fisher phono input question

[madwing]

i am running a chassis 50 mono integrated amp at work, that originally came from a model 101 gramophone. the turntable (a garrard 121/D) ran fine through the amp as originally configured, using a ge vr2 mono cartridge and diamond stylus.

i am currently trying to finish off the rebuild of my rek-o-kut B12, with an sme 3012 tonearm. i've put in (temporarily) a stanton 681eee cartridge, and connected it to the amp with a home-made interconnect, tied into a stereo-to-mono mixdown cable. the s-t-m cable works fine from my ipod. the home-made interconnect shows continuity, as do the tone arm wires.

when i plug it all in, set the amp to the RIAA (or any other) phono curve, and put the needle on a record, it makes no sound. neither does gently running my fingerprint along the stylus. at any volume level.

i am thinking the cartridge/impedance matching is wrong, or the cartridge type is incorrect for the fisher to use. i don't know the language to say it, though. should a 681eee be able to be amplified through a late '50s fisher mono tube phonograph system's phono circuitry (that worked using a variable reluctance cartridge)?

i'll be asking a similar question over in turntables, just to get a handle on terminology and cartridge types (mc, mm, vr, etc.).

thanks.

 

[cademan]

It could be that the original cartridge was a ceramic. If you replaced it with a magnetic cartridge, that is your problem.

A ceramic cartridge works in any line level input such as TUNER, TAPE, AUX, etc.
A magnetic cartridge will only produce sound in a "PHONO" or "MICROPHONE" only inputs.

Plug your turntable into an integrated amplifier's "PHONO" only input and see how it works.

 

[madwing]

cademan, that's where it was plugged in. the phono input. no sound.

thanks.

 

[TheRed1]

First off, let me say that it is so refreshing to hear you use the more historically accurate term: gramophone. I'm almost finished reading a biography of Emile Berliner and it has begun to irk me that we Americans somehow continued to use the term phonograph long after that invention was dead and buried. (I will accept turntable as a politically neutral and generally more modern term.)

I believe your GE cartridge was of the variable reluctance type. I *think* their output was the equivalent of the ceramic cartridges. So it's likely that your MM cartridge output isn't high enough to drive the amp's input stage. I am about to get hammered by a thunderstorm so I don't have the time to verify but I'm sure others are familiar with this issue and will chime in.

Signing off . . .

 

[dumptruck]

I don't know... sounds like he's saying there's either no output from the cart whatsoever. Is there anything else with a phono stage around your place? It would certainly speed this up if you knew that the TT setup was working fine into a regular old SS receiver or something.

 

[Scuzzer]

The VR cartridges are 10mv output and require a standard MM phono stage so that's not the issue. Perhaps you won't get as loud of sound using a more modern 5mv (or so) cartridge but you would get sound especially running your finger across the needle. If you sum the channels incorrectly you'd get cancellation instead of addition. Are you sure the cartridge wires are hooked up correctly?

 

[madwing]

the cartridge wires are hooked up correctly, but i haven't checked across the bridge at the bottom of the sme, to make sure they're wired to the right cups. i will check that. thanks, scuzzer.

dumptruck, i'll also check it with a ss integrated on monday (i have to bring it from home).

 

[Scuzzer]

An easy way to check if you have a cancellation issue would be to remove either the right or left headshell connections and see if you get any sound.

 

[cademan]

I haven't seen your Fisher 50, but the way you describe that it has an RIAA selector on it, it could be the older Fisher integrated (and other older integrateds) where its phono input, could be like a line level input.

I have an older Bogen mono amplifier which has "TUNER", "AUX", and "PHONO" inputs, where the "PHONO" input is actually a line level input with a RIAA selector on the front panel which acts like an EQ setting. It has no magnetic input on it anywhere, and I have tried my magnetic cartridge Pioneer turntable on my Bogen and it does the same thing you are describing when rubbing your finger across the stylus. No sound!

Just something to check out. Also, if you have a microphone, and if there is a way to plug it into the phono jack, and if you get sound from the microphone, then that eliminates your amplifier as it does have the magnetic preamp section built in.

Then, on to trouble shooting your turntable's replacement cartridge!

 

[madwing]

ok, here's what seems to be happening.

i traced all the wires for continuity, and found continuity for them all, from the cartridge connectors all the way to the interconnect plug. they line up the way they should (channel_1 signal/channel_2 signal/channel_1 screen/channel_2 screen).

i tried each channel (through my home-made interconnects) separately into the phono input on the amp, and ran my fingerprint over the needle...YES! we have scratch, on each channel. the rig is good.

i then re-tried it through the stereo-to-mono converter plug my electronics tech buddy john made me, and...nothing (using both channels). the stereo-mono works from my ipod to the aux input on the amp; it combines the two screen wires and the two signal wires into a single screen and a single signal.

apparently it's cancelling the two signals from my tonearm/cartridge. it's good to know! now i have to figure out what else to do to make it work (other than a dedicated mono setup, which is still being worked out...).

 

[dumptruck]

If this stereo-to-mono converter plug is just a y-cable, that would explain it..

 

[madwing]

nope. two rca female jacks with wires jumpering between the signals/screens into a mono wire.

however, it's a stereo single into a stereo y, then into the two jacks from the ipod.

 

[dumptruck]

Well there needs to be at a minimum some resistors in there to prevent the signal from feeding back into the table or it is equivalent to a y-splitter cable.

 

[Scuzzer]

now i have to figure out what else to do to make it work

Switch the two cartridge leads for either the right or left channel.

 

[Scuzzer]

Well there needs to be at a minimum some resistors in there to prevent the signal from feeding back into the table or it is equivalent to a y-splitter cable.

Resistors would screw up the cartridge loading. Using two Y connectors back to back is a very standard way of making a stereo signal mono. A slightly more elegant solution is to simply tie the two positives and two negatives together at the cartridge.

 

[madwing]

Switch the two cartridge leads for either the right or left channel.

make right signal screen and right screen signal?

 

[dumptruck]

oh yeah, I was thinking we were at the other end of the phono pre for a minute there, but still this going into a mono amp so it would be a single Y rather than back-to-back, so it's still wrong, right?

 

[Scuzzer]

Since it's going to a mono amp you'd only need one. I was talking about people routinely using back to back connectors for making a mono signal for a stereo preamp and cartridge. No resistors needed.

 

[Scuzzer]

make right signal screen and right screen signal?

Your language does not compute. You have a + and - for the right and left channels on a stereo cartridge. Simply switch the + and - leads for one channel on the cartridge.

 

[madwing]

swapped the right screen and right signal leads at the cartridge, and no love.