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Capacitor Replacement - Orange

aryasridhar

Member
Messages
459
So I replaced the filter caps in my Orange OR15, after facing hum issues, hum was constant and was not affected by the volume control, whether a cable was plugged in or not also did not matter, the hum would stay constant, but what I also observed was a “High Pitch Noise”, that was not very high also was present.


I was suspecting the issue to be with the tubes, filter caps or with grounding.


So i did the following, took my amp to a friend’s place to try and did have the same hum/buzz there too.


Then tried it at my work place and had the same hum/buzz.


Tried with pedals, without pedals, tried with nothing other than a cab hooked up to the amp and still had the hum.


Then replaced the V1 with a known good JJ 12AX7, the stock one was also a JJ, and the noise did go away quite a bit, but I still had that high pitch squeal/noise.


Spoke to a few guys around my place who build amps, and they suggested I replace the filter caps with better ones, so i got some SamWha/Sam Young/Panasonic/Keltron caps and replaced some, yet to complete the replacement...


While i have the amp open, is there anything else I should check on please?


A couple of images of the replacement here...


Had a tough time getting those caps off of the board safely, they were glued on hard, hair dryer' heat was not sufficient, Xacto blade did not help either as there was very little room to manoeuver so had to de-solder the legs properly, then had to cut the outer shell of the caps (where the markings and values are written), and then shake the caps a little to pop them off, I found this to be the safest from all the options I'd read online, at least to me.


I also want to change the tone stack caps, with better quality caps and resistors there; I'd want to keep the values the same as they are but just better components.


Wondering if I can make this amp sound a lot more like a Marshall, any tips would be great in that direction please.


Here's an image of the schematic of this amp, and some pictures I'd taken while working on the filter cap replacement.

OR15 Schematic IMG file.




Original Guts




Guts Now:-




How I ripped the capacitor’s outer shell




I would highly appreciate your inputs please.


Regards

Arya
 

J M Fahey

Member
Messages
2,149
Ouch !

Parts Brands don't have sound of their own [tm]

There is not a brand which will give you "the Marshall sound" , it depends on the project in full, specially then circuit, and parts *values* (again, not Brands)

I also want to change the tone stack caps, with better quality caps and resistors there; I'd want to keep the values the same as they are but just better components.
Nice, but sound won't change.
 

aryasridhar

Member
Messages
459
Ouch !

Parts Brands don't have sound of their own [tm]

There is not a brand which will give you "the Marshall sound" , it depends on the project in full, specially then circuit, and parts *values* (again, not Brands)



Nice, but sound won't change.
I'm sorry if my post implied that a "branded" part would make it sound like a Marshall, but if you read again, I mentioned I wanted to remove the caps that were not good quality, I am not expecting any change in sound/tone doing this.

Also I do agree on things that may affect the tone, I am just asking what replacements may bring about that change, again, NOT implying a brand here....
 

pdf64

Member
Messages
7,060
Are the hum and high pitch noise new, or has it always had them?
Did you try to swap in known good tubes into every slot, and a matched pair of power tubes?
Did you try adjusting the hum balance control?

I acknowledge it may be tempting, but it far better to fix faults first, then when the fix is confirmed, attempt mods.
To attempt fixes and mods at the same time could invite trouble.
 

TweeDLX

Member
Messages
3,756
Did you try to swap in known good tubes into every slot, and a matched pair of power tubes?
Microphonic tube was the first thing I thought of. As far as changing the circuit to sound more like a Marshall, you're somewhat limited by the PCB. You could: change some values in the phase inverter (Change the 1K2 to 470 ohms, and the 47K to 10K) and output section (change the 150K bias feed resistors to 220K, but that won't make a huge difference, and may raise new issues). THEN, you need to decide WHICH Marshall you want to emulate, and change coupling cap values, cathode resistors and caps to match that schematic. Marshalls usually incorporate a cathode follower to feed the tone stack, and your amp doesn't have that. No big deal, but if you're changing part values willy-nilly, you may destroy what you have. Each gain stage has component values that work with what the stage does in the overall scheme of the amp. You may want to rephrase your question to be something like: "How can I get rid of this annoying high end?" or "How can I add more mids?"
 

Motterpaul

Tone is in the Ears
Messages
12,510
Just the most logical question - did you check the bias on your output tubes? I have found over-biased tubes to be the most common cause of hum.
 

axpro

Member
Messages
628
Hmmmmm, I don't have much to add that's constructive lol. NOT trying to disagree with Mr Fahey, though I do think some caps do have a difference brand wise.... not a huge difference, but cumulatively through an entire amp, I found that Orange drops were a little bit brighter than Mallory caps... but it also could be attributed to part drift and inconsistencies...

As for getting more of that Marshall type sound, that's going to be tough, as it would involve some changes to your layout if you wanted to replicate a Marshall type circuit... But when you say "Marshall" are you meaning the tone of their amps, or just "More Gain"?

You mention that it is buzzy, but is it significantly buzzier than other OR15's? I tried one and it was good, as long as you didn't crank the gain... with it cranked it got a little noisy.

As has been stated by others, unless the problem is a failing part, a "better part" won't get rid of the noise. Better filtering i.e. rebuilding the power supply filter section for less noise might help. but that would mean again, reworking a the circuit. Easy to do on a point to point amp, but not so easy on a board.

If you are trying to "improve" an OR15, it's a bit of a losing battle. Modern Amp companies have wrung out the most performance, for the least money out of small amps. Parts swamps to change tones is an option, if you don't like something. But just putting in better caps and resistors is going to give you essentially the same amp at a higher price point.
 

axpro

Member
Messages
628
as for the squeal, it could just be wire placement... not easy to correct for when most "wires" are solder traces.
 




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