Ben -- I have a V-4BH, and I love it. To answer one of your original questions, the V-4B and V-4BH probably refer to the same amp, although V-4B might be the vintage 70's version, and V-4BH the newer reissue (I'm not sure about that one). It's a 100 watt bass amp head that's all tube. The big thing is whether it's a newer model or a 70's model.
I've heard only good about the 70's models. I don't have any first-hand experience with them, though. Others here have, and can probably help you out if you're looking for a vintage V-4B.
The newer V-4Bh's were reissued, starting in 1996. I got mine new that first year of the reissue, '96. Basically, it's an all-tube head that, because it's only 100 watts, is really great for playing small & medium clubs or when you want to really push the tubes hard without having nuclear level sound. Mine has been my club gigging head for 10 years now, and I love it and am not even interested in any other amps. There's enough power to rock a club up to about 200-250 people with no problem. When we play bigger gigs than that, I will use the XLR out jack on the back of the head to send a direct signal to the PA, then use the PA for extra volume. The V-4BH has always been plenty for volume on stage.
The plusses of the amp are being able to push the four 5881's/6L6's hard at lower volumes to get sweet tube tone, and the fact that since it's only 45 lbs, you can actually carry it yourself. The minuses (compared to an SVT) - less thundering volume and headroom available.
I use mine with 2 cabinets - an Ampeg 4x10 and an Ampeg 1x15. Works great, I love the rig and get all kinds of good feedback from folks here in Springfield, IL clubs.
Hope this is helpful! Listen to the other folks here, too - there are lots of helpful gigging bassists here who are great with help.
Tube Amp question
Moderators: rickenbrother, ajish4
OK guys and gals...what is the difference in these two SVT heads.
This one is a Classic(CL)
and this one is an Anniversary model(AV)
Both seem to have the same controls and specs.
Which one is more desirable and why?
This one is a Classic(CL)
and this one is an Anniversary model(AV)
Both seem to have the same controls and specs.
Which one is more desirable and why?
'73 4001 MG '88 4003S JG '89 4003S FG '91 4003S MG
I have a Magnavox V4B, which I had the output tubes changed to 6550's and it puts out 128 watts at 40 cycles, I played a show with it and the 8-10 when the headline act would not let me change the tone controls on the svt brain, the v4b was plenty with the 8-10, and I usually see the old v4b's go for around 400.cdn, I highly recomend it....tone!, mind you I also have an svt brain and mostly use it with 4 of the cheap 10's out of the 8-10, and have yet to blow a speaker up and most people think I play loud.tfb
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soundmasterg
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Ginger, there isn't really too much of an impedance mismatch between an output transformer designed for use with 6550/KT88 and 6L6GC's, but the 6550/KT88 would be a better match for your V9 as that is what is was designed to use. The amp will put out more power with the 6550/KT88, and will have more headroom too. Also, the 6550/KT88 tubes will last a lot longer than 6L6GC's will in that circuit due to the higher voltages present.
Rob, 5881's are NOT the same as a 6L6 BTW.
If you're talking old stock tubes, the 5881 was a military/industrial version of the 6L6GB, and it's max dissipation is 23 watts. In the 6L6 family, there is the 6L6 (metal), the 6L6G (glass), the 6L6GB, and the 6L6GC. Any 6L6 earlier than the 6L6GB has a 19 watts max dissipation rating and a lower max voltage rating, the GC version has a 30 watts max dissipation rating, and the GB and 5881 have a 23 watts max dissipation rating and a lower max voltage rating.
If you're talking new manufacture, the Sovtek 5881 is not even a real 6L6. It's a Russian designation (6P something or other, can't remember) that is a similar tube to a 6L6, so they call it a 5881. It works fine and sounds rather bland, and probably has a 23 watt max dissipation like the old 5881, but these are VERY strong tubes and will withstand a beating.
The only other 5881 type being made today is the new Russian made Tung-Sol 5881. These are supposedly copies of the old Tung-Sol 5881 as far as the internal dimensions of the tubes, but with inferior metallurgy and vacuum as compared to the older tubes. This basically means that they won't last as long as the NOS stuff, but that is the case with any new tube made today so it isn't much of a worry. These new Tung-Sol 5881's have a great reputation so far for how well they sound and perform, especially in Tweed Fender applications. As far as their specs....its a little hard to tell because the manufacturer (New Sensor corp in New York) doesn't share the specs on their tubes, but they are probably a 23W max dissipation tube also.
Both of these 5881 types can take higher voltages than vintage 5881's, but they work better when biased to a 23 watt max dissipation level. All the other 6L6 types made today are 6L6GC types and can take the true GC specs for voltage and dissipation. This would include the Sovtek 6L6WXT, EH 6L6GC, JJ 6L6GC, Winged C 6L6GC, and various Chinese brands.
Dean, the V-4BH refers to the new one, and the V-4 or V-4B refer to the 70's one. The 70's one would be preferred if you have to work on it as even though it is a PCB, it is better made than the new ones in a lot of ways. They both sound and perform well however.
Ben, there are quite a few places online that describe how to properly and safely bias tubes, and I could explain it too, but it is a bit of typing, and there are different methods too, some safer than others. I'll give you a little info about bias here, but not too much in depth. Setting the bias in an amp CAN be dangerous if you don't follow the proper procedures and don't have the correct equipment. It usually only has to be done when you replace the power tubes too, which isn't as often as you would think.
You only have to set the bias for the power tubes, not the preamp tubes. There are two different bias methods used in amps that you might see but within those, there are sub-types and special models that you set the bias differently on. The two different bias methods are either fixed bias or cathode bias.
Cathode bias amps "usually" are plug and play, meaning that you can put the tube in and not have to actually set the bias because the tube will choose it's own bias level. I say usually because that isn't always the case. It depends on the specs of the tube, and the value of the cathode bias resistor the designer chose to use in the amp. Usually cathode biased amps are lower power amps like a Vox AC30 for example.
For fixed bias, there is adjustable, and non-adjustable fixed bias amps. Most higher power amps are one of these two fixed bias methods. An Ampeg SVT is fixed bias, but uses it's own unique method to set the bias. Most amps are similar to a blackface Fender in that they are adjustable fixed bias, but only use 1 bias pot so you still should use matched tubes. Most Mesa-Boogie amps and many Ampeg amps are non-adjustable fixed bias. All this means is that instead of a pot they choose a resistor value to set the bias. You can change the resistor value to set the bias to some other range, or put a pot in to be able to adjust it more readily, which is something that many techs do. Most commercial amps will have the bis setup quite cold because they want to make sure the tubes will last until the warrenty runs out. The amp can be biased hotter and will sound better in almost all cases.
Actually setting the bias can range from easy and not so dangerous to moderately hard and very dangerous depending on which method you use to try to set the bias. I won't go into the dangerous methods here, but all of these methods require you to have a DMM or voltmeter, a way to check the cathode current of the tubes, have access to the max dissipation rating of the tubes, and to do some simple math.
The easist way to set the bias in an amp is to use the Bias Rite meters from webervst (www.tedweber.com) to check the cathode current and plate voltage, and then adjust the bias accordingly with the bias pot and an INSULATED, NON-CONDUCTING screwdriver. If the amp doesn't have adjustable bias, then unless you know what you are doing, you should take the amp to a tech and let him/her set the bias. If you're interested in learning how to do it, and learning the safety aspects of it, I can give you some specific info relating to how to bias whatever amp you decide to buy. Just be very careful around them because they use voltages inside them that can kill you if you aren't careful.
Rob, 5881's are NOT the same as a 6L6 BTW.
If you're talking old stock tubes, the 5881 was a military/industrial version of the 6L6GB, and it's max dissipation is 23 watts. In the 6L6 family, there is the 6L6 (metal), the 6L6G (glass), the 6L6GB, and the 6L6GC. Any 6L6 earlier than the 6L6GB has a 19 watts max dissipation rating and a lower max voltage rating, the GC version has a 30 watts max dissipation rating, and the GB and 5881 have a 23 watts max dissipation rating and a lower max voltage rating.
If you're talking new manufacture, the Sovtek 5881 is not even a real 6L6. It's a Russian designation (6P something or other, can't remember) that is a similar tube to a 6L6, so they call it a 5881. It works fine and sounds rather bland, and probably has a 23 watt max dissipation like the old 5881, but these are VERY strong tubes and will withstand a beating.
The only other 5881 type being made today is the new Russian made Tung-Sol 5881. These are supposedly copies of the old Tung-Sol 5881 as far as the internal dimensions of the tubes, but with inferior metallurgy and vacuum as compared to the older tubes. This basically means that they won't last as long as the NOS stuff, but that is the case with any new tube made today so it isn't much of a worry. These new Tung-Sol 5881's have a great reputation so far for how well they sound and perform, especially in Tweed Fender applications. As far as their specs....its a little hard to tell because the manufacturer (New Sensor corp in New York) doesn't share the specs on their tubes, but they are probably a 23W max dissipation tube also.
Both of these 5881 types can take higher voltages than vintage 5881's, but they work better when biased to a 23 watt max dissipation level. All the other 6L6 types made today are 6L6GC types and can take the true GC specs for voltage and dissipation. This would include the Sovtek 6L6WXT, EH 6L6GC, JJ 6L6GC, Winged C 6L6GC, and various Chinese brands.
Dean, the V-4BH refers to the new one, and the V-4 or V-4B refer to the 70's one. The 70's one would be preferred if you have to work on it as even though it is a PCB, it is better made than the new ones in a lot of ways. They both sound and perform well however.
Ben, there are quite a few places online that describe how to properly and safely bias tubes, and I could explain it too, but it is a bit of typing, and there are different methods too, some safer than others. I'll give you a little info about bias here, but not too much in depth. Setting the bias in an amp CAN be dangerous if you don't follow the proper procedures and don't have the correct equipment. It usually only has to be done when you replace the power tubes too, which isn't as often as you would think.
You only have to set the bias for the power tubes, not the preamp tubes. There are two different bias methods used in amps that you might see but within those, there are sub-types and special models that you set the bias differently on. The two different bias methods are either fixed bias or cathode bias.
Cathode bias amps "usually" are plug and play, meaning that you can put the tube in and not have to actually set the bias because the tube will choose it's own bias level. I say usually because that isn't always the case. It depends on the specs of the tube, and the value of the cathode bias resistor the designer chose to use in the amp. Usually cathode biased amps are lower power amps like a Vox AC30 for example.
For fixed bias, there is adjustable, and non-adjustable fixed bias amps. Most higher power amps are one of these two fixed bias methods. An Ampeg SVT is fixed bias, but uses it's own unique method to set the bias. Most amps are similar to a blackface Fender in that they are adjustable fixed bias, but only use 1 bias pot so you still should use matched tubes. Most Mesa-Boogie amps and many Ampeg amps are non-adjustable fixed bias. All this means is that instead of a pot they choose a resistor value to set the bias. You can change the resistor value to set the bias to some other range, or put a pot in to be able to adjust it more readily, which is something that many techs do. Most commercial amps will have the bis setup quite cold because they want to make sure the tubes will last until the warrenty runs out. The amp can be biased hotter and will sound better in almost all cases.
Actually setting the bias can range from easy and not so dangerous to moderately hard and very dangerous depending on which method you use to try to set the bias. I won't go into the dangerous methods here, but all of these methods require you to have a DMM or voltmeter, a way to check the cathode current of the tubes, have access to the max dissipation rating of the tubes, and to do some simple math.
The easist way to set the bias in an amp is to use the Bias Rite meters from webervst (www.tedweber.com) to check the cathode current and plate voltage, and then adjust the bias accordingly with the bias pot and an INSULATED, NON-CONDUCTING screwdriver. If the amp doesn't have adjustable bias, then unless you know what you are doing, you should take the amp to a tech and let him/her set the bias. If you're interested in learning how to do it, and learning the safety aspects of it, I can give you some specific info relating to how to bias whatever amp you decide to buy. Just be very careful around them because they use voltages inside them that can kill you if you aren't careful.
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soundmasterg
- RRF Consultant
- Posts: 1923
- Joined: Tue Oct 01, 2002 1:06 pm
The max disspation rating isn't the same as the max power you'll get from the amp Richard. The max dissipation number is only used when biasing the amp. In a true Class A amp, the max dissipation rating is where you set the bias at idle, but almost all guitar and bass amps on the market from the dawn of time to today are Class AB, and so the bias should be set to the 70% rule or thereabouts. The actual power the amp puts out depends on the plate voltage, the screen voltage, the power tubes used, and the output transformer's size and capabilities.
Your BF Showman probably has around 460v of plate and screen voltage, uses four 6L6GC's, and has a good sized output transformer, so 128 watts sounds about right. It depends on where your tech was setting the volume control on the amp and how much distorting he was allowing of the sine wave on the scope before measuring for power output. Power output should be measured at RMS levels and peak levels, and RMS levels should have a completely clean sine wave.
A Silvertone Twin Twelve 1484 model amp has 475v of plate voltage, but only 340v of screen voltage, and a very small output transformer, so it is only about 25 watts, and it uses two 6L6GC's. I modded my brother's to have a screen voltage of about 405v, and added adjustable bias, which lowered the plate voltage to 460v. His amp is now 30 watts. If a larger output transformer was used, it would be about 50 watts RMS.
Those Sovteks will hold up for a long time in your amp, but you could get a better sound by using Winged C 6L6GC's or JJ 6L6GC's. You can get them from Antique Electronics Supply (www.tubesandmore.com) or places like Watford Valves if you're overseas. Winged C tubes are sold as Svetlana outside of the US and Canada btw.
Your BF Showman probably has around 460v of plate and screen voltage, uses four 6L6GC's, and has a good sized output transformer, so 128 watts sounds about right. It depends on where your tech was setting the volume control on the amp and how much distorting he was allowing of the sine wave on the scope before measuring for power output. Power output should be measured at RMS levels and peak levels, and RMS levels should have a completely clean sine wave.
A Silvertone Twin Twelve 1484 model amp has 475v of plate voltage, but only 340v of screen voltage, and a very small output transformer, so it is only about 25 watts, and it uses two 6L6GC's. I modded my brother's to have a screen voltage of about 405v, and added adjustable bias, which lowered the plate voltage to 460v. His amp is now 30 watts. If a larger output transformer was used, it would be about 50 watts RMS.
Those Sovteks will hold up for a long time in your amp, but you could get a better sound by using Winged C 6L6GC's or JJ 6L6GC's. You can get them from Antique Electronics Supply (www.tubesandmore.com) or places like Watford Valves if you're overseas. Winged C tubes are sold as Svetlana outside of the US and Canada btw.
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ginger_lee
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ty greg..I knew the only reason I was getting away with it was that I was using old stock 6L6Gc's..all the others I had like the g's and b's only lasted minutes lol..but yes true I should have 6550's in her..although i like to get the tube distortion when i play hard..I'm unlike a lotta bassists who like a clean tone..iI use a lotta mid to facillatate the fretless singing cello tone and where possible like guitar rigs..my fav cabinet on the V-9 is still my 71 bottom part of a g412 combo transistor guitar rig was a good amp but she finally blew years ago..i had each 2-12 pairing in parallel each into the two four ohm outs on the V-9..the only solid state amp i still have is an old acoustic 370..nice an dirty too..lol..I'd rather the kt88's in the v-9 tho....lol..and yes what they call 5881's now are pretty laffable...my brothers an electronic/computer tech and started off in tubes...tho more into computers and programming now..someplace I even have an old Stark tube tester (back at his house probablee) I used to test tubes I found and keep all that were reasonable..I have a matched pair of Ballantyne theatre (film projector)amplifiers (circa late 1940's)with consecutive serial numbers..and an earlier one too boot, 2 old Heathkits one with 2 6L6's the other with 2 12L6's..a Multivox Premier 120 (2 6V6's) with only volume and tone I use as a preamp sometimes for my Bogen 200 watt rms into 8 ohm god knows what into 3 ohm ..lol..power amp that has 8 8417's in it..but ty very much for all the info!..I normally let my brother do my tech work, but hes 3 hour drive away these days
1981 4002 FL wal
"it aint braggin' if you can back it up"...Jaco Pastorius
"I'm not bad I'm just drawn that way"...Jessica Rabbit
"it aint braggin' if you can back it up"...Jaco Pastorius
"I'm not bad I'm just drawn that way"...Jessica Rabbit
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soundmasterg
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You're welcome guys and gals.
Ginger you could "probably" also use EL34's in your Ampeg. You'd have to check to see how the sockets are wired before you could tell. Pin 1 has to be free among other considerations. The EL34's can take the high voltage of the Ampeg circuit as long as you use some good quality ones, and they will give you a bit of those mids that you like. They won't be as brittle and clean as 6550/KT88's when pushed either. I'd recommend to put at least a 1k 5 watt screen grid resistor in for each EL34 though. They should be soldered in right at the socket. Your brother should know how to do it if you don't from what you say about him. Good brands would be any NOS except for Siemens (they can't handle high voltages well), and for new stuff the Winged C's and JJ's sound nice and perform well.
That power amp with 8 8417's sounds like a monster! An expensive one to keep up too as 8417's aren't widely available or cheap these days.
Ginger you could "probably" also use EL34's in your Ampeg. You'd have to check to see how the sockets are wired before you could tell. Pin 1 has to be free among other considerations. The EL34's can take the high voltage of the Ampeg circuit as long as you use some good quality ones, and they will give you a bit of those mids that you like. They won't be as brittle and clean as 6550/KT88's when pushed either. I'd recommend to put at least a 1k 5 watt screen grid resistor in for each EL34 though. They should be soldered in right at the socket. Your brother should know how to do it if you don't from what you say about him. Good brands would be any NOS except for Siemens (they can't handle high voltages well), and for new stuff the Winged C's and JJ's sound nice and perform well.
That power amp with 8 8417's sounds like a monster! An expensive one to keep up too as 8417's aren't widely available or cheap these days.
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ginger_lee
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ginger_lee
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and rear