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At long last...(V4b content)

animal52

animal52

Jul 1, 2006
447
1
DC area
#1
After jonesing for an all tube amp for some time, I lucked out and found this V4B on craigslist the other day. I'm still waiting on a speaker cable, but before I plug her in, I had a few questions for the ampeg gurus here at TB:

I've got the B25 cab that goes with the V4B (though maybe not the original cab since the cab's grill is black). The ohm selector switch on the back of the amp is currently set to 8 ohms. Can anyone verify for me that the B25 cab is an 8 ohm cab?

The seller wasn't sure of the exact year of this amp? The Ampeg badging tells me it's a later V4b, but maybe someone here can give me a better idea of what year this amp was made?

The seller also told me that he had a tech replace one, just one, of the tubes about ten years ago. Is this possible? I was under the impression that tubes normally had to be replaced in pairs or all together?

How power hungry are these amps? Am I good just plugging in to a furman power conditioner strip and then into the wall? I only ask because of some threads I've seen where tube amps (SVT-VR specifically) go into standby when the wall isn't delivering enough voltage. I'm hoping this isn't too common a problem since I currently live in an older house with older wiring.

I know to connect the amp and cab with a speaker cable (i.e. connect the amp to a load) before turning it on, but any other advice on how to operate this amp so as to keep it running smooth is much appreciated.


I'll get some photos up as soon as I can figure out how to resize them for TB. She's got plenty of "character," but I'm smitten just the same. Sounded amazing when I played thru her before buying.
 
#3
animal52 said:
I've got the B25 cab that goes with the V4B (though maybe not the original cab since the cab's grill is black). The ohm selector switch on the back of the amp is currently set to 8 ohms. Can anyone verify for me that the B25 cab is an 8 ohm cab?
Click to expand...

The B25 cab was not original to the V4b, the B25 cab came with the B25 head, and I believe was originally 16 ohms. There was a 2x15 cab that came with the V4b which was 4 ohms. You may want to take the speakers out and see how they are wired and what they are rated for before you use this cab with that head. If they are 8 ohms in series, it's a 16 ohm cab, and it's a no go.

animal52 said:
The seller wasn't sure of the exact year of this amp? The Ampeg badging tells me it's a later V4b, but maybe someone here can give me a better idea of what year this amp was made?
Click to expand...

From the pictures in your second post it's a post-75 model. Check out www.ampegv4.com for more specifics on the differences, but mainly it relates to the addition of the master volume control.

animal52 said:
The seller also told me that he had a tech replace one, just one, of the tubes about ten years ago. Is this possible? I was under the impression that tubes normally had to be replaced in pairs or all together?
Click to expand...

It should be fine if the tubes were tested/matched. It would probably be fine anyways if it's been running that long and the tube hasn't been an issue.

animal52 said:
How power hungry are these amps? Am I good just plugging in to a furman power conditioner strip and then into the wall? I only ask because of some threads I've seen where tube amps (SVT-VR specifically) go into standby when the wall isn't delivering enough voltage. I'm hoping this isn't too common a problem since I currently live in an older house with older wiring.
Click to expand...

The issue with the VR relates to a modern "protection circuit" which prevents voltage drops from damaging the amp. I don't believe there is anything like this in the V4. You shouldn't have an issue, I've never had problems with mine and I've lived in some very old places.

animal52 said:
I know to connect the amp and cab with a speaker cable (i.e. connect the amp to a load) before turning it on, but any other advice on how to operate this amp so as to keep it running smooth is much appreciated.
Click to expand...

Let it warm up in standby for at least 30 seconds before turning it on fully. As far as shut down, it's been debated, but I always do the same coming out, give it some time in standby before going completely off.

animal52 said:
I'll get some photos up as soon as I can figure out how to resize them for TB. She's got plenty of "character," but I'm smitten just the same. Sounded amazing when I played thru her before buying.
Click to expand...

Congrats on the amp.
 
#4
Looks nice. I believe the white rocker switches indicate a later date, but I'm not sure exactly when they changed.
Check here for exact info:
http://www.ampegv4.com/dating.php


Once you get the speaker cable, plug it in, flip the power switch, let it stand for about a minute, then flip the standby and get ready to rock.

With my V4 I found that anything above 12 o'clock on the gain was just more distortion. You can get an extreme, face melting, amazing distortion my turning every knob up to 10. Maybe not recommended with that cab, though.
I found mine (a '72 V4-B) sounded best after about 20 minutes of solid playing.

Have fun with your new amp! It's a great one.

edit: coreyfyfe beat me to pretty much everything :p
 
#5
What you have is a mid to late 1970's amp ..... these are a pretty good designed amp .... you might want to have a tech go through it ( the caps and some of the other components may have drifted out of spec over the last 30-35 years ) ...the power draw is in the range of 4-6 amps .... the preamp/drive tubes a fairly common ...check the 12DW7 tube, you can easly swap that tube for a fresh 12ax7 ( as this tube uses only 1/2 if it's self for the inverter/driver stage ...the other half is used for the preamp out ) ...the output tubes ...well that is what will cost money if you use NOS 7027a's .... I'm running mine with JJ 6l6GC and I'm happy with what I'm hearing ...you might want to get an extra 6k11 preamp tube ...just to have, as this is the only really oddball tube ..... other than that you've made a pretty good purchase !!!!!
 
#7
If you don't want to take apart your cab, you could go buy a cheap multimeter from RadioShack or even a hardware store. Search online or read the manual to figure out how to measure impedance (AKA ohms). Then plug the speaker cable into the cab and probe the other end using the one probe on the sleeve portion of the plug and the other probe on the tip. You won't get an exact 8 or 16, but it will be close. That is the only way to be sure short of taking the cab apart as suggested above.
 
#8
The B25 cab was not original to the V4b, the B25 cab came with the B25 head, and I believe was originally 16 ohms. There was a 2x15 cab that came with the V4b which was 4 ohms. You may want to take the speakers out and see how they are wired and what they are rated for before you use this cab with that head. If they are 8 ohms in series, it's a 16 ohm cab, and it's a no go.



Let's assume the worst and say the cab is 16 ohms. What would be the consequences of playing it at modest volume (house practice)? Any possibility of damaging the head or cab?
 
#9
animal52 said:
Let's assume the worst and say the cab is 16 ohms. What would be the consequences of playing it at modest volume (house practice)? Any possibility of damaging the head or cab?
Click to expand...

The V4 should have a switch for 2, 4, and 8 ohms (better than the SVT). You may be able to rewire the cab for 4 ohm operation.

In any case, run it off the 8 ohm tap for some low volume testing. It won't destroy it right away. More stress on your tubes, transformers. In the long run, look for a properly matched cab, which shouldn't be difficult seeing as the V4 is so versatile. There are almost no production bass cabs @ 16 ohms.
 
#10
Yeah 16 ohms is really weird for bass stuff, not so much guitar, but definitely an odd ball bass cab. That's one reason I've stayed away from B25s when they've come up for sale cheap, they've probably either been run at the wrong impedance for a long time or modded.

Either way, you should be ok in the short term, these amps are known to have beastly transformers, but not something I would do long term. Definitely try to check out the speaker wiring, it may have been altered from the original set up to work with the head.
 
#13
Well...Thanks everyone for the info. That's kinda lame about the cab being 16 ohm. That's a real oddball resistance value. I imagine I'll get clearer tone out of a newer cab anyhow.

What cab do you guys recommend to pair with this head?
 
#15
I would pull the back off, and check the wiring, and check the speakers for their ohm readings, and if the measure 5-6 on a mulimeter, then they are 8 ohm spreakers, seems like a hassle, but when you buy something used, you really need to find out exactly what you have ...you just might get lucky, in having the speaker cab wired in series
 
#16
jastacey said:
I would pull the back off, and check the wiring, and check the speakers for their ohm readings, and if the measure 5-6 on a mulimeter, then they are 8 ohm spreakers, seems like a hassle, but when you buy something used, you really need to find out exactly what you have ...you just might get lucky, in having the speaker cab wired in series
Click to expand...

Well that doesn't sound too tough to do. Now just to be sure, the multimeter I want to use is something like this...

Invalid Link Removed

A previous poster mentioned that I might just take the speaker cable out of the head so that it's just connected to the cab, then use the multimeter to measure the resistance across the unconnected end by placing one probe on the tip and one of the body of the 1/4'' jack. If that could work it would save me the trouble of opening up the cab.
 
#19
animal52 said:
Is that too much cab for this head?
Click to expand...

Not at all...

l_e6427b949e69d9abf16dcaa4aaddbc38.png
 
#20
Ya that'll work for these purposes. As a point of reference my pair of 410 Ampegs wired up together [call it an 810] are nominally a 4 ohm load, but actually read 3.6 ohms on a Radio Shock digital multi-meter and a bit under 5 ohms on an old analog meter [after adjusting to zero]. In other words not a precise way to measure, but good enough to figure out what you got.... if it reads 12, it aint 4.
 

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