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.

[electra225]

I have listened to the old Imperial for a considerable time since the repair. I can't wait to get the changer back in to see how it sounds. I have been tinkering with a Bluetooth and amplifier setup. I am not impressed with Bluetooth. I know, I know, I'm an antique and can't stand technology. Messing with Bluetooth causes me to spend too much time using a cellphone. That said, what I was looking for was fidelity using the tape input. The line amplifier is the improvement. If I use it with a CD player, it can overload the amp when there is heavy bass in the signal. I am using YouTube audio, which is probably not the best, so there is that. The output is louder with the line amp, but not necessarily has better fidelity. My next step is to see what a graphic equalizer does for it. Both with YouTube audio and with a CD player. There was a discussion on "Vintage" where one of the guys used a graphic equalizer on his CG then blew the speakers. We don't need any of that.

I would also like to know the difference between a 6V6 and a 6V6S tube. The only information I have found tells me that the "S" can handle higher plate voltages and behaves more like a 6L6. All the guitar-amp techno-babble aside, I think I like how they sound. I've got some more tinkering yet to do. I have looked at tape input circuits in bi-amps and regular stereo amps and see no difference in how they are wired. The output, how they sound, is totally different. Why is the tape input fidelity on regular stereo amps, such as the 88- and 93-series amps better than that found on the bi-amps? Both amps have the tape input directly into the volume control via the function switch. There's gotta be an impedence mismatch someplace, but where?

[Hydrolastic]

Hello, It is a bit of a rabbit hole. Bluetooth has issues. Here is an article I found https://www.nytimes.com/wirecutter/blog ... oth-audio/ I noticed one day while playing the CG there was a version of a song Brandi Carlisle did that was crystal clear and had a noticeably better recording of it. I was on Pandora at the time but it made it clear that the Recording of the music seems to be the biggest factor. I purchased a audioengine B1 adapter for its higher rating ACTX but found out my apple devices don't support it. For now I just use the JL audio MTB-RX receiver and the PAC ld1 line amp. It seems to have a high enough fidelity for me. In fact I was showing my friend the CG and I asked for his favorite music he is a Beatles fan so one of the songs came on right at the beginning there was a cough from someone in the band my friend and I were amazed cause it was so clear. Someday I would like to get the Apple Music version and the B1 working at its highest fidelity. Like most of you I like to just know I have the best sound possible with my setup. I also like the PAC line amp cause it has a balance feature (two inset screws one for each channel) my listening position is just off the left side of the CG.

[electra225]

Hi, Hydro! Per your comment about how the music is recorded, I'm beginning to seriously consider that. PART of the wimpy performance with the tape input is my homemade CD's. The equalization on some of them is not that good. Part of that is how the record was recorded. Perhaps a part of why the 88 and 93 series amps sound "better" on the tape input is that they are not quite as "honest" in reproduction as the bi-amps are. Since I went thru the Imperial, I have heard sounds in recordings I had not heard before. You can almost hear a fly fart when it lands on the drummer's sticks, the reproduction is so accurate. I may have to trade my simple little music conversion software for something more complicated like Audacity so I can improve the fidelity in homemade CD's. I'm wondering if time would be better spent not trying to improve how the signal is handled, but to improve the input signal. Again, I don't believe we are lacking bass, we are lacking FIDELITY...What do you think?

[electra225]

I have the changer back into the cabinet. All I can say is "Oh, my goodness!" Magnavox built this Imperial as a record player. It does that in spades. The bass is almost boomy. I found I have to run the treble amps up more to get some records "bright" enough. The changer even will change stereo 45's. A VM 1200- series changer will not. The replacement cartridge sounds at least as good as did the original Euphonics E-1.

The cartridge kit Gary supplied features a glued-in cartridge. I was suspicious of such a setup. It couldn't have been easier and I only had one hitch in the project. There is a bolt that runs thru the rear of the tone arm, thru a weight. There is another screw in the front of the tone arm bracket. It uses a coil of wire inserted in the plastic tone arm, much like a Heli-Coil. When I removed the screw, the coil turned out of the tone arm. The head of the screw was on one side of the bracket, the coil on the other side. The coil would not pass thru the hole in the bracket, so I had to "booge" it a bit. This stretched the spring so it was unusable. I drilled a hole in the tone arm and used a bolt to hold the front of the tone arm on. I tried using just the bolt thru the weight, but when the tone arm tapped the record to index the changer, the tone arm would get out of adjustment and would miss the starting groove in the record after about five records or so. Using a bolt in the front with a lock washer stopped the arm from becoming out of index. Adjusting the setdown is accomplished by ever so slightly turning a screw in a hole in the changer base located between the tone arm pivot and the tone arm rest. You only need a tweak at a time. I turned it a quarter of a turn the first time. The tone arm landed in the middle of the record!