Fisher 400 high level inputs

[notdigital]

Congrats on the successful execution!

Dave

Wouldn't have been possible without your help. Thanks again!

And yes, I saw the possibility of a third AUX input. I'm maxed out at two after working in such tight quarters. However, I did print out the instructions that Drew posted in the 400 thread and, well, who the hell knows.

Thanks again :thmbsp:

 

[audiodon]

If you don't make those changes now, it'll take longer later if you want to do it.

You know how the first time you do something it takes an hour, the second takes 40 minutes and then repetition settles in at between 30 and 40 minutes?
That reality applies in this case.
If you wait, slate an hour again.

 

[notdigital]

If you don't make those changes now, it'll take longer later if you want to do it.

Don, you're right. Exceptin that I've been unraveling this 500-c now going on a month. I got it in the not-so-usable condition, if you know what I mean. Between the electrical stuff and the cosmetic stuff, I've had just about enuf of it! Now, I just gotta rework the bias cap area, work on the brights, cab, festoon issues, and just confirm a weird buzz in the right channel FM (only) is alignment related and I'M DONE! So you see, another AUX would be nice but not on the radar at the moment :yes:

 

[JObeast]

I route the sound of my iMac digitally via USB to an M-Audio MBox III and its main outs into the Aux. input of my Fisher 400. Listening to such 'web-radio' broadcasts as NorthSeaSurfRadio.com through my 400 to a pair of Klipsch Heresies witha Paragon Subwoofer (from the 'center channel' RCA out of the 400) gives my family great pleasure! Who needs a bulky 5.1 home theatre? To me, this is a great solution as the MBox is fairly high quality in the D/A conversion department, and the Fisher/Klipsch combo is so easy on the ears I can listen to surf guitar music all day.

 

[bhamham]

I route the sound of my iMac digitally via USB to an M-Audio MBox III and its main outs into the Aux. input of my Fisher 400. Listening to such 'web-radio' broadcasts as NorthSeaSurfRadio.com through my 400 to a pair of Klipsch Heresies witha Paragon Subwoofer (from the 'center channel' RCA out of the 400) gives my family great pleasure! Who needs a bulky 5.1 home theatre? To me, this is a great solution as the MBox is fairly high quality in the D/A conversion department, and the Fisher/Klipsch combo is so easy on the ears I can listen to surf guitar music all day.

I'll look into an MBox sounds interesting. I use a Squeezebox mainly playing flac files not much radio, but surfmusic - v cool - is that like the Ventures? That's my generation

I used to play Heresys with my 400 and really liked it. Might still have them if I'd gotten a sub

 

[monkboughtlunch]

On the 400, let's say I have a CD player plugged into the "Aux" inputs. And I have a 2nd line level source, let's say an iPod, plugged into the "Tap Mon" jacks.

The input selector on the 400 has a combined "Aux-Tape" position.

I experimented with this and discovered that the circuit favors "Aux." For example, if the selector switch is at "Aux-Tape" and the ipod is plugged into "Tape Monitor" inputs but there are no cables in "Aux" then you hear the line level Tape signal. However, when you plug cables into "Aux" the circuit defeats the "Tape" signal and only plays the "Aux" signal.

This makes sense as you wouldn't want to play two signals on top of each other.

But here's where it gets strange. Let's say I turn off the CD player that's plugged into Aux. And I try to play the iPod plugged into "Tape" (with the selector stll at "Aux-Tape"), I only hear faint attenuated signal of the source plugged into Tape. Remember, the device plugged into Aux is turned off. It's only after I have unplugged the Aux cables do I hear the Tape signal at the normal, unattenuated volume level.

What was Fisher trying to do with this circuit redesign? I don't get it. The 500b and 800b had separate "Aux" and "Tape" inputs on the selector switch. Why did Fisher combine them on the 400, 500c and 800c? What was the governing logic of essentially eliminating a line level input for all practical purposes?

Unless I'm missing something, on the 400, 500c and 800c, you can't listen to the high level Tape signal via the rotary selector switch IF you have an AUX source plugged in (even if the Aux device is turned off and not feeding a signal to the Fisher). So it appears you can either have an Aux source plugged into the 400 or a Tape source but not both if you want to hear them via the rotary selector. The only way to hear Tape in this case is via lower fidelity Tape Monitor slider switch which the Fisher manual describes as follows:

Tape Monitor (slider switch) - "This switch is used only when making a recording with and instrument having separate record and playback heads. At all other times it should be left in the OFF position."

Puzzling. Anyone know what Fisher was thinking when they combined Aux and Tape into one selector input?

 

[dcgillespie]

Monk -- You've got two things going on:

1. Fisher did in fact intend for the tape monitor switch to only be used for tape decks with three heads: The monitor position let you monitor the signal off of the third head during recording, while the Tape/Aux position allowed for normal playback from the third head after the recording was made -- with both of these settings picking up a signal presented to the Tape Monitor jack. Used in this way, the relative gain of the unit -- whether monitoring a recording via the Tape Monitor switch, or playing back a recorded tape via the Tape/Aux setting -- was about the same for both functions.

If a standard two head deck was used, its output signal was presented to the Tape/Aux input jack, and the Tape Monitor jack then was not used.

If no tape machine was used, then the Tape/Aux jack simply became an Aux input, selected by the Tape/Aux setting.

Remember, other than FM Stereo and phonograph, there really were no other recordable sources generally available when this unit was designed. Therefore -- at the time -- who needed any more high level inputs? You either recorded off the air, or records.

I'm not saying I agree with all of this at all, but that was the thinking.

2. As for the weird operation you've noted, there is nothing wrong with your Fisher, but the scenarios you've noted are because you are using modern SS sources with it. Modern sources have very low output impedances, particularly when they are turned off. That's why you saw the jacks act weird whether or not something (something being a modern SS source) was plugged in or not, or whether or not it was turned on or not if plugged in. With higher impedance vacuum tube devices, the events you noted would not occur -- or if they did, not nearly to the extent that you witnessed them.

I hope this helps!

Dave

 

[monkboughtlunch]

2. As for the weird operation you've noted, there is nothing wrong with your Fisher, but the scenarios you've noted are because you are using modern SS sources with it. Modern sources have very low output impedances, particularly when they are turned off. That's why you saw the jacks act weird whether or not something (something being a modern SS source) was plugged in or not, or whether or not it was turned on or not if plugged in. With higher impedance vacuum tube devices, the events you noted would not occur -- or if they did, not nearly to the extent that you witnessed them.

I hope this helps!

Dave

Thanks! So back in the 60s, if I had 2 different line level vacuum tube devices plugged into the Aux and Tape Mon inputs respectively, then the deivce plugged into Tape Mon would be amplified at full volume, provided the device plugged into Aux was powered off?

 

[monkboughtlunch]

Also - can anyone recommend an indoor antenna for the 400 that is better than a standard folded dipole?

 

[larryderouin]

Also - can anyone recommend an indoor antenna for the 400 that is better than a standard folded dipole?

Where are you located?
What is the construction of the building? Concrete block, wood frame, steel?
What level is the 400 on (Basement, 1st flr, etc)?
How far from the Station transmitter?
Are you in the city,suburbs, in the boonies?
Are there hills, tall buildings, etc., btwn you and transmitter?
Has the 400 had the tuner aligned recently?

I use a Folded Dipole with an extended downlead. The "T" is in the attic for the living room antennna. A normal Dipole in the basement. 30-50 miles from nearest transmitter. Some rolling hills, but nothing really high.

 

[freeman5]

I built a J-Pole from copper pipe with the intent of mounting it outdoors, but it works quite well just leaning up against my bookcase. So well infact that, well, it never made it outside. FM reception is unbelievable with the 400 and the Stereo Beam tube is sooooo groovy. I am looking foward to modding mine to use the second input. Great thread!

 

[monkboughtlunch]

Where are you located?
What is the construction of the building? Concrete block, wood frame, steel?
What level is the 400 on (Basement, 1st flr, etc)?
How far from the Station transmitter?
Are you in the city,suburbs, in the boonies?
Are there hills, tall buildings, etc., btwn you and transmitter?
Has the 400 had the tuner aligned recently?

I use a Folded Dipole with an extended downlead. The "T" is in the attic for the living room antennna. A normal Dipole in the basement. 30-50 miles from nearest transmitter. Some rolling hills, but nothing really high.

About 40 miles from most 100k transmitter towers. Fisher is on 2nd floor of my home. Am using a regular dipole now.

Does anyone have experience with the Godar or Magnum Dynalab FM antennas?

 

[larryderouin]

Are your issues with FM STEREO fading in and out, or an extreme amount of hiss, or just plain poor reception in FM STEREO? Have you tried FM MONO as a comparision?

FM MONO needs less signal strength than FM STEREO. The MPX has to break out the individual L & R channels, that are piggybacked on the subcarrier signal (at least how I understand it). Which takes more signal strength.

Even with 100KW on the transmitter at 40 miles you are hitting the Fringe area for most STEREO FM. I've found that FM STEREO signal starts to degrade compared to mono at about 10-15 miles. Up to 10-15 miles the signal meter will usually stay pretty much the same. After that the stereo signal will degrade faster than the MONO signal. 40-50 is Fringe for FM STEREO, and 60-70 for MONO in an ideal setting.

You can also get time delayed signals that cause a phenomenon that is very much like Ghosting on over the air TV. It's called multipath, and is mainly caused by obstructions between the transmitter and the receiver bouncing the signal enough that it can/will sound distorted.

Google FM Multipath & FM SIGNAL STRENGTH.

Orientation on the DIPOLE is important too. The top of the "T" is HORIZONTAL with it perpendicular to the direction of the transmitter. If the station you listen to is north or south of you, orient the "T" east/west. it doesn't have to hang on the wall, it can lay flat on the floor.
From all reports I've heard the GODAR is very good provided that the tuner is aligned to it's specified performance parameters. The 400 has a very good tuner when it's aligned correctly. It's a wide bandwidth tuner so the selectivity isn't as good as a modern tuner with narrow IF Filters. So you have a slight handicap in an area where the stations are right on top of each other. Back when it was made, the amount of FM stations in operation was a lot less and were spread out more.

I'd spend the $$ on a good alignment 1st, including the MPX.

Larry

 

[monkboughtlunch]

So glad it's working well for you!

The Tape Monitor modification and removal of the Aux/Tape Monitor bleed circuits were just a couple of the common sense improvements undertaken in that thread, to help bring the 400 (or any of the Fisher stereo receivers) into the 21st century, while still letting it retain the integrity of what it is: A wonderful Fisher receiver.

Now you can enjoy two separate high level inputs with both having the same Aux level sensitivity. I think I also posted in that thread (or it got reposted maybe) how you can also turn the tape head position into a third high level input if needed.

Congrats on the successful execution!

Dave

This mod sounds very beneficial. With this modification, is the high level input from Tape Monitor only audible via the "Tape Monitor" slider switch? In other words, does the mod remove the Tape input signal from being able to be heard via the combined "Aux-Tape" rotary selector switch?

 

[dcgillespie]

Absolutely. The Tape Monitor and Aux Input jacks and panel settings work as two completely separate entities once the modification is made, with no interaction between the them at all after modification is performed.

Dave