# Holy mother of power caps and iron!!!



## Alan Small (Dec 30, 2019)




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## Alan Small (Dec 30, 2019)

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## Alan Small (Dec 30, 2019)

Quick Share


Expired




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## Alan Small (Dec 30, 2019)

The pdf link is the manual and schematic: it is well written and comprehensive


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## Latole (Aug 11, 2020)

$550 ! Too expensive


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## Paul Running (Apr 12, 2020)

Those lab amps are becoming very rare...I believe that it is worth the coin to a few just on this forum alone.


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## tomee2 (Feb 27, 2017)

Paul Running said:


> Those lab amps are becoming very rare...I believe that it is worth the coin to a few just on this forum alone.


Imho it's a pretty fair price for what it is. They were asking $650 a month back.
If you Google the model you'll find a following in the vintage tube hifi market. The designer is fairly well known in the recording industry, high end stereo world.
There was also a guy buying these, rebuilding them and selling for I think $30,000 per pair. 
They're a wide bandwidth lab amplifier, with regulated power supplies for everything, with an output transformer that would be very expensive to make today.


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## Granny Gremlin (Jun 3, 2016)

Wowzers. .Must be running at super low distortion if they're only getting 50 watts from a quad of 6550s .... 0.005% is better than consumer level solid state today by a whole decimal place. ... all of the specs are absolutely astounding even by today's standards (aside from the output power to weight ratio ;P).

Correction; 35 watts (at min distortion - gotta mismatch OT Z to get 50, and that iron such a brick shithouse they tell you to go right ahead in the manual). Gotta admit I have no understanding of that 4 coil output primary. .... or the power filtering - filter cap bypass resistors? V1 has it's own separate isolated and solid state rectified power supply - just for the 12BZ7's heaters so they could filter all the ripple out with 2000uF. JUST FOR THE V1 HEATERS. Main power supply, has a switchable choke for extra filtering. I just . This is insane (and incredibly well documented - they even show the regular heater supply explicitly).

This isn't an amp it's test/control equipment from NASA.


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## tomee2 (Feb 27, 2017)

Granny Gremlin said:


> Wowzers. .Must be running at super low distortion if they're only getting 50 watts from a quad of 6550s .... 0.005% is better than consumer level solid state today by a whole decimal place. ... all of the specs are absolutely astounding even by today's standards (aside from the output power to weight ratio ;P).


And low distortion at both low and high frequencies. You need a big core and a very special winding to get that.
Guitar amps are 50 to 8000Hz beasts.. these amps might be 20 to 20,000?


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## Granny Gremlin (Jun 3, 2016)

tomee2 said:


> And low distortion at both low and high frequencies. You need a big core and a very special winding to get that.
> Guitar amps are 50 to 8000Hz beasts.. these amps might be 20 to 20,000?


Manual claims ruler flat response (+/- 0.5db) from 0.5hz to 30kHz! (don't even look at the +/- 3db spec -it's frightening). Power a subwoofer with this thing, I dare you. That's so good they need a rumble filter on the front end so you don't Marty McFly yourself or Jericho your pants. Forget LRAD, this is a fucking weapon.

Also, re that distortion spec - that's measuredf at 50 watts with the OT mismatched for higher power. They don't even bother giving you the 35 watt spec.


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## tomee2 (Feb 27, 2017)

Granny Gremlin said:


> Manual claims ruler flat response (+/- 0.5db) from 0.5hz to 30kHz! (don't even look at the +/- 3db spec -it's frightening). Power a subwoofer with this thing, I dare you. That's so good they need a rumble filter on the front end so you don't Marty McFly yourself or Jericho your pants. Forget LRAD, this is a fucking weapon.
> 
> Also, re that distortion spec - that's measuredf at 50 watts with the OT mismatched for higher power. They don't even bother giving you the 35 watt spec.


0.5Hz! Yikes that's the lowest spec I've ever seen for a tube amp!


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## nonreverb (Sep 19, 2006)

Lots of global feedback and ultra low THD but from what I've read about them in the past, some say they don't really sound that good as a Hifi amp.


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## Alan Small (Dec 30, 2019)

80 or 90 lbs I am guessing


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## Paul Running (Apr 12, 2020)

Colloquially known as a "boat anchor"


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## Paul Running (Apr 12, 2020)

We used to have vibration tables at Leigh Instruments for environmental testing that used similar servo amps, loaded with KT88s for drive tubes. The extended bandwidth is great for low and high frequency vibration.
McIntosh has a few models that are good for lab use.


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## nonreverb (Sep 19, 2006)

Paul Running said:


> We used to have vibration tables at Leigh Instruments for environmental testing that used similar servo amps, loaded with KT88s for drive tubes. The extended bandwidth is great for low and high frequency vibration.
> McIntosh has a few models that are good for lab use.


Still have the set I got from you Paul.


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## Granny Gremlin (Jun 3, 2016)

This is the amp House Atreides built.


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## 2N1305 (Nov 2, 2009)

Krohn-Hite was (still is) a company devoted to making laboratory grade equipment. The type of stuff McIntosh would use to test their amps, similar to Hewlett Packard (yes, that _HP_). 550$ seems like an ok price because those who know will recognize the value. It's practically a museum piece more than something to use. I know it seems overpriced for a guitar project but it's not really meant for that. I mean, low distortion, in the guitar world, especially the vacuum tube guitar world, we _want_ distortion!


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