OR15 presence

[rvgoslin]

Does anyone know if the OR 15 uses a feedback loop. I was considering adding a presence control and have looked quite a bit for a schematic with no success. If it does use a feedback loop its a fairly straightforward mod.

[Jondog]

Can't really say without a schematic or visual inspection. But the schematics I've seen of the Tiny Terror don't have a negative feedback loop. I've got a dark terror schematic kicking around somewhere I'll have a look at. I'm assuming all terror style amps have the same power section. But the TT and DkT may be different. If you can look at the PCB it's possible you might see it labelled.

[rvgoslin]

Makes sense....I cant imagine leaving out a presence control if there was negative feedback. Its pretty much 3 parts. Just thought id ask before opening it up and tracing the pcb. If it does have negative feedback ill be sure to explain the mod if anyone's curious.

[Man1ak]

Resurecting this thread: has anyone been successful in adding presence control to their OR15? I am looking for such a mod on mine, but could not find any info anywhere.

[jontheid]

I very much doubt it has a negative feedback loop, most 2 x EL84 amps dont.
Why do you want a presence control so much?
Doesn't the EQ on the amp do enough for you?

[Man1ak]

The EQ is ok for cleans. For high gain i am left wanting. The mids range is spot on, the bass is acceptable, but the treble is not helping to cut the fizz. I have an EQ in the FX loop and that works better, but i find the sound a bit too dark. Not bad, but too dark nonetheless.

I am using the PPC212OB with V30s. I will change the speakers with Eminence Maverick and Reignmaker, i am hoping that this will tame the fizz. But I would still be interested in the presence control.

[jontheid]

Installing a presence control will only enable you to boost high frequencies, not cut them.

[Jondog]

Are the V30's new?

[Randy Bass]

Oranges are dark amps - that's what they're known for generally. Are you sure you've got the right amp for you?

[Man1ak]

My understanding is that the presence control allows to vary the amount of NFB. In an amp without NFB adding it will tame the highs. Have I got it wrong?

The V30s are new and I know that they will get better after wearing in. But i never play at proper volume for wearing in the speakers. So i need another way to get rid of the fizz.

Regarding the dark side of Orange, I don't know really. I have not tested it against other amps. I find it reasonably bright and i love the mids rush you get cranked. It's just the fizz that I don't dig.

[jontheid]

Adding a NFB loop lowers the overall gain of the power section and extends the frequency response of it.

A presence control works by filtering out some of the high frequencies in the FB signal - thus these frequencies aren't reduced by NFB and are thus effectively boosted.

NFB will tend to smooth out humps in the frequency response of the output section, trouble is you don't know if there are any significant humps until you install the NFB, unless you trace out the frequency response of the amp. The fizziness you are experiencing may not be caused by a hump on the power section's frequency response at all.

Good page on NFB here:
http://www.aikenamps.com/NegativeFeedback.htm" onclick="window.open(this.href);return false;

I'm not quite sure how an amp can be 'dark' sounding and 'fizzy' at the same time.

Modding the amp by installing a NFB seems a bit much to me.
There's probably a much simpler solution.

The original Tiny Terror tone control used a pot in series with a capacitor across the two outputs of the phase inverter.
All it can do is cut highs, nothing else.
The dark terror doesn't have this - I expect the OR15 doesn't have it either.

You could get your tech to install something like that and see how you like it - it won't change the overall gain of the amp at all.

That said, I reckon you should break your speakers in first.

Cheers
Jon

[Man1ak]

Jon, thanks for the link, good read.

I will rephrase the dark vs fizz part: with the standard eq of the amp there is fizz at high gain. If I cut the treble it makes the sound dull. I am using another EQ in the FX loop to cut 12 and 16 khz, but that makes it too dark sounding.

I will see if the Eminence speakers make it more suitable to my taste. Supposedly these FDM speakers are warmer as the attenuation increases. Also one of them is "American" voice, which is supposed to filter all frequency above 5khz. Will post back here once I give them a try.

[Man1ak]

I have finally received the Emi speakers and have installed them. After playing with them separately to understand how the sound on their own i have now reached a final (or maybe a longer temporary) setup.

i am very much thrilled with the sound of the Maverick. I find it has a great balance, with a tight and percussive low end and sweet highs. It complements the OR15 and it filters all that nasty high end that took me to desperation with the Vintage 30. At maximum attenuation it sounds smooth and sweet, while reducing the attenuation brings back some mids and highs. Overall it remains very well balanced.

The Reignmaker is a different animal. It resembles the Vintage 30 in character and it displays the spiky high end. On its own it projects the amp's fizziness on high gain even at maximum attenuation. On cleans i find it bright (which is good), with a flabbier low end.

I set them up in my PPC212OB like this: the Reignmaker is on the top position, Maverick on the low position. I have removed the back completely and have positioned the cab some 30-40 cm away from the wall. The Reignmaker is fully attenuated, while the Maverick is at 50%. I play in a 25 sqm room 1.5 m away from the cab at a 30-40 degree angle on the Maverick side. If it sounds like i am mad to give all these details, i won't blame you but it makes a world of difference where you sit vs the fully open back cab.

I have changed the preamp tubes in my amp with EH 12AY7 and the power tubes to JJ EL844. Now I get a much smoother and gradual gain curve, which I find more satisfying. I can keep it clean up to 12 o'clock (with a bit of spark, but very mannered), while after that it becomes dirty. At 3 o'clock it becomes fully distorted with humbuckers, while with single coils it takes a bit more. Overall I find this setup as giving best of both worlds.

Now to sounds: the cleans are sweet and full sounding. The tight bass of the Maverick keeps things warm, while the highs of the Reignmaker bring it a bit of sparkle to emphasize harmonics. The dirt is progressive from crunch to hard rock and it is much improved in the mids and highs. The EQ reacts better with these speakers especially the mids and highs and I am able to get more workable tones than with the V30. For some reason the Emi's seem more suitable for the tone shaping capabilities of the OR15. The V30s were more stubborn in showing their character, the Emi's are more responsive.

Overall i am very pleases with the new speakers. If i could choose again i would be tempted to skip the Reignmaker and get another Maverick. Somehow i feel that it would get me even closer to my dream tone.

[Bensnake]

Presence is evil!

[Randy Bass]

I'm glad to finally hear someone's experience using the FDM Eminence speakers with an Orange. I really like how Eminence speakers tend to balance out Oranges without completely killing the mids.