Ti Vintage Audio

Modified 1960's Roberts/AKAI Tube Tape Recorder Preamps

The current look for modified units. This is just one thing that sets our Ti Modified preamps apart from units just taken from a Roberts tape deck. Future upgrades will include no empty holes... As with current models, knobs and VU meter designs will vary depending on the original unit (see below for variations). If you're trading up, you may not be able to get one that exactly matches your current one immediately, you may have to wait or take a different one. The unit pictured here is the more "modern" looking square VU meter. NOTE: we're currently experimenting with adding input and output switching. This will change the appearance of the face plate somewhat from what is shown.

UPGRADE POLICY FOR ORIGINAL PURCHASERS
Don't you hate buying software only to find out that in two months there's an upgrade that you have to buy that adds up to more than the new cost? How about buying a computer one day, and the next day a new model is out that goes faster, has more memory, and costs less?? Technology is always advancing, why hasn't anyone figured out a way to honour those customers who are the first to buy?
This is why I've set the following policy for the original purchaser of my preamps:
If you've bought ANY Roberts modified preamp from me, I offer the following upgrade: Return your unit to me (insured), along with the difference between what you originally paid for the unit and the current price for a "new" unit, plus the shipping amount to get the new unit to you, and I'll send you a "new" one with the current set of mods done. If you've drop kicked your current one, please don't expect me to honour this without contacting me honestly beforehand with details of what has happened with your preamp, I'm sure we can work something out. This offer is only for original purchasers.
If you just can't part with your first unit, I'll give you $50US off the price of a second one!

If you purchased one of our older style units (pre June 2005), now may be a good time to trade up! You may catch us at an upgrade junction where the price hasn't been adjusted up yet. email me for details on your specific case.

PRODUCTION UPDATE

Feb 1, 2007: Eight months; one more move, several months preparing a leased location, false start due to a leaky roof/ceiling, finally the work on the workshop is able to be continued. Those awaiting backorders deserve sainthood, those who would like to order units should wait until notification is posted here that I've been able to catch up with production.

May 24th, 2006: I am in the last stages of a move of both my home and workshop. Weather permitting, I will have my workshop set up again by this coming weekend and be able to resume production on the seven units currently backordered for clients. Once these are completed and shipped, I will again post units to ebay. It has been a frustrating past six months for myself and some of my clients with production problems related to the aluminum cabinet supply. These problems are now resolved, with a new design for the aluminum parts that allows more flexibility in suppliers. I will post another update before the end of May.
GENERAL NOTE ON PRODUCTION: Please note that if you've ordered or won one of these preamps recently, production is slowed down by a few factors, some out of my control. From time to time parts are in short supply, especially if I've made a decision on a new modification. My apologies to the delays, rest assured that you will receive more than what you expected.
As I am constantly looking for ways to improve on this preamp, I will also occasionally hold up production for a few days if I'm tackling a new change.
 
NOVEMBER 14th: I am exploring ways to isolate ground in the units, to overcome low level loops. I have the assistance of a good friend, Charlie (a wizard on tube circuits as well as a mighty fine fellow), when designing challenging modifications. We are currently exploring fairly major upgrades to the circuit, amongst other things - possibly adding phantom power, polarity reverse switch, input pad, EL84 bypass switch.
 
These changes will sometimes cause production to slow down, but in most cases you will automatically get any new modifications done to your unit, even if the price has gone up on new units. Please email me if you're concerned. Note that I am not currently emailing if a unit's production is being held up, unless it is over 3 weeks. If you haven't received notification of your unit shipping two weeks after payment has been sent, please feel free to email me for an update on your order.
October 24th update: I'm installing an input selection switch on units produced as of today. This will result in the unit having one xlr on the back and one high impedance input on the front. You will be able to select which tube circuit is being used for either input. I may also add an output selection switch, for line or speaker level.
November 16th update: Along with trying to confirm the ground status in the preamps, I'm also finding a generally questionable quality level in some small switches related to my changes in circuit path. This has delayed the work on input and output selection, but I hope to have it resolved in the next few days. I have found a lighter weight shielded cable that is allowing for less strain in some of the tight wiring spots.
I've received the first shipment of the new aluminum cases. These have a full depth bottom with vents, and the top still goes only as far forward as the tube section, which is covered with vented aluminum panels as with the current model. I will post photos over the next few days of all new parts.
The rack ears have also arrived. They will ship with holes for attaching to the preamp, but not for the rack, this will be up to how one wishes to mount them. I'll post photos of these as well in the next few days.
 
Prices for raw parts: aluminum case with vented top piece and rack ears (new model) $93US plus shipping
Same as above, wired with xlr, fuse holder, fuse, power cable, output jack, ready for installation, includes screws (requires some soldering and drilling) $143US
Simple instructions for attaching/installation included as well.
PERFORMANCE UPDATE
Ti Modified preamps have been used by me in performance with Valdy, Bill Henderson (Chilliwack), and Corbin Keep (the wild cellist) and Jaime RT. I run my pickup from my 1921 Weissenborn style slide guitar through one of these tube preamps. Corbin Keep used one for his cello in performance on Oct 1, 2005 with great results! For that same performance, I ran an RCA 77DX ribbon mic though one for my vocals. Rodney Gage (pedal steel with Roger McGuinn) is currently using one with a Neumann U87 for recording vocals, I'll let you know what he says about it! (sadly, we lost Rodney to cancer just before Christmas. In a short time he grew to be a cherished friend, we will miss him dearly).
If you've used a Ti Modified Roberts AKAI preamp on a recording, please feel free to send a good quality mp3 file and I'll post it on this site. Please note what the preamp was used on so that folks can tune in to the specific instrument or voice.
WHERE TO BUY
TI Modified Roberts AKAI preamps are currently available direct from this site, on ebay (search for username "donnting"), and from Long & McQuade music store in Victoria BC, Canada (ask for Mike Arensen). Long & McQuade has sold 1 unit so far, and has one that they keep in rental rotation in the Pro Audio department.
Booklet/Manual
I'm working on a printed booklet/manual which will also be available in pdf format, covering information on the preamps and their use. I will post the pdf when it is completed (update 2/1/2007).
The manual will cover all units to date, with variations on circuits noted.
Note that we've also begun to assign serial numbers to the units and if you've purchased a unit you will receive a sticker to apply to your unit. This serial number will be assigned to a registration record here, in your name.
IMPORTANT: We will also ask that you check out the style diagrams below and email us with your name, current contact info including address and phone, and the specific style(s) you've received. This would also be a good time to let us know how the unit is working out for you (please specify if we can quote you on our site). It is an especially good time to let us know if you're having any problems!

HISTORY

My experiments with the Roberts preamps from their early 1960's preamps began AFTER looking for a totally tube high voltage mic preamp and buying a "BRICK" made by Groove Tubes. The concept looked great, but I found that the BRICK didn't have as much gain as I was hoping for, and lacked a meter and more importantly, didn't impart any real character to the sound. It also cost quite dearly. It should be noted, Groove Tubes builds some fabulous gear, and the "Brick" is no exception - it was just too clean for what I was looking for.

Units NOT up for Auction on eBay! Please see notes above for details.

NOTE: If your preamp has the added case on it as shown, inserting a 1/4" plug in the front mic jack will increase the gain for a microphone plugged into the xlr jack on the back. Use an rca to 1/4" phone plug available from Radio Shack, NOT a 1/4" plug with cable attached. If in doubt, please email me.

I'm not sure when I clued in to using eBay to look for what would suit me better, but it did happen. I furiously started buying up various sleepers, anything that looked like it had a nice combination of tubes and a self contained power supply. This is when I also started buying up old tube broadcast consoles and grabbing parts for my own Frankentarris recording console.

When I first picked up a pair of the Roberts mic preamps, I didn't know what they were - well, I did by the time the auction closed. After researching, I found that they were from early 1960's tape decks made by AKAI/Roberts. When the first pair arrived I was impressed with the completeness of the circuit - a fully contained power supply in each unit AND they were modular - could be removed from the tape recorder case. The lower one could even be plugged into a wall socket (in most models) and used as a complete standalone unit. Note that they were unbalanced input, fine for instruments or high impedance mics, but lacking for low impedance xlr microphones. Some more audio samples will be posted soon, please check back often. For now, check out this one (click here for mp3 file)

I added transformers, several different varieties of makes and models, looking for the one that complemented the preamps the most. Currently, I am expecting an order of new "vintage style" Sowter transformers soon. I'm not sure of what the actual input/output impedance is on some of the used transformers, but they sound nice and bright with a tight bottom end when used with my Apex 450 condensor mic (35% volume setting), and have enough gain to get good signal from my RCA 77DX ribbon microphone (80% volume setting).

In each preamp there are actually two circuits; one for the mic and line input, and one for the tape head playback. I've just begun to experiment with the head circuit, which includes the tone control. You want to be careful taking the output via the speaker out when using this input, and may want to use the "pre amp out" instead, which cuts the VU meter out of the circuit and protects its needle from a permanent bend. In future I will be placing a pad across this input to tame the circuit for a mic input.

A wee note of thanks - to Rod Childers for kindly sharing information on his own modifications done to this model of preamp. I haven't had a chance to complete a unit using his instructions, but will note the results once I get time to do so. Following that, with his continued permission, I will post his instructions for those who are familiar with high voltage electronics and feel comfortable trying modifications themselves. Note that we aren't currently using Rod's instructions on our units, but this doesn't mean that they're not good, just that we haven't had a chance to try them.

Custom Enclosures

(Last version shown, photos of new design coming)

I now have metal cases to cover the back of the units and rack ears for standard 19" rack space, while also allowing for better connections for xlr input as well as power cord and fuse assembly. These are offered for sale in various configurations;

  • raw (back, top vent, rack ears, screws; photo coming soon) $93US each set.
  • simple prepped (as above with the back punched for power cord, fuse assembly, and xlr input jack; purchaser responsible for final fit on holes. Includes 2 plastic spacers for top mounting, screws; photo coming soon) $119US each set.
  • full dressed (as above, complete with power cord and fuse assembly mounted, along with XLR input jack and 1/4" output jack) $143US each set. (photo coming soon)

Email me if you want to order one. Shipping is extra, BC residents pay GST and PST, other Canadian provinces pay GST. More photos will be posted soon. The three pieces consist of a vented top, vented bottom, and solid back. They dress the unit up very nicely, as well as protect the high voltage areas from wandering fingers.

Face Plate Labels

This is the faceplate design (although "Preamp Out" has now been added just below the "Mic Input 2") These labels are printed on photo quality paper, followed by a spray process for added durability. The back is self-adhesive. Care should still be exercised when cleaning the faceplate, best done with a soft lint-free cloth.

New labels are available now for $25US each plus shipping. Two on one sheet are $40US plus shipping. The labels are supplied with adhesive backing. Layout is similar to what is shown. Purchaser must perform the final cut and trim. We have settled on a laminating process for the labels. Labels ordered for units we haven't modified will NOT have reference to "Ti Modified".

Knob and VU Meter Styles

These are photos of original units that I start modifications from. Unless you specify one particular style, you will receive whatever one is pulled from the shelf next. I am producing units in the K3M4 style first, then working back in vintage from there. If you want me to jump the line, I may have to charge an extra $20US if your order leaves me without a pair of a particular style left. You would be notified of this before payment was expected.

Note that colours in these photos are not correct. Unless specifically asked for, we never supply units with the original faceplate as it doesn't reflect the changed purpose of inputs and controls (would be confusing to the end user).

Roberts AKAI K1VU1 - knob style 1 (plastic), meter style 1 (large plastic)

Roberts AKAI K2VU3 - knob style 2 (plastic + metal), meter style 2 (small plastic)

Roberts AKAI K2VU3 - knob style 2 (plastic + metal), meter style 3 (large plastic or glass)

Roberts AKAI K3VU4 - knob style 3 (metal), meter style 4 (large metal + glass)

PURCHASE

If you're interested in buying one of my modified preamps, you can do so by contacting me at donn@tarris.ca and I can calculate shipping. To the 48 lower states the cost is $40US, to Canada the cost is $30US. The preamps are sold in auction at eBay (search for items for auction by "donnting"), or you can buy direct for $429US plus shipping based on where you are. As I do more modifications the price will go up, but you'll get more for the money. On eBay you may get a chance to buy one at a lower price - it could work out to a great deal!

If you find, or have, a Roberts or AKAI tube tape recorder

and would like me to modify its premps for you, write to me and we can discuss the details. Basically, you'd have to cover shipping/insurance to and from my location (V8K 2M2 in BC, Canada or you can ship to 98281 in Washington, USA, and the return from Canada), plus $145US per preamp for labour (plus 7% GST for Canadian residents) PLUS the cost of the parts, including input transformers. Total for parts (as of October 24, 2005) is $179US plus applicable taxes. New or tested tubes would cost extra, quoted before replacing. This is a total of $324US per unit.

I will buy!

If you have an old recorder sitting around collecting dust, I will purchase specific models of working Roberts/AKAI tube preamps, including tubes, for $25US each (there are two in each recorder usually) plus shipping, in or out of the recorder case. Payment is by paypal or money order, whichever you prefer.

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This site belongs to Tarris Innovations on Salt Spring Island in beautiful British Columbia, Canada. Tarris Innovations supports Apple Mac computers as well as fine audio gear for analogue and digital recording!

www.tarrisinnovations.ca