Vintage tube amp speakers

mikje · 3rd June 2008, 12:50 AM

I recently picked up a Packard Bell tube stereo, model 7TU12, and have a question about the speakers. They are each driven off a transformer. These are obviously the type of speaker that needs the transformer. If, however, I want to run some other speakers off this amp, do I need to use the transformers? I ran this amp/receiver up to make sure it works before I put any money into it, and it really sounds nice with the speakers that came with it. But I'd still like to try some other speakers too, just for the fun of it. Thanks for any help you can offer!

nickmckinney · 3rd June 2008, 01:35 AM

It sounds like a field coil and if so those "transformers" on the back of the speaker is also the filter for the power supply of the amplifier section.

mikje · 3rd June 2008, 01:43 AM

Thanks for the reply. The transformers are on the amp. From what you're saying, it sounds as though I'll need to use them for any speaker I hook up. Is that correct?

nickmckinney · 3rd June 2008, 01:51 AM

Yup, you need those transformers.

sreten · 3rd June 2008, 01:14 PM

Quote:

Originally posted by mikje
These are obviously the type of speaker that needs the transformer.

Hi,

A valve amplifier that has output transformers needs them to drive
any normal speaker. Its the amplifier that needs the transformers.

/sreten.

mikje · 3rd June 2008, 02:28 PM

sreten,
Thanks for the reply. The next question would be polarity. Both terminals on each of the transistors are the same and none are marked to indicate any polarity. Am I correct to assume polarity is not an issue?
Thanks again.
Mike

sreten · 3rd June 2008, 04:18 PM

Quote:

Originally posted by mikje
Am I correct to assume polarity is not an issue?
Thanks again.
Mike

Hi,

Absolute polarity is a unlikely issue. The 2 channels must be in phase,
so the relative polarity of the two connected speakers does matter.

/sreten.

mikje · 3rd June 2008, 04:29 PM

Do you know how I can tell which is positive and which is negative? Thanks!!!

sreten · 3rd June 2008, 05:02 PM

Hi,

Place the speakers facing each other. Reverse one speaker connection.
If you get lots more bass it is correct. If you get lots less bass then it
was correct and reverse the connections back again.

/sreten.

P.S. Positive and negative are a moot point for AC on a transformer,
however The "negative" will be directly connected to earth and the
"positive" will not be, it will have the feedback connection. Should
be able to work this out by inspection, e.g. the "negatives" may
be joined to each other whilst the "positives" cannot be.

3rd June 2008, 12:50 AM	#1
mikje Soakin' up the Sound! diyAudio Member Join Date: Feb 2008 Location: Bismarck, ND	Vintage tube amp speakers I recently picked up a Packard Bell tube stereo, model 7TU12, and have a question about the speakers. They are each driven off a transformer. These are obviously the type of speaker that needs the transformer. If, however, I want to run some other speakers off this amp, do I need to use the transformers? I ran this amp/receiver up to make sure it works before I put any money into it, and it really sounds nice with the speakers that came with it. But I'd still like to try some other speakers too, just for the fun of it. Thanks for any help you can offer! __________________ Marantz PM8003 amp, HRT Music Streamer II DAC, Squeezebox Touch, DIY Krystals

3rd June 2008, 01:43 AM	#3
mikje Soakin' up the Sound! diyAudio Member Join Date: Feb 2008 Location: Bismarck, ND	Thanks for the reply. The transformers are on the amp. From what you're saying, it sounds as though I'll need to use them for any speaker I hook up. Is that correct? __________________ Marantz PM8003 amp, HRT Music Streamer II DAC, Squeezebox Touch, DIY Krystals

3rd June 2008, 02:28 PM	#6
mikje Soakin' up the Sound! diyAudio Member Join Date: Feb 2008 Location: Bismarck, ND	sreten, Thanks for the reply. The next question would be polarity. Both terminals on each of the transistors are the same and none are marked to indicate any polarity. Am I correct to assume polarity is not an issue? Thanks again. Mike __________________ Marantz PM8003 amp, HRT Music Streamer II DAC, Squeezebox Touch, DIY Krystals

3rd June 2008, 04:29 PM	#8
mikje Soakin' up the Sound! diyAudio Member Join Date: Feb 2008 Location: Bismarck, ND	Do you know how I can tell which is positive and which is negative? Thanks!!! __________________ Marantz PM8003 amp, HRT Music Streamer II DAC, Squeezebox Touch, DIY Krystals

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3rd June 2008, 01:35 AM	#2
nickmckinney diyAudio Member Join Date: May 2008	It sounds like a field coil and if so those "transformers" on the back of the speaker is also the filter for the power supply of the amplifier section.

3rd June 2008, 01:51 AM	#4
nickmckinney diyAudio Member Join Date: May 2008	Yup, you need those transformers.

3rd June 2008, 05:02 PM	#9
sreten diyAudio Member Join Date: Nov 2003 Location: Brighton UK	Hi, Place the speakers facing each other. Reverse one speaker connection. If you get lots more bass it is correct. If you get lots less bass then it was correct and reverse the connections back again. /sreten. P.S. Positive and negative are a moot point for AC on a transformer, however The "negative" will be directly connected to earth and the "positive" will not be, it will have the feedback connection. Should be able to work this out by inspection, e.g. the "negatives" may be joined to each other whilst the "positives" cannot be.

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