2013 Ampeg V-4B 100W Reissue

[Turock]

Do you guys think the tube driven mid range circuit of the original V4B is part of it's distinct character ? Along that line, how did Ampeg implement the mid-range in the 90's V4B-H ? Why didn't guys like that iteration and what will differentiate this new head from the 90's version?

I like 'em; I bought two of 'em. Those V4BH are my favorite amps. I have one from the mid 90s and another from 2006 (for comparison, I also have an SVT, B100R, Demeter VTBP201, good stuff). The only complaint I can remember is some thought they didn't go loud enough (evidently they didn't have the right speakers). Never a volume problem (or any other problem) with either of mine. They have been reliable, problem free, and they sound great.
What's not to like?

 

[Groovy_Gravy]

Yeah it's gonna overhang about 1 & 1/2 inches on each side, but it will do until I can get another cab. I will keep the NeoX 212T for my GB Streamliner 600. Will an Ampeg 410HE be a good match for the V4B? I know the tone will be there but I'm not sure about volume. I might get one and then another later.

i use a 72 v4b and a 410he and its killer! plenty loud for bar gigs

 

[Bassics101]

Wow, been away from the forum for a while. I guess it's "there go the kids new school shoes". Luckily, they've all moved out.

 

[JimmyM]

Wow, been away from the forum for a while. I guess it's "there go the kids new school shoes". Luckily, they've all moved out.

Yeah....isn't it awesome? It's like getting a $2000 a month raise!

 

[jastacey]

6k11 is the same as a 12ax7 plus one triode of a 12au7 (1/2). It could be that the combo of the two in the RI do the same job as the 6k11?

12dw7 is missing too isn't it? What was its job?

I'm going on memory here ... the 12DW7 tube was used as follows, on one side ( the high MU ) was used for the driver/phase inverter for the power tubes and the Low MU side was used as a cathode follower, I think it was used for the slave out

The 6K11 ... one section was used for the midrange controls ...can't remember what the other 2 sections were used for ... i don't have the schematics near by .... if they are useing a baxall type of circuit, it should get close to the old V4-B ...IMHO

 

[solodb]

GAS is forming. It's going to weigh 42 lbs, almost 20 lbs. lighter than the original, it's going to be 3" shorter than the awkwardly long 70's model. Mmm, no more goofy overhang on cabinets...or ugly aluminum knobs and a nice D.I. Could I safely hump 42 lbs.... oh right.... got no bread..... what could I sell....?

 

[96tbird]

The aluminum knobs are, imo, sweet! So 60's - 70's. Something permanent about metal that plastic just doesn't have. But the plastic are true to the years of V4's that the faceplate line scheme is modeled after so that's good.... And they don't overhang on the proper cab!

 

[pgk]

a question for Ampeg; will the new amp take 6550's safely, like the old models did? or would it need a separate filament tranny? i know it won't buy me any more power (and i don't want more, frankly). no, i'm interested in them them as a tonal option, to get closer to an svt's more wide open, deeper vibe. an original fitted with 6550's is a thing of beauty to my ears, and every bit as hip as a stock unit with 6L6's.

 

[P Town]

Wow, been away from the forum for a while. I guess it's "there go the kids new school shoes". Luckily, they've all moved out.

My "kids" are 24, and 34 yrs. old, and all moved out, but I'm still the 1st National Bank of Dad.
Now when they need money, it's more likely to be $1000.00 than $100.00.

 

[AmpegUSA]

a question for Ampeg; will the new amp take 6550's safely, like the old models did? or would it need a separate filament tranny? i know it won't buy me any more power (and i don't want more, frankly). no, i'm interested in them them as a tonal option, to get closer to an svt's more wide open, deeper vibe. an original fitted with 6550's is a thing of beauty to my ears, and every bit as hip as a stock unit with 6L6's.

I talked with Ampeg engineer, Dawn, who worked on V-4B about this. Here's what she had to say. If you guys need clarification, I will really need to reference her awesomeness, so a response might take a little.

Here's the points she wanted to make:

1) The power section was designed around 6L6GCs, lots of time went into this, so I recommend they actually listen to the amp in person before deciding to swap tubes.

2) Both the KT88 and 6550 have higher plate dissipation characteristics in comparison to the 6L6s. What this means is that with the bias settings “as is,” the KT88 and 6550 will be “cold” in comparison to the 6L6GCs, so crossover distortion is more of a risk and in general the distortion characteristics will be different. The bias current could be increased, but this is an internal control and shouldn’t be messed with unless the person knows what they are doing.

3) Also, the KT88 and 6550 have lower plate to plate impedance than the 6L6GC, which means that the output transformer is going to be seeing a smaller load than it is designed for. For example, the primary of the V-4B is 2200ohm, designed to see 6L6GCs. The SVTCL/SVTVR primary is 1850, designed to see 6550s. This can translate into a sagged plate voltage, which can affect the power supply in the whole amplifier slightly.

4) Mechanically and Thermally, the clearance from the 6L6GC to the wooden chassis is around 15mm. The KT88 and 6550 are 10mm taller, so that cuts it down to 5mm, which means a really hot tube is really close to a wooden cabinet. Side note on KT88, width is quite a bit bigger than 6L6GC, so spacing between tubes will be cut down a lot, which means less airflow and everything getting hotter. Tube clamps will need to be removed as they are not wide enough for KT88 or 6550 base, so there will be nothing securing tubes to amp while hanging upside down.

 

[pgk]

Thanks for the excellent response, that's many sensible reasons not to do it

 

[WretchedExcess]

The difference in turns ratios on the OT is not significant. Comparing Ra-a of 1850 to 2200, the impedance ratios are within 20% of one another. Compare that to a 100% mismatch when you plug an 8 ohm cabinet into a 4 ohm jack (which is generally considered safe) and you'll see that this isn't a problem.

Yes, bias adjustment is mandatory, but Ampeg failed to mention the most likely mode of failure in a short-cut conversion to using 6550: the filament current requirements for the 6550 are 1.6A per tube compared to 0.9A per tube for the 6L6. The difference for a quartet of tubes is 6.4A vs. 3.6A. If the filament transformer is not adequately rated to deliver the extra 77% of added current, then the filament voltages will sag causing decreased thermionic emission in the tubes. The tempearature of the filament transformer windings will also rise, thereby shortening transformer life. These problems are avoided in a proper 6550 conversion which requires the use of a supplementary filament transformer.

In comparing 6L6 to 7027 we've already discussed that the main factor that needs to be considered is the anode voltage on the tubes. The question has been asked several times but it's not getting answered. Instead, we're getting answers to questions that aren't even significant. I don't want to come off as a grump, but as long as someone at Ampeg is talking to the engineers and bringing answers here, would it be possible to ask Dawn about the B+ voltage spec? Thanks.

 

[beans-on-toast]

The space between the tubes and heat dissipation/ventilation issue is also a concern that I would have. Too much heat in there isn't good.

 

[WretchedExcess]

great point, beans.

the intertube spacing spec seems to get ignored a lot. you may not see it on some of the 6550 data sheets, but the KT88 data sheet clearly states that the on-center distance between the tube sockets for a KT88 that is not actively ventilated needs to be 4 inches. I've never seen anyone honor that spec, so it seems that forced air cooling would be a good idea.

look at most hifi amps, like the crazy Carver designs, and you'll see that the 6550-based hifi amps often have passive cooling, but the tubes are packed in there like sardines.

 

[JimmyM]

The difference in turns ratios on the OT is not significant. Comparing Ra-a of 1850 to 2200, the impedance ratios are within 20% of one another. Compare that to a 100% mismatch when you plug an 8 ohm cabinet into a 4 ohm jack (which is generally considered safe) and you'll see that this isn't a problem.

Feel free to do it on your own amp, not mine. It's only not a problem till it is.

Yes, bias adjustment is mandatory, but Ampeg failed to mention the most likely mode of failure in a short-cut conversion to using 6550: the filament current requirements for the 6550 are 1.6A per tube compared to 0.9A per tube for the 6L6. The difference for a quartet of tubes is 6.4A vs. 3.6A. If the filament transformer is not adequately rated to deliver the extra 77% of added current, then the filament voltages will sag causing decreased thermionic emission in the tubes. The tempearature of the filament transformer windings will also rise, thereby shortening transformer life. These problems are avoided in a proper 6550 conversion which requires the use of a supplementary filament transformer.

So the idea is to stick tubes in there that run too hot for the chassis and just barely fit and then add a 3rd tranny to it to make sure the tubes run too hot for the chassis? Where's the payoff? Starting a fire is not much of a payoff if you ask me.

In comparing 6L6 to 7027 we've already discussed that the main factor that needs to be considered is the anode voltage on the tubes. The question has been asked several times but it's not getting answered. Instead, we're getting answers to questions that aren't even significant. I don't want to come off as a grump, but as long as someone at Ampeg is talking to the engineers and bringing answers here, would it be possible to ask Dawn about the B+ voltage spec? Thanks.

You're coming off as a grump. Not trying to tell you not to ask the question, but whether Ryan or Dawn answers it or someone on here answers it, it's the same answer...7027's are simply not as feasible in this day and age for a new production amp as 6L6's are. Two companies makes 7027's now, and neither of them make them in any significant quantity, nor do they have any edge over 6L6GC's. Why risk obsolescence in a new amp? Just to make a few spec nerds happy? Ampeg did the right thing using tubes you can find all over the place. Had they gone with 7027's, I doubt I'd be so interested in getting one, because that would just be a headache for the future.

 

[Dan55]

Yep, I don't have a problem with Ampeg using 6L6GCs. Seems like the smart thing to do.

Dan

 

[solodb]

Somebody get one of these re-issues quick somehow so we can all quit speculating. JimmyM, you got any special pull to get an advance shipment seeing you are the Ampeg spokesperson?

 

[JimmyM]

I'm not really the Ampeg spokesperson. That title belongs to Dino Monoxelos. I'm not hired by Ampeg, nor do I receive compensation from them, nor do they let me in on big news any sooner than you guys. Once in a while I get tipped off to something they're working on if Dino or Stu the AR guy thinks I'd be interested, but I'm basically a glorified end user who gets a discount

That said, I've got my order in but it hasn't shipped yet, and I probably won't get it any quicker than anyone else. If I do, though, I will certainly brag my ass off about it

 

[Tim1]

All is speculation. It simply boils down to volume, tone and reliability IMO. I actually have confidence in Ampeg that they have nailed the volume/tone issue - there appear to be enough passionate people involved these days (Dino, Hodgy et al ....) to trust that if they say it sounds the same it will sound the same. The PF and SVT7 did pretty well tonewise to my ears, but reliability questions raised on this forum put me off their purchase. I need to be patient and wait a few months to get some reports from people who are regularly gigging them, if they prove reliable or Ampeg/Loud treat the odd issue fairly and promptly then I will be in. This discussion is just wetting my appetite....I feel like a fish being reeled in.

 

[WretchedExcess]

> "So the idea is to stick tubes in there that run too hot for the chassis and just barely fit and then add a 3rd tranny to it to make sure the tubes run too hot for the chassis? Where's the payoff? Starting a fire is not much of a payoff if you ask me."

Yes, the conversion would use a 3rd tranny, just like an SVT.

You know, doing a 6550 conversion on this amp wasn't *my* idea -- I'm only pointing out important reasons for why it's not a good idea to try to shoehorn 6550 into an amp that's designed for lesser tubes, and the reasons I mentioned are the really important reasons that the Ampeg people should not have left out. Seeing the most important information get left out gives me pause.

When it comes to running the amp on 6550, the question that we should be asking is not how to perform a 6550 conversion on a 6L6 amp. (The fact that this question even comes up does indicate that somebody senses a potential problem with 6L6.)

The real question that needs to be asked is that if suitable 7027 aren't available to perform an accurate reissue, then why wasn't the amp designed around a 6550 in the first place? We already know that today's 6L6 aren't what they used to be and they aren't 7027 either. 6L6 are going to require a voltage reduction in order to stay alive, and that brings up the question of why if Ampeg decided that a tube specification change was required to reissue the amp, then why didn't they make an incremental move up to a 6550 instead of making an incremental move down to a 6L6? Number crunching tube geeks who understand how numbers effect tone & reliability want to know.

> Feel free to do it on your own amp, not mine. It's only not a problem till it is.

I do it on my amps all the time. No problems if you know what you're doing.

On the subject of buying the new amp, I have to admit, I'm a little bummed that the announcement for this amp came out a week after I bought a pair of SVT-2 Pro. Sometimes the timing just doesn't work out. That said, I'll be eager to hear your review after you get the product. I'm enough of a nerd that I want to know how the B+ voltages have been worked out before making a decision about whether or not I want to own the new design/implementation.