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Whats on the workbench today...
Tracy Dae
#1 Posted : 2/7/2016 7:24:56 PM
Tracy Dae


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On the workbench today is a Ross Grey Compressor with a heavily corroded input jack. Aside from the corroded input jack, this is a very clean example of a rare vintage pedal. I have saturated the input jack with DeoxIT and have situated it in this container to slow down the drying time to give DeoxIT more time to work it's magic before it dries away.

The owner has given the okay to replace the jack if it cannot be saved but we both want to keep this example as original as possible.






Later today I hope to have time to take the head out of my mid 90's 3x10 Roland Blues Cube and clean the pots. The volume pot on the clean channel was a little scrathy during last nights gig. So I am going to clean and lube them all. Will post pics if I get a chance to do that today.
The mind is like a parachute...
...It only works when its open.
Tracy Dae
#2 Posted : 2/15/2016 11:28:03 PM
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A 1997 Fender Priceton Chorus with a broken #1 input jack. After the repair I played the daylights out of this amp and found that I absolutely love it. I want one. Haha







I did not use an original Fender part to repair this amp. I used a compatible part from another supplier that is made of less brittle plastic and does the correct switching for this model amp. I would like to have been able to use metal Switchcraft jacks on this but these jacks do switching when you plug into them, so your more common jacks are not compatible. Switcraft does in fact make a 1/4" jack that will perform the correct switching but it is uber expensive and there is no way it will fit in the spot available to put it on this model amp.
The mind is like a parachute...
...It only works when its open.
Tracy Dae
#3 Posted : 4/3/2016 3:24:03 AM
Tracy Dae


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I liked that 97 Princeton Chorus so much that I went on a search to find one for myself - and I found one. When I was testing that other Priceton Chorus I thought it sounded great but wondered what it would sound like if I replaced the general purpose TL072 op-amps with OPA2134 op-amps, which are specifically designed for professional music applications. Let me just say I was not dissapointed with the results. The amp sounded great before. It sounds absolutely amazing now. I did not replace all of the TL072's on the board, just most of the ones that would make a difference in the quality of sound that comes out of the amp. The amp has seven TL072's in it. Six of them have an effect on the sound but I only had five OPA2134's on hand. So I replaced all but the op-amp that drives the Chorus circuit.

Here is a pic of the bottom of the circuit board showing where I marked out which Op-amps I am going to replace.






When I swap out op-amps in a guitar amp or pedal, I put a socket in it's place. This allows me to try other op-amps if I want to in the future. I have been pretty happy and impressed with the OPA2134 over the years though. It sounds great and it is versatile enough to use in almost any audio circuit you can think of.





Here are four of the five TL072's out. This went along pretty quickly. That is perhaps the only customer benefit of wave soldering I can possibly think of.





And here are a couple of shots of the top of the circuit board with the OPA2134's installed in their sockets.







As I said above, the amp sounded great before. Now it sounds amazing. Much more musical. Now that this is done, I plan to upgrade the reverb tank from a short tank to a long tank. The specific reverb tank this amp is designed for is available in both long and short versions. I will installed the MOD long tank version in this. I need to make longer (and better) reverb tank cables though. The cable I want to use for that is currently on back-order. So as soon as that arrives I will likely post pics of that as it is happening.
The mind is like a parachute...
...It only works when its open.
Artcores4me
#4 Posted : 4/5/2016 9:49:29 AM

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Hi Tracy.
I think you are quite knowledgeable with the Roland Blues cubes and I have a BC60 combo that does not power up.
Could it be as simple as just a fuse or defective power switch? Any ideas or suggestions?
Thanks in advance for any help.
Tracy Dae
#5 Posted : 4/7/2016 3:35:27 AM
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Sorry I just now saw this. Yes it could be a fuse. The 90's Roland Blues Cube amps are relatively easy to repair. They are pretty straight forward. With that said, if you check the fuse and find that it has blown, make sure to check the speaker as well. A blown speaker can cause an amp to blow fuses. Other things can cause that as well of course but the most common cause for most amps to blow it's fuse is that the speaker has blown.

If you find that the speaker has blown, I recommend the Eminence Swamp Thang as a replacement for the 1x12 BC60. I don't have a recomendation for replacement speakers for the 3x10 BC60 though. Just that you need to make sure they are 16 Ohm 10 inch speakers of appropriate wattage.

If it is more than a blown fuse and/or speaker and you decide to throw the amp away instead of repairing it, please PM me.
The mind is like a parachute...
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Artcores4me
#6 Posted : 4/7/2016 10:36:03 AM

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Thanks Tracy. I am pretty sure it does not have a blown speaker. It worked fine then a few days later it would not power on.
I will keep you in mind if I can't get it work.
Tracy Dae
#8 Posted : 4/8/2016 2:39:53 AM
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You can test the speaker with a 9-volt battery by disconneting the speaker wires and touching the contacts of the 9-volt battery to the speaker's terminals. You should hear a "pop" when you do that. If you hear nothing, the speaker is blown.

The mind is like a parachute...
...It only works when its open.
renton481
#9 Posted : 4/9/2016 5:25:08 AM

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What sonic improvements did the new OPAmps add to the amp?

I have a 1990's era Fender Bronco that has TL072s and it's a great blues / rock amp. I think at least some of it is the TL072's, because the gain channel has them in it.

TL072's were used in Tube Screamers for a while, I think. Are they more of a distortion OPAmp, or is does it just depend on how the chip is used in a circuit?
Tracy Dae
#11 Posted : 4/9/2016 10:48:45 PM
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Originally Posted by: renton481 Go to Quoted Post
What sonic improvements did the new OPAmps add to the amp?


That can be a difficult question to answer fully because part of the answer is inherently subjective and different players have different goals. My goal was to reduce the noise floor in specific areas of this amps circuit. Also, from past experience with using OPA2134's, I find the sound going through an OPA2134 to be more refined and natural sounding. Very much like a nice old tube amp played clean. I like that and see it as an improvement. You might not. I also like how the OPA2134 sounds in over drive circuts. The audible difference can be very subtle depending on the support components and your setup. The OPA2134 is an op-amp that was specifically designed for pro-audio use. It has been tweaked from the design stage up to provide excellent audio performance - and it does that very well. The TL072 is just a garden variety general purpose op-amp. In fact, of the seven TL072's in the Fender Princeton Chorus amplifier, only six have an effect on the overall tone of the amp. One is not in the signal path at all and has no chance of making an impact on the tone of the amp.

There is a long standing myth that the op-amp in a distortion or over drive circuit is the main player in the tone of that circuit. This is mostly a myth. Though different op-amps do sound slightly different in distortion or overdrive circuits, the part they play in the tone of the circuit is very minor and often just barely noticable - if at all.

If you are interested in this kind of thing. I highly recommend investing in a soldering class and a guitar pedal kit or two. Most kits include one or more IC sockets to go in the place of the op-amp(s). This gives you the chance to test out different op-amps to see for yourself which op-amps sound the best to you. You might find that you like one op-amp in one circuit but an entirely different op-amp in another circuit. It's fun to experiement.
The mind is like a parachute...
...It only works when its open.
Tracy Dae
#7 Posted : 4/14/2016 3:06:10 AM
Tracy Dae


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Originally Posted by: Artcores4me Go to Quoted Post
I will keep you in mind if I can't get it work.

Just curious to see if you found the problem and resolved it.


The mind is like a parachute...
...It only works when its open.
Tracy Dae
#10 Posted : 4/27/2016 1:20:48 AM
Tracy Dae


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Originally Posted by: renton481 Go to Quoted Post
What sonic improvements did the new OPAmps add to the amp?

I’m coming back to this question because this past weekend I spent some time in the studio with my band mates and a few other musicians we all know. One of the other guitar players has a Princeton Chorus and was curious to A/B my modified Princeton Chorus with his. So we each brought our Princeton Chorus amps to the studio and I brought three cables that are completely identical and a BOSS A/B switch. We spent quite a bit of time going back and forth. Every guitar player took a turn fiddling with the knobery on both amps and stomping the A/B footswitch. The verdict was that my modified Princeton Chorus not only sounds better than an unmodified Princeton Chorus – but it sounds a lot better. Which is pretty good cause the Princeton Chorus already sound great out of the box. Everyone agreed that replacing the Op-Amps made the tone of the amp more defined and more dynamic. It made me feel better about spending the time and money on the mod. I knew it was an improvement but since I had nothing to A/B with at the time that I finished the mod, I had no way of knowing how much of an improvement it was.

Now the other Princeton Chorus owner wants me to do the same mod to his amp. LOL

I still haven't upgraded the reverb tank to a long 3-spring tank because I need longer reverb cables and the cable I want to use to make those longer reverb cables has been on back-order. I have everything else. A long MOD 3-spring reverb tank of the correct number, two Switchcraft metal shell right angle RCA connectors and a reverb tank bag. Just no cable. When the cable arrives, I'll post some pics as I upgrade the reverb tank. On the Princeton Chorus, the reverb tank cables are soldered in on the board end. The tank end are standard RCA connectors.

I will likely replace the OEM Fender special design Eminence speakers with Eminince Ragin Cajun's eventually. One mod at a time though.

The mind is like a parachute...
...It only works when its open.
Rickrew
#12 Posted : 5/5/2016 10:46:00 AM
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Tracy, in what circumstances do you prefer the Princeton over your other amps? Is there a style in which you believe they outshine the others?

My little 30 watt Fender Champ DSP is beginning sound "less good" and I've always felt it was a bit underpowered for the clean tones and smaller venues in which I use it. It sounds - from your description and others I've read - that a Princeton might fill the bill more appropriately, and at a cost effective price.

Rick
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Tracy Dae
#13 Posted : 5/5/2016 6:28:42 PM
Tracy Dae


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Originally Posted by: Rickrew Go to Quoted Post
Tracy, in what circumstances do you prefer the Princeton over your other amps? Is there a style in which you believe they outshine the others?

It's more of a convenience than a preference. The Princeton Chorus is a great sounding amp and Fender sold a ton of them. However, I prefer my 1990's Blues Cube 60s for drive and my 1980's Jazz Chorus amps for clean. The thing about the Princeton Chorus is that the drive sounds almost as good as my Blues Cube amps and the clean sounds almost as good as my Jazz Chorus amps. It is much easier on my back to take one amp to a gig than two. The better OpAmps improved the tone of the Princeton Chorus more dramatically than I originally thought. I would say that now it sounds on par with my Roland amps I mentioned above. Upgrading the short 3-spring reverb tank to a long 3-spring reverb tank was an even more dramatic improvement. Especially if you love the 60's surf sound. The next upgrade will be a pair of Eminence Ragin Cajun speakers. I am currently in the process of bartering my way into a pair of those. Haha

Another thing is I would never tinker around with my Blues Cube or Jazz Chorus amps. They are just too hard to come buy and cost too much when you do. So the Princeton Chorus gave me something I wasn't afraid to tinker with. If I screwed it up, I could easily find another one for a decent price and try again. LOL

The mind is like a parachute...
...It only works when its open.
Rickrew
#14 Posted : 5/5/2016 9:59:40 PM
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Makes perfect sense. My back likes the Champ a lot better than my Blues Deluxe. Add to that the difficulty in controlling the Deluxe volume setting on low (what's the deal with that master volume pot anyway?), and it just isn't suitable for anything but louder gigs.

I was using the Champ recently for a loud rock and roll band rehearsal in a basement - so much easier to carry down there than the BD, even though I have a two-wheeler for it. Two-wheelers don't solve the stairs problem. The champ sort of sounds like a transistor radio at high volumes levels - not a very pleasant sound at all, although it's really amazing at lower levels. It started making strange noises toward the end of the last rehearsal. Still sounds okay at lower volume levels so it may last a while longer for my guitar/vibes duo, where it's just about perfect tone/volume-wise. If it packs up I may well look for a Princeton to replace, as they are pretty available, and not too expensive.

Thanks for your response.

Rick
AF75 TRS
AS73-12
Epi LP dbl cut w/p90s
Epi Nighthawk RI TA
Oscar Schmidt OM-30/Mean 90s
Ovation 1984 1612
Fender Blues Deluxe
Tracy Dae
#15 Posted : 5/8/2016 4:44:25 PM
Tracy Dae


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Originally Posted by: Rickrew Go to Quoted Post
The champ sort of sounds like a transistor radio at high volumes levels - not a very pleasant sound at all, although it's really amazing at lower levels.

You might want to consider replacing the speaker. Those "Fender Special Design" speakers are generally not very good, even though they are made by Eminence. Eminence makes them acording to specifications provided by Fender. I put Eminence Ragin Cajun's in my Princeton Chorus last light and they sound fantastic all over the volume sweep on both channels. I giged with that amp last night and it dd a great job.
The mind is like a parachute...
...It only works when its open.
Rickrew
#16 Posted : 5/9/2016 12:00:07 PM
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Thanks for the recommendation on the speaker. It could be the problem - I replaced it with a higher watt capacity speaker several years ago, because I was getting some distortion and noise. I don't remember the brand I used, but it was not something special. Probably deserves a closer look and some general trouble shooting. I just stopped using the amp after the noise started, and have been using the BD for everything. No wonder I've been having more back pain!
AF75 TRS
AS73-12
Epi LP dbl cut w/p90s
Epi Nighthawk RI TA
Oscar Schmidt OM-30/Mean 90s
Ovation 1984 1612
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renton481
#17 Posted : 6/3/2016 12:40:33 PM

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Another option with some of the smaller Fender amps (at least the ones with an external speaker jack) is to plug the amp into a 2x12 or 4x12 box. I do that with my Fender Bronco (the 1990's solid state tweed version of the amp) and it sounds incredibly better than through its internal speaker.

You can't crank the amp up all the way -- at least not with my 15W nominal / 20W peak Bronco. About 2/5 volume is all it will put through the box before it gets really muddy; because the box is made to handle 50-100 watts and you're pushing a 15 watt amp into it.

But it's loud enough to play in a basement with a couple other players, and it has a great sound for recording.
Rickrew
#18 Posted : 6/3/2016 12:51:40 PM
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Excellent idea, Renton. Certainly worth a try, though it seems to defeat the portability appeal of these small amps.

The little guy still sounds good for my low-volume jazz gigs, and bedroom shedding. Meanwhile, the practice space for my rock band has another amp I can use, so convenience is preserved and so is the health of my back.

Thx again.

Rick
AF75 TRS
AS73-12
Epi LP dbl cut w/p90s
Epi Nighthawk RI TA
Oscar Schmidt OM-30/Mean 90s
Ovation 1984 1612
Fender Blues Deluxe
Tracy Dae
#19 Posted : 3/6/2017 8:33:15 PM
Tracy Dae


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I was off work last Friday so I did some guitar pedal mods/repairs. A BBE Ben Wah that was full of cold solder joints. A BBE Boosta Grande that the owner wanted to replace the general purpose TL071 opamp with a quieter pro audio OPA134 opamp. And my own BOSS GE-7 EQ that I pulled out the three general purpose (and noisy) TL022 opamps and replaced them with much quieter and cleaner LM4562 HiFi pro audio opamps.

I thought about using OPA2134PAs in the GE-7 because I am very familiar with how great that opamp sounds for guitar circuits but since it is an EQ I wanted it to be as tonally transparent and HiFi as possible... Mission accomplished. Both the GE-7 and the Boosta Grande sound fantabulous now - and much quieter than before.

Re-melting all the cold solder joints in the wah resolved it's issues as well.


The mind is like a parachute...
...It only works when its open.
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