Traynor YBA300 Test

GregL · #1 08-25-2011, 07:01 PM

Hello,

I may be testing a Traynor YBA300 amp next week. I notice that the amp is rated for 300 watts at 2/4 ohms.

From what I have read, I should be able to connect this head to a 400 watt, 2X10 cabinet with 8 Ohms impedance, but this is not the best thing to do to a tube amp.

Am I correct?

Thankee

Marton · #2 08-25-2011, 07:13 PM

I'm pretty sure plugging the head into a 8 ohms is not a good idea. Anyways, I don't think that a 2x10 cabinet is the best match for this head, unless you like blown speakers.

GregL · #3 08-25-2011, 07:22 PM

What would you suggest as an alternative to the 2X10 Cab?
Thanks

Marton · #4 08-25-2011, 07:25 PM

Another similar 2x10 cab would be great. Or a 4x10. Or a 2x12. It just need to be 4 or 2 ohms.

Webtroll · #5 08-25-2011, 07:29 PM

i think an 8 ohm cab will be fine with a 4 ohm head load, but not the other way around.

Marton · #6 08-25-2011, 07:30 PM

Quote:

Originally Posted by Webtroll

i think an 8 ohm cab will be fine with a 4 ohm head load, but not the other way around.

True with solid state stuff, not so much with tubes.

coreyfyfe · #7 08-25-2011, 07:48 PM

Quote:

Originally Posted by Marton

True with solid state stuff, not so much with tubes.

The general opinion with the tech types around here is that if you're going to mismatch with a tube amp, under the rated impedance is better than over. A higher-than-rated impedance can cause flash over in tubes, potentially causing shorts in the transformer windings and eventually take out the output transformer. With lower-than-rated impedance the amp can't output the same amount of power, but if there isn't much of a current increase then over heating wont occur to an extent that it will damage the amp.

Either way, not something I would do with my own amp if I didn't have to.

Technical explanation:

Quote:

There is magnetic leakage from primary to secondary and between both half-primaries to each other. When the current in the primary is driven to be discontinuous, you get inductive kickback from the leakage inductances in the form of a voltage spike.

This voltage spike can punch through insulation or flash over sockets, and the spike is sitting on top of B+, so it's got a head start for a flashover to ground. If the punchthrough was one time, it wouldn't be a problem, but the burning residues inside the transformer make punchthrough easier at the same point on the next cycle, and eventually erode the insulation to make a conductive path between layers. The sound goes south, and with an intermittent short you can get a permanent short, or the wire can burn though to give you an open there, and now you have a dead transformer.

So how much loading is too high? For a well designed (equals interleaved, tightly coupled, low leakage inductances, like a fine, high quality hifi) OT, you can easily withstand a 2:1 mismatch high.

For a poorly designed (high leakage, poor coupling, not well insulated or potted) transformer, 2:1 may well be marginal. Worse, if you have an intermittent contact in the path to the speaker, you will introduce transients that are sharper and hence cause higher voltages. In that light, the speaker impedance selector switch could kill OT's if two ways - if it's a break before make, the transients cause punch through; if it's a make before break, the OT is intermittently shorted and the higher currents cause burns on the switch that eventually make it into a break before make. Turning the speaker impedance selector with an amp running is something I would not chance, not once.

GregL · #8 08-25-2011, 08:24 PM

Appreciate the education.

Don't know why Traynor didn't mention this to me when I told them what cab of theirs I was planning to use.

lo-freq · #9 08-25-2011, 09:42 PM

A Bergantino NV610 or NV412 (or both cabs) would be a great match-up with that amp.

I would check with the manufacturer about the 8ohm usage.
8ohm cabs are so common, you'd think they would have taken that into consideration when designing the amp.

u84six · #10 08-25-2011, 09:46 PM

Personally, if I was going to "test" a head like this, I'd hook it up to a 4 ohm 810 or 2 8 ohm 410s for 4 ohm load, even 2x15 at 4 ohm.

rodl2005 · #11 08-25-2011, 11:33 PM

+1 Definitely at least a 4 ohm 410, or 2 even. Give it a good No. of drivers & let it rip, & let us know how it goes.

coreyfyfe · #12 08-26-2011, 04:35 AM

Quote:

Originally Posted by lo-freq

8ohm cabs are so common, you'd think they would have taken that into consideration when designing the amp.

The output impedance matching depends on the output transformer, which might not have been available in quantities they needed with the specs/tone they wanted to do 2/4/8.

**Lazarus.Bird** · #13 08-26-2011, 05:06 AM

2/4 ohms is very common for a 300w tube amp (see SVTs).

Webtroll · #14 08-26-2011, 05:59 PM

I've used the same or one step down on ohms for many years and never had a problem; tubes and solid state alike. Guitar combos I've seen that can handle 8/4 ohm loads often have 8 ohms speakers and 8 ohm extension cabs available. I'm up for learning anything about this that I have wrong, but please know what you are saying is true and not just believe it to be true.

coreyfyfe · #15 08-26-2011, 06:11 PM

The quote from above is from here:

Tube Amp FAQ 1/20/99 (Frames supported)

which has a ton of other information if you want it. But it all really depends on the amp, how good the components are/design is, and how well it's been treated in the past. Fender bassman amps came with a rating that said "4 ohms minimum" on the outputs and I used my bassman 70 for years with 4 and 8 ohm cabs with no issue before I really had a good understanding of tube amps in that respect. Many people use SVTs at 8 ohms without problems. Again, if it was my amp, I'd always go for matching impedance unless I really had no other option.

kimmyt · #16 11-14-2011, 07:44 PM

I read somewhere that there is a tap on the output transformer that will change the 2-4 switch to 4-8. So I emailed Traynor to ask how the tap is used, is it a manual switch or does it just automatically work? Here is what I got today.

The amp can be set up to give its full rated power at either 4ohms or 2ohms. Wit a single 8ohm cabinet the output power will be slightly attenuated. Probably closer to 250 watts.

Regards,

YV Sound

As this didn't answer my question I responded with another request as to how do you use the "tap" on the output transformer. I am awaiting an answer. I also would like to purchase on of these but have a 4 x 10 and 1 x 15 cab both 8 ohms. I know I could run them both and would have the 4 ohm load needed but I find myself using the 4 x 10 cab by itself much more so this would only be 8 ohms. Does anyone know how to "tap" the output transformer? This is one of the reasons I don't want to by and SVT along with the weight. I owned the Traynor YBA 200 ands loved the sound I got but not enough headroom.