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#1 2012-10-13 23:14:27

Matthew1623
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Registered: 2012-10-13
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Early 70s v4b needs new tubes. Help

Just got an early 70s v4b and need new tubes. Seems like there is a shorter tube in the 3rd slot so I'm figuring I should change all four and get the amp biased and looked over as well. Wondering where a good tech might be in nj and also any ideas on which tubes I should be looking into. Sound is most important to me. I am flexible on the price of it means having better sound. Thanks for any advice

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#2 2012-10-13 23:50:40

hangman
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Re: Early 70s v4b needs new tubes. Help

have a tech look it over... I find that NOS 7027s work best.  For a modern replacement I have had very good luck with the Winged C 6L6GC.  the JJ7027 or 6L6gc is good,  but doesn't take the beating like the winged C.

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#3 2012-10-14 03:21:03

Matthew1623
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Re: Early 70s v4b needs new tubes. Help

I have heard the nos 7027 are expensive. I'm confused though. What Is the difference between 7027 and the 7027a and also what company makes the nos 7027?  This is my firs tube amp and I know it's old so I really need to know what I need to do to keep it in good shape. Do I need to bias the amp before putting in tubes etc? Or can I plug them right in? How are the sovteck 7027?

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#4 2012-10-16 00:57:49

Matthew1623
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Re: Early 70s v4b needs new tubes. Help

Anyone? Anyone?? Any takers??

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#5 2012-10-16 15:22:39

hangman
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Re: Early 70s v4b needs new tubes. Help

RCA, GE and Sylvania all made the 7027a (which is the one you are looking for,  I should have been more clear on that. )
I have not found the sovtek to be a good option.  But I know others on the forum do use them.
One should be able to just plug new tubes in without biasing the amp (there is not bias adjustment anyway... Although you could add one)
But becaue the amp is new to you,  I would recommend having it checked out before you pop new tubes in.   Especially if you get nos ones.  As one small problem could result in the new tubes being ruined.  Better safe than sorry in this case. 
I will be honest with you,  if you are worried about the expense of the nos 7027a,   The winged C. 6L6gc is your next best option.   Those are still more expensive than the sovteks,  but they sound better and will last longer.

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#6 2012-10-16 17:42:01

Liquids
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Registered: 2010-08-01
Posts: 491

Re: Early 70s v4b needs new tubes. Help

Rich Koerner at Time Electronics might be able to help you - he seems quirky but passionate about vintage equipment repair.  Plenty of old time ampeg employees and designers are in NJ too if you can search around a bit. 

IF you're balking at tube prices, and especially if the amp is not in for an overhaul of some degree (it should be, but I've said and detailed in many posts...), check out the SINO 6L6GC tubes that tubesandmore.com offers for 7.50 per tube.  Get a quad, or two quads.  They hold up, and sound at least 'alright.' At that price, it's a deal.  Good to have a backup quad as it is.

And, if you don't get an amp overhaul because of cost or a fender-minded vintage-part preserving tech, you'll probably blow a tube or four in the near future anywhere since something old is bound to blow or go intermittent and take out tubes with it...so don't spend for good tubes until you're amp is stable, clean, and fully overhauled, or you're throwing your money at glass that's gonna face premature death in a difficult environment to survive...may as well blow cheap tubes in that case.

Last edited by Liquids (2012-10-16 17:44:29)


Matthew

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#7 2012-10-17 04:50:54

Matthew1623
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Re: Early 70s v4b needs new tubes. Help

Thanks for the great advice. Ok here's the story. I bought an early v4 with the silver metal knobs from eBay. I really wanted a v4b as I play bass but since they are harder to come by and I've heard many a bass player say they are just as good I figured I would go for whatever I could get my hands on. So I came across a v4 that was recently serviced. Cap job and new tubes. All new sovtek preamp tubes and sovtek 7027 power tubes. It sounds Great except for the fact that the sound breaks up a little early for my taste. I live the distortion. But would love a little lore headroom before it starts to break up. But then all of a sudden a v4b shows up for a really good price and bam I win that one too. It has not been serviced and has all original magnavox preamp tubes and ge power tubes except one power tube is a little shorter and I can't tell what type of tube it is. So I get the v4b and it sounds great no crazy noises except a little hum when I crank it. Also the power light doesn't work and when I switch it out of standby it pops a little bit. I opens this baby up cleaned all its parts. Dust the whole inside out with a dust sprayer. This thing looks really clean and in great shape. I am def planning on having it serviced. So I guess my question was answered about the sovteks. I'm assuming that if I get get different tubes for my v4 instead of the sovteks it will sound better and not break up so quick. My other question is about the v4b with the shorter mystery tube. After I get it serviced I'm wondering if I should just keep the tubes that are in it or should I get a new set if tubes and what kind. Thanks

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#8 2012-10-17 15:54:35

Matthew1623
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Re: Early 70s v4b needs new tubes. Help

Another thing hat confuses me is the whole bias thing. Now I have been told that I should b able to just plug in new tubes because this amp is self biasing but I hear other people saying that I need to have the bias checked before replacing tubes. If you can't adjust the bias on the amp what's the reason for having the bias checked. It should be fine as long as tubes are all matched right??  Every time I hear one side and get comfortable all of a sudden someone starts saying the opposite.  Also it' seems that my v4 has 2 extra preamp tubes vs my v4b that has two less.  Didn't know that until I was checking out the sovteks in my v4. I have to say I love this amp and totally love the sound and all I want is to enhance the vintage tone of this beast. So other than making sure amp is in good working order I'm just concentrated on getting the best sounding tubes for my bass playing. And you guys were right the nos 7027 tubes are obscenely expensive. I'm moving towards the winged c 6l6 gc. I've read they are the next best thing and not as expensive.  What about the 6550. I heard they Are great for bass but need an little mod before sticking them in. Thanks for the replies

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#9 2012-10-17 17:14:52

Liquids
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Posts: 491

Re: Early 70s v4b needs new tubes. Help

The amp's bias is set via a resistor, rather than adjustable via a potentiometer.  Some people try and arrange for the resistor to become an adjustable potentiometer + resistor for some range, others measure and might increase/decrease the value of the resistor by soldering in a different one.

At the end of the day, this amp's bias is considered 'cold' for 7027s/6L6GCs.  I've tweaked bias, and to my ears, on this amp, it's set perfectly (see some of my older posts for more details).  From a design standpoint, it's set 'cold' in the sense that there should be no GOOD set of 6L6GC/7027 tubes that can be plugged into the sockets that will run a bias approaching 'hot.'  You do no real danger to your amp by not having the bias tweaked for a new set of tubes here.  I can do my own work and while I'd tweak the bias for a Fender black/silverface amp as hot as I was comfortable with for that particular set of tubes, I leave this one alone with it's set 75k resistor after expirimenting with bias.

That said, you're got 2 old V-series ampegs that may look dust free, but are in a state where they are surviving despite them being way overdue for a tune up/overhaul.  I'd prioritize that over bias concerns.  For example - if the bias network goes screwy, and it's been known to in these amps, than you're amp will then be 'self-biasing' itself into frylater land in no time.


Matthew

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#10 2012-10-17 17:31:19

Liquids
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Registered: 2010-08-01
Posts: 491

Re: Early 70s v4b needs new tubes. Help

Also, if you want less distortion, and play bass, you might want to make sure you're bass signal isn't too hot, and the sensitivity switch on the V4 is in the position with the LEAST volume - I have a V4b, and there is no sensitivity switch - the circuit is configured in the lowest gain/volume setting in comparison to the V4. 

This may seem counter intuitive, but set the switch for the quietest setting, and then compensate with the volume knob.  If you have a modern bass with high output pickups or especially have active pickups, turn down your volume knob.  If you're getting distortion, it's probably because the preamp is being driven by your instrument and/or that tube stage amplifying more than it needs to.

Lastly, if you're plugging into a modern bass cabinet, the efficiency ratings on modern bass speakers are lackluster in the sense that they 'steal' power from the amp and make it seem quieter than it is.  With efficient speakers of older days (like an old ampeg cabinet that sits under an SVT), before bass speakers seemed as if they all switched to low speaker efficiencies in favor of lighter weight or something, because the assumption is now that a bass player will be driving them with 1000+ Watt power amp anyhow, that V4's power output would have been plenty for most situations.

If the V-series ampegs don't have enough clean power for you, I'd always advise that people use the ext out into a big honkin solid state amp and a separate speaker cab (maybe driving a 1x15 or something) in order to make up the apparent needed volume/power if you want the ampeg sound, clean power, but not an SVT.


Matthew

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#11 2012-10-17 17:33:56

Liquids
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Registered: 2010-08-01
Posts: 491

Re: Early 70s v4b needs new tubes. Help

This explains it pretty well...the context is the Fender SVT-matching amp attempt, the PS-400, but it's good info:

http://www.timeelect.com/400-faq.htm#7. … version%29


Matthew

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#12 2012-10-17 18:18:16

Matthew1623
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Re: Early 70s v4b needs new tubes. Help

Ok cool so in theory if my amp is checked out and serviced and everything is in good working order I should be able to get a good quad of 7027s or 6l6s and be able to pop them right in with no problem? Right?

Right now I am using a modern svt 8x10 cab. What do you think of using the ext out into my v4 b or vice versa and run them together?  My svt cab can be split into 2 4x10s so each amp will have a cab.
I think I am going to prob go with the winged c 6l6. What do you think of those?? Now I must find a good tech that can service this beast for me as my first step. Then Onto the tubes.  Thanks for the advice

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#13 2012-10-17 21:58:50

hangman
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Posts: 1848

Re: Early 70s v4b needs new tubes. Help

Liquids wrote:

That said, you're got 2 old V-series ampegs that may look dust free, but are in a state where they are surviving despite them being way overdue for a tune up/overhaul.  I'd prioritize that over bias concerns.  For example - if the bias network goes screwy, and it's been known to in these amps, than you're amp will then be 'self-biasing' itself into frylater land in no time.

Agreed.   I wasn't suggesting that you have a tech look at the amp to bias it,  I was suggesting that you should have everything checked over in the event that there were bad components in the power amp/ power supply. 

The amp isn't a known quantity until a tech looks it over.   
If there is no problem,  the bill should be quite low and you can toss some new tubes in without even thinking about bias.   

If there is a problem you can get it addressed... And THEN put brand new tubes in it.  If you are buying a set of winged Cs,  you don't wanna risk stressing them or ruining them in an amp until you have reason to believe that amp is in full working condition.
That's my feeling on the matter.

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#14 2012-10-18 03:10:54

Matthew1623
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Re: Early 70s v4b needs new tubes. Help

Agreed!!! Very good advice!! I will definately take it somewhere to get it checked. So I guess my only problem is where to take it. Any ideas or any leads on someone respectable in nj?  I will google it I hues but if anyone knows of someone please pass it along  and thanks again very informative stuff guys and its much appreciated.

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