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Old 6th January 2012, 02:48 AM   #31
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The converter will feed a DCB1 with 20K pot in front, so it should be fine.

D.
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Old 6th January 2012, 05:16 AM   #32
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Hi,

Quote:
Originally Posted by Nikon1975 View Post
So, I have two of these:

http://www.jensen-transformers.com/datashts/11p1bn.pdf

As I understand, I can use them to convert a balanced signal to feed an SE amp, but I am not sure it will have good performances the other way around, as there is an RC network built in.
You can use them as "input" Transformers. This means place them near the input of a unbalanced Amplifier or Preamplifier to give it a balanced input, or reverse, you can keep them in line just SE->SE or BAL->BAL. make sure the load on the secondary side is > 15KOhm and do not have long or high capacitance cables after the transformer.

The official line out from Jensen is this:

http://www.jensen-transformers.com/datashts/11bmcf.pdf

A friend of mine cloned this one (only a few for testing) and gave me a pair, they are excellent line outs and as long as you drive from a very low impedance they are capable to drive any length cable.

IF (a big if) I was to make a Line Pre using transformers and solid state it would probably look like this:

Input switching (balanced) with XLR inputs and RCA's connected between Pin 2 & 3 of XLR, switch to connect pin 3 to chassis (earth) via 100R/100n if needed (hum on input as source is floating)

Jensen JT-10KB-D Input transformer

2.5K Stepped Attenuator, 4-deck true ladder preferred

AD815 as Linestage with 18dB or 24dB (selectable) gain for 6 or 12 dB Linestage Gain (basically Carlos FM linestage)

JT-OLI-2 Load Isolator

Jensen JT-11-BMCF Output Transformer

XLR outputs and RCA's connected between Pin 2 & 3 of XLR, switch to connect pin 3 to chassis (earth) via 100R/100n if needed (hum on output as Amp is floating)

The result will be a very nice pre with the ability to handle any kind of source.

Other line stage amplification options may of course be applied, instead of AD815, but it is known to work well together with the Jensen Output transformer, it was used in one of the Jeff Rowland Line Preamp's like that.

Ciao T
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Old 6th January 2012, 05:26 AM   #33
Previously: Kuei Yang Wang
 
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Hi,

Quote:
Originally Posted by Nikon1975 View Post
The converter will feed a DCB1 with 20K pot in front, so it should be fine.
Yes, this will work splendidly. Add a JT-11-BMCF which you can directly couple the the DCB1 and you will have your own "Virtual Reality Engine" that can drive SE or Balanced Amplifiers.

Ciao T
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Old 6th January 2012, 01:24 PM   #34
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Output transformers with an upper limit of 15MHz! wow! The bandwidth of these Jensen transformers is incredible. Does anyone have an inexpensive source for these? I see they cost anywhere from about $60 and up at all the sites I've looked at. Even used ones are expensive.
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Old 6th January 2012, 02:27 PM   #35
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Hi,

Quote:
Originally Posted by dirkwright View Post
Output transformers with an upper limit of 15MHz! wow! The bandwidth of these Jensen transformers is incredible.
Not incredible, almost any bifilar would audio transformer gets into the MHz region.

Quote:
Originally Posted by dirkwright View Post
Does anyone have an inexpensive source for these? I see they cost anywhere from about $60 and up at all the sites I've looked at. Even used ones are expensive.
There is a very large chunk of 80% nickel alloy in there. They cannot be "cheap", sorry.

Also, it is my experience is that cheap transformers are usually too bad to be worth having. Diyhifisupply have a box of 1:1 line transformers which even at their best options and even driven from 50 Ohm are so bad, I'd not touch them with a bargepole.

Ciao T
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Old 6th January 2012, 02:47 PM   #36
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I get them from Markertek.com. I guess I'll just have to pay the price for high quality. Thanks.
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Old 8th January 2012, 12:56 PM   #37
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So let's experiment with transformers...

My son is still wondering where one of his wooden block ended up :-) Bad daddy!!

Maybe orange wood would give more "juicy" sound.

D.
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Old 8th January 2012, 04:43 PM   #38
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Quote:
Originally Posted by Nikon1975 View Post
So let's experiment with transformers...

My son is still wondering where one of his wooden block ended up :-) Bad daddy!!

Maybe orange wood would give more "juicy" sound.

D.


Hope the transformers are performing well.
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Old 9th January 2012, 08:15 AM   #39
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I am sure that there is a smarter way to do what I want, but up to now the solution that satisfy all my nees is the following, with two interconnected pre, one for SE input and one for Bal input:

1) The se amp will have an additional balanced output placed just after the source selection, before the volume control
2) The se amp will have a balanced input.
3) The balanced pre will have an additional balanced output just after the source selection.

Like this I can have all the balanced sources and balanced amps connected to the balanced pre and all the SE sourcesand amps connected to the SE pre.

When I mix them the signal will go alway through a single conversion, buffering and volume control.

Additionally I have the SE pre, with enough space to fit the extra in and out.

Any thoughts ?

D.
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Old 9th January 2012, 10:42 AM   #40
NicMac is offline NicMac  Italy
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Quote:
Originally Posted by Nikon1975 View Post
Like this I can have all the balanced sources and balanced amps connected to the balanced pre and all the SE sourcesand amps connected to the SE pre.

When I mix them the signal will go alway through a single conversion, buffering and volume control.
Nikon1975,
I'm very interested in these plans for a "universal" pre-amp, but I'm not sure I can follow your scheme. Could you draw a block diagram?
Are two volume controls required (one for Bal and one for SE)?
How many buffers and Bal:SE converters are needed?
Cheers,
Nic
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