Anyone tried the Hammond 1642SE in a BIG SE amp? - Page 2 - diyAudio
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Old 4th February 2010, 10:16 AM   #11
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Hi Tony,

I was actually inspired by your postings in other threads about your 826 amplifier to build one.

Unfortunately I had a very hard time getting good 826 Valves. Of the 7 I tried I found only 1 good one.

So I have now moved on to a 833 SE, (as well as a GM70 PP!)

The Hammond's are on order so will post back when I make some progress.

Best Regards

James
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Old 4th February 2010, 02:38 PM   #12
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Quote:
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
Did you ever measure the frequency response? I posted this question about the 1642SE over 4 years ago because of my bad experiences with the 1628SE.

I got a pair of 1628SE's. Their frequency response was 6db dowm at 20KHz with a sharp notch at 28KHz. The phase shift across the high frequency end of the audio spectrum is not normal either.

I have since tried the 1628SEA and found it to be better, but still not meeting the published specs.

"Frequency response at least 20 Hz. to 20 Khz. at full rated power (+/- 1 db max., ref. 1 Khz.) "

I could consider a project using the 1642SE in the future, but not until someone has independent test data on one.
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Old 4th February 2010, 03:23 PM   #13
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Quote:
Originally Posted by tubelab.com View Post
Did you ever measure the frequency response? I posted this question about the 1642SE over 4 years ago because of my bad experiences with the 1628SE.

I got a pair of 1628SE's. Their frequency response was 6db dowm at 20KHz with a sharp notch at 28KHz. The phase shift across the high frequency end of the audio spectrum is not normal either.

I have since tried the 1628SEA and found it to be better, but still not meeting the published specs.

"Frequency response at least 20 Hz. to 20 Khz. at full rated power (+/- 1 db max., ref. 1 Khz.) "

I could consider a project using the 1642SE in the future, but not until someone has independent test data on one.
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Old 4th February 2010, 05:14 PM   #14
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sorry something wrong of my computer I reply again, I built that amp around 8 years ago and I don't care too much of distortion and frequency although I got things to check. mainly for the out put power, the rest by listening judge only. looking for transformer go for over 20K but the speakerwill not follow, in multi system gain control in crossover will adjust to match the others for best result
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Old 9th April 2012, 09:50 PM   #15
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Quote:
Originally Posted by tubelab.com View Post
Did you ever measure the frequency response? I posted this question about the 1642SE over 4 years ago because of my bad experiences with the 1628SE.

I got a pair of 1628SE's. Their frequency response was 6db dowm at 20KHz with a sharp notch at 28KHz. The phase shift across the high frequency end of the audio spectrum is not normal either.

I have since tried the 1628SEA and found it to be better, but still not meeting the published specs.

"Frequency response at least 20 Hz. to 20 Khz. at full rated power (+/- 1 db max., ref. 1 Khz.) "

I could consider a project using the 1642SE in the future, but not until someone has independent test data on one.
I just "bite a bullet" and purchased the 1642SE. Life is not rose at all. It has a dip/resonance right at 17.4 kHz with the 8-Ohm output. The 4 and 16-ohm outputs does not have this dip but none of them better than 28kHz ... Moreover, somehow the winding ratio is totally off from spec. I will check the winding ratio again but the dip/resonance is definitely there. I am contacting Hammond Canada engineer and waiting for their feedback. Hammond in US and resale in US cannot help any technical issue.
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Old 11th September 2014, 11:54 PM   #16
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I realize this thread is 2.5 years old...but that passes in the blink of an eye for us old farts.

So, was the winding ratio issue making the transformer's source impedance higher or lower than the 5000 rating? Got any data with the 16-ohm output tap, where the winding ratio is less?

Last edited by cyclecamper; 11th September 2014 at 11:57 PM.
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Old 11th September 2014, 11:56 PM   #17
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Advertised prices are all over the map, with Digi-key at $320.81 which is $100 less than some others.
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Old 12th September 2014, 02:33 AM   #18
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Why use a SE OT at all? The "anti-triode" scheme solved this years ago.

You put the tube on one side of a P-P OT, and a high gm HV Mosfet on the other side of the OT primary. Then a CCS tail below them both. The tube gets driven by the audio, and the Mosfet gets a quasi static DC bias. The tube will generate some inadvertant DC imbalance with large signals due to its 2nd harmonic distortion, so some provision is needed to dynamically adjust (below 10 Hz audio band) the Mosfet gate bias to keep the DC in the OT in balance.

This gives twice the power output as the single tube alone would give, and the CCS tail along with the high gm Mosfet guarantee true complementary current in the opposite OT primary phase. The high gm of the Mosfet keeps the voltage on the tail constant, so the tube operates in a SE environment. (normal P-P split phase operation cancels the even harmonic distortion by dynamic (audio band) variation of the tail voltage, which is not allowed here.)
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Last edited by smoking-amp; 12th September 2014 at 02:42 AM.
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