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Old 21st January 2005, 02:05 AM   #1
Sherman is offline Sherman  United States
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Question Hammond vs. James?

I am getting to the nitty gritty of my winter amp project and all that is left before building is deciding on and ordering the iron. My budget is sufficient for either Hammond 1628SE or James 6123HS.

There was a thread here a while back about frequency response issues with the Hammonds (a big drop out at 15K IIRC and another anomaly lower down, 3K?). I haven't seen any actual data on the James, nor do I know anyone who is using them.

My feeling is that if the Hammonds have a systemic issue that hasn't been resolved I would probably go with James. But if the Hammond thing was a temporary production glitch or something that has been fixed I'd go with Hammond since the other iron, PTX and choke will be Hammond and it would be nice to have everything match.

Any input on either the Hammond issue or any real-world measurements and use of James?
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Old 21st January 2005, 04:17 AM   #2
rdf is offline rdf  Canada
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I use the 1628Se and don't recommend it. My samples have severe issues in the 13 kHz range. For more info see:

http://www.sacthailand.com/transformerTest1.html

Edit: For what it's worth, the amp in my avatar uses them. It makes 3 watts and the problem is still evident. The PS iron is also Hammond and it appears to be wound 10% over on the primary. Both the HV and filaments read high, the latter at 7 volts which I discovered late and after cooking a few EL84's. I might consider a 125se for benching, but I'll never build another serious amp with Hammond iron again.
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Old 21st January 2005, 11:19 AM   #3
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Quote:

I use the 1628Se and don't recommend it. My samples have severe issues in the 13 kHz range.

The last time I tested my hearing I had to strain to hear 14khz.

You must either be a heck of a lot younger than me or are blessed with very good hearing.
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Old 21st January 2005, 02:26 PM   #4
morfeas is offline morfeas  Greece
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Even thu I m very happy with the 1640SE I wouldn't call HIFI the recorded qualities of the 1628SE
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Old 21st January 2005, 03:12 PM   #5
rdf is offline rdf  Canada
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Approaching 50 and, as of yesterday, hearing still good to 15 kHz.

Measurement-wise the TX problem - in my amp - manifests itself as a short, quick 2 dB rise at 13 kHz under rather large amounts of purely resistive feedback, significant ringing on square waves and rapidly rising distortion with frequency. Ironically I spent the night before Sherman's post on the bench tuning the feedback capacitor trying to minimize just these issues. The best I could achieve was dead flat response to 14 kHz, a 1 - 1.5 db downward knee to 16 kHz, relatively flat to ~ 18 kHz, followed by a rapid rolloff (~ -3 dB @ 20 kHz) and then an ultrasonic rise in the 40-50 kHz range. A very odd frequency response. It wasn't possible to eliminate a large spike on the rising edge of square waves or the rising distortion with frequency. This is at 1 watt output.

The problem is suprisingly audible as a 'dirty' high end, to my ear similar to speakers with high freuqency issues, for example the Tang Band W4-657s with its very narrrow 4-6 dB rise centred at 8 kHz. It's not as obvious but very similar in character. Carefully tuning the feedback cap reduces it significantly but the highs never really sound clean and extended. Cymbals suffer the most.

Check the SAC Thailand test results. That's nasty stuff.
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Old 21st January 2005, 07:46 PM   #6
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I think you'll find the James in a different league from the Hammonds... i view the Hammonda as budget OPTs, the James are pushing for top tier.

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Old 21st January 2005, 09:18 PM   #7
Sherman is offline Sherman  United States
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Quote:
Originally posted by planet10
I think you'll find the James in a different league from the Hammonds... i view the Hammonda as budget OPTs, the James are pushing for top tier.

dave
Dave,
That is interesting since they are the same price at ~ $90US each. I'm not discounting what you are saying but all I seem to find on James is "they used to be with xyz and build top notch trafos" etc. I have yet to find someone that has said "I have used them and they sound great" or "I use them and have measured a flat FR from 20-20K Hz +/- 1dB" or something like that.

However I doubt I could hear a -3dB dip at 15K Hz (or even a 9dB dip ). But it would be nice to know the TX is making noise where it is supposed to be!

If I decide to go with James do you have any idea where I might find covers for a Hammond PTX and choke that will help them match the James OTX? (The equivalent James PTX is US $190 vs. $51 for Hammond, and the equivalent James choke is $90 vs. $25 for Hammond. I'm building monoblocs to I need 2X .)
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Old 22nd January 2005, 03:54 AM   #8
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Quote:
Originally posted by Sherman
That is interesting since they are the same price at ~ $90US each. I'm not discounting what you are saying but all I seem to find on James is "they used to be with xyz and build top notch trafos" etc. I have yet to find someone that has said "I have used them and they sound great" or "I use them and have measured a flat FR from 20-20K Hz +/- 1dB" or something like that.
There was a recent joelist thread on James OPTs... quite a few stepped up and said good things about them... no one had anything to say against them.

A local fellow built a monster PSE 300B amp with James with excellent results.

Woody -- a member here -- has gotten at least a couple pairs. The latest for a 6C45pi spud amp.

dave
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Old 22nd January 2005, 11:00 AM   #9
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If you want "dirt" on James transformers, do a search. Someone here posted a link with measurments showing that the James universal output transformer performance was clearly inferior to some of the Tango universal units. The link was a sight showing the measured performance of many transformers.

Of course, the Tango are much more expensive.
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Old 22nd January 2005, 01:20 PM   #10
kmtang is offline kmtang  Canada
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First of all, I believe it is not fair to take only the Hammond 1628 for comparison with others. My friend built a 2A3 power amplifier with Hammond 1627 OPT. He measured the frequency and square wave response and the result was excellent. The frequency response is very flat from a few hertz to almost 100kHz. The square wave at 10kHz has a very little spike at the edges. The important thing is, his amplifier sounds much better than the Audio Note Kit One using 300B output tube.

I built myself a 45 tube amplifier with 1628 OPT. I measured the frequency response at both 8-ohm and 4-ohm output taps. The result for 8-ohm looks a bit urgly but at 4-ohm it is reasonaly good. The frequency response at low end frequency is extremely good. I believe it is because of the big inductance it has. By the way, I having measure the response for 16-ohm tap because I am rather lazy to rewire the wires at the primary of the OPT.

My measurements for 1628 is attached in Excel file.


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