VTB-1 tube amp alternatives? Or how could I fix mine?

P

purplepeople

Member
Mine appears to have broken. The level bar doesn't light up and the sound quality is a little off. It's almost as if it's clipping even at super low volume levels. Maybe the tube is going bad?

I have a NT1-A mic. It used to sound amazing, but now IMO it sounds pretty metallic. Like the last 3-4 songs I've recorded on it sound like the highs are clipping in a weird metallic tone. Some of the clarity appears to be gone. It sounds sorta flat.

For the past week, I've been trying to record myself saying something with a prominent "P" but no matter what I do, it won't capture the P. Instead it changes it to an S.
What would cause this? It's almost like it's clipping/ducking, but it's not when you look at the waveform visually.

I went to buy a new one and learned it's discontinued.

Are there alternatives for a similar sound?

Any ideas what would the problems with my VTB-1 that I could somehow fix or repair?
 
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It's possible the tube is shot. I don't know a lot about the VTB1. There are used ones for sale on Reverb for around $125. What in particular about the VTB1 did you like vs just using the standard preamps in your interface? Did you typically add in some of the "tube sound"?

The VTB1 is a starved plate design, somewhat akin to the ART Tube MP Studio V3 or Presonus TubePre V2. Both are in the $150 range new, and use a 12AX7 like the VTB1. From there you can step up to something like the ART TPS II.

You could step up to something like a ART Pro MPA II which gives you gain, impedance adjustment and difference in tube voltage. It also has a variable low cut filter. It's 2 channel so you can run two mics at a time.

From there you go up quickly in price, especially if you are wanting to stick to tube gear.
 
TalismanRich said:
It's possible the tube is shot. I don't know a lot about the VTB1. There are used ones for sale on Reverb for around $125. What in particular about the VTB1 did you like vs just using the standard preamps in your interface? Did you typically add in some of the "tube sound"?

The VTB1 is a starved plate design, somewhat akin to the ART Tube MP Studio V3 or Presonus TubePre V2. Both are in the $150 range new, and use a 12AX7 like the VTB1. From there you can step up to something like the ART TPS II.

You could step up to something like a ART Pro MPA II which gives you gain, impedance adjustment and difference in tube voltage. It also has a variable low cut filter. It's 2 channel so you can run two mics at a time.

From there you go up quickly in price, especially if you are wanting to stick to tube gear.
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I like a slight tube sound. I've always recorded with it on 1 or 2. It cuts through an instrumental better.

Could a messed up tube mess with the volume levels bar? That's what I find strange... Regardless of the input volume it never glows more than the first green bar.
 
It is quite a complex wee beast! I cannot find a schematic but have found a photo of the PCB and there is a LOT on there.
About all you can do is check the filament voltage. Should be 12V across pins 4 &5 but they might have gone for 6V across 4/5 and 9. If that is right, are there two reddish points of light in the valve envelope? If not the heater has failed but that is very rare.

If you have glows check anode volts, pins 1 and 6. Without a manual, not a Scooby but somewhere between 4 and 9 V I would guess assuming they are using a 12V "HT" .If you find a supply higher than that anodes should be about half of that. If these checks pan out buy a valve but I make no promises! In such low voltage circuits an ECC83/12AX7 is practically immortal! Even bashed around and hit with 300V they tend to last decades.

If you take it to a tech he will struggle without a schematic (so get on the net!) and "struggle" means "time" and time means MONEY!

Dave.








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ecc83 said:
It is quite a complex wee beast! I cannot find a schematic but have found a photo of the PCB and there is a LOT on there.
About all you can do is check the filament voltage. Should be 12V across pins 4 &5 but they might have gone for 6V across 4/5 and 9. If that is right, are there two reddish points of light in the valve envelope? If not the heater has failed but that is very rare.

If you have glows check anode volts, pins 1 and 6. Without a manual, not a Scooby but somewhere between 4 and 9 V I would guess assuming they are using a 12V "HT" .If you find a supply higher than that anodes should be about half of that. If these checks pan out buy a valve but I make no promises! In such low voltage circuits an ECC83/12AX7 is practically immortal! Even bashed around and hit with 300V they tend to last decades.

If you take it to a tech he will struggle without a schematic (so get on the net!) and "struggle" means "time" and time means MONEY!

Dave.








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Thanks, but I'm not an electronics guy. What you wrote sounds like a foreign language to me.
We have zero repair shops for anything like this around here.
You think it's unlikely to be a simple tube problem and more likely an issue with the motherboard?
I had another of these break about a decade ago. It was a similar problem. But in this case, recordings started to feel incredibly sharp/piercing.
So I know they aren't quality products that last a long time.
 
purplepeople said:
Thanks, but I'm not an electronics guy. What you wrote sounds like a foreign language to me.
We have zero repair shops for anything like this around here.
You think it's unlikely to be a simple tube problem and more likely an issue with the motherboard?
I had another of these break about a decade ago. It was a similar problem. But in this case, recordings started to feel incredibly sharp/piercing.
So I know they aren't quality products that last a long time.
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Nobody has electronics repair shops any effing where anymore! Your only hope is someone on a forum (would have offered 10 yrs ago if in UK) The planet is doomed if we don't wake up very soon and start repairing shit and making it so it CAN be repaired. Trouble is EVERYONE wants cheap and disposable.

I would not waste your money trying a new valve ($20+?) unless you can borrow one.

Dave.
 
The snag is that real costs are going up all the time - today I paid £55 for 45 minutes of a chimney sweeps time. In the office, I sold B2B a radio to a firm who wanted to supply it to their customer - who has burned it out, and I'm sending a new one to them, and I get a duff one back. If I look at my time like the chimney sweep, then to dismantle and identify the fault, order the part and fix it will probably be two hours. The cost price of the replacement (not what I sold it for) is the same as the chimney sweep. repairing it will be stupid. write off the cost price of the one I've sent out and walk away. I can probably salvage the brackets and the microphone. I could pay to have it ecologically disposed of. Or, it will be landfill. I'll opt for landfill. If I fix the damn thing, I'd be lucky to cover the cost, 2nd hand on ebay!
 
rob aylestone said:
The snag is that real costs are going up all the time - today I paid £55 for 45 minutes of a chimney sweeps time. In the office, I sold B2B a radio to a firm who wanted to supply it to their customer - who has burned it out, and I'm sending a new one to them, and I get a duff one back. If I look at my time like the chimney sweep, then to dismantle and identify the fault, order the part and fix it will probably be two hours. The cost price of the replacement (not what I sold it for) is the same as the chimney sweep. repairing it will be stupid. write off the cost price of the one I've sent out and walk away. I can probably salvage the brackets and the microphone. I could pay to have it ecologically disposed of. Or, it will be landfill. I'll opt for landfill. If I fix the damn thing, I'd be lucky to cover the cost, 2nd hand on ebay!
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Rob, don't you have a recycling centre with a "WEEE" bin where you can dispose of electrical stuff?

Dave.
 
yep - but to visit I have to book a slot, confirm that I am a private resident and the item is not business related and my van is private. As it's 100% not domestic, and my van is not private, I'd have to lie. So in the black bin it goes!
 
rob aylestone said:
yep - but to visit I have to book a slot, confirm that I am a private resident and the item is not business related and my van is private. As it's 100% not domestic, and my van is not private, I'd have to lie. So in the black bin it goes!
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"Fourteen years of the small business man's party"! And they wonder why fly tipping is endemic.

Dave.
 
I ordered a new tv antenna for my house. Threw the packaging in my home bin, and got a 'fine' for putting business waste in my recycling bin - because it had my business name on it. I appealed, sent a photo of the chimney with the antenna clearly shiny and visible and it got cancelled - but since then, my business waste doesn't go in my bin.
 
I looked at a pic of the VTB1 circuit board, and things that I would look at would be the multiple capacitors. Over the years, there have been issues with some electrolytic caps which will exhibit themselves by having a bulging top and or leakage. I have recently replaced capacitors in an old receiver, and in a Panasonic DVD recorder. It restored both to working order. The VTB has about 30 electrolytic capacitors. A simple visual examination might show a bulging top on one or more of the caps. Resistors are usually pretty reliable, as are most diodes. If you see something looking suspicious, have an electronic savvy friend replace them or find a repair shop (I'm sure there is one someplace close. They just aren't as conspicuous as they once were).

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I noticed my waveforms have looked odd the last couple of songs. They look similar to this picture... I learned today this is called DC offset. Is that more likely an amp or mic issue?
 

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I really don't see any DC offset. but I do see some of what looks like nasty noise or distortion. That makes me suspect bad components in the VTB1 (see above).

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Bypass the VTB1 and record straight into the interface, then use the VTB1, and post a quick MP3 sample of each. Just a 10 second passage should be plenty.

On the other hand, you were thinking about spending up to $5K on a mic. Just buy a new mic for $1000 and use $500 or so for a new preamp. Put the other $3500 in your IRA and let it sit there for 40 years. You'll probably be better off.
 
In any case Samplitude has the function "remove DC offset" I dare say most other DAWs do? Reaper would I am sure.

Dave.
 
TalismanRich said:
I looked at a pic of the VTB1 circuit board, and things that I would look at would be the multiple capacitors. Over the years, there have been issues with some electrolytic caps which will exhibit themselves by having a bulging top and or leakage. I have recently replaced capacitors in an old receiver, and in a Panasonic DVD recorder. It restored both to working order. The VTB has about 30 electrolytic capacitors. A simple visual examination might show a bulging top on one or more of the caps. Resistors are usually pretty reliable, as are most diodes. If you see something looking suspicious, have an electronic savvy friend replace them or find a repair shop (I'm sure there is one someplace close. They just aren't as conspicuous as they once were).
Click to expand...
It is a neat design. But was built with cheap parts. I wondered who really made that circuit considering SP copies designs. The biggest offenders were the electrolytic capacitors and the glass diodes by the tube for the repair I did on one a while back.
 
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