Magnavox Imperial model 1ST233

[electra225]

I've played this for several hours. It pulls 227 watts from the line, including the MPX. I think I can honestly recommend checking and changing every resistor and cap in the entire instrument, keeping a 5% tolerance. Besides bass response, it even cleans up the treble and increases the definition and presence of the audio. I'm not sure I can describe the difference. If you are familiar with "fairy dust" that Disney used to use, where you can "hear" fairy dust falling. I have a Lawrence Welk recording that has that. IT is amazing to hear that, produced on an unknown instrument, as it passes between channels. I can hear fingers sliding on guitar strings. You can imagine where Floyd Cramer would light his cigarette, the realism is so much better. Then add a set of matched output tubes and you are well on your way to making whatever you are working on, particularly with Magnavox bi-amps, to perform as well as it was intended to when they built it.

[William]

[electra225]

I was playing a CD that has 45's on it. I heard a distortion that I thought was coming from the electronics. I didn;t see any smoke, so I started listening closely. I determined it was that little hash you get from a worn record. I had not heard that before. I was chasing wimpy bass when I decided to go thru this stereo, but I honestly believe that improving the treble made the most difference. I have the treble input controls on the amp set at about 1/4 of the way. That seems to be its sweet spot. More makes the treble too bright. Less makes the treble too mushy. The timbre control affects the bass as well as the treble. I made sure the components were tight on tolerance as well as matched between channels in the treble amps. And I used a set of matched output tubes. I'm becoming impressed with the old Imperial.

[AlanBienlein]

Looks like I need to read thru this thread a few times as in my opinion my imperial amp is also lacking in bass. I have completely rebuilt it. I did find the 6401 series tuner had a modification by magnavox that dropped the sensitivity of the FM. I ended up converting it back to what was in the 54 series tuners and now stations come in nice and strong. As for the volume of the mpx adapter you should be able to easily make it louder than mono.

[electra225]

Welcome, Alan! This was quite the project. I learned a lot, chased my tail some, too. I have learned that Magnavox bi-amps have bass. It is just "different" than we are use to if we have had a Japanese-built receiver from the 1970's. What the Imperial lacks if you are running original components is fidelity. I plan on doing a similar operation on my Concert Grand.

[AlanBienlein]

Glad to be back!. Hey I uploaded the Magnavox factory service and alignment manual for the 7001 thru 7006 FM MPX adapter.

[TC Chris]

Tell us about that tuner change. I cant imagine why they'd do that unless the design had a problem with adjacent-channel interference and instead of improving selectivity, they just decreased sensitivity.

Chris Campbell

[electra225]

Thanks, Alan. I see you have found Downloads. I appreciate your contribution....

[William]

Hi Allen and thank you for adding to the downloads and contributing to Greg's post. As you read through Greg's Imperial post, please take note on what I posted. I seem to be the odd duck here, as my Imperial has all the bass anyone would want. Greg has the schematic for both his and mine and he only found a couple of differences from mine. I still remain totally confused why my Imperial has bass and others do not.

Bill

[Motorola minion]

Hi Allen and thank you for adding to the downloads and contributing to Greg's post. As you read through Greg's Imperial post, please take note on what I posted. I seem to be the odd duck here, as my Imperial has all the bass anyone would want. Greg has the schematic for both his and mine and he only found a couple of differences from mine. I still remain totally confused why my Imperial has bass and others do not.

Bill

It cannot be overstated to follow Magnavox's speaker wiring diagram in your cabinet.
I discovered that after I restored and reinstalled the 93-02 amplifier in the 63 Imperial (not one with a 413 V8 ), one connection was reversed at the crossover board.
Correcting this brought everything out and clear where before, it sounded distant and failed balance/phasing playing test record.

[electra225]

My Imperial has a wiring diagram about a foot square pasted to the back of one of the speaker cabinets. The speaker wiring was correct on mine. I remembered a comment about that awhile back, and checked it to be sure. If I had to point a finger at what I believe helped the Imperial the most it would be tightening the tolerances on resistors and using matched output tubes.

[electra225]

I have the Imperial and the Symphony connected so they are both playing the same CD. Sitting in the same room at a 90 degree angle to each other. The CD I have on is a copy of two factory Asleep At The Wheel CD's, "Asleep At The Wheel" and "Willie And The Wheel". These two CD's are arguably the best by AATW, but they never recorded a bad note. I hate to say this, never thought I would, but the Imperial holds its own against the Symphony. This music has all the good "sounds", twin fiddles in two channels, steel, drums, plus a full complement of big band instruments, trumpet and cornet, trombone, sax, clarinet, piano. I am a fan of the six "little cones" in the Symphony, vs, the horns in the Imperial. The horns just do their job better, cleaner, better definition. I haven't compared the Imperial to the Stereo Theater yet, but that may be coming. Bill, I wondered when you said you liked your Imperial better than your Symphony. I'm not sure I'm ready to say "better" yet, but I can say "as well". That is a HUGE improvement in itself......

It would cost a fortune to do to a Concert Grand what I have done with this Imperial. If the difference was as great as with the Imperial, the result would be mind-boggling....

Can you imagine buying two sextets and a quartet of matched JJ's? Not to mention a bucket full of 12AX7's.....

[electra225]

Yessir, if I was smart, I'd make the Concert Grand my major summer project. Do exactly with it like I did to the Imperial. There are songs where the Imperial is almost BOOMY! I also know that some of my homemade CD's have not weathered time well. I need to redo some of them. Now that I know what the deal is, I'm not so worried about it. I have made adjustments in my music conversion software that will give them a touch more bass/lower midrange and make sure the volume channel to channel is the same. I believe part of the reason CD's sounded better on 88 and 93 series amps is that they have balance controls. If one channel is weaker than the other there are provisions for that. No so with bi-amps.

[William]

I am anxious to hear your comments after getting your Collaro sorted, and you play your first record. I think your will really be impressed.

Bill

[electra225]

Bill, I think I have it. All I need is a platter mat and some needles, and it's ready to go back into the cabinet. The changer sounds good running thru the Stereo Festival and a couple of 8" speakers. Details in the topic I started in Changers......

[AlanBienlein]

Tell us about that tuner change. I cant imagine why they'd do that unless the design had a problem with adjacent-channel interference and instead of improving selectivity, they just decreased sensitivity.

Chris Campbell

It's the 6401 chassis that needs this modification. For some reason they are using feedback from the discriminator circuit through a. 005uf cap to ground and a 220k resistor connected to the grid of the 6CY5 rf amp tube. They also tied pin 2 to ground. The 6402 an 6403 along with the 5401 thru 04 series doesn't have this feedback loop and pin 2 of the 6CY5 is connected to ground thru a 68 ohm resistor. That resistor is connected to pin 2 thru a .001uf feed thru capacitor just like they use to bring in power to the shielded area for the AM/FM circuitry. There is a night and day difference in tuning in stations. I have found that the 5405 tuners are done like the 6401 tuners even though the 5405 schematics don't show it.