Connecting dual 1225 to modern phono preamp

[Yodude120]

Hello,

I’ve recently gotten my hands on a dual 1224, I restored it and it seemed to be working almost perfectly. To test it, I had connected it to my vintage HiFi system via the turntable input socket (Wega System 3220, with similarly a dual turntable and and a WEGA receiver with EQ). Up until testing it with my WEGA system, everything seemed perfect.

This is a turntable I intened as a gift, so I cannot use it with my own WEGA Hifi system though. I had thought switching the pre-amp would not cause any trouble though, until I actually tried it with a new preamp to be intended as part of the gift. Unfortunately, unlike with the WEGA system, connecting the dual 1224 via a DIN 5 pole male - stereo RCA male adapter consistently caused the right channel to go away / just produce huge humming. I don’t understand this, as the DIN-RCA adapter is not faulty (I’ve used it successfully with other turntables), I merely switched the preamp. Actually, I tried 3 different preamps (Behringer PP400, Behringer PP500, and N-Audio AK750S), and they consistently produced the same problem. I’ve alslo tried replacing the carttridge on the dual 1224 with the cartridge from my dual 1229, which definitely works, but that AGAIN shows the same problem. The same cartridge works fine on my WEGA system though.

I don’t understand why the Dual 1224 only works with the preamp on the WEGA system but no other pre-amp. Am I missing something / does the vintage WEGA preamp have some extra hardware not present in the modern pre-amps ?

 

[mrwood200]

Am I missing something .... ?

You got the suave box checked ...




I am not sure what you got ....... let me know if summary below is correct:
- existing TT works
- new TT w/ DIN cable works when plugged into Wega phono input (?)
- new TT does not work when you convert DIN & add phono preamp and pull into ??? Wega input? which input?

 

[Yodude120]

You got the suave box checked ...

Thank you ! The WEGA 3220 is really my darling. Along with Grundig 210 boxes I’ve gotten a ridiculously surprising output from it, I . The WEGA is really a swiss army knife, the variants and amount of filtering it can do is really rare (esp. the adjustable presence filter, never seen it on other hardware). I only had the lights on the radio go off, it seems complicated to fix them though as they’re not easily swappable (might just replace the whole radio selector)

Regarding the TT / preamp issue:

- existing TT works

- yes indeed, has some other small issues but nowhere near this. I use it very regularly and it sounds awesome with the WEGA.

- new TT w/ DIN cable works when plugged into Wega phono input (?)

- yes, connecting it directly via its DIN cable to the WEGA without any preamps works normally.

- new TT does not work when you convert DIN & add phono preamp and pull into ??? Wega input? which input?

I am trying to monitor with IEMs directly from the new turntable / new/external preamp via its headphone output, no connection to the WEGA system (intended use is with headphones). I also tried a 2-RCA-to-TRS plug to my headphones (monitoring form RCA not the headphone output), same issue. The left channel works, the right channel hums like crazy (no actual audio at all, just hum).

The only peculiarity with the dual 1224 is that it has a VERY long (2-3m) DIN cable. But that doesn’t seem to cause any issue when connecting to the WEGA system, only when connecting to the external preamps (the 3 different ones). The same external preamps work just fine with a basic Philips 22GA427 turntable.

 

[mrwood200]

I am trying to monitor with IEMs directly from the new turntable / new/external preamp via its headphone output, no connection to the WEGA system (intended use is with headphones). I also tried a 2-RCA-to-TRS plug to my headphones (monitoring form RCA not the headphone output), same issue. The left channel works, the right channel hums like crazy (no actual audio at all, just hum).

The only peculiarity with the dual 1224 is that it has a VERY long (2-3m) DIN cable. But that doesn’t seem to cause any issue when connecting to the WEGA system, only when connecting to the external preamps (the 3 different ones). The same external preamps work just fine with a basic Philips 22GA427 turntable.

Lot of variables here, which makes troubleshooting difficult.
But it appears you have some DIN ****ery going on here. It is known you may lose a ground w/DIN/RCA conversions (AI - If you use a DIN-to-RCA adapter without modifying the internal ground bridges, you might run into a ground loop causing a loud hum.).
Not sure how you lose a channel. The too-long (replacement) cable is not a good sign for capacitance or confidence.
I am not sure of the best solution.

This is a turntable I intened as a gift...

The gift recipient is going to use this for headphones? hopefully using one of your 3x phono preamp??
I am leaning towards new RCA phono cord w/separate ground.

Let's see if we can get some input from DIN/Dual users.

 

[Yodude120]

The gift recipient is going to use this for headphones? hopefully using one of your 3x phono preamp??
I am leaning towards new RCA phono cord w/separate ground.

yes, the idea is for them to use the turntabe first with headphones. They can then get a full amplifier on their own as they please / if they need to.

My thinking for now is also that there’s no way around re-wiring from DIN to RCA from inside the dual 1224. I didn’t want to do heavy surgery though… I didn’t have this problem before with DIN/RCA conversions though, for now I did it with 3 other turntables with no problems.

 

[lini]

(...) The only peculiarity with the dual 1224 is that it has a VERY long (2-3m) DIN cable. But that doesn’t seem to cause any issue when connecting to the WEGA system, only when connecting to the external preamps (the 3 different ones). The same external preamps work just fine with a basic Philips 22GA427 turntable.

Might be a wiring standard problem. I.e,, in the very early days of stereo the turntable manufacturers would still hook the new additional channel (= the right one) signal/+ to pin 1 of the DIN plug - rather than to pin 5 later on. For your WEGA system that doesn't matter, 'cause according to the schematic its phono input has a (or respectively the usual) bridge fron pin 1 to pin 5 installed (just like many other amps, receivers et cetera with a DIN phono input also do). However, maybe your DIN adaptor isn't a dedicated phono adaptor and hence doesn't sport that bridge and requires the right channel signal/+ to arrive at pin 5, while I'd suspect that rather long output cable of that 1224 exemplar to not be original, and maybe it still has the right signal/+ connected to pin 1 rather than pin 5 of the DIN plug - in which combination the right channel signal/+ simply wouldn't arrive at the inner contact of the right RCA output plug of the adaptor.

Do you have a multimeter at hand? If so, I'd suggest you to check the pin assignments of that 1224 exemplar and your DIN adaptor. Correct newer DIN assignment for the 1224 would be: Left signal/+ -> pin 3; right signal/+ -> pin 5; left & right ground/- as well as headshell, tonearm & chassis/drive ground -> pin 2. And for a non-dedicated-phono DIN coupling input to 2x RCA plug output adaptor it should be: Pin 3 (left signal/+) -> left RCA inner contact; pin 5 (right signal/+) -> right RCA inner contact; pin 2 (left & right combined ground/-) -> both RCA outer contacts.

Greetings from Munich!

Manfred / lini

 

[Yodude120]

Do you have a multimeter at hand? If so, I'd suggest you to check the pin assignments of that 1224 exemplar and your DIN adaptor. Correct newer DIN assignment for the 1224 would be: Left signal/+ -> pin 3; right signal/+ -> pin 5; left & right ground/- as well as headshell, tonearm & chassis/drive ground -> pin 2. And for a non-dedicated-phono DIN coupling input to 2x RCA plug output adaptor it should be: Pin 3 (left signal/+) -> left RCA inner contact; pin 5 (right signal/+) -> right RCA inner contact; pin 2 (left & right combined ground/-) -> both RCA outer contacts.

this was very insightful, I could get some improvement already by bridging the pins 4 and 2 on the DIN adapter (right ground and gnd) and pins 1-5, I the buzz/hum greatly reduced and I can hear a very very faint signal on the right channel, but it’s extremely damped wrt the left channel. I’m at a loss what I can do more as all the pins are now connected and the problem is still there ,