The Prophet 5 was the first truly programmable polyphonic synthesizer and was produced by Sequential Circuits for the last part of the 70’s and the better part of the early 80’s.

As with most things on the internet, there is a massive amount of misinformation, especially concerning the quantifiable differences between the Rev 2 and Rev 3 units, the Prophet 10, the production Prophet 10… on and on. In this blog post, we aim to share our knowledge of the Prophet 5 to aid you in your next synth purchase, sale, or maintenance ideas.

 

How Many Prophet 5’s are there and why?

(p5=Prophet 5, p10=Prophet 10)

To put it simply
Rev 1 P5: First revision of the p5. Generally, but not always, unstable due to early design choices. Very few production models still in existence (many were recalled to factory in exchange for rev 2). Same SSM chipset as Rev 2 but CPU and voice boards have differences, biggest being the additional ribbon header to support 10 voices. Rev 1 be visually differentiated from others by noting the top panel mounted power switch.

Rev 1 extremely hard to find, not worth owning unless you collect, and can be decently stable if you have a good tech. We are happy to work on them, and we know that Greg Montalbano in Oakland CA has had great success restoring them.

Rev 1 P10: This is the model you will likely never see in your life (we have seen one). This is the same as a Rev 1 p5 except it has a second voice board installed. Extremely unstable due to heat. 

Rev 2 P5: The rev 2 was a more refined version of the rev 1 architecture. There are less flying trimmers and strange kludges but surely not free of them. Uses again the SSM chipset. Repairs can be difficult on this. Only recommend if you have a trusted local tech. EPROM voltage requirements and a beaten-to-death 5v regulator can make lockups sort of regular on these, but may be indicative of other failures. If restored (see future blog post for the difference between restored and repaired) can be very stable and very useable. Modern custom firmwares have proven to increase its practical usability to boot. 

We only recommend this synth for those who must have the SSM sound and maybe already own a Rev 3.1+. They can be visually identified by looking at the volume knob position. On the Rev 2, the volume knob is on the same row as the master tune, near the rear of the synthesizer.

Contrary to inaccurate information on the interwebz, yes, you can add midi to the rev 2 prophet 5.

Rev 3.0 P5: This revision series is the actual “classic” synthesizer (whether you want to believe it or not). Most of the hits the Prophet 5 is known for were performed with Rev 3 series prophet’s. The Rev 3 was born out of necessity, as the Rev 2 proved unstable for the studio or the road. Additionally, problems and loose tolerances offered by the SSM chipset caused production issues for SCI, sparking the change to a CEM chipset.

The Rev 3.0 however is the worst Rev 3 you can possible own, and that’s not from a sonic perspective. In essence, the Rev 3.0 prophet is a Rev 2 computer architecture that is optimized for the new CEM chipset. The boards are totally different than a Rev 2, however specifically the 6508 ram chips (of which there are 8) can be troublesome as well as the 2708 EPROM’s which require 5 voltage rail PSU’s. If the machine can be converted to a triple voltage rail, it will be more stable, however the 6508 RAM chips will always be problematic, and will account for some very annoying bugs in your patch programming that can only be avoided by replacing the RAM architecture, which is available through other sources. Though the Rev 3 isn’t a misfortune to own, if you’re in the market for a Rev 3 prophet 5, you may consider sourcing higher Rev 3 revisions.

Rev 3.1, 3.2, 3.3 P5: These were the final prophet 5’s made, and contained the same voice card as the Rev 3.0. The only notable difference is the CPU boards which are optimized to use 3 voltage rail PSU’s and use a different type of RAM and EPROM architecture, allowing for higher reliability, and an easier time troubleshooting for your tech. These are often fitted with midi from the factory or were retrofitted during their first ownership. It is not too common to find these revisions without midi. Generally, these are usually also fitted with the 120 program factory mod, allowing for more patch storage.

Prophet 10 (SSM): I only know of 2 that exist, and neither of them work. These are prototype dual-manual prophet 10’s that used a rev-2 like architecture, SSM chips and all. 

Prophet 10 (Production model, CEM chipset): These are essentially 2 Rev 3.1+ prophets in one case with two keybeds. Contrary to internet nonsense, there are no prophet 10’s that don’t have auto tune. Also, yes, it’s two prophet 5’s. The voice boards are prophet 5 voice boards. They’re not hard to get running, and should they be properly restored, they stay in tune just fine. 

To touch on some slight differences, the prophet 10 does have some new panel features.
1. Initial LFO amount, which sort of frees up the mod wheel
2. Two pedal assignments. This is my favorite feature. You can use this to blend between the two layers, which is amazing
3. Reverse polarity LFO shapes for layer mixing
4. Programmable active EQ

 

And to round out this post:

Prophet 600: A slimmed down prophet 5 using digital envelopes and a combined VCA/VCF CEM chip. Not truly a “6 voice Prophet 5” GliGli mod does make this unit a lot more useable envelope wise.

Prophet T8: An 8 voice Prophet 600 (not a prophet 5) with weighted keys, velocity, polyphonic aftertouch, splits and layers! A truly fabulous instrument. 

Which One Sounds The Best?!

In our opinion, with all things in consideration, the Rev 3 Prophet 5 is the winner over the Rev 2.

The Rev 2 does have a difference character, but that’s it, and it’s only a tad different. The Rev 3 is not harsh, and has a very exaggerated low end compared to other synthesizers, same as the Rev 2. We are 100% convinced that the people making judgments between the Rev 2/3 either have not owned both at the same time to compare or did not have well calibrated machines. Further, there is the assumption that more drift between oscillators is a warmer tone.

After a long rental of both to a well known indie rock band:

“I wanted to believe the Rev 2 sounded better but blindly there was no difference granted I could get a well tuned take on the Rev 2. I had to hit tune between takes, and it takes forever to do that and overall I spent more time getting it to sound right than actually recording. The Rev 3 was straight forward and got me the Prophet sound immediately. I had to hit tune once every half hour or so.”

The Rev 3 made it onto the record.

Yet psychosomatic internet forums will swear to you up and down and from here to there that the Rev 2 is the only Prophet 5 worth owning. To each their own, I suppose.

 

Which Has Midi?

All of them, perhaps sans the Rev 1, can host midi. Contrary to easily accessible info, Kenton has had a Rev 2 midi kit for over a decade now. Most Rev 3’s have midi from the factory or a JL Cooper board inside. There is no kit that is better than the other for the Prophet 5. The Prophet 10 can also be upgraded with midi. As with all of these, they should really really be installed by a competent synth tech.

What Should I Look For When Buying One?

This is an important question. The first thing to discuss is the dangers of owning a Prophet 5. After, it’s important to understand what services your prophet should have if it’s advertised as already serviced, and thusly what type of costs you could be looking at to have it serviced after buying a questionable/virgin unit.

Dangers:

  1. All Prophet’s are littered in tantalum capacitors. These tend to fail causing a short, and that can heavily damage the the Prophet’s valuable IC’s.
  2. Rev 2 Prophet 5’s contain SSM IC chips, which are very difficult to find and expensive when found. The SSM VCO is not user replaceable. Rev 3’s contain CEM3310’s which are now reproduced, and cheap. It is critical you bring your prophet to great condition before using it.
  3. Due to their architecture, many tech’s will not work on a Prophet 5, and when they do, it might burn a hole in your wallet.

The first thing you want to find out is the service history and ask for photos of the inside (especially if it will be sold “as-is”. Below is a photo of the tantalum capacitors in the PSU and voice/CPU cards. If you see those anywhere, either walk away or ask for a lower price. Do not power the Prophet until you bring it to your tech and they rid it of those capacitors and check for voltage rail shorts.

Ask the seller if the keyboard is “loud” or “clacky”. If they tell you it’s been rebushed, ask who did it and where the bushings came from. If the bushings were lubricated with vaseline, which is common, expect keys to start sticking soon as the bushings swell up. Our bushings don’t swell and come lubricated with the proper compound.

If the Prophet needs a full service, you can expect to probably be out about $4-800 depending on your tech. Assuming all of your signal path’s work, most prophet 5 repairs average about $600 including parts.

How Much Do They Cost?

An unknown condition prophet 5 with no service history, or one that is a “closet find”, found in a garage, storage unit, etc, should generally be sold for ~$800-1500 After all, you are literally buying a pile of parts to be presumably brought back to life by someone reputable. Lower end assumes the parts cannot be guaranteed to be working. To qualify that as a question, just ask the owner if they’ve tried to turn it on. If their answer is yes, and no sound came out, but they swear 30 years ago it worked fine, that doesn’t mean turning it on didn’t ruin the chips inside.

A Prophet 5 Rev 3.1+ that has been restored by your average technician with replacement parts of unknown origin and unknown history of all calibrations and alignments should be sold for $3000-4500 (higher end with midi)

A Prophet 5 Rev 3.1+ that has been restored by a reputable technician, with proof and description of all calibrations, services, and high quality replacement parts, in decent or good cosmetic condition, should be sold for $5000-6000 (higher end with midi)

A Prophet 5 Rev 3.0 worked on by your an average tech should fetch $2800-3500, if worked on by a reputable tech, no more than $4000

A Prophet 5 Rev 2 seeing as it is a collectors piece should be sold as a virgin for $2000. If it has been serviced by your average tech, they should fetch you $4500. If they have been serviced by a reputable technician, they should be sold for $5500-8000. The higher end of the spectrum should include a converted PSU to triple rail, a stabilized 5V line, midi, and a warranty 🙂

A Prophet 5 Rev 1 should always be sold AS IS with no guarantee. A virgin unit is maybe worth $2-3000. A restored unit can fetch 8K+

A Prophet 10 should be sold for 3-5k in virgin or average tech’d state. $8500-11000 depending on the tech and level or service. Higher end should have midi and be fully serviced.