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Old 11th August 2008, 03:13 PM   #1
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Default Noob question

Hi all,

Sorry about the noob questioon, but I need to know how to do this. Unfortunately my specialties are on a computer and not on the equipment itself.

How do I hook up a bass amp (heathkit a-7{e?}) to a single woofer? I recently picked up an ibanez 2388 bass and said amp at a yard sale. I have experimented a little bit and can get minimal sound out of it.

I am sorry if there is some kind of noob primer somewhere on such a simple subject, but alas here I am (and I obviously could not find it).

Thank you for your help.
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Old 11th August 2008, 05:03 PM   #2
kevinkr is offline kevinkr  United States
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Default Re: Noob question

Quote:
Originally posted by dumbo800
Hi all,

Sorry about the noob questioon, but I need to know how to do this. Unfortunately my specialties are on a computer and not on the equipment itself.

How do I hook up a bass amp (heathkit a-7{e?}) to a single woofer? I recently picked up an ibanez 2388 bass and said amp at a yard sale. I have experimented a little bit and can get minimal sound out of it.

I am sorry if there is some kind of noob primer somewhere on such a simple subject, but alas here I am (and I obviously could not find it).

Thank you for your help.
Not a stupid question, however plugging in an amplifier as old as an A-7 without checking it out first is what I call a risky behavior. This usually results in shorted, smoking electrolytic caps and a fried power transformer. This thing should be checked out by a competent tech and rebuilt before you attempt to use it. It might even be an electrocution hazard.

Depending on the version you have it may not have sufficient gain for use with your bass guitar. Incidentally the A-7 is a low end, low power hifi tube amplifier - it is in no sense a bass amplifier. You need far more power unless you are looking for very modest output levels.

The speaker would connect to the speaker output terminals on the back of the amplifier, you need to know the impedance of your woofer and then you connect it to the 0 ohm and the output terminal (tap) marked with the same impedance as your speaker.

I doubt the results will be very satisfactory in any event. I would put this amplifier on eBay in the vintage amplifier area of consumer electronics and get something more appropriate. You can probably make a little money on the transaction.
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Old 11th August 2008, 07:40 PM   #3
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Thank you very much.

I was only able to get a limited (over-driven sounding) response in the lower frequencies, and only on the upper end of the high string was I able to get a clear, concise sound.

I was originally worried that I was somehow hooking it up wrong, but your reply tells me I was probably right.

Thankfully, nothing was wrong (outwardly) with the amp, and the speaker I had it hooked up to was part of the $5 spent on the amp, so I was not too worried about destroying anything. (the bass was $120 though. A good price in my book.)

Any opinions on a decent amp on a decent (low end of decent) budget?
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Old 11th August 2008, 08:20 PM   #4
kevinkr is offline kevinkr  United States
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Here's a link to a bunch of suitable bass amplifiers:

http://www.musiciansfriend.com/bass-guitar-amps

This one might be worth looking at a bit further if your budget can stretch that far:
http://www.musiciansfriend.com/produ...age?sku=482546

Otherwise cheaper alternatives from Peavey and Behringer are available.
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Old 11th August 2008, 10:02 PM   #5
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The schematic indicates that it could be converted to a moderate power guitar head but for Bass it would be essentially a practice amp.
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Old 11th August 2008, 11:56 PM   #6
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I think I'll drop by the local Dave Phillips store and see if they have any of the affordable ones to try out on the floor. Thank you for your help.
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Old 12th August 2008, 02:43 AM   #7
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I've played bass thru my A7-C. It works, but nothing amazing.
Doesn't really go low enough at a reasonable level of output.
That was thru my Karlson K15 cabinet loaded with a slightly
undersized Eminence DeltaPro12.

The K15 bass bin isn't to blame. Takes my Fender BXR300 fine
with no hiccups and very little cone excursion. Its definately
about the little 7W Heath amp not quite cutting the mustard.

I don't care for Heath's "stock?" non-UL output transformer on
the version I got stuck with, and a brand new Edcor just sittin
here waiting upgrade/installation. I may make some additional
changes while I'm at it.

I also have hum issues with the SJ/SH Pentode in the pre-amp.
Very similar Pentode either way, but one is audio the other RF.
Course I got the RF version which the schematic sais will work,
but the spec sheet for the actual tube warns will cause hum in
audio circuits.... And it does. But easily disabled/bypassed by
throwing the switch over to the 2nd input...

So I just use my Korg AX1B stomp box as the pre-amp. Levels
are more than adequate to hear the Heath act very wrong in
overdrive. again, I got more changes than just OPT in mind...
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