Anyone tried the Hammond 1642SE in a BIG SE amp? - diyAudio
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Old 3rd September 2005, 11:49 PM   #1
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Default Anyone tried the Hammond 1642SE in a BIG SE amp?

I am wondering if anyone out there has used the Hammond 1642SE in a high power SE amp. Something over 60 Watts. This would be a PSE amp with 2 X 845 or 2 X 211 or an SE with an 833A. If so has anyone measured the frequency response of that amp. Are there any other SE transformers out there that could be used at the 50 to 100 watt level that costs under 250 USD.

I am looking for an output transformer that would work in an 833A SE amp at the 75 watt level or higher. I had an OPT custom made by a transformer winder, but the high frequency response was very uneven above 14 KHz, but I could get over 100 Watts down to 42Hz and 60 Watts at 30 Hz. I know my hearing is nonexistent above 14 KHz, but I want flat response out to at least 20 KHz. The amp did sound awesome, and the bass was unreal, even with my small speakers. I looked at the Electra_Print CU5KB, but they are beyond my budget. The Hammond is also about 10 pounds larger than the Electra-Print, and 8 pounds larger than my custom transformer. Weight = Bass response, and I like bass.

I am still looking for that magical amp that shakes the walls with the low end punch that my 300B PP amp has, and still retains the SE magic that my 845SE has. Maybe the SE 833A is it, I won't know until I have built it!

http://www.tubelab.com/833SE.htm
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Old 4th September 2005, 12:49 AM   #2
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Back in the 70's, when I was just a young foolish pup.
During my early garage band days. I ran an ampeg SVT 300W all tube head into a 6-12" cab.

I played my old Gibson Melody Maker and eventually an SG standard into it.
Though the SVT was intended as a bass amp. I really loved the earth shaking bottom end with the guitar. One noteable pleasure was the intense presence of this amp, Its difficult to come up with a verb that actually does it justice.
I would be willing to guess that an OPT from one of those might be located thru evilbay at a reasonable cost. As I remember it must have weight in about 15 lbs!(guessing)

Another HUGE tranny that might work if it could be located would be from an old univox 1511. They hold up pumping 150W with a quad of 6550's PLUS, they are less than popular items .

Couldnt those types of trannies run in SE config?
Just A Thought
Gene
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Old 4th September 2005, 01:35 AM   #3
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I too spent some time frying my ears playing a Hagstrom guitar through an SVT. It did sound cool. The early SVT's used 6146 tubes that were intended for mobile radio use. Ampeg switched to 6550's after too many SVT's erupted in flames, including one in a stadium show by the Rolling Stones. I saw an SVT catch fire, but it was because the owner tried playing it at full volume through a Traynor 8 X 10 cabinet that was meant for a 100 Watt head. When the speakers blew, the amp was running at full tilt into an open load. The output transformer, the power transformer, and all of the 6550's were fried!

I have experimented with using push - pull transformers on single ended amps, with varying results. Some just flat don't work, some work pretty good, but most will distort the bass frequencies. The ones that work will only pass about 10 to 20 % of the power that they would pass in push - pull mode. This is because a push - pull transformer was designed such that all of the magnetism created by the DC current will cancel out. A single ended transformer is designed to work with this standing DC current. This is done by placing a gap in the magnetic circuit. To offset the effects of this gap, the core is made MUCH larger. The transformer I am looking for will weigh at least 20 pounds. The Hammond weighs 28 pounds. I have tried modifying push - pull transformers for SE use by removing the laminations and reassembling them with a gap. This is not an exact science, and is not the approach I want for this amp.

It would be possible to use a push - pull transformer by using a parafeed configuration, but this requires an expensive choke that is usually matched to the output transformer.

I appreciate the thought, but I will probably try the Hammonds for this amp, I was hoping that someone out there has already done this. I will use the prototype transformer that I have to build a seriously wicked guitar amp using an 833A. Imagine a 60's vintage Fender Champ that puts out 200 Watts.
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Old 1st February 2010, 09:41 AM   #4
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Hi Tubelab,

Did you ever try the 1642SE with the 833?

I am considering giving it a go and was wondering if you ever did get around to it?

Best Regards

James
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Old 1st February 2010, 02:43 PM   #5
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Quote:
Did you ever try the 1642SE with the 833?
At the time I had visions of building a really big SE amp. I almost did it, but the vendor who had advertized the 1642SE on his web site for a low price refused to honor that price. In fact he wanted almost twice what he quoted on the web site. That project stalled for lack of a suitable OPT.

I have since realized that such an inefficient amplifier would not get much use since I live in a very warm climate. In fact my 845SE amp has not been turned on in at least two years.
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Old 1st February 2010, 02:58 PM   #6
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There was an article in Glass Audio a few years ago where someone used a Hammond 1650W push pull transformer, sliced a gap with a hacksaw, and used it for a 50W+ SE output. He was very precise about how he gapped it. Not necessary to take it apart, except for the end bells. A little searching would find the article.
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Old 1st February 2010, 06:25 PM   #7
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The 1642SE is a rather singular monster. One could dream about pairing it up with a couple of GM70s at 900-1000V B+ (not that hard to drive). At the lower voltage, one would need A2 operation to squeeze out the last bit of juice, but w'ere no stranger to that here. Finding someone who actually stocks the 1642 is another matter, as none of my usual suspects apear to. However, if I really got serious about a project like this, I could probably find someone with a little more effort. This is one application where switching power supplies could be of use, transforming a project that would otherwise be a titanic boat anchor (or a huge separate power supply) to a couple of beefy monoblocks. It might be interesting to query Edcor to see what they would charge for a 1642-like transformer.
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Old 1st February 2010, 09:38 PM   #8
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Quote:
Originally Posted by dshortt9 View Post
There was an article in Glass Audio a few years ago where someone used a Hammond 1650W push pull transformer, sliced a gap with a hacksaw, and used it for a 50W+ SE output. He was very precise about how he gapped it. Not necessary to take it apart, except for the end bells. A little searching would find the article.
Like this
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Old 3rd February 2010, 10:13 AM   #9
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Thanks for the feedback guys, I will post back if I make any progress!

Best Regards

James
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Old 3rd February 2010, 02:19 PM   #10
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Quote:
Originally Posted by JamesHill View Post
Hi Tubelab,

Did you ever try the 1642SE with the 833?

I am considering giving it a go and was wondering if you ever did get around to it?

Best Regards

James
Hi James
I did a amp 1642SE with 826 in Shisido style, 1.25k load for 826 was what he designed, but out-put only 8 watt, SE amp most for sound quality not for power, I use my 826 for supper high section in multi amp system
Tony Ma
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