Ampeg V4B- the good, the bad, and NOS tubes

[beans-on-toast]

I also added a bias adjustment pot, 1 ohm cathode resistors with four rear panel test points. Darn amp techs can't leave anything alone

Always liking to change things isn't a bad thing is it?

When you had your fan installed, did you keep the back panel in place? A lot of people like to remove these to keep things cooler.

 

[B-string]

Always liking to change things isn't a bad thing is it?

When you had your fan installed, did you keep the back panel in place? A lot of people like to remove these to keep things cooler.

Yes I kept the back panel. The fan was at the front of the chassis angled to "blow" at the center of the quad. The rear panel helped to diffuse the air flow. Did not aim for thermal efficiency from the airflow, the compromise worked well enough. It ran cooler than with the 7027As w/o a fan.

 

[DavidEdenAria]

The NOS 7027 are really rugged tubes....I've collected tubes for 25+ years but unfortunately have very few 7027....Angela.com used to have a bunch.

That's what I would run...the others I have plenty in my stash but the NOS 12au7 are really common and easily obtained for relatively cheap.

 

[beans-on-toast]

Yes I kept the back panel.

Thanks for the info. I'm wondering about adding a fan on mine.

Was the amp an early or later model? The early pre 74 model (top) was more blocked where the tubes are. The later model had the screen. I assume that they did this to help heat dissipation.

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[B-string]

I have a US quad around with low hours, matched by GT before FMI bought them out. Should sell them but never know when someone here will be at the door with an old V4-B in need.

 

[beans-on-toast]

I see NOS 7027A's going for around $50 each. Not that bad for what they are.

 

[B-string]

Thanks for the info. I'm wondering about adding a fan on mine.

Was the amp an early or later model? The early pre 74 model (top) was more blocked where the tubes are. The later model had the screen. I assume that they did this to help heat dissipation.

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Mine was the early (1973). Would have to rethink with the "newer" rear panel. Lost my password with photobucket when the laptop died, one of these days I'll recover it.

 

[B-string]

I see NOS 7027A's going for around $50 each. Not that bad for what they are.

From what I have researched the 7027A was really a 6L6GC with thicker plates and extra pin connections?

 

[beans-on-toast]

...one of these days I'll recover it.

This must be it.

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[B-string]

That is her....er it . Took those pics for the new owner before she....um it left me.

 

[beans-on-toast]

From what I have researched the 7027A was really a 6L6GC with thicker plates and extra pin connections?

Yes but they were able to take a higher plate voltage because of better plate dissipation.

 

[DavidEdenAria]

Any tube that has 4 digits is an industrial rated tube.

Ampeg used industrial tubes where they could thru the years.

 

[B-string]

I always suspected Magnavox/Ampeg used the 6K11 triple triode to further the use of the Magnovals they spent the R&D on.

 

[beans-on-toast]

I always suspected Magnavox/Ampeg used the 6K11 triple triode to further the use of the Magnovals they spent the R&D on.

It isn't like there was a space issue and they couldn't fit a 12AX7 and a 12AU7 in there. Ampeg wasn't the only company to use that tube in an amp for some strange reason. It looks like R2D2.

 

[B-string]

It isn't like there was a space issue and they couldn't fit a 12AX7 and a 12AU7 in there. Ampeg wasn't the only company to use that tube in an amp for some strange reason. It looks like R2D2.

Yes more than enough room. Magnavox used them in TV sets, but wouldn't release the rights to other set manufacturers. Not the best plan considering SS devices were knocking hard at the door.

 

[beans-on-toast]

Ampeg used industrial tubes where they could thru the years.

Back in a time when their tubes costed next to nothing. In this 1960 price list, a 5AR4 is $4.50 list, dealer price was typically half of that. It was often a Mullard.

 

[B-string]

Back in a time when their tubes costed next to nothing. In this 1960 price list, a 5AR4 is $4.50 list, dealer price was typically half of that. It was often a Mullard.

I remember in '72 the repair shop I was apprenticing at sold me a quad of 6L6GC RCAs for $1.65 each (dealer price).

 

[coreyfyfe]

I always suspected Magnavox/Ampeg used the 6K11 triple triode to further the use of the Magnovals they spent the R&D on.

I think the V series were a Unimusic creation which would have predated the sale to Magnavox by a year or two. I'd guess they probably got a discount on a big lot of 6K11s no one else wanted.

 

[coreyfyfe]

It isn't like there was a space issue and they couldn't fit a 12AX7 and a 12AU7 in there. Ampeg wasn't the only company to use that tube in an amp for some strange reason. It looks like R2D2.

I remember there used to be someone on ebay selling refit boards for the V4 that allowed you to replace the 6K11 with a 12AX7 and 12AU7.

 

[B-string]

I think the V series were a Unimusic creation which would have predated the sale to Magnavox by a year or two. I'd guess they probably got a discount on a big lot of 6K11s no one else wanted.

Interesting, that could have been the door opener for the Magnavox buyout?