I ususally haunt the amp builders forums. I got a hearbreaker years ago and like many others I was pretty happy with the love channel but thought the lust channel was dark and not really usable. I also found the reverb lacking. I know there are companies that do mods for hearbreakers. I do not know what they do.
My approach to the lust channel was simple. What does a Marshall have that my hearbreaker does not? For the reverb I checked some other boogie designs and compared. I did mod the love channel but returned it to stock.

So here goes:
Most non boogie amps have input resistors so I put in a 22k. Not a big deal but I went with it. I think it improves the dynamics a little based on my experience with implementing this in a 5e3 clone I built.

The key to brightening up this channel though is to steal from the schematic of the bright channel of a real marshall. I left the resistors stock although the marshall has a 2.2k as the cathode resistor for v1b. This may be worth a look but I did change the cap.
The cathode bypass cap is now a .68 uF for v3b. This boosts the highs while the stock cap boosts more of the whole freq. band.
I also noticed that the grid 330k resistor to the cathode follower V4a (470k in a real marshall) is not bypassed with a resistor in the lust channel. So I put in the 500 pF cap accross that resistor. The final mod to the marshall channel is to add the missing .68 uF cap accross the 820 ohm cathode resistor of the cathode follower v4a.

This amp lives next to an old ptp marshall metalface 100 watt head. The mods gave the lust channel the same distortion as the marshall. The tone is not quite as rich as the real marshall but that could be chalked up to a number of things including pc board, the reverb insertion loss. Also my theory is simply the more components between your guitar and speaker, the less harmonically rich the tone.

My current set of tubes consist of jj 12ax7 small box for the distortion and tone circuit, chinese 12ax7 for the reverb and effects circuit. I'm running new svetlana el34s. I always have only 2 power tubes in. I can't say much about making it sound like a plexi since I don't have one but following the line of thought for the mods I already made it seems obvious that further component changes may get you close. The tweed switch and tube rectifier will help get you there. The tone stack can also be modded. I'm thinking about poking around with the warm/ bright switch and see if I can implement a 33k to 56k switching arangement for the tonestack slope resistor. This would help get it more plexi like.

The reverb mod is simple too. If you compare the design to other boogie reverb designs you'll find that the 22k resistor from the transformer input to B+ is a bit large. I decreased it to 2.2k. I think I also decreased the v6b cathode resistor size. The reverb is good now.

One final thing. There are 2 caps, a 220 pF and a 120 pF cap in the power circuit post phase inverter. A real marshall uses a 47 pF. Quite simply all of these large shunt caps in this circuit make the amp darker by design. While I could not go with a 47 pF cap (it was a little unstable and noisy) I did manage to remove the 220 pF and put the 120 pF in its place and leave a cap out of the original 120 pF position.

With the amp all the way up (I use a hotplate) and the treble maxed it is a bit too bright. But now the lust channel with the tone controls are quite usable and it would likely fool most of us into thinking it is a real marshall.

I may mess with the negative feedback on the bold/ curv switch but I'm pretty happy with where it's at.

 

[jamme61]

great stuff! thanks. You don't see much info like this, on this forum. I don't have a heartbreaker but was thinking of adding a bright cap for my clean channel on my stiletto. Your post gave me some ideas. I was thinking of just adding a pull pot to the channel volume on the first channel, and add a small cap to the pot(maybe 100pf) did you try a bright cap on the Heartbreaker volume pot? I think your right on, with the NFB thinking. IMHO the NFB can make a good amp great.

 

[jonamojo]

time to bring this thread back to life very good information. I went ahead and replaced the V3b cathode bypass cap with a sozo .68 as well as adding another to to the cathode of V4a. Since the grid resistor to the cathode follower is 330k I believe you would need approximately 700pf to keep the same frequency cutoff as a marshall anyways for now I left that alone. channel 2 is alot more usable now thanks to the original poster super easy mod takes 5 minutes

 

[212Mavguy]

Like to see this kind of thread here...nice work!

 

[Tommy_G]

The original poster was using an old ptp Marshall Metalhead 100 as a reference. I've never heard one before. What is the lineage of that amp?

 

[jonamojo]

metal face ptp marshalls would be from 1969 to 73 the early ones were similiar to the plexi but as time went on things changed such as B+, filtering and resistor and capacitor values changed 72,73 sound quite a bit brighter. To me, this mod brings you closer to to the sound of a jcm 800 rather than a plexi theres quite a few other things that can be done to channel 2, as I try them I will post what was done and how it affected the tone. As soon as I get my camera back from a buddy I will take pictures and post them so if you want to try these mods you will have a guide

 

[Tommy_G]

Thanks...I've been thinking about a Marshall mode on Ch2 for quite some time, and I think there are a lot of people on this forum that are pretty thrilled about you sharing your work on these mods !

The Heartbreaker could well become the go-to amp of choice for a lot of performing musicians if Ch2 had vintage Marshall tone...and Marshall on steroids with the extra tube stage.

 

[jonamojo]

I decided to use a 22k resistor in parallel with the 10k in the bias circuit. I just installed 6l6 winged =c= from tube depot rated at 20 on their scale, this bought my bias up to 37.7ma where as before it was 26.3ma this made quite a bit of difference, much warmer and throatier, I mounted the 22k on the empty lug on the bias switch opposite of the lug which goes to the 6.8k for el34's this way when I switch to el34 mode the 22k is not connected.

 

[rennie]

Hi!
New in this forum and new on the Heartbreaker too !
I read all what is crawling over the internet about the Heartbreaker till I finally bought it from ebay, and i have been doing it more and more after that. I think is the revision version because of the Mesa/Boogie badge, the purple jewel and the reverb kicks, really :mrgreen:
I don't consider this a blind buy because of all the references have build me a very accurate idea about it should sound (Santana overdrive, Mark I liquid), and it didn't disappoint me happily.
I'm very pleased about this lovely monster but, as many of all the other owners I found that if its round, warm and articulated at high volumes, the lust channel sounds too scooped at low-mid volumes and it has a little lack of brightness and crisp overall. :?
I'm sure this doesn't affect my love/lust for the Heartbreaker but I feel it's too powerful that it can cover a little more the sound spectrum I search.
I'm watching this thread almost diary because I believe that with no great mods it still can do it and I don't think I would like to make bigger alterations, especially because I'm in southamerica so there are not too much people who can make these mods confident here.
As I'm not a so-much-tech-man, I'll be expecting for some news so please all of you that are in mods (thanks burnt fingers, jonamojo), be descriptive with your results :wink:
Go on!... I'll really appreciate that!!