Ohms in Tube amps???

novo · #1 08-05-2011, 12:01 PM

I just got my first Tube amp...SVT VR and a 610HLF....

what exactly do ohms mean??? and how should I set up my head to get the best out of it on a 610HLF Cab...also there is a circular knob on the back of the cabinet...what does that do and how should I set it??
Thanks

bigbottomend · #2 08-05-2011, 12:06 PM

Ohm - Wikipedia, the free encyclopedia

The knob on the back of the 610 is to control the HF.

anonymous02282011 · #3 08-05-2011, 12:10 PM

whatever you do, do NOT turn your amplifier on before plugging it into the speaker cabinet.

Munjibunga · #4 08-05-2011, 12:13 PM

You should read the Amps FAQ five times before you ever touch the On/Off switch on your amp. Making an incorrect connection can be the demise of a tube amp. Why did you buy a tube amp without knowing anything about them?

RickenBoogie · #5 08-05-2011, 12:19 PM

+1 - but here's a clue, (for free). You have a 4 ohm cab, so set the switch on the back of the amp to 4 ohms.

moebass · #6 08-05-2011, 12:23 PM

Ohms is mesure of the restance.4 ohms will deliver more power that 8 ohms because of the restance.make sure your cab and amp have matched ohms.If your amp has a switch that goes from 4 ohm to 8 ohm.You can have have one 4 Ohm cab or 2 8 Ohm cabs if in the 4 Ohm setting.If in the 8 Ohm setting you can have 1 8 ohm cab or 2 16 Ohm cabs.
1 4 Ohm 4X10 will sound louder than the 8 Ohm version of the same cab because the amp is running at half power in the 8 Ohm setting.Theres all kinds of info on this subject on talk bass that can run you through what ya need to know better than I can.Hope that helped a little.

BassmanPaul · #7 08-05-2011, 01:10 PM

it's not resistance Moe it's impedance. Plus a tube amp will give the same power into any of its taps. I think you are thinking of SS amps.

**IvanMike** · #8 08-05-2011, 04:00 PM

Quote:

Originally Posted by Munjibunga

You should read the Amps FAQ five times before you ever touch the On/Off switch on your amp. Making an incorrect connection can be the demise of a tube amp. Why did you buy a tube amp without knowing anything about them?

cause they're cool!

but good advice - a lot of work went into the amps FAQ. I kinda started it, but in my absence the other AMPS mods really did a good job with it. Most any question you have can be answered there.

ps - i think the link is still in my sig, but it's a sticky right on top of the forum...

billfitzmaurice · #9 08-05-2011, 04:18 PM

Quote:

Originally Posted by novo

what exactly do ohms mean??? and how should I set up my head to get the best out of it on a 610HLF Cab...also there is a circular knob on the back of the cabinet...what does that do and how should I set it??

Read The F******Manual. If you don't have them you can download them from Ampeg.

Immigrant · #10 08-05-2011, 05:55 PM

Sounds like a nice rig!

As stated earlier, the dial is for high frequency level. Adjust to taste.

I think ALL NEW 610 HLFs are 4 ohm. It says on the back, near the input jacks.

The head (if anything like a CL) has a 2/4 ohm switch. Set it to match whatever the cab says. If the cab is 8 ohms, you need to add another 8 ohm cab to make it 4 ohms. Don't try to run an 8ohm cab with a head set at 4 ohms.

Like the other guys said, some not so nicely, read the FAQs and hook it up right.

Congrats on your new setup!

novo · #11 08-06-2011, 07:54 AM

Quote:

Originally Posted by billfitzmaurice

Read The F******Manual. If you don't have them you can download them from Ampeg.

chill dude, was just askin

Dethrats · #12 08-06-2011, 08:58 AM

Quote:

Originally Posted by novo

chill dude, was just askin

uh..... IDK if I would have told Bill to chill, just take his advice.. he is WELL respected around here, as a lot of others, you'll learn young grasshopper, you'll learn

JimmyM · #13 08-06-2011, 12:16 PM

OK, everyone just calm down!

You don't need to know everything about tube amps to own one. All you need to know is you have a 4 ohm cab, so run it at 4 ohms. However, reading the manual is never a bad idea.

dsanders · #14 08-06-2011, 12:35 PM

Quote:

Originally Posted by Dethrats

uh..... IDK if I would have told Bill to chill, just take his advice.. he is WELL respected around here, as a lot of others, you'll learn young grasshopper, you'll learn

Wether he is respected or not is beside the point. There will always be new players around that need our help. NONE of us like addressing the same questions over and over again. But if your panties are in a wad over it just keep your respected opinion to yourself...IMO.

Let the flaming begin. At this rate we will be no different then guitards before long.

billfitzmaurice · #15 08-06-2011, 02:55 PM

Quote:

Originally Posted by dsanders

Wether he is respected or not is beside the point. There will always be new players around that need our help. NONE of us like addressing the same questions over and over again. But if your panties are in a wad over it just keep your respected opinion to yourself...IMO.

Let the flaming begin. At this rate we will be no different then guitards before long.

He's a self described newbie. What logical reason would he have for not reading the manuals? What logical reason did he have for ignoring the post at the top of the page that clearly says AMPS FAQ!! Info on OHMS, Allsize RIGS-OverUnderPowerCabs DIY TechTalk-Links
Manuals and FAQs exist for a reason. Forums exist for answering questions that aren't covered in manuals and FAQs.

**B-string** · #16 08-06-2011, 03:31 PM

I taught may son to read the manuals before touching the power. He thanks me for this now.

1958Bassman · #17 08-06-2011, 03:44 PM

"whatever you do, do NOT turn your amplifier on before plugging it into the speaker cabinet."

And don't turn it off with no speaker plugged in, don't mess with the plug when it's on and don't plug a second cabinet into the first if it has a switching jack. If it makes no sound, turn it off before checking the connection at the jack or plug.

Sartori · #18 08-06-2011, 05:16 PM

Okay, here's the short of it.

Your head (the Ampeg SVT-VR) can operate at either 4 ohms or 2 ohms. There's a switch on the back. Your cab (the SVT-610HLF) is a 4 ohm cab. Use a speaker cable (NOT an instrument cable! They are different and not interchangeable!), preferably one with speakon connectors (the connectors that don't look like instrument cable connectors) to connect the speaker output of the head to the input of the cab. These are labelled, as I recall.

Make sure that the little switch on the back is set to "4 ohms," since your cab is a 4 ohm cab.

After checking to make sure everything is connected properly and the switch is set at 4 ohms, turn the power on. Wait a minute (you can use this time to tune or something) and switch it from standby to on (the second switch on the front of the head near the little light).

Absolutely NEVER turn the amp on without it being connected to a speaker.

Also, the little dial on the back of your cab is to control how loud the tweeter (high frequency speaker) is. Turn it to whatever position sounds good to you. However, I'd be cautious if you're playing at volumes high enough that you're getting overdrive from the SVT. Tweeters and overdrive sometimes aren't the best of friends.

And now for the long version.

There's good advice in this thread, but I'm going to restate it anyway.

"Ohm" is a measurement of impedance. Tube amps such as the SVT-VR have output transformers (if you look through the grill on the back, there should be a couple big square/rectangular metal things... these are the transformers, one of which is the output transformer). These basically exist, IIRC, to convert the high impedance signal from the power tubes (again, looking through the grill on the back of the head, these are those large glass things) to the low impedance of the cab(s) you're using. This is probably an oversimplification, but it'll work for now. The output transformer has a couple "taps," which are basically points at which the signal can be sent out to the speaker cabs. The SVT-VR has a 4 ohm tap and a 2 ohm tap. The switch on the back of the head determines which of the taps is in use.

If you were, say, to get another 610HLF (having two), you would switch to the 2 ohm setting. When wired in parallel (which the vast majority of amplifier outputs are), the impedance the two cabs present to the amplifier is divided. The 610HLF is a 4 ohm cab, so two of them would make a total of a 2 ohm impedance.

The reason you must never turn your amp on without a speaker cab connected is that a tube amp reads no load as an infinite load. This can cause some pretty major trouble for the amplifier. Some amps are designed to short out if this happens to avoid more significant damage, but others aren't. To avoid having to take your amp to a tech to repair it (which can get very expensive, depending on how bad the damage is), always have your amp connected to a speaker cab when you turn it on. If you turn the amp on and there's no sound, immediately turn it off and make sure that it's connected to a cab properly and that it's set correctly. Do NOT turn it up if you don't get any sound when you play.

Also, as Bill said, read the manual. A lot of this information is in there. Additionally, there are some very helpful links with lots of useful information at the top of this forum.

Pilgrim · #19 08-06-2011, 05:20 PM

In general, Novo, it's a good idea to check for a manufacturer's manual and/or do a bit of Internet research before asking this kind of question in any forum. Sometimes the question you have is unusual and well worth raising, but sometimes it's so basic that it become apparent the person asking hasn't made any effort to do their own homework.

There is a great deal of info about tube amps here, and all in all, the members here would rather that you did ask if you don't know. Just be ready for some nudging if it turns out that you're asking a really simple question.

incidentally, I typed "svt vr manual" into a Google search window and this link was the first hit: http://www.ampeg.com/pdf/SVTVR.pdf. On page 5 there's a nice table that helps you match cabinets by impedence, and there are also some sections with very helpful info about tubes and how to take care of a tube amp. I think all that info will be very helpful to you. (It would have been a good move to do the same search before posting.) It looks like a nice amp, and I hope it works well for you!

seamonkey · #20 08-07-2011, 12:04 PM

The funny thing is if Novo actually reads the manual and then posts a question like how often the manual recommends to change tubes - he'd get many posts telling him to ignore the manual.

I recommend reading and following the manual. It's how you get warranty service to keep you from doing inadvertent damage to the amp. Follow the manuals advice. It should be your first line of advice while the amp is under warranty.