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Q. Why is my Dual Tube Channel so noisy? Is it a faulty unit?

By Hugh Robjohns

Mindprint's Dual Tube Channel (DTC) remains the top choice of many professional users.Mindprint's Dual Tube Channel (DTC) remains the top choice of many professional users.

I recently purchased a Mindprint DTC and I've noticed that it produces quite a lot of hiss. It is not so obvious to the ear at first but after individually compressing instruments and playing them together, it becomes quite nasty. Also, if you are monitoring the signal from the DTC, you notice quite a large amount of noise on the analyser. I purchased the 24-bit S/PDIF module to find the same happens there. Whilst I was sold this as a mastering tool I am wondering if this is a design flaw. I have read some good reviews (including yours from SOS June 2002), but on a few web sites, similar problems are mentioned. I have done all the regular troubleshooting, such as changing cables and checking the power distribution of my system, and it all looks fine. I am wondering why my DTC is so noisy and if it is supposed to be?

Chris Frost

SOS Technical Editor Hugh Robjohns replies: This is tricky to answer without actually hearing the problem you are complaining about and knowing how you are using the product. However, the DTC remains a favourite processor of mine, and I've not had any serious noise problems when I've used it, so I would suspect either an operational problem or a faulty unit.

As it uses valves, it is possible that you have a faulty one, which could lead to excessive noise. Changing the valves is not difficult and replacements aren't expensive — but it might be worth getting the product properly checked-over by a qualified technician, in case anything more serious is wrong. Unlikely, but it's always best to get it checked.

Perhaps the more likely problem is an operational one. Setting an appropriate gain structure is important to optimise the signal levels through the unit. The other thing that intrigues me is that you say: "It is not so obvious to the ear at first but after individually compressing instruments and playing them together, it becomes quite nasty". Noise will always add and build in level, so processing individual instruments with the DTC will always produce a noisier result than simply processing the final mix. But I wonder if, in fact, you are over-compressing the instruments.

Ideally, you could send a short extract of some affected material, but it may be easier and quicker to get the unit checked-out or compared with another unit to make sure all is working as it should.

I've always found Mindprint to be helpful in resolving issues like this, so giving them a call might be a worthwhile step to take as well. Mindprint +49 6851 9050. 

Published October 2006