AKAI M8 Tube R-R input problem - diyAudio
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Old 8th May 2004, 09:52 PM   #1
abmoggy is offline abmoggy  United States
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Unhappy AKAI M8 Tube R-R input problem

Hello eveyone,

I hope that someone might be able to help me with a problem I have with my Akai M-8 Tube RR player. It plays fine from the R-R tape but when I connect my CD-player to the Line input using a home made RCA-PHONO connector, I'm getting really bad buzzing sound. This happens on both channels. I tried the MIC input and it's the same. It's when I connect it to the PHONO PLAYBACK INPUT jack that I'm getting some sound out of it. However, It will distort badly if I turn the volum more than say 10%. What I don't get is when I play R-R tape, it sounds pretty good but using LINE in it's acting up on me. I would like to use the mono amps since I head that these 6bq5 amps are pretty good, but I don't know how to get it functioning properly.

TIA

Abmoggy
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Old 9th May 2004, 08:55 PM   #2
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Quote:
using a home made RCA-PHONO connector
shouldn't you check this one first ?

looks like this is the culprit.

Dick.
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Old 10th May 2004, 08:26 PM   #3
abmoggy is offline abmoggy  United States
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djmiddelkoop,

That was the first thing I checked and it tested fine. Could the problem I'm having due to output voltage or impedence from my CD player to the line input of the AKAI R-R ? The sound is really distorted even at the lowest volume level.

Thanks!

ABMOGGY
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Old 11th May 2004, 10:42 AM   #4
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Quote:
Could the problem I'm having due to output voltage or impedence from my CD player to the line input of the AKAI R-R ?
Nope, should be fine.
I guess there is something wrong with the line input, or switch ?
Mic or phono inputs are not suitable, due to the low sensetivity and the high output of the CD player.
As I'm not familiar with this Akai M-8, it's rather guessing what's wrong.

Dick.
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Old 11th May 2004, 10:57 AM   #5
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Hi,

Quote:
Mic or phono inputs are not suitable, due to the low sensetivity and the high output of the CD player.
Don't you mean "high" sensitivity?

Without a circuit diagram of the R2R it's hard to tell what's wrong but it could be a bad tube in the line amp part.

Cheers,
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Old 11th May 2004, 03:32 PM   #6
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You are probably overloading the input stage. generally both inputs cannot go bad the same way at the same time unless the power supply is faulty.
Forget the phono input. Drop your input signal using resistors and then try it out at the mic input. Mic inputs are in mV . Might be 2mV. CD player outputs are 1000 times higher.

try -----/\/\/\/\/\----|-------- to mic input
| 100K |
CD signal /
\ 100 ohms
/
|
|
GND
On each input.
Cheers.

My sketch comes out wonky. Thats a series 100Kresistor to the mic input and a 100 ohm resistor to ground from the mic input .
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Old 11th May 2004, 08:43 PM   #7
abmoggy is offline abmoggy  United States
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Quote:
You are probably overloading the input stage. generally both inputs cannot go bad the same way at the same time unless the power supply is faulty.
Thanks Ashok!

I'll give it a try tonight.

ABMOGGY
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Old 12th May 2004, 03:04 AM   #8
abmoggy is offline abmoggy  United States
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Ashok,

I modified my connector cable per your suggestion. The problem with the MIC and LINE Input are still flat, BUT the PHONO PLAYBACK Input is now listenable! I can use the volume control and there is no distortion. My question is is the LINE Input stage dead? On both sides? even when they are Mono amps? What should I check next?

Thanks for your help!

ABMOGGY
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Old 6th April 2006, 06:48 PM   #9
AKAI M8 is offline AKAI M8  United States
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Default LINE IN

old thread but could not resist-

if you want the "line in" jacks to work properly on an Akai M8, you must put the deck in "record" mode. This allows the line in signal to pass through the amp, and output through the speaker jacks and headphone jack. The power output will be reduced from the nominal 6 WPC to around 3 WPC, but the unit will still perform excellent and sound stunning- while allowing you to still use the existing preamp built into the M8

if you want to use the phono in jacks, with something other than a phono, you will have to reduce the input signal, with an external preamp first- otherwise you are overloading the phono in jacks and that's why you get the distortion

If using the line in jacks (what I recommend for tape and CD), you can turn the drive motor "off" (the middle position on the switch), and also disengage the capstan by sliding the deck auto stop lever up to "off" (to avoid putting a permanent indention in your rubber pinchroller wheel)- the deck will then sit there in record mode, but without any spindles turning and without the motor running- you can then turn the motor back on if you want to run the fan to cool the unit- but I have run the M8 for 12 hours straight without the fan, in this mode, with no ill effects

using the M8 as a low-budget "SET tube amp" will give you sound equal and above modern tube amps costings $1500 and more new

I got my M8 for $10- it's been my main system amp now for 2 years. By comparison, I find SS now unlistenable and boring.

note- the record switch contacts on my M8 needed to be sprayed clean with CRC to get it to work right- and the linkage also adjusted to the record switch fully engaged. Another problem my deck had was the 1/4" jack grounds on input side were loose, which will cause the deck to not operate correctly in any mode- after resoldering them, it worked great.
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Old 7th April 2006, 02:02 AM   #10
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I have a friend with an M8. It always sounded very good.
I think it can compete with a lot of current day amplifiers.

Will see if they have a circuit diagram. I used to be their main repair guy ( for free ! ) until they moved to CD players and ss amps. I think it must still be around and see if they will sell it ( to me !).

Does anyone else have a circuit diagram ?
Cheers.
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