I’ve now gotten confirmation that issues working at 44.1kHz are present on the original Ensoniq SCSI boards. At this point it seems that certain manufacturers, or possibly batches of IC’s are the source of the problem.

The SCSI board provides circuitry to isolate the signals to and from the DAC and ADC to eliminate noise and jitter. One of these signals is the 256Fs clock (256x sample rate) which is over 11 Mhz. Because of the design of the circuit, IC’s that are slightly out of spec won’t work properly. This isn’t the whole source of the problem, though. Some ASR-10’s exacerbate this situation, which I believe may be related to the revisions of the custom chips on the main board. So a SCSI board with an out-of-spec IC may work fine in one machine and have problems in another.

I have suggested a possible fix to a user who has this issue, if the fix is successful I’ll post it.

I’ve finally resolved the issue that was affecting some ASR-10’s from working properly with the SCSI board.

I’ll do another post with an in-depth discussion of the issue, but I’m almost certain that this issue affects the original Ensoniq SCSI boards as well. Unfortunately I sold the only genuine SP-3 board that I owned, however I’m building a few of the older generation of the SCSI board (which is 99% the same as the Ensoniq board) to verify this.

If you have an original Ensoniq SCSI board in your ASR-10, you can check for the problem by toggling between 30kHz and 44.1kHz. At 44.1kHz you will hear distortion or audio artifacts. It doesn’t happen every time you switch, and it will sound slightly different each time.

If it turns out the problem does exist on the original SCSI boards, I will be offering a solution to fix it.

I haven’t updated things in quite a while. I hope that you are all well and that the pandemic hasn’t impacted you too severly.

Personally I have had some substantial changes this year. I quit my day job back in July. Besides having to spend 3 hours each day in the worst traffic in North America, I absolutely hated the job. I’ve had more time to work on some of these projects (though, a lack of income has hampered that somewhat…)

Here’s the status of various projects at the moment:

KORG DSS-1

Parts are becoming more scarce and the ones that are available have had an increasing defect rate. Nevertheless I have been making small quantities of the upgrade. Some very good news is that there will be a firmware update that fixes some major MIDI bugs with system exclusive transfers. I’m also working on a Midi Quest profile to handle the expanded sound and sample banks.

The DSS-1 upgrade will be $350.00 including installation once it’s available.

ENSONIQ ASR-10

I stopped selling the SCSI board for the ASR-10 as an issue cropped up with some ASR’s when using a 44.1kHz sample rate. Frustratingly, my ASR-10 here didn’t have the problem, nor did a second unit that I purchased. Finally, I just received and ASR-10 that exhibits the issue and I have been able to trace the source of the problem. I’ll do a separate post about this. Hopefully the problem will be resolved and the boards will be available again in January 2021.

Once available the SCSI kit will be $199.00 plus shipping.

The DI-10 digital I/O board will be undergoing a redesign to make it all surface mount (as many companies won’t do through-hole assembly anymore, and through-hole components are disappearing from many suppliers’ inventories). Many of you have asked if the overheating problem with the rack ASR-10’s have been solved (as it relates to the sample rate of the interface). I now believe that it is not limited to the rack but the keyboard as well. It seems that the earliest revisions of mainboard (the ones with lots of wire jumpers) are prone to this issue. One of the ASR’s that I have has this issue, so I may be able to come up with a solution.

The DI-10 kit is $179.00 plus shipping.

ENSONIQ EPS16 PLUS

Both the SP-2 SCSI kit and FB-2 Flash Bank are both available. I did have an issue with an incorrect resistor on the FB-2 which resulted in intermittent operation. This has now been corrected.

Both kits are available for $159.00 plus shipping.

SEQUENTIAL PROPHET VS/STUDIO 440

The CEM5530 clone is still available.

The price is $75.00 each plus shipping.

SEQUENTIAL PROPHET 3000

I have both the I-627B adapter (for rev A machines) and the 4 MB memory expansion available. Rev. A machines require the I-627B voice chip upgrade to properly address additional memory. Unfortunately the only source for this chip was Wine Country Productions, who have stopped selling it due to a high defect rate. Those lucky few who have purchased and I-627B with hopes of upgrading can upgrade to the full 8 MB (4 Megaword).

Both the adapter and the memory expansion are $99 each plus shipping.

SEQUENTIAL PROPHET 2000

I have developed a memory expansion for the Prophet 2000. This will be going into production soon.

Price TBD.

DYNACORD ADS/ADS-K/ADD-TWO

I have the 2MB memory expansion available as well as the memory terminator.

The price is $129.00 plus shipping.

OBERHEIM OB-Mx

Though the OB-Mx voice board has been complete for some time, some of the IC’s are completely unavailable now, particularly the CEM3382. I have made an adapter board to use the SSI2162 VCA, which is undergoing testing. At this point it’s not economically viable to produce these boards but that may change in the future.

Price increase: Sharp-eyed readers will notice that prices have gone up. I’ve had to outsource most of the assembly and testing, and component prices have gone up, as well.

Shipping: I now ONLY use Parcel Monkey for international shipping. The rates are not much more than shipping through the post office and they are much more reliable, and faster. Generally, shipping outside of the lower 48 states will be $40-$50 (Canada is slightly cheaper).

IF YOU ARE INTERESTED IN ANY OF THESE UPGRADES, OR HAVE A QUESTION, PLEASE USE THE CONTACT FORM, NOT THE COMMENTS SECTION. THANK YOU.

IF YOU HAVE PREVIOUSLY PURCHASED AN UPGRADE, AND ARE HAVING ANY ISSUES WITH IT, PLEASE LET ME KNOW!

Specifically, the older ASR-10 SCSI boards with a “WD” square SCSI chip need to have this chip replaced. Also, the Flash Banks that I have sold that have a 2.2k resistor in the R9 position need to have that resistor replaced with 100 Ohm. I will do either repair free of charge.

The ASR-10 SCSI boards are now back in stock. Featuring an all-new design using surface mount components, jumper-selectable active SCSI termination, and a new lower price of $199.00 USD (down from $249.00).

The board also supplies SCSI termination power and can power a SCSI2SD with it.

Use the Contact Form (not the comments) to order a kit. Shipping is 10.00 USD in the continental USA, 30.00 rest of the world. When ordering, let me know your PayPal email address and where you live.

I no longer ship USPS, as there have been too many lost packages and delays.

All new SMT design.

I did a RAM upgrade for the Prophet 3000 a few years back. Unfortunately, it didn’t work correctly, and I didn’t have the motivation or the time to figure out why. It was strange in that it would fail some tests and pass others.

To give a bit of background, the Prophet 3000 has several custom chips. Two of them, the “I-627” (voice controller) and “I-628” (DMA controller) share control of the sample memory. The I-627 plays back samples and the I-628 transfers samples from SCSI or the main processor to sample memory. The diagnostics let you run memory tests with either the I-627 or I-628 controlling the test. The board I built was passing the I-627 tests but failing the I-628 tests. I figured that the problem was somehow timing related but I decided to shelve the project.

A few months ago a friend purchased a beat-up P3000 that had been in a storage shed for years, and asked me to restore it. After many hours of ultrasonic cleaning, rust removal bath, IC socket replacement, re-capping, and replacing regulators and a few defective parts, it was up and running again. I decided to revisit the memory board issue. I used a logic probe to look at the memory timing and discovered that the I-628 is much more sensitive to timing than the I-627. The memory address and data buses are multiplexed and the address bus itself is multiplexed. Therefore, the 16 lines share three pieces of information: address row, address column, and data. Two other lines, RAS and CAS, go active as these transitions take place. What happens with the I-628 is that the address row and column transitions are too close to the RAS and CAS signals. Memory chips have a “setup time” where the address has to be valid for a certain period (usually a few nanoseconds) before the corresponding RAS or CAS signal activates. The onboard P3000 memory has IC buffers that add a bit of delay for these signals, and my board was lacking those. I had assumed that the buffers were there to reduce the load on the sample memory bus, but it was also adding the necessary delay.

I modified my design with simple logic gates to buffer the RAS, CAS, and memory read and write signals and got a few test boards made by OSH Park. And now it tests perfectly.

I also discovered that certain brands of RAM fail the memory tests due to out of spec timing (this is the RAM that goes in the expansion sockets on the motherboard). Hitachi was OK, the original AT&T RAM was OK, but Mitsubishi would fail testing after a while (due to heating up, I guess).

And finally, none of this would be possible without a new I-627 rev B chip. I made an adapter for the first generation P3000’s with the PGA style I-627 to enable fitting the PLCC package I-627B. The original I-627A couldn’t deal with more that one bank of RAM for some reason. Unfortunately Wine Country seems to have stopped selling the I-627B’s, so at this time the only P3000’s that can be upgraded are the second generation.

To start the new year, the EPS16 SCSi boards, the 5530 replacement modules, and the DI-10 are all back in stock. Use the contact form (not the comments) to get in touch if you’d like one.

I’m going to try and get at least a prototype of the new DSS-1 upgrade finished by June. It’s been a difficult couple of years with work related turmoil and other issues preventing serious progress on any projects. But, so many people are asking for the DSS-1 upgrade that I feel I need to finally produce results!

In recent months I’ve been learning KiCad, which is an open source EDA package available for many platforms. Version 5 has just been released, and it now imports EAGLE projects. EAGLE has been purchased by Autodesk, and they have been rapidly improving and updating the software. The only problem is that it is now a yearly subscription model, and I can’t justify spending $500.00 per year when I don’t do PCB design on a regular basis. EAGLE version 7.70 has served me well up to this point but KiCad is free and also has many of the features of the new Autodesk EAGLE. It doesn’t have an autorouter, but I’ve rarely used one in the past anyway. It does have interactive push and shove routing which I find to be more useful.

I’ve also updated the links section with a few corrections and additions.

 

Just received the SCSI boards from the manufacturer and they look great. This time, made them ENIG instead of HASL (better quality). And because I got more made this time, the price is now $129.00 instead of $149.00.

Send me an email (via the contact form) and I will send you a PayPal invoice. Make sure your shipping information in PayPal is up to date, and let me know the PayPal email address, and where you are located, so I can calculate shipping.

 

 

I’m currently organizing to get another batch of EPS16 SCSI boards made. I’m doing a bigger order this time so I won’t run out as quickly.

I have completely sold out of all the other boards, but will get more made, depending on customer demand. This includes the 5530 clone board and the ASR-10 SCSI and digital input boards.

I had some left over bare boards and parts from the first generation DSS-1 upgrade. It’s been quite a while since I built those, and getting all the pieces together was more work than I thought…the parts are harder to get now, the Xilinx ISE software won’t run properly on Windows 64 bit, I didn’t properly document which versions of the design files should be used, etc. Finally got them finished, though.

Many people have been asking about the new version, and unfortunately I don’t have an answer yet. I do have a large amount of the hardware design done, and getting the last of the original upgrades finished off has put me in the right frame of mind to continue on with the project. Time is the biggest resource that I lack. I’m at work 60 hours a week and unable to do work on outside projects during that time, and those of you with children know how your free time disappears on the weekends.

In the meantime I’ve started a few smaller projects, experiments really, to keep active. One of these is a digital output board, so you can bypass the DAC’s. For those synths and samplers which are mostly digital anyway. I’m going to try modifying a few of my synths and see how it goes. Will it sound better, bypassing the ancient analog sections? I’m going to find out.