I recently came into possession of a vintage, Fender 1965 Princeton amp that's in excellent shape. It's got a great, warm and clear sound, but I'm used to having a "gain" knob on an amp so I can also get it to sound a little less clear and a little more dirty -- gritty -- fat -- etc... The Princeton doesn't have one.
Does anyone have any suggestions as to how I might tweak things to get a thicker sound? I'd be much obliged for the guidance.
Well... I think playing style and mic technique might play a roll here. I've heard stock blackface Princeton non-reverb amps sound mighty fine. I'd love to have one.
Heres some mod suggestions from the Harp-L archives-
Juicing up a Princeton? Forget any hacks that require major butcher jobs. Here's some simple reversable mods that still keep it looking and sounding like it's supposed to.
1. - You might replace the stock wimpy output transformer with one from a Deluxe, they're beefier.
2. - Consider replacing the stock speaker with one that's more efficient. Stick with the 10" to avoid a hack job, just get one that puts out more dBs of sound for a given input power.
3. - The stock phase inverter circuit is kind of lame. You can get major improvements by increasing the headroom. Do this by moving the supply connection for the phase inverter to the next higher tap on the power supply voltage divider. (Yeah, I've seen some that didn't have enough headroom to drive the 6V6s to saturation.)
4. - Install a set of good NOS tubes, and have the thing properly biased. (This isn't a mod).
5. - Have a cap job done if it needs it. (This isn't a mod either)
A stock Princeton that's totally healthy puts out about 18 Watts. Putting in a more efficient speaker will gain you 1 or 2 dB. Putting in a Deluxe output transformer should get you yet another dB. The result will be a net gain of 2 to 3 dB in sound level, assuming everything else is ship-shape. That's about all you can do without resorting to unadvisable hacking.
>>>How much should the other mods cost?
>>>How much should the other mods cost?
Increasing the phase inverter headroom is a matter of moving a wire or two inside the amp, say 15 minutes of bench time.
Replacing the output transformer with a Deluxe transformer costs about $40 for the transformer and another half hour or so of bench time.
Putting in decent preamp tubes you do yourself. You can get NOS 12AX7s for about $15 each.
NOS 6V6s are uncertain. Whatever you pay for a matched pair, plus a little more bench time for biasing.
You can get a little more poop out of a Princeyton if you want to do some work on it. As Tim mentioned, the stock phase inverter circuit falls way short on being able to drive the output stage all the way to saturation. However, you don't have to resort to such drastic mods as Tim talks about to fix it. Basically, the stock phase inverter lacks sufficient dynamic headroom to develop enough grid drive. That can be cured by moving that stage's B+ supply connection one step higher on the voltage divider in the power supply. Increase it's supply voltage, and you simultaneously increase it's headroom. Be careful to move only the phase inverter's supply to the next higher tap, and leave the remainder of the preamp where it is. You'll have to move a couple wires to do this. You may also, depending on several variables, need to rebias the phase inverter by changing the 1500 ohm bias resistor to 1200 ohms. Anyway, if you do this, the thing will then (with little room to spare) be able to fully drive the output stage. Be sure the output tubes are properly biased between 25 and 30 ma each at idle.
You can also change the output transformer to that from a Deluxe if you want, it doesn't hurt. I have two friends with a brown Princetons. In both, I've put in the Deluxe transformer, and changed the 5Y3 rectifier tube to a 5AR4 to give more voltage to the output stage. Those amps now put out 18 Watts. I' ve also done the phase inverter mod alone to a 64 Princeton Reverb, and it also now puts out about 18 Watts.
Lastly, unless you have the proper test equipment, maybe you should not tackle this yourself, because you'll need to look at the actual effects of your work using an o-scope to make sure you're achieving your goals.
Last Edited by on Sep 27, 2011 6:23 PM
This weekend I tried a DR output transformer in my silver face Princeton Reverb. This resulted in a cleaner sound. I put the original back.
You probably want to avoid modifications that will give more headroom, as your stated goal is less.
I agree new tubes, filter caps and cathode bypass caps will probably help the overall tone. Do not change out the signal caps if they are mustard color or blue. The medium brown caps are generally not well liked and are often replaced. Would be best do do these things and give a listen before doing circuit mods.
Don't do any mods! That amp is a classic...make sure it is up to snuff, but don't do anything beyond tweaking tubes and speakers. Don't wreck the amp! ---------- Mike Quicksilver Custom Harmonicas
There is so much variety in tone available by using different mics. If the amp has been checked out by a tech and is OK, just try out some different mics: weak, strong, etc. I have found so much of tone depends on the combination of mic and amp (and the player!). If you have a good functional vintage amp, just try different mics! Amp mods should not be the first thing you try. Then try tube swaps, then speaker, if you must... ----------
Once upon a time, i had a silver face Princeton Reverb. I didn't know any better, so i had it modded to add a gain stage with an extra control knob. Got a lot of feedback, and the tone wasn't all that great even when it wasn't feeding back. Live and learn....
But, you know, if you want dirt, pull one of the power tubes and run it w/one tube. I got a Princeton Reverb Reissue a couple of years ago. I re-tubed it with JJs and didn't realize that I broke one of the power tubes installing them. Sounded pretty dirty, which was cool if you like that sort of tone. Eventually i figured out what was going on. After i replaced the broken tube, the amp sounded much cleaner. Live and learn...
Last Edited by on Sep 27, 2011 9:52 PM
If you can't get enough dirt from a '65 Princeton then it can be a number of things.
1. Your playing technique needs looking at. 2. Your cupping technique needs looking at. 3. The amp needs a good service. 4. You need to use a different mic. 5. You want to play with a thrash metal type distortion.
A '65 Princeton is one of the most versatile amps around. It responds perfectly to technique and will go from crisp clean tones to overdriven "Rocker" style tone in a heartbeat.
Here's a video of me playing through a stock '65 Princeton Reissue with no effects. Does yours overdrive like that? If not see the list above for cures to the problem.
Also here's Michael Art playing through an original '64 Princeton
5Y3GT rectifier (NOS) & bias to 15mA-20mA per tube.
You actually say "Princeton" not "Princeton Reverb". Non Reverb Princetons have very low gain for a Fender, due to the fact that they are missing a gain stage in the preamp. A quick & easily reversible mod might be to dispense with the Treble/Bass controls & rewire like a 6G2 Princeton that just has a single tone control, leave out the 500pf bright cap that bridges vol & tone controls. ---------- www.myspace.com/markburness
Last Edited by on Sep 30, 2011 3:06 AM
Also +1 for HYVJ's pull a tube trick, replacing the single power tube with a 5881/6L6 shows the output transformer a better match, you may well have to rebias the 5881/6L6 to 30mA-50mA? ---------- www.myspace.com/markburness
A further observation about a Princeton Reverb and "distortion." These amps really come alive at higher volume settings. So, if you crank the volume on the AMP and turn down the output of the mic using a volume control on the mic to control feedback and set performance volume level, you can get really nice tight warm break up out of the amp. Not really the tone i usually go for, but for certain applications, it's perfect.
Now, the tone of some bullet mics may tend to degrade if the output is reduced, but i use a 545 Ultimate, and on that mic, it's not a problem.
The Princeton does not have a standby switch. But if you are playing through a tube amp that does, consider not using it between sets. Letting the tubes cook and get really hot can have very positive effects on tone. Maybe not so good for prolonging tube life, but there's nothing like the tone of a tube amp when the tubes are really hot. FWIW.
If it is a princeton reverb anything over volume level 4 should crunch. If not then have a trained professional who you trust go over it with the official schematic and fix it up. But def don't change anything xcept the tubes and speaker if you mod it! My Princeton Reverb has such a bad ass distortion. I have custom speaker and JJ tubes and it rips hard. Its been my main harp amp for my whole career.
I would listen to Kingley. Princetons and Princeton Reverbs are fine harp amps. If you aren't happy with the sound coming out of it, you have to assess what's going in. Sure, some amps are turds, but if yours is in good condition, it should sound pretty good. There is a reason why those amps are pretty popular among harp players.
I can only say that you guys are great! First, I will work with the controls while working it at a higher volume. I'll also try my old Sure 545SD -- I've only run my bullet mic. Then I'll look at mods. I promise not to change anything except the tubes and the speakers -- if that. I am amazed at the amount of knowledge and generosity of knowledge that you've offered.
"I'll also try my old Sure 545SD -- I've only run my bullet mic."
Hmmmm. If you can't get a Princeton to overdrive with a bullet mic. Then you'll be very unlikely to get it to overdrive using a 545SD. Unless the amp has some problems, I suspect it's your technique that is most likely at fault here. I'd look at your cupping/playing technique first before swapping tubes, etc.
Well, bullets tend to be "hotter", so one is likely to feedback at a lower volume level using a bullet, which may have something to do with it. You may actually be able to drive the amp harder by cranking it up more using a 545 than you might be able to with a bullet.
Also, a 545 and a Princeton Reverb (or a Super Reverb) are a particularly good match. Sort of a symbiotic relationship, IMHO. Certain mic/amp combinations work better than others.
Btw, +1 on what Iceman said about the tone controls.
"Well, bullets tend to be "hotter", so one is likely to feedback at a lower volume level using a bullet, which may have something to do with it. You may actually be able to drive the amp harder by cranking it up more using a 545 than you might be able to with a bullet."
In my experience a bullet doesn't feedback until the amp is around 7 on the volume. With proper technique a Princeton overdrives around 3 easily. I still maintain that the player is most likely the problem and not the amp. I'd encourage looking at that area first before spending any money on tubes etc. If I did change a tube I'd only change V1 for a 12AY7. That in my experience is the best tube change for the Princeton.
I do agree though that a 545 and a Princeton Reverb are a particularly good match.
Peter still hasn't told us whether this is a Princeton Reverb, or a non-reverb Princeton. The non-reverb amps are very low gain for a Fender, a reasonable amplified tone is certainly available, but if you're used to gain/master controls it's probably not the amp for you without circuit modification to boost up the gain to more typical Fender levels. A master pot installation is feasible & simple for this amp but it tends to make for a fuzzy distortion (I don't like it, I'd rather go the 6G2 conversion route), but will return to "stock" tone...Peter let me know if this sounds like something you are interested in. ---------- www.myspace.com/markburness
@Kingley: I can't get my PRRI to break up on 3. In my experience, the tone fattens and deepens considerably at 6 and above and at that level the amount of dirt depends on how hot the tubes are and how far I open the VC on the mic. At 7 and above, breakup is more easily achieved. It's certainly possible to get a certain amount of overdriven sound at lower volume settings with technique, but like I said before I think this amp really comes alive at higher volume settings--at 6 and above the tonal and response characteristics change. But I don't actually use a bullet, so YMMV. Princeton Reverbs can sound pretty decent with the right bullet mic.
@5F6H: "A master pot installation is feasible & simple for this amp but it tends to make for a fuzzy distortion" Yeah. When I had a gain stage installed on my old silver face Princeton Reverb, it gave me a "fizzy" or "fuzzy" tone when it was not feeding back. Not a particularly appealing distorted sound.
@hvyj - On the clip of me playing a PRRI the amp was on 4. I was using a JT30 with 99A86 element. The PRRI was miced up using a 545SD into the PA. I never played my PRRI above 5 on the volume ever with either a bullet or a 545, as I never needed too. It was always plenty loud enough on stage. If I needed more out front I just miced it into the PA.
@5F6H - In the clip above Michael Art is playing a '64 Princeton (non reverb model). Sounds good for my taste. Mind you I prefer a fairly clean sound with just a tad of overdrive.
Roger that Kingsley, but I'm guessing if Peter had Michael Arlt's chops & R7 (if that what he's still got in the green JT30 shell) this thread wouldn't have started (no offence to Peter, for those who don't know, the Arlt brothers are two of Germany's, if not Europe's, most respected & talented blues musicians, collectively known as BB & the Blues Shacks).
Even so Michael's sound in the clip is no patch on the sound he had through his bassman when I saw him & probably not in the realms of someone who is used to gain/master controls is expecting. I'm not keen on the idea of adding a master to a Princeton myself, but hey, it's a £3 pot and few inches of wire, 1/2 hr of tech time & goes back to DEAD NUT stock when full up.
If I had a non-reverb Prnceton, I'd junk the tone controls for the 6G2 style tone pot...the treble & bass controls suck a lot of signal in this amp that isn't made up later, like it is in the reverb version.
I haven't played every Princeton, but I've played every style from 5F2A to the 80's. ---------- www.myspace.com/markburness
Last Edited by on Sep 30, 2011 1:09 PM
@Kingley: Oh, i don't crank my PRRI up to 6 or above for VOLUME. I crank it up that high for TONE. Then I use a VC on the mic to reduce/control the performance volume. What I've been trying to explain is that the TONAL characteristics and response of this amp change in a very positive way at higher volume control settings. So, i use the volume control on the amp to establish TONE and the VC on the mic to establish volume level. I use the #2 input.
It works. I do the same thing with my Super Reverb Reissue. It may not be effective with every amp, but these two Fender amps really come alive a higher volume settings and both of them interact particularly well with a 545. And, of course, the 545 Ultimate has an integral VC.
Last Edited by on Sep 30, 2011 4:23 PM
I think adding a middle pot is ok,but not a master volume-from Andy Ruhl-
This mod is requested far too often. People don't understand what a master volume does, but they ask for it anyway. Amps that have a master volume to get distortion do so through preamp clipping. This means that there was some sort of previous thought involved in shaping the preamp gain and response to make it sound good with a master volume. I get people asking me to add a master volume to a blackface Fender because they want it to sound like it does cranked up, but at a lower volume. Guess what folks? IT AIN'T HAPPENING. And I can't seem to convince people of this. That nice distortion you get from your Super Reverb is due to preamp, power amp, and speaker clipping, and other issues that happen only when the amp is up loud all at the same time. Since the master volume removes the latter two factors from the equation (the master volume is installed right before the power section on most amps), how can you expect to get that tone at lower volumes? Fender preamps don't clip all that nicely anyway (brownface and later). Here's another example: I've had a few people that own Deluxe Reverbs that say they love the sound of it cranked, and want me to install a master volume on it to get it at lower volumes. The preamps of the Deluxe Reverb and Twin Reverb look VERY similar. Do they sound the same cranked up? No! So why assume that adding a master volume is going to capture that sound? Here's another one: Fender installed master volumes on later model silverface amps. Does it make it sound like a Marshall? No! Let's get off the master volume ignorance! You can get closer with a speaker load simulator (such as the THD Hot Plate, or Marshall Power Brake), but that still neglects the speakers. Speakers do contribute to the distortion characteristic.
I have an early SF PR. Mods I have done and like include- increased coupling cap values mid pot, mounted in instument 2 input hole Stokes mod Paul C mod master volume, just before PI grid, mounted in the extension speaker jack hole. It does provide more grind at low volumes, not withstanding the message above. Weber P10R speaker
