SERVICE INFORMATION FOR
VAIC REFERENCE 62B MONOBLOCK

© 2012 www.jacmusic.com

IMPORTANT WARNING:

In case you want to do service on this amplifier, voltages inside are exceptional high. You should only do this yourself when you are a qualified High Voltage Technician, and trained on this particular product too. All service work as described here is only how I would do it myself.

Rhodium plated hardware. The deck plate and transformer pots are RHODIUM plated. Rhodium is more expensive as gold, and also used for signal connectors, as a better alternative to gold plating, since this is a hard metal, so it won't scratch off easily. The appearance is not the color as the Chromium plated amplifiers of the 1980's. Rhodium has a touch of blue-grey color, very nice, specially in artificial light this becomes visible. Imagine am amplifier which is all gold plated, and imagine the cost. Well, this one os all RHODIUM plated. This is the VAIC REFERENCE!

I scanned this from the official Catalog, that is with the amplifiers.
This new price of those was 21.000 Euro including taxes, including AV8B driver tubes, but not including power tubes.

These are the reference models.. and hey... that's what they are. If you look inside, it makes your heart beat faster. All triode amplifiers, no feedback. Directly heated driver tube AV8B, and 6SN7 input tube. Gold plated connectors. Even the bias switch at the back for the bias control is gold plated. It has an RCA and XLR connectors input, you can hand-adjust the bias yourself, with a precision build-in digital reading. After adjustment, the digital meters can be switched off, if you don't like the red- letters of it, in the dark. So you'll see the tube glow only. The amps has tube rectification, 6SN7 pre.amp tube, and a beautiful directly heated driver tube AV8B, and two 1605 or 520B output tubes, Parallel Single Ended for each mono block.

Note, that this amp allows to do a tube replacement without having to send the amplifier to a company. The user can check the status of End Tubes tubes and re-adjust them periodically as needed. It may not seem important now, but it will be after some years of use, and it's a MAJOR advantage of this amplifier over the lower class VAIC models.

This is the BEST and largest VAIC amplifier EVER MADE. There has never been a larger or a better one.

It consists of TWO mono blocks

VAIC REFERENCE 62B Parallel Single-Ended mono blocks.

These are truly amazing amplifiers. There is not saved on anything.

The metal of the deck and transformers are Rhodium plated. Read this. By the time this amplifier was made, Rhodium had little industrial need. Though not cheap, prices were acceptable. Today, rhodium prices have rocketed. It is more expensive than gold, and nobody would dream to build an amplifier with so large surface, thick Rhodium plating. Rhodium looks like Chrome, but doesn't have that cheap "mirror" effect. Rhodium has a more blue-grey color, and is a hard-metal, which was the reason to use it. So scratching will be very little. Also the looks are very nice. Wooden side panels are thick piano lacquered, in black.

Run any tube you like. This is a miraculous feature of this amplifier. Normally you are bound to using a particular tube. So buy a 300B amplifier, and you need to use 300B. Well, not so with the VAIC REFERENCE. It's not the reference without reason. This amplifier can be adjusted from the inside for three plate (anode) voltages, and there are large power slide resistors inside, to adjust to any heater voltage from 2.5 up to 6.5 Volts at a few ampere. Add to this, the beautiful bias electronics, which is a classical auto bias circuit, combined with a variable set point. So it is auto biased, but you can still adjust the bias point it is supposed to take. Tubes possible are: 300B, 300B-Mesh, 300-BXLS, 520B-V2, 520B-V3, 1605, 300Bn+, AV32B, PX25, and many many more tubes, even 2A3. For hard-core tuning people, it is even possible to exchange the sockets to Octal, or B4, and use tubes with such a base.

Output impedance. An interesting option, this is a bit of a hard core modification, and it needs a good technician. He should not do this when he has questions about it. Only when he naturally knows what this is, and how to do it. To begin with, the amplifier has normal 4 Ohms or 8 Ohms outputs. However some high impedance loudspeakers are 16 Ohms. In many cases these are high efficiency speakers, meaning they need less output power. It is possible to run this amplifier on one output tube per channel only, given the technician adjusts the anode voltage by means of the internal switch, to the lowest voltage. This makes sure the power supply capacitors will not damage, due to lower load. After this is done, the amplifier can run on one tube only, and this will double the output impedance. So where it is written 8 Ohms on the outside, it becomes now a 16 Ohms (low power) output. Mind you the amplifier must have also re-adjusted the heater voltage and the bias, but after this is done by a tube technician, you have now doubled the output impedance.

Another way do double the output impedance, is run the amplifier on a pair of 45 tubes. So two tubes per channel. This may require some extra attention of the technician to get all the settings right. I do not know for sure if this is possible, but I see no reason why not.

Alternatively, you can always run the amplifier with higher impedance speakers anyway, so connect a 16 Ohms speaker to the 8 Ohms output is possible already, but there is some risk to damage the output transformers by too much output signal. Given this is a very high power amplifier, this is a risk. So you should do this only if the amplifier is set for low anode voltage and low bias. So this is possible way to use very high efficiency 16 ohms speakers.

Control and adjust bias yourself. Some tubes are very expensive, suppose you want to run the amplifier on very expensive NOS Western Electric 300B, you have the user option to reduce the bias setting, and save the tube's lifetime during normal operation. Then, for very high loudness listening sessions, you can bias them to maximum, and after that set them back to medium or minimum. This can be done with the digital meter, carefully and nicely hidden at the back of each mono block. This is so important, to be able to exchange tubes yourself. The digital meters are industry precision meters from Farnell, which have cost 250 Euro each (!). So you have alone for 500 Euro precision meters inside. The meters are for check up after switch on, and then can be switched off during normal use.

The bias set screws can be conveniently operated from the from the front deck. This amplifier is AUTO BIAS, so it will adapt by itself for changes of the mains voltage. Yet, the SET POINT of the auto bias can be changed by hand. (Perhaps it confusing when I call it "adjustable auto bias", but that's what it is). The auto bias regulation is not very strong, but it does compensate for variations of the mains voltage, and for tube aging. Like this, you can use up the lifetime of the power tubes nicely, much better than with auto bias only. Moreover you can adapt the required power level of the output tubes. In the case when you need medium volume only, you can set the tubes to medium bias. In this way, also achieving a softer sound character as will be appreciated for voices, soft jazz, or string music. It is a merit of the 1605 tube, it will develop a silky kind of the sound this way, as known from legendary tubes such as PX25. Yet, since you have two tubes in parallel, there is a lot of output power present still. Alternatively you can set the tubes to maximum allowed bias, in order to produce high dynamic signal, at maximum power. This is likely appreciated for classical music at loud listening level.

The required setting depends on the tubes you choose, this will be from 10...20 when using the EML 1605 tube. It is recommended to experiment with this, and find the most pleasant setting for your the music you prefer, in combination with the speakers and listening room.

The potentiometers for the setting are wire-wound 10-turns type. These cost 20 Euro each, so that was again 80 Euro materials cost. As you can see by this, there was no saving anywhere.

Service: There are no serviceable parts inside, if you do not want to change the type tubes used. In that case you can simply plug in the new tubes, and continue. All critical capacitors are foil type, so these last for ever. The only replaceable part is the light bulb which illuminated the VAIC logo from the inside.

Output impedance: Since there is a lot of output power present with this amplifier, you should try the 4Ohms output at 8 Ohms speakers. As this will double the damping factor of the loudspeakers, there may be cases where this improves the sound.

IMPORTANT NOTICE ABOUT THE METERS. These meters are expensive industrial meters, but they have one disadvantage, maximum input voltage is 30 Volts and above that they damage. This 30V can happen when there is a spike on the mains, or when you do a setting above 30V by mistake, when you knock on the power tubes by mistake, etc. Read below, under "service" how to prevent this.

SERVICE NEEDED: Some small service may be needed after all those years. Actually this is amazingly little ever since 1998.

  1. Add 50mA radio fuse in meter circuit.
  2. Set the voltage to the power tubes right. You can not say what tubes were in there before, or what settings somebody made
  3. Replace the 12V light bulbs under the VAIC logo. Like all light bulbs, these last just a few thousand hours. These are normal light bulbs same as used in a car.
  4. Tighten all screws from the inside. This includes the screws of the transformer pots.
  5. Check and/or improve the ground wire to the chassis.
  6. If there is crackling noise in the amplifier, replace the anode resistors of the AV8B tubes when they are from the "RS" brand. Or don't even wait for it, just replace them. They are very difficult to replace on the same position. The screws are just behind a transformer. You could mount the replacements on another place, and just leave the old ones in.
  7. AV8B driver tubes are often weak.
  8. Power tubes are often at the end of life.
  9. The high voltage selector needs cleaning (read below here) .
Inside the meters is an over voltage protection, but this is something like a Zener diode. So functioning is very limited, this Zener diode will burn out also, and then the meters are damaged. The meters are still for sale at RS Electronics, but they cost 250 Euro each. (Blue ones excists too). To protect the meters, simply add a small radio fuse into the V+ wire to the meters. That is the center wire of the meter switch. These meters have only a V+ wire and a ground wire, and take their own operation power from the voltage itself. The value of this fuse is 50mA. The internal protection can blow such a fuse, and then the meters itself will not damage. Please take this serious. This is the only known design error in this amplifier, for the rest it is perfect. A replacement of such a meter is a TERRIBLE project, it takes a full day. You need to remove the power supply board completely, and the transformers partially, and even the old meter needs to be hacked out as it's clamped in with a steel clip. The potential risk of wiring errors when desoldering the whole power supply board is large. So don't save on a 50 cents radio fuse.

On the power supply board are two selectors that allow to change the power supply voltage to the Power tubes. (So not to the rest of the amplifier). The voltage selection is done by choosing transformer taps. So there is AC signal on those selectors, coming directly from the transformer. This is meaningful, as 520B-V2 tubes needed higher voltage then 300B tubes, and 1605 needs the highest voltage. The selectors have each three settings. One selector is for "coarse" and the other is for "fine". So one gives big steps, the other small steps. Just measure the high voltage on the anode of the power tubes, and you will see what they do. These selectors are made of a small clamp with a screw, and some solder work is done on the PCB. It looks good on first sight, but when you take it apart, and desolder everything with desoldering litz, you probably see the solder was a bit loose underneath, and there is the risk of a loose contact, or a short. Moreover, the solder is much too thick, and solder is not a stabile material. When there is force on it, over the years, it will flow, and the contact can and will become loose. The amplifiers I serviced, needed not just resolder it quickly, and tighten the screw, but it was needed to remove the solder completely, clean it well, and resolder it nice, but thin. So use as little solder as possible.

High Voltage Switch Setting:

300B: Low or Medium
520B-V2 Medium or High
1605 High

Output transformers These are litz wound, and have two output impedances, 4 and 8 Ohms. In case you are using very sensitive 16 Ohms horns, you can use this Parallel Single Ended amplifier with just one tube per channel, thus giving half the output power, which is enough on that case, AND this automatically produces doubles the output impedance, because we have parallel output tubes but use only one in that case. So we have 4 and 8 Ohms outputs at full power, and the option to have 16 Ohms at half the output power.

Pre-heating electronics. This is a nice feature of most of the VAICs, and these have it also. The tube heaters are warmed up at first, and pre-heated at 20% anode current. During this time the sound is shut off. Then, after the warm up, the anode current is ramped up gradually which takes 2 seconds, and the amplifier starts to work without any click noise, and no stress for the tubes. This is done with the NE555 timer, the most classic timer IC ever, so in the unlikely case it needs a repair, this can be bought easily. That being said, this part and the digital meter, are the only integrated circuits you find in this amplifers. All other electronics is analog. Even the lamp behind this panel is a light bulb, no LED. From experience with other users, we know this light bulb is the only serviceable part inside. This is a normal light bulb as with cars, so can be replaced easily.

Power Off
Pre-heat. Dark blue
Run. Bright blue

Inputs. These are normal phono jacks, or XLR

Short specifications:

All tube amplifier, with 5U4G tube rectification
Slow ramp up "pre-heating" for the output tubes, with shut off during pre-heating.
Output Power: 50 watts per channel with EML 520B Tubes
Output Power: 60 watts per channel with EML 1605 Tubes
Frequency Response: +/- 0 dB 7 Hz-35 kHz; +/- 2 dB 5 Hz-100 kHz
Two Outputs: 4 or 8 ohms
Input impedance: 55 kilohms
Signal-to-Noise Ratio: 98 dB
Input Connectors: 1× RCA, 1× XLR
Weight 55kgs, for one mono block.
Dimensions (cm): 37.5×60×27

Some of the highlights, I probably forget some here:

  • Rhodium plated deck + transformer cases.
  • Gold plated hardware at the back
  • RCA and XLR input
  • Litz Wound output transformers.
  • Mains transformer, chokes, output transformers, all separately encapsulated, and potted.
  • High temperature wiring. Transformer wiring partially with glass fiber sleeves.
  • Solid red wood sides. Polished, Piano lacquered, very thick layer.
  • Can be internally configured for a VERY large choice of output tubes.
  • Driver tube can be changed to 300B if needed.
  • Normal tube exchange, can be done by end user, amplifier can stay closed.
  • Can be adjusted for 110V, 115V, 120V, 220V, 230V or 240V mains. We change the setting for you, when you order it. Now it is set for 230V
  • Output impedance 4 or 8 Ohms at full power. Can be set of 16 Ohms at half power.
  • Different bias levels of output tubes is possible. You can save tube life if you need not full output power. Also you can choose for specific sound at relatively low bias, which you may prefer when using very high efficiency speaker. You have all options open here.
  • Digital meter control of bias level. Bias setting with very precise, wire wound, 20-turns devices. Can be done by the end user. Use the setting holes in the amplifier deck, and a screw driver. Read bias level from the digital meters. A reading of "20" means 100% bias. A reading of "10" means 50% bias.
  • Many of the very expensive AUDYN Foil caps are used.
  • Pre-heating electronics with very high functionality. Absolutely ideal system, which gives you the best tube life.
  • Very high focus on using old fashioned electronics, no tricks or strange things. Any good technician can service this amplifier now, and 25 years later.
  • We have the factory schematics, which we supply to the buyer.
  • Universal output connectors, for forks, wire, or banana plugs
  • Aluminum Spike feet


Click on image for a 3Mb Picture

 


Click on image for a 3Mb Picture


Choose AUTO BIAS Set point. So you determine a value, and afterwards the amplifier
will auto-bias to this value. Here it is set for 11.2 which is just an example. You can
choose from 10...20, where "20" is 100% of maximum.

 

IMPORTANT. Click above image for service information.

Shipment: CAN AND SHOULD only be done in the wooden crates. When you ship in carton boxes, you have the situation that such boxes CAN and WILL be kicked around, and any drop of the amplifier will sag the amplifier deck, which repair becomes extremely difficult.