AKAI GX 747 dBx and no dBx

[KAMELEON]

Urban legend or not ?

AKAI GX 747 dBx model sounds better ( rec,play ) than AKAI GX 747 model even when dBx function is OFF .

Data : GX-747 (1982-1983) and GX-747dbx (1983-1984)

The GX-747dbx is just like the GX-747 but it has additional dbx decode/encode pcb's - early DBX 2:1 Type I compression / expansion. The GX-747dbx was not a more expensive version of the GX-747. It was its substitute. Instead of LED bar meters, the GX-747dbx got back the more conventional VU meters. Akai probably had to omit the LED bar meters because the GX-747dbx otherwise would become too expensive with both dbx and LED bar meters in one set . Also the dbx version has glossy rosewood side panels compared to pine woodgrain veneer on regular 747.

 

[sssmokin99]

There is no reason for any difference. The last paragraph I have read before and I dont buy the "too expensive" argument either- this was a high end deck, and the difference wouldn't have been enough to put it out of its price range. Teac stuck with the traditional meters, and I believe that is what the market wanted in that type of deck
...so that is what Akai used.

Full disclosure: I have one (non-dBx version) and love it. So there....

 

[Tinman]

No, they did indeed fit the VU meters in the DBX version to keep costs down.

Personally I like the look better. They both should sound EXACTLY the same without DBX.

I have discovered that the huge linear switch inside CAN alter the sound when it's dirty, though.

DBX leaves a lot to be desired, though. Set up is CRITICAL to get the proper performance from it.

 

[beatdrum]

Akai 747 with DBX

You fellows seem to know this deck quite well. I have one with DBX that I bought off of eBay. I took it in to be serviced and it was cleaned, lubed, adjusted, etc. However, the main concern that I had was not rectified.
In the forward direction, the left channel lacks highs. The right channel has excellent sound. In the reverse direction, both the right and left channels sound excellent. The tech said that all the heads looked good and had no noticeable wear. I was told that I need a new head for the forward mode, but that they are no longer available. Does this sound like a correct diagnosis? Is there somewhere else (I am in Greenville, South Carolina) that I could take or ship my Akai 747 to get it up to par? I had planned for it to be my "final" reel to reel (I just sold my five other ones on eBay). Thanks for any thoughts you have on this. BTW, this is the first reel to reel that my wife actually liked in our living room. Nothing to do with performance, just appearance! Audio/video equipment = furniture in her eyes.

 

[AAA3330]

You fellows seem to know this deck quite well. I have one with DBX that I bought off of eBay. I took it in to be serviced and it was cleaned, lubed, adjusted, etc. However, the main concern that I had was not rectified.
In the forward direction, the left channel lacks highs. The right channel has excellent sound. In the reverse direction, both the right and left channels sound excellent. The tech said that all the heads looked good and had no noticeable wear. I was told that I need a new head for the forward mode, but that they are no longer available. Does this sound like a correct diagnosis? Is there somewhere else (I am in Greenville, South Carolina) that I could take or ship my Akai 747 to get it up to par? I had planned for it to be my "final" reel to reel (I just sold my five other ones on eBay). Thanks for any thoughts you have on this. BTW, this is the first reel to reel that my wife actually liked in our living room. Nothing to do with performance, just appearance! Audio/video equipment = furniture in her eyes.

Probably something to do with the forward playback head. Should be the third from the left. Assuming that it is cleaned and demagnetized, it's probably slightly out of adjustment. There are two adjustments: Head Height and Azimuth. The service manual should describe both in detail, if you decide to tackle it yourself.

 

[Tinman]

This is the exact problem I had with my own 747. It WAS the long head-switch switch.
A deoxit bath restored all the brilliance to the deck.

It could be the head, it's not unheard of. But don't twiddle adjustments before trying the long switch first. Drove me NUTS!

 

[steerpike2]

No, they did indeed fit the VU meters in the DBX version to keep costs down.

Perversely, moving coil meters nowdays would be far more costly than bargraph displays.

 

[FAB1]

Also the dbx version has glossy rosewood side panels compared to pine woodgrain veneer on regular 747.

The "rosewood" panels arent real wood veneer. Mine had damage on the top right panel and the pretty stuff was cracked and coming off a little.

Fortunately, the panels are drilled at the exact spots so you can just swap sides and flip them over - I did so and hid the bad spot on the bottom left

:scratch2: Will have to look in the service manual concerning this switch inside, maybe mine could use a deOxit bath too, although it sounds pretty decent to these ears anyway.

 

[rajkumar_]

Tension arm standby position

Hello!
Anybody can help me, Akai GX747 tape reel tension arms both side normally (without tape reel) standby at inboard or outboard? I saw online many pictures this arm normally standby at outboard, but my deck stayed on inboard. There was no any problem with machine operation everything good? Please answer me is it normal?
Raj:

 

[Tinman]

Tension arms should move outboard, so you can load a tape. Then move inboard when play is pressed.

 

[cabinover]

The tensions arms should return to outboard position on their own. Mine (dbx model) almost does it so that tells me new rubber bands for them are needed.

Another project for someday.

 

[rajkumar_]

Thanks! Even arm inboard, still lock position, without lodaing tape can't play. (Note: during play mode the arm normally intermediate position, still perfect)
I saw on Akai SM the tension arm rested on inboard!
Rgs,

 

[rajkumar_]

I’m the new owner of Akai GX-747, I don’t know full operation and function of controls (I just download Service Manual online) what is the purpose of “Cue / Review Lever”
By the way, help me where do I find download Akai GX-747 Operator's manual?
Thanks!

 

[Tinman]

The cue/review lever allows the tape to touch the heads while rewinding or forwarding the tape so you can hear/listen for the gaps between songs, etc. It's used for editing, mostly.

 

[rajkumar_]

Thanks for your information about Cue / reveiw lever!
By the way, Finaly I find out the problem on my tension arm belts both side loose, today I was replaced them and test run! Wow working good! You are correct tension moved outboard when not loading. (Before replaced belt stayed inboard) Thanks!
Is there possible download OM?

 

[authorjim]

DBX or not to DBX

No, they did indeed fit the VU meters in the DBX version to keep costs down.

Personally I like the look better. They both should sound EXACTLY the same without DBX.

I have discovered that the huge linear switch inside CAN alter the sound when it's dirty, though.

DBX leaves a lot to be desired, though. Set up is CRITICAL to get the proper performance from it.

I have several RTR's and I am considering buying a 747 DBX. Here is the question. If I buy the 747 with DBX and use it to record then it will not sound right on my other 747. Instead if I buy a standalone DBX unit, which one I'm not sure then I can use it with all my tape decks. Is that logic flawed or is the DBX in the 747 better than what I can buy separately on ----- Ebay?

Thanks
Jim

 

[goldear]

I have several RTR's and I am considering buying a 747 DBX. Here is the question. If I buy the 747 with DBX and use it to record then it will not sound right on my other 747. Instead if I buy a standalone DBX unit, which one I'm not sure then I can use it with all my tape decks. Is that logic flawed or is the DBX in the 747 better than what I can buy separately on ----- Ebay?

Thanks
Jim

The answer to that is not as simple as you might guess.

Yes can can buy external dbx units. But deciding which one to chose is not so easy.

The 747dbx came with dbx Type I NR (the professional version) which I have always felt was a poor choice for a consumer machine due to its extreme dropout sensitivity and extreme sensitivity to the type of HF response roll-off that one experiences at 3.75ips.

If you want a type I unit for the purposes of maintaining compatilbility, then get a DBX 150.

But if you actually intend to use DBX NR, I recommend that you get a DBX 224 series unit (dbx type II NR). These are far less sensitive to drop-outs and HF compression problems that you will have on virtually all consumer machines.

 

[Westy56]

This is the exact problem I had with my own 747. It WAS the long head-switch switch.
A deoxit bath restored all the brilliance to the deck.

Drove me NUTS!

What is the "long head-switch switch"?

I also have had problems with the highs rolling off. It got so frusterating I stopped using it and stored it away.

IIRC, the gx-77 heads will work on the 747.

Steve

 

[jan_stevns]

What is the "long head-switch switch"?

I also have had problems with the highs rolling off. It got so frusterating I stopped using it and stored it away.

IIRC, the gx-77 heads will work on the 747.

Steve

It's the switch that switches between the two sets of heads when you change direction - kind of ever returning fault on autoreverse Akai's of this sort - it on the bottom board , activated by a solenoid, that pushes it

 

[Westy56]

It's the switch that switches between the two sets of heads when you change direction - kind of ever returning fault on autoreverse Akai's of this sort - it on the bottom board , activated by a solenoid, that pushes it

Thanks, I'll have to look at my service manual and see if I can get at it (with my novice skills).

It sure would be nice to get it running again.


Steve