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Old 4th March 2005, 01:47 PM   #1
jeapel is offline jeapel  Canada
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Default questions about transfo

hi

For the low cost hammond 125ese transfo i read :

100hz to 15khz
max. dc bias = 80ma

that s mean ?? for the best linear operation ??:

- 80ma is really the max just before saturation (not linear)
and i have to cut to 40ma for best linear or 80ma is
the best point of bias ??
- if i drive this transfo with a low rp tube like 6as7 i
get better frequency low or high ?? or its a
misunderstanding of me
- for the bias is it the same principle for all company transfo

thanks
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Old 5th March 2005, 06:28 AM   #2
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I believe 80mA is around where the OPT will saturate.

Have a read of some basic tests Joseph Esmillia did on the 125ESE here. Apparently it had not much trouble reproducing 20Hz-20kHz at 1W with a 2A3 with 60mA bias (the output valve and op point is important because the DC bias and the rp of the output valve will affect frequecy response).
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Old 5th March 2005, 11:50 AM   #3
jeapel is offline jeapel  Canada
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thanks audiousername very interesting link

20hz to 20khz 1w

maybe the secret is there for best value for money

hammond test transfo frequency at full power

if a design a 5 watt amp buy the new model 125GES 25 watt
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Old 5th March 2005, 03:41 PM   #4
Sherman is offline Sherman  United States
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Default Re: questions about transfo

Quote:
Originally posted by jeapel
hi

For the low cost hammond 125ese transfo i read :

100hz to 15khz
max. dc bias = 80ma

that s mean ?? for the best linear operation ??:

- 80ma is really the max just before saturation (not linear)
and i have to cut to 40ma for best linear or 80ma is
the best point of bias ??
...
thanks

All single-ended trafos lose low-end when bias approaches max and it saturates. Use the trafo with bias lower than max to get more "bottom". The 125ese can go down to 20Hz with lower currents.
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Old 5th March 2005, 09:41 PM   #5
jeapel is offline jeapel  Canada
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ok lower bias=better bass good info but

therefore 125ese is only good for very

low 1w or 2 watt se amp not a good new

for my wallet :-)
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Old 6th March 2005, 12:03 AM   #6
Sherman is offline Sherman  United States
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Quote:
Originally posted by jeapel
ok lower bias=better bass good info but

therefore 125ese is only good for very

low 1w or 2 watt se amp not a good new

for my wallet :-)

Well, Hammond doesn't advertise the 125ESE as a full-range "hifi" trafo but for $30US it is pretty good. I don't know about ultimate output but I do know that Steve at Angela has used the 125ESE in designs of more than 2 watts!

Here in the US a James 6123HS is $90US and it is a very nice trafo. The smaller James is even less if you can use a lower Z.
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Old 6th March 2005, 12:45 PM   #7
jeapel is offline jeapel  Canada
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I check the 6123HS and find a discussion with
hammond 1628 vs james 6123HS

and now are you happy with the nice looking james
but give me details

1-your B+
2-2.5 3.5 or 5 tap
3-output tube +bias
4-feedback or no and output watt
5-and the sound :-) or :-( or so so
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Old 6th March 2005, 02:56 PM   #8
Sherman is offline Sherman  United States
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Quote:
Originally posted by jeapel
I check the 6123HS and find a discussion with
hammond 1628 vs james 6123HS

and now are you happy with the nice looking james
but give me details

1-your B+
2-2.5 3.5 or 5 tap
3-output tube +bias
4-feedback or no and output watt
5-and the sound :-) or :-( or so so

1- B+ is 430V
2- 5K tap
3- 80mA
4- output- initial measurement indicates somewhere between 6
and 8 but I'm going to give them several more hours of burn
in time before really measuring. Plus I'm waiting for a new
8 ohm dummy load as my previous one has gone missing.
5- sound is excellent. Base is deep and full, highs are crisp and clean and the midrange is smooth and detailed. (Plus it does look really nice!
6- You didn't ask but I'm using the UL tap which at 5K is
about 35%

Schematic-
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Old 6th March 2005, 03:58 PM   #9
jeapel is offline jeapel  Canada
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thanks sherman with all these infos my transfo
choice will be the good one
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Old 7th March 2005, 02:22 PM   #10
kmtang is offline kmtang  Canada
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Hammond 1628 is bit odd. However, their 1627SE OPT is extremely good with very flat frequency response. The price for the 1627SE is very reasonable too.


Johnny
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