Help: Quiet Magnavox 185 with new TT

[xXTomcatXx]

Hi, all.
I posted here about 5 years ago when I was refurbishing my Magnavox console (lots of photos in there for background). Thanks to all your help I was able to get my console working and we've had countless hours of enjoyment from it. The amp is a Magnavox 185 and everything has been working well for the last 5 years, but I'm ready to move on from this setup.

Situation:
My biggest frustration so far has always been the Collaro record player. Mechanically it functioned just fine, but the needle and tonearm required constant tweaking. I have a new Project DC Evo turntable that I connected directly into where the original Collaro was connected, but the sound is significantly quieter. I'd estimate it's half as loud at best. I'd like to leverage the 185 and the speakers in the console until I get new speakers. Then I'd like to use the amp as a standalone once I have new speakers.

Questions:

1. Is there something wrong with my pre-amp circuit on my 185 or do I now need a standalone pre-amp? I'm going directly into the "Phono" inputs on the 185 so I'm not sure why it's so much quieter.
2. What mods should I be considering when I go to a standalone setup?
3. Any members in the northern Virginia area that might be interested/willing to check my refurb work from 5 years ago (happy to pay )? Like I said, it worked (very loudly) with the Collaro TT, but I've always been dubious of the quality of my work and want to make sure it's in tip-top shape for the new TT.

Appreciate any and all help this amazing forum offers. So thanks in advance.

Cheers ,
Tomcat

 

[cademan]

The collaro uses a ceramic cartridge. The evo turntable probably uses a magnetic cartridge so you would need an external phono preamp.

 

[gadget73]

exactly this. Fit a phono preamp between the original connections and the new turntable and you should be in good shape.

 

[Dswankey]

For external mods you might want to consider this

New power cord
Fuse
RCA connects
Speaker connects

For Aesthetics a wood base with rubber "feet" is a go to move I and others have used in the past






As for internal mods (Circuit, caps, etc) I'll leave that to the knowledgeable to suggest

 

[RWood]

You can spend a lot of money for a phono preamp but in my console I used one of these from Gary at VOM Audio Enthusiasts. It does what I need it to do:

https://www.thevoiceofmusic.com/cat...ype=AssociatedItem&MfgName=&Categories=Preamp

 

[Hifi Dave]

If you cascade two phonograph preamp you will really mess up the RIAA curve.

 

[xXTomcatXx]

The collaro uses a ceramic cartridge. The evo turntable probably uses a magnetic cartridge so you would need an external phono preamp.

Thanks! The more I thought about it, the more I thought this would be the case. Now the question is what kind of a pre-amp can I use through the current 185 pre-amp circuit. To Dave's point above, wouldn't I risk applying the RIAA curve to the signal twice with the pre-amp? Are there pre-amps that don't apply the RIAA curve?

Also, I'm starting to look at speaker options for my long term setup solution. My understanding is that the 185 puts out about 12 WPC. Can I include 4 ohm speakers with this amp?

 

[cademan]

The 185 employs an extra preamp tube (7025) and some 185's have two sets of input jacks where one set bypasses the 7025 and act like line level inputs.

If yours has the extra inputs, just plug your external preamp into these. If not, then you will have to know how to delete the 7025 circuit to effectly make it a line level input amplifier.

The 185 with no 7025 tube makes it work exactly like a 175 model amplifier. The 175 series of amplifiers are exactly like the 185 except with no 7025 tube because the 175 series came with a tuner/preamp which had the RIAA circuit.

 

[xXTomcatXx]

The 185 employs an extra preamp tube (7025) and some 185's have two sets of input jacks where one set bypasses the 7025 and act like line level inputs.

If yours has the extra inputs, just plug your external preamp into these. If not, then you will have to know how to delete the 7025 circuit to effectly make it a line level input amplifier.

The 185 with no 7025 tube makes it work exactly like a 175 model amplifier. The 175 series of amplifiers are exactly like the 185 except with no 7025 tube because the 175 series came with a tuner/preamp which had the RIAA circuit.

Good news is that adding a preamp in the circuit fixed the volume as expected.

HOWEVER, now I’m getting a right channel hum above a certain volume. I’ve also seem to have lost bass control.

Will deleting the 7025 circuit impact the cabinet-integrated Bass, Treble, and Loudness controls? At the moment those are my only means of control. Eventually I’d like to get rid of them but need to figure out the best way of doing it.

 

[cademan]

Since the 185 uses passive controls, I believe that other people can explain the reason why you lost the bass control. Has something to do with the original 7025 circuit and the ceramic or crystal cartridge the turntable uses. Gadget73 explained it before but since I have never owned a console with simple passive controls, I just tend to skip over those explanations.

You should probably get rid of the 7025 tube and circuit and look for an active or powered line level preamp. Lots of people here have done this mod. I own a 175 series amp, tuner/preamp, and original speakers so I have not had the need to convert anything on it. I use my amp with a mixer along with a pair of 12 inch tower speakers.

On the 175 and 185 (and others) series of amps, stock speakers and output transformers are 3.2 ohms.

If you want to make it a stand alone amp, this is what I would do:
Do a search on the Magnavox 185 conversion to a 175. All kinds of info out there. Probably should start by acquiring a 175 schematic. There are also tons of schematics out there. I have several myself.

 

[gadget73]

I'd have to see exactly what they did for tone controls on this, I don't know for sure. Purely passive with a ceramic may just be variable load on the cartridge though. If thats what it is, they basically don't work with any other source besides the original setup.