Here are some things to try first:
1. Try different cables on the input and output.
2. Connect a different preamp/line level device with the same cables and see if it works.
3. With preamps, try a different mic. (make sure phantom power is on or off as required).
4. Bypass all patch panels and connect the inputs and outputs directly.
If you are still having a problem, contact us by e-mail (firstname.lastname@example.org). We can often offer suggestions that may help you to do the repair yourself, especially if the problem is a defective tube.
To return one of our products for warranty repair, out-of-warranty repair or for a check-up, please use our RMA form. Print the form and include it in the box with your unit.
1. Use the original box and packing material if possible.
2. If you use your own box, make sure it has at least 2 inches (50cm) of room on all sides of the unit. The box should be a heavy-duty type (275lb — see the circle on the bottom of the box).
3. DO NOT USE PACKING PEANUTS! The majority of units we receive this way arrive with some damage. Packing peanuts are for light-weight, fragile objects. They should not be used with heavy equipment like we make.
4. Surround the unit on all sides with at least 2 inches (50cm) of bubblewrap or foam inserts designed for shipping rack-mounted equipment.
5. Be sure to include the RMA form.
We give priority to warranty repair items. Other repairs may take a little longer. Our shop is small and we do not have a dedicated service staff, so please allow a couple of weeks for us to work on your unit.
Replacement Tube Information
The tubes used in our products are operated with tightly-regulated voltages on all elements, and the equipment is designed to provide good air flow. Tubes should last a long time.
How long? It’s difficult to predict, but a recent review of our records indicates that tubes replaced for failure are less than 0.3% of all the tubes in equipment manufactured since 1993!
If a tube does fail, it usually becomes more microphonic (it picks up mechanical vibration in the room where the preamp is located). Occasionally a tube will completely fail for no apparent reason, but we have only seen a few of those over the past 16 years.
If you have a defective tube (or suspect that you do) contact us via e-mail or telephone and we can suggest some easy tests to help determine where the problem lies. We will be pleased to replace any defective tubes under the 90-day warranty.
If you need a replacement after that time, we can supply them. These replacements will meet all the original specs of the equipment. The current prices (plus shipping) are listed below.
FOR VT-1, VT-2, VT-24, or VLC-1 MIC PREAMPS:
The VT-1 VT-2, VT-24, and VLC-1 have exactly the same circuit. The VT-1 has two tubes; the VT-2 and VLC-1 have four; the VT-24 has eight tubes. All are type 6072A, but the tubes used in the input stage of either preamp must be selected for low-noise and microphonics. The output stage tube is less critical. We test and grade all our 6072As and assign them to either Input or Output duty (or throw them away if they don’t make the cut).
The supply of GE NOS (new old-stock) Mil-spec 6072As that we have used since the beginning have been depleted and are no longer available. We have switch to a Russian-made version of the tube, which we find can be an excellent performer but the yield of tubes that meet our specs is very low. We typically run the tubes for 1 to 2 weeks before testing, and then we find only 1 out of 20 is good enough for the input stage of our products. Many of the remaining tubes are fine for the output stage. We throw away about 10% of the tubes as being unuseable. The long-term life of these tubes is not yet clear, but some of these tubes were used in our products in the past and seem to have held up well (at least 5-10 years.)
The low-noise select 6072A for the input stage is $76.00 and the tested 6072A for the output is $51.
FOR THE VT-4/VT-5 EQUALIZERS
The VT-4 uses 4 tubes, all type 6N1P. Completely tested and graded tubes are $40.00 each.
FOR THE VT-7 COMPRESSOR
The VT-7 uses 8 tubes. Serial numbers below 300 use 2 type 6072A and 6 type 6N1P. The 6072A must be a low-noise select tube, available from us for $76.00 each. The 6N1P completely tested and graded are $40.00 each. Serial numbers above 300 use 8 6072A tubes. Only 2 need to be low-noise select tubes.
For the VT-I/F Instrument Interface
The VT-I/F uses a single 6072A in each channel. The $51 version is fine for replacement, although the higher-spec $76 tube may give you a few dB better noise performance. In practical use, it is unlikely to be a noticeable difference.
For the VT-3 Vacuum Tube DI
The VT-3 uses two 6N1P tubes. Replacements are $40.00 each.
You can order spare or replacement tubes directly from us. Please contact us at email@example.com.