Jess Oliver's legacy - AMPEG PORTAFLEX CLUB part 9

[Duke21]

Originally Posted by JimmyM

Nice thing about two cabs is not having to unscrew the dolly because a cab is up by your ear. And while I wouldn't say it doubles your available volume, it adds a good amount. That said, I'm taking either my Micro VR or BA110 to my gig today

You do mic the BA10?
Btw, my step son had a BA115 which I liked a lot, but he didn't like as he didn't get the Burton sound.... He was 16 back then. Today I will bet he would love it.
So. How are the BA108 and BA110 regarding sound/ tone? Like the BA115 or?

Btw, here is a short clip on my virtual B15 from
Jamup XT
http://soundcloud.com/duke21/free-rip-no-comp-la2a-red-comp

[JimmyM]

Originally Posted by Duke21

You do mic the BA10?
Btw, my step son had a BA115 which I liked a lot, but he didn't like as he didn't get the Burton sound.... He was 16 back then. Today I will bet he would love it.
So. How are the BA108 and BA110 regarding sound/ tone? Like the BA115 or?

I didn't mic the BA110...I have the REDDI right next to it, but you can't see it too well because of the mic stand. Not sure what other current models they sound like, though. I get an Ampeggy sound out of it and the BA108, just a little smaller and brighter.

[beans-on-toast]

Originally Posted by Bass 45

Here is a price list from '75. At that time the "EXB15N" was $240.00 without a dolly or an Altec upgrade.

Other things in this document that I found interesting was the price of the Altec upgrades - which are very high - and the B15N head was available separately. I guess some of those cab-less heads were not orphaned after all Also, no dolly for the SVT cab. I used to have a '74 square back - that must have been the last year for that style 810.

Thanks Rich! I've been drooling over it. If I could go back in time, I'd stock up on about ten B-15's, an SVT, and a V4B.

It shows how you could mix and match heads and cabs. The Altec speakers were even more expensive when you consider that you paid full price for the cab. They didn't sell you an unloaded cab for less and then added the speaker. So their true cost of the 421A would have been more than $150. Also note that the 418B was $20 less and they marketed it as a dual purpose guitar and bass speaker.

The other interesting thing is that the dealer cost for parts was 50% off list. That may have applied to amps as well.

[D Bopp]

my 62 B15 has what I believe is the original tubes. The 2 6L6's seem to fire up properly. But the bigger tube on the end just lights up at the top. I don't see any blue flame when standby is off. How do I know if the tubes have gone bad? Should I replace them?

[portaflexer]

In short, the only way to truly "test" a tube is with a tube tester. Few people have these laying around the house, but most repair shops have one. You could always take the tube in and have it tested. Realistically though, if the amp works and you're happy with the sound coming out of it... why change anything?

[stiles72]

The big 5U4 tube on the end is your rectifier tube. It won't give off the blue glow like the the two 6L6 power tubes. Your three preamp tubes won't give off the blue glow either. As long as your amp powers on and works without making funny noises, there's nothing to worry about. Tubes can last for years and years and there is no reason to replace them as long as the amp is working fine.

[beans-on-toast]

To add to what was said.

The tubes have what is called a heater in them. It is a coil of wire, much like what is in a space heater. When power is applied, the heater glows and warms something in the tube called a cathode. This causes electrons to boil off the cathode and they are attracted to the anode. Current flows and the tube amplifies. By controlling the flow of electrons you control how much the tube amplifies.

Anyway, the glow from the tube can vary from tube to tube. If a tube doesn't glow brightly, that isn't a sign that it needs to be changed. On some tubes, the heater is covered and you don't see a glow at all. The amount of glow can vary from tube type to tube type so don't be concerned with that. The rectifier tube either works or it doesn't. If the amp is working, your rectifier tube is ok.

Tubes do wear out with time but you don't need to change them as often as some people would have you believe. Your tubes look original but that doesn't mean that they need to be changed. More than likely in a 50 year old amp like yours, the power supply and power tube cathode capacitors need to be changed.

If the amp sounds good as is without any hum and hiss, use it and enjoy it. Otherwise, I would suggest that you take the amp to a good tech and have them check it out and determine what needs to be done. It might need more than just a tube change. This will ensure that it is performing to spec and is reliable.

[jnewmark]

Well, after noodling around for about a week with my newly acquired '71 B15N, at lower volumes, I cranked it up today to straight up noon, with treble and bass the same, and it started farting out, mostly on the A string, which seemed a little odd to me, but there you have it. I'm toying with replacing the 15 with another 15, like a JBL K140. I would like to get a little more volume out of this amp as I was going to try to use it in a low volume , Blues band, but, noon on the volume dial aint gonna cut it. When switched to the " Bright " channel, the farting goes away, ( so maybe the stock 15 is'nt blown ? ), but, of course, it sounds like the bottom drops out, and also there seems to be a loss of volume using this channel with the volume knob still at noon. The K140 has a pretty good efficience rating, along with a nice Xmax. I did a search through this thread and heard some clips of the D140, which I really dug, but, now I'm wondering if anything past noon on the volume dial is gonna give me the same results ? I know I could just add another 8 ohm cab, but, that's kinda defeating the whole, just roll the B15N into the gig and start playing thing which I was looking forward to. Any thoughts ?

[christw]

At noon you're probably entering the realm of overdrive and may well be running out of power. 11 o'clock seems to be the turning point for most B-15's I've come across. My stock CTS and D130 (offered as an upgrade by Ampeg) will both take everything my '67 has to give although I have a loose bit of tolex in the port that will buzz at high volume.

I'm guessing that you might just be hitting it's upper limit of the amp's power. There still could be a rattle, speaker issue, or something else contributing though. Have you ruled out other possibilities besides the speaker?

[jnewmark]

Yeah, pretty much. If you scroll back a pge, you will see pics of the amp itself. It is pretty much pristine, like it's been sitting in a closet for a long time. I have'nt really tried the voice coil rub thing yet, but, other than that, everything checks out.

[Black Sheep]

I just came across something that I suppose could be an issue with amp output. I was doing some Deoxit on my '67, and wanted to clean the aux speaker jack switch that takes the output through to the main speaker wire. Just tweaked it a little to get the Deoxit in the contacts, and was going to try some dental floss or something to clean further, and found that the contacts won't close now. So I know it won't work at all for me now, and I'll need to replace that jack. I wonder though, if that switch appears to be closed but has poor conductance, how that would affect the amp with more current.

(I think to get by right now, I'll just wrap a small piece of bare wire between the two tabs to make contact)

[beans-on-toast]

These switches can be a problem when they get old. Corrosion or gunk, they both act as a resistance and degrade the sound. Sometimes cleaning these contacts can make a night and day difference. Unfortunately, Ampeg used jacks with switch contacts in all their amps. Not the best thing to put in the signal path. Shorting the switch till you get a new one with a wire is fine. You can also solder a jumper wire on the terminals.

Old jacks can be a problem. If the plating gets worn off, the contact will corrode fairly quickly after cleaning it and affects how the amp sounds. You can try bending the switch tab at the base where the insulators are, to see if you can re-establish the contact. Being spring metal, it sometimes doesn't want to cooperate when you try to bend it. In these cases, it is easier to simply replace the jack. That is the jack that has the insulation washer and collar to isolate it from the chassis. The jack needs to have a long bushing (the threaded part) so that it is long enough with the washers in place. The Switchcraft part number is L12A. They sell them here (http://www.tubesandmore.com/products/W-SC-L12A).

[Black Sheep]

Thanks - yes, I went ahead and soldered for now, for a better connection, until I get a new jack.
Oh - and by the way, finally got the amp up and working. Thanks for all the tips! The result is oh-so-sweet. Such tone!!

[beans-on-toast]

Originally Posted by jnewmark

I cranked it up today to straight up noon, with treble and bass the same, and it started farting out, mostly on the A string, which seemed a little odd to me....

To add to what Chris said, the health of the power supply caps will also affect the onset of distortion and headroom. If they are original, you might need to change them. As they age, they loose their ability to supply the needed current and the amp farts out. If you hear a 60Hz hum that is a clear indication that they need to be changed.

If the caps are in good shape, optimizing the power tube bias can make a difference in the performance of the amp. The bias drifts as the tubes wear and should be checked from time to time to ensure that it is set optimally. The bias circuit components need to be checked out as well. There is a resistor that can drift and a cap that needs to be replaced. If the power supply caps are changed, it is a good idea to change these components at the same time. For a gigging amp, I like to check that bias once a year as part of a regular maintenance program.

The rectifier tube will sag when the amp is pushed hard. A solid state rectifier like the WS1 can help if you don't want the sag and compression. A lot of people like this.

Mod'ing the amp to boost the capacitance in the power supply will allow you to get more out of the amp before the onset of distortion.

When everything else has been looked at, a different speaker can make a difference. Some of these old speakers are tired and a re-cone can help as well.

In general, it's usually a good idea to have a new vintage amp checked out by a tech to bring it up to spec.

[jnewmark]

^ Thanks for the tips, as always. Is the WS1, a direct , plug and play replacement ? I was hoping to avoid a trip to my tech, as the condition of this amp was pristine, and really, showed hardly any signs of use. But, as a general rule of thumb, as far as the B15N goes, is noon on the volume knob pretty much all you are going to get before fart out, all other things being stock on the amp ?

[ddbassGA]

Originally Posted by jnewmark

^ Thanks for the tips, as always. Is the WS1, a direct , plug and play replacement ? I was hoping to avoid a trip to my tech, as the condition of this amp was pristine, and really, showed hardly any signs of use. But, as a general rule of thumb, as far as the B15N goes, is noon on the volume knob pretty much all you are going to get before fart out, all other things being stock on the amp ?

11:00 in my experience.

[coreyfyfe]

Originally Posted by jnewmark

as far as the B15N goes, is noon on the volume knob pretty much all you are going to get before fart out, all other things being stock on the amp ?

Yup, that's about it. I have a SS rec plug in for mine, but don't really use it, though I'm sure it would help keep some bass thump when cranked.

[beans-on-toast]

That's with the tone controls set at noon. Push the bass up and distortion can occur sooner. Adding a second cab to get more volume seem to be the best solution.

Although your amp has been sitting unused, the power supply caps slowly degrade as time passes. This is why, if yours are original, they might need to be replaced.

The larger power supply caps in the amp are called electrolytic capacitors. These caps have both a shelf life and a limited operational lifetime. Using the amp can reverse these effects to some extent. That's why if you have an amp that you are not using, it helps the caps to turn it on in playing mode (standby off) from time to time. As a minimum, I find that every six months for half an hour works well enough.

There is a chemical reaction going on inside these caps that breaks down an oxide layer that the cap needs to work. Using the amp helps reverse this chemical reaction and reforms this oxide layer. Eventually the oxide breaks down to the extent that it can't be reformed and the capacitor needs to be replaced. Turning on an amp that has been sitting for a really long time can also damage that caps. The current punches through the thinner oxide layer, damaging the caps. That's why techs recommend bring a long idle amp up to full wall voltage with a variac. By slowly increasing the wall voltage, you avoid a fast inrush of current. The caps have a chance to react and rebuild their oxide layer.

_____________

The WS1 and the WZ34 are both direct replacements for the rectifier tube. They are diode modules with a part in there that turns on the amp slowly (less than a second) like the GZ34 rectifier tube does. Actually not quite as slowly as a GZ34, the tube does it a little slower, but good enough to help. The purpose of the slow turn-on is to allow the power supply capacitors to ramp up to a full charge. Otherwise there is a fast inrush that can strain your power supply. The WZ34 has resistors in it that the WS1 doesn't. The resistors add some sag when the amp is pushed. This emulates what a real rectifier tube does. It doesn't sag quite as well as a GZ34 tube does but is close. People choose the WS1 when they want a stiffer response from the amp. They choose the WS34 when they want a solid state module that is closer to a real rectifier tube, with performance somewhere between the WS1 and the GZ34 tube. A lot of people prefer the amps's performance with the real tube in place. These module change things a bit add some versatility. They're also good in a pinch if the rectifier tube blows.

[jnewmark]

When you say " stiffer response " , what are you meaning here, less compression, distortion, etc ?

[beans-on-toast]

Stiffer = less sag, less distortion, less compression, more headroom when the amp is pushed. At lower volume levels you wouldn't notice a difference, this only applies when it is cranked.

I should point out that in the latest revision, the Heritage B-15, they designed the amp with a stiffer power supply. Jess Oliver felt that this was a shortcoming of the classic design. They retained the tube rectifier because it would be heresy to put the amp out without the classic tube lineup. But they added a choke to the power supply and boosted the capacitance (I mentioned this mod earlier). Both these changes allow you to turn up the volume a little higher, getting more out of the amp, before the onset of sag and subsequent distortion sets in. I've done the cap mod on my 63 before the Heritage model came out so we seem to feel the same about this. It isn't an easy mod but the end result is a nice improvement.


David