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Discussion Starter #1
So, I just nabbed another one of those sweet old Traynors from the 70s (the big Fender Twin Reverb styled one). I already have this same model, so having the second is giving me the courage to try adapting one into a bit of an Overdrive Special HRM version. I am more of an all amp-section distortion type guy a la Trainwreck, but I got one of those, and once in a while I'd like to try a little bit of that smooth and thick HRM blues stuff for fun.

The first thing I want to try is actually keeping the amp stock for the clean (effects) channel and then ripping out the normal channel to use the gain stages and controls for an HRM overdrive circuit that can be switched into the remaining (effects) channel.

Anyways, I did some modifications to the YGL-3 schematic to add this overdrive circuit. Aside from removing all components to do with the normal channel, I am also trying to successfully remove the master volume (because it is after the Trem and Reverb), and plunk in a "Clean Master" right at the point the Overdrive Circuit would switch in.
Anyways, I would appreciate anyone looking over my modded schematic to let me know what sorts of things I may have missed:
(just right-click and open the images in a new window to see them bigger)


Thanks. Oh, here is the original Traynor Schematic that I worked from and chopped up:
 

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Can't help your with deciphering the schematic as I'm rubbish with that stuff, but I'm going to keep tabs on this thread as I have a YGL-3 that I've been thinking about doing some work to.
 

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"just right-click and open the images in a new window to see them bigger"


I couldn't get this to work...not that I will be able to help you, but I enjoy looking at schematics (I really must try to get out more often...LOL)

Cheers

Dave
 

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Discussion Starter #4
Can't help your with deciphering the schematic as I'm rubbish with that stuff, but I'm going to keep tabs on this thread as I have a YGL-3 that I've been thinking about doing some work to.
Heheh, me too. I'll let the one be the guinea pig. If it goes really well on the one, I might even consider it on the other.


"just right-click and open the images in a new window to see them bigger"
I couldn't get this to work...not that I will be able to help you, but I enjoy looking at schematics (I really must try to get out more often...LOL)
Oh, I guess this was a bit of assumption just because my browser gives me that selectable option with the images when I right-click them. Isn't there any other options that appear when you right-click on the image? Isn't everyone using a mac and safari? I suppose I should be using my google chrome...
 

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Oh, I guess this was a bit of assumption just because my browser gives me that selectable option with the images when I right-click them. Isn't there any other options that appear when you right-click on the image? Isn't everyone using a mac and safari? I suppose I should be using my google chrome...
I'm using Chrome and if I right click and select "open in new tab," they are, indeed bigger and zoomable! Mac-shmac.
 

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Discussion Starter #6
So, I'll draw up something neater and with all the correct values later, but this is the piece of board that would be added containing the overdrive circuit.

I was thinking that I could use spacers or something and have it hovering over the very end of the old board. Then no butchering of the original Traynor has to occur (in the event that the stock traynor model is someday desireable). The old leads would just be removed from that first tube socket and the normal channel front panel controls (as well as where they connected to the rest of the amp) and taped up.

The HRM also has trimpots for Treble, Mid, and Bass adjustments but I think I would use real pots on the front panel since it is already labeled.
 

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Discussion Starter #7
Well, despite buying some neat little breadboard type things in B&E in Calgary during my stop there, I decided to just rip components off the Traynor board and build right there on the end.

After a couple days, I would not say it is completely finished. I ended up keeping the original master volume in the amp, and adding the "Clean Level" and "OD Level" pots in place of the High and Low inputs from the Yanked (Normal) channel. The Normal channel volume becomes the OD Gain Level and the Bass, Mid, and Treb become the OD tone controls. However, they don't work too much like a typical amp tone-stack would and do not lend themselves well to guests. Oh, and the Bright switch for the normal channel has been replaced with a DPDT switch of the same style and is now the switch that engages the OD. I'll post pics if I can find a camera cable here to borrow.

The Effects Channel continues to function the same and the tremolo and reverb are still great. Then I can engage the OD switch and can achieve a nice smooth lead tone not crunchy or abrasive at all (just thick). The notes sing well. I am not finished however, because there is a parasitic oscillation that appears if he gain is too high, or if the signal is too bright (only when OD is engaged). Sounds like a steam whistle and is quite annoying. I can set up the amp to work fine, but that is usually just shy of whistle territory. Also, If I switch to a brighter pickup and the tone knob is not rolled back, it will also start whistling.
That thick dumble overdrive is a little harder to get out of single coils without really rolling back the guitar tone knob or else it will also start whistling.

I should also mention that the plate voltages are around 150v and a typical ODS goes for about 200v usually. I've heard that is an important element to the sound as well. However, I'm too dumb to figure out how to boost plate voltages and I've really been more concerned with the oscillation at this point.

So, it's finicky right now. I can basically grab my choice of about half the knobs on the amp and turn it in order to get that whistle to appear (while in OD mode). I've been chop-sticking, adding shielded wires in places, changing the first OD grid resister, added 250pF caps between the plates and cathodes of the OD tube, etc, and still have not been able to eliminate that oscillation.
Any suggestions would sure be appreciated.

IN the end, even if I can't eliminate that oscillation, I will keep this amp this way, because it does sound decent, and I don't lose my original Traynor clean channel whenever I want it. It's definitely not a fool-proof design that I can recommend to others yet though.
 

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Discussion Starter #9
thats awesome!
keep comin with the updates...pics and sounds would be cool too!
Well, I continued to try other things, like increasing grid resisters and even a larger value OD drive pot and nothing improved anything so I put it all back to the values on the schematic. (It's a good thing too, because I had to spend $10 on a PEC pot because I couldn't get any other 250K pot on short notice.)
Here is a pic of the current state of the inside:


It turns out that if I plug the guitar into the normal input instead of the high input I have more usable range before whistle territory. It's enough to let me put the lid on for now until someone gives me another good idea (because I am at a total loss). Here is the front of the amp:


And, here is a quick video of some off-the cuff playing. Regular clean channel at first and then you see me switch the OD on. As you can see, I am too lazy to make a better recording, or ever practice guitar (or even think about what I am gonna play first).
http://www.youtube.com/watch?v=FUvGBqz44xs
 

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Looks like it should work

I am on my third Dumble type amp now, which also happens to have HRM in it. It's a Bluesmaster w/HRM in a BF Bassman head, w/buffered loop and 4x6l6GA power. Looks like your insertion of the basic ODS stages should work fine.

I'm not conversant with old Traynors' circuit fine points, but they are certainly "good ole amps" with the same heavy duty build characteristics as Dumbles. Never did find out who did the two storey drop test first, Traynor or Dumble!

Here's a 100W #124 clone which was my first Dumble type amp. Still tweaking it to minimize some fizz in OD mode but it sounds great. I run it thru a 2x15 w/pair of JBL E130, a 1x12 Boogafunk TL806 w/old EVM12L, or an Avatar 2x12 w/pair of Altec 417B. All different, all great.

Also a 50W '70s ODS in a BFPR chassis. This one I gutted a 67 Bassman AB165 head for. That old iron makes a big difference. Both amps running used RCA blackplates, want to try Sylvanias like Dumble used. Runs in a combo w/Altec 417B and a satellite Avatar 1x12also w/Altec 417B.
 

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Discussion Starter #13
Layout is paramount with these circuits and adapting to the Traynor board isn't optimum. You've got positive feedback somewhere in there, but where????
Exactly! There is no guarantee it is even caused by my layout. The increase in gain may just bring it to light in an otherwise very low-gain amp. I've heard that having a scope helps find these things but I don't even understand how (not that I know anyone who owns a scope anyways).

The amp still works, and actually the most annoying thing about it is that the Overdrive activation has do be done by hand instead of foot. Still would be nice to have the freedom to dial in tone safely. It's working great as a Rhodes amp right now though. The Overdrive is a neat affect once in a while as long as the amp is close at hand to the Rhodes players left side.

I have some new caps for the overdrive circuit in the thought that it might improve things...


Leghorn, let me know how your gutted Bassman build goes. My Traynor never had much resale value, so it seemed like a great amp to mess with, but the reverb and cleans are pretty sweet, so it seems risky to completely gut it for a build.
 

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Discussion Starter #14
So, I was reorganizing (with more expensive components) the OD mod section of this amp. I also moved the OD insertion point to where the existing Master Volume was located in the schematic. (It is after the trem and Reverb, so I'm not sure if that sounds ok to me yet).

It now takes some very aggressive gain and treble to get any oscillation type squeals from the OD, so the amp is very useful with some of those HRM type overdrives now.
I had made the NFB switchable on or off from the front panel (with long wire routing). That was causing some noise so I put a 250K pot on the back panel in place of one of the speaker jacks. I basically found the sweet spot and will return the jack and change the resister in series to match the value of what the pot was adding up to. It really opens up the amp in a pleasing way for me and gives the (clean-unmodded)amp some much needed gain.
So, if someone is wanting an idea on modding their YGL for more gain, I'd try this simple resister swap first and see if it gets you where you are trying to go.I'm guessing that the value will be somewhere in the 56k -100K area bumped up from the original 10K, resulting in a decrease in Negative Feedback and opening up the sound a bunch.
I'll get some pics up later to help illustrate what is going on...
 

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Discussion Starter #15
So, I used this amp today for band practice and I must say that it is very versatile and great sounding now. I had no problems with it , and I didn't experience any hint of squeals, oscillations, feedback, or unstableness anywhere near the sounds I was dialing in. (I should have tried even harder to find some, but didn't feel the need. Things are pretty good since I have had this layout settled on. I have some pictures now too.
So, everything left of the blue electrolytic capacitor is part of the HRM overdrive circuit:

And so all the controls that used to be for the normal channel are now for the HRM overdrive. Very tweakable with a huge of range in styles of tone. The Master Volume for the overdrive channel is on the very left beneath the toggle that activates the overdrive:

So, I'm thinking the next step is to venture into the world of relays in order to put this overdrive switch into foot pedal form. Also, because I now have the overdrive circuit occurring after the reverb and trem in the Traynor circuit (right where the Clean Master Volume is), any significant amount reverb gets sort of too much when the overdrive is clicked in. So, I may think of doing something about this. Not sure if I would just always have the reverb footswitch ready, make another relay for it, or think about moving the overdrive again...
I'm not worried about it right now; because I go light on the reverb anyways.
 

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Discussion Starter #17
I'd love to hear what you've done to the old girl. Can you post a recording?
Actually Matt, this is the YGL that I owned already. The one I got from you I didn't defile at all. It is sort of ironic because, the one I did modify was more original, (even has the original Mullard 6Ca7 power tubes going strong still). Buying yours was what gave me the courage to mod mine (knowing that I now had a spare). The plan was to mod yours, but I couldn't wait the week for it to arrive before digging in.
Anyways, I'll try to record a clip this week to show what this amp sounds like now. My friends have a decent camera for music (Zoom Q3HD), so I'll try to borrow and get something up. I'll let you know.
 

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Hello bcmatt,
I was reading your thread here and it brought back memories of an amplifier I built a long time ago, which also whistled at high gain. At that time I didn't know as much about electronics as I do now, but when I read "positive feedback", it suddenly made lots of sense... The crime is, I have an oscilloscope, actually I have a lot more than one...
If I remember correctly I managed to kill the oscillation by using lower gain tubes (12au7 versus 12ax7) as the "capacitor across plate resistor" solution didn't work for me. I'll take a picture of it tonight, maybe a picture of the innards (but it's ugly!)

It's actually a hybrid based on an old EICO power amplifier design.
 

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Discussion Starter #19
Hello bcmatt,
I was reading your thread here and it brought back memories of an amplifier I built a long time ago, which also whistled at high gain. At that time I didn't know as much about electronics as I do now, but when I read "positive feedback", it suddenly made lots of sense... The crime is, I have an oscilloscope, actually I have a lot more than one...
If I remember correctly I managed to kill the oscillation by using lower gain tubes (12au7 versus 12ax7) as the "capacitor across plate resistor" solution didn't work for me. I'll take a picture of it tonight, maybe a picture of the innards (but it's ugly!)

It's actually a hybrid based on an old EICO power amplifier design.
Oh, cool, that would be interesting. Thanks.
 
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