Arcam A60/Rothwell Rialto/Pro-Ject Xpression 3 distorted sound

[DanielP]

Hi all, I’m pretty new to decent audio equipment and slightly out of my depth so bear that in mind.

I have a Pro-Ject Xpression 3 turntable and a Rothwell Rialto mm/mc phono stage which I’m trying to get working with an Arcam A60 amplifier. I’m plugging the phono stage into the Mag P.U. din port through a din to RCA converter cable.

When I play a record the sound is really distorted. If I take the phono stage out and plug directly into the turntable the sound is clear but the level is really quiet, even at full volume.

I have tried the same set up with a different amplifier (NAD C330BEE) and it works fine so I know it’s not an issue with the speakers, turntable or phono stage being faulty.

I also used the Arcam amp to play music from my computer and that sounds fine as well.

Does anyone have any idea what might be going on here? It’s possibly a rookie error…but then I am a rookie. Any help would be much appreciated.

 

[Del monaco]

What cartridge do you have?

 

[chartz]

You should plug the phono stage into a line input, or just plug the turntable into the MM phono input of the A60 – unless you have an MC, but it looks unlikely, because a Red is usually bundled.
You don’t normally need the phono box at all actually.
Get rid of it.

 

[DanielP]

Thanks for your help guys. Yeah, it’s an Ortofon red cartridge.

the A60 only has the following sockets:
Tape
Preamp out/Power amp in
Tuner
Mag PU

 

[starbuck]

Assuming you're not already using the input on the A60, I would plug your Rothwell phono stage into the Tuner input on the back of the A&R amp as that will be a line level input. You should then hopefully get good/undistorted sound from your turntable set up. The connection order would then be Project turntable going into Rothwell Phono going into Tuner input of A60, ensuring that the Rialto is set for MM(moving magnet) and not MC cartridges. You can use the Tape Input socket on the A60 if the Tuner input is already in use(or Aux input if the A60 has a spare Aux input).

 

[linnfomaniac83]

Use the tuner input, or as suggested above, plug the turntable directly into the MM input.

 

[Craig B]

Thanks for your help guys. Yeah, it’s an Ortofon red cartridge.

the A60 only has the following sockets:
Tape
Preamp out/Power amp in
Tuner
Mag PU

MAG PU (aka Magnetic Pick-Up, later labelled 'DISC' on A60) is the in-built MM phono input. Your Ortofon 2M Red should work straight in on MAG PU; that is, assuming you have a suitable RCA to DIN cable/adapter that matches the A60 pin-in pattern (see pics below). Plugging the Rialto into MAG PU will only overload the internal phono circuit, hence the 'really distorted' sound.

As you are getting virtually no volume with the tonearm plugged directly into MAG PU, you'll want to investigate the suitability of the RCA to DIN cable or adapter that you are using. Should pins 1 and 4 (with 2 as 0V) be connected instead of pins 3, 5 and 2 then you are likely to be hearing low level 'bleed through' via the ground plane, hence the very low volume even with the volume pot fully open.

Once you get MAG PU working properly, should you wish to compare this in-built phono input to the Rothwell, then, again, you'll need have a suitable DIN to RCA cable connected from the Rothwell to AUX*, TUNER, or TAPE ('suitable' meaning with the RCA to DIN connected correctly, as per the images below).

A60 DIN inputs (note the labelling above each indicating Lch in on pin 3 and Rch in on pin 5 (pin 2 is 0V):

5-Pin 180º DIN socket numbering (the opposite when looking at the cable male pins from front on):

* unless yours is an A60AP version, then the DIN located between TAPE and TUNER is AUX, just another line level input, same as TUNER. If it is an 'AP' version then AUX in is on TUNER pins 1 and 4 (meaning one uses a 'tape' 4 x RCA to DIN to accommodate two line level inputs into one DIN socket). IOW, regardless of version, all A60 variants have 3 x line level inputs plus MM phono.

 

[Craig B]

Just to add to the above, should you have access to a multimeter then this can be used to determine which cable/adapter DIN plug pins connect to the RCA plugs. Specifically, DIN plug pin 3 should connect to Lch RCA pin, DIN plug pin 5 to Rch RCA pin, and DIN plug pin 2 to the outer ring of each RCA plug.

Let us know if you have a meter and we can walk you through this.

 

[DanielP]

Thanks all for your help so far, this is really useful information. Bear with me, I’m going to do some investigation based on the above when I next get a chance (got family over), then I’ll report back.

 

[DanielP]

Right, back on it.
I do have a really cheap multimeter that I bought years ago that might do the job. What’s the process for checking the din/RCA pin pattern then?

 

[Craig B]

Here is a well written primer on continuity testing from a maker of expensive digital multimeters...

https://www.fluke.com/en-ca/learn/blog/digital-multimeters/how-to-test-for-continuity​

Whether the meter be a digital or analog type, the meter is set to Ohms/Ω, and contact is made via the probes either end of that which is to be tested (i.e. black probe touching one end, red probe contacting the other end). With digital multimeters, 'OL' is often what is displayed when no electrical connection exists between the two points; otherwise there will be a numeric impedance reading (some models will also sound a confirmation 'beep'), the value isn't critical here but is likely to be more or less the same for each conductor path that involves the same sort of wire (DIN pin 2 will likely show a different value as it will usually connect along the cable shield). Should the meter be an analog type (with needle pointer against a printed scale), when set to Ohms/Ω expect to see a reading of infinity for open circuits (i.e. no conductivity) and 0 for closed circuits (conductivity). For a pretest reading, set to Ohms/Ω and simply observe the meter with the probe ends touching one another ('closed' i.e. continuity) vs. not touching ('open' i.e. no continuity).

As to the specific paths to test, there should be continuity between DIN pin 3 and RCA Lch pin, DIN pin 5 and RCA Rch pin, and DIN pin 2 to each of the RCA plug outer rings. It doesn't matter which way round the red vs. black probe leads go, in this case, as polarity makes no difference whilst testing cables. Keep in mind that the pin numbers need be swapped L to R when looking at the DIN plug male pins (i.e. relative to the pin numbering graphic of the female DIN socket above). IOW, DIN pin 3 will be top RH of the 'U'-pattern, with pin 5 next one along (pin 2 is always bottom centre).

Let us know what you have, and we can work from there.

 

[DanielP]

Thanks again for your help.

just tested the two RCA to DIN leads that I’ve got and I’m getting a reading from the 3 and 5 pins so it seems like they are connected correctly right?

 

[Craig B]

If pins 3 and 5 are the one's on the RH side of the 'U'-pattern when looking at the male plug mating face, then yes, they are connected correctly.

 

[Alun Rains]

Personally, if you are still unable to resolve it then I would refer back to your dealer for advice regarding obtaining the correct DIN cables etc. It beats me as to why Arcam have chosen to go with DIN inputs versus Phono or XLR anyway.. I don't think I would buy an amp with DIN inputs, too much hassle and lacks flexibility to easily connect other components.
As others have said though, you do not actually need the Rothwell Phono Stage as you could connect directly into the MM (M.U.) input on the amp.

 

[DanielP]

Craig B,

Yep, I reversed the pattern when testing the cables as mentioned. I’m also certain I’ve got the right button pressed when testing the different inputs.

If I plug directly into the turntable using the MAG PU I get low volume. If I use a different input (tuner/aux) with the Rialto I get a low volume. If I plug the Rialto into Mag PU I get distorted sound, as expected, but notably, higher volume but not very high.

Starting to worry that there is a more fundamental issue going on.

 

[Craig B]

Craig B,

Yep, I reversed the pattern when testing the cables as mentioned. I’m also certain I’ve got the right button pressed when testing the different inputs.

If I plug directly into the turntable using the MAG PU I get low volume. If I use a different input (tuner/aux) with the Rialto I get a low volume. If I plug the Rialto into Mag PU I get distorted sound, as expected, but notably, higher volume but not very high.

Starting to worry that there is a more fundamental issue going on.

You mentioned having used the A60 successfully with your computer to play music.

I also used the Arcam amp to play music from my computer and that sounds fine as well.

This suggests that the amplifier works fine on at least one of the line level inputs. At least it must have done so with whichever cable you had used with the computer.

As you appear to have had no success with the Rialto into any of the line level inputs, I am still skeptical of these RCA to DIN cables. There exists too much of a coincidence that these cables are the common denominator, when a presumed to be 1/8" phone plug to DIN* worked from your computer, therefore eliminating the amplifier as culprit.

Is your multimeter a digital or analogue type?

* Or, perhaps it was 1/8" phone plug to 2 x RCA plus RCA to DIN adapter, in which case, try the RCA to DIN adapter with a standard RCA to RCA interconnect between deck and MAG PU and/or Rialto and line input.

 

[Craig B]

Following on from my previous post, although it doesn't explain why you are having issue with Rialto into any line input, there also exists the possibility that your MAG PU input has the optional MC60 moving coil board fitted. Contrary to expectation, feeding a MM cartridge into an MC input often causes the sound to become muffled, as the input impedance of this particular MC stage is circa 142x away from what a MM cartridge requires. You'd only have to have a look inside the A60 to confirm the presence or absence of MC60.

WARNING: Always disconnected from the mains electricity before opening the case.

If MC60 is present, it isn't hard to miss as it will be mounted vertically just in from the DIN sockets. Although far less likely to be present, there could also be a smaller loading module present with DIP switches on, again mounted vertically just between the socket for MC60 and the DIN sockets, nearest to the phono input DIN. If present along with MC60 then this is likely to be ULM/C ('C' for moving coil loading vs. ULM/M for moving magnet); if ULM/C, this should also be removed for use with MM phono cartridges.

Let us know if you find anything here.

MC60 Moving Coil Input Board:

ULM/M or /C 'Universal Loading Module', very rare:

 

[DanielP]

Actually, I've tested it again with my computer and what I said was not entirely correct.

On my model the DIN plug between 'Tape' and 'Tuner' is labelled 'Pre Amp Out/Power Amp In' not 'Auxiliary' like in the photo you posted (everything else is the same). Actually the only way it works when connected to my computer is by attaching this port to my audio interface (Audient ID4). In this scenario the amp controls (volume, tone etc) no longer have any influence over the sound, I can only control the volume with the ID4. Is the amp even doing anything in this scenario or is it just a conduit to the speakers? I can't get it to work through the other inputs.

I'll have a look to see if there is an MC60 board installed.

Once again, thoughts and time greatly appreciated.

 

[Craig B]

Actually, I've tested it again with my computer and what I said was not entirely correct.

On my model the DIN plug between 'Tape' and 'Tuner' is labelled 'Pre Amp Out/Power Amp In' not 'Auxiliary' like in the photo you posted (everything else is the same). Actually the only way it works when connected to my computer is by attaching this port to my audio interface (Audient ID4). In this scenario the amp controls (volume, tone etc) no longer have any influence over the sound, I can only control the volume with the ID4. Is the amp even doing anything in this scenario or is it just a conduit to the speakers? I can't get it to work through the other inputs.

I'll have a look to see if there is an MC60 board installed.

Once again, thoughts and time greatly appreciated.

Ok, this explains everything. Your amp is in AP configuration and therefore requires a link plug be fitted into the 'Pre Amp Out/Power Amp In' socket such that the pre-amp and power-amp sections are joined. This can be a DIN plug with pins 1 and 3, as well as pins 4 and 5 linked via jumpers within. As things stand the amp is the equivalent of separate pre-amp and power-amp within one chassis, it needs connecting between the two sections.

As alternative to a link plug, two short pieces of solid wire the equivalent thickness of DIN pins can be fashioned into 'U'-shapes with one such jumper inserted across pin sockets 1 and 3 (Lch), the other across pins 4 and 5 (Rch). The hardest part is finding suitable diameter solid core wire. For reference, DIN pins are spec'd at 1.45mm in diameter, therefore, 1.5mm diameter solid core can be persuaded to fit.

If making up a DIN-5 180º link plug, make sure that the lower link between pins 4 and 5 doesn't come into contact with pin 2 at the bottom, else the Rch be shorted to ground; no damage will result, there'll just be no sound on that channel. Paper clip wire soldered across the solder bucket side of the DIN will do here.

Naim DIN-4 link plug (cover off):

 

[Operajulian]

Daniel:
It might well be that you have the AP version. Is the DIN socket at the Aux position upside down in relation to the other three DIN ? When you open it up there might be another "card" mounted by the DIN socket. If it is an AP a shorting DIN plug would then link the pre-amp circuit to the power amp circuit. ( Aha edited reply as crossing in the ethernet with Craig )

Just a general note - A&R did change the printed screening on the back for the AP versions but in the end did not produce an Aux printed version thereafter - causes some confusion all round but the upside down DIN is the big giveaway.

I hope you can get it all to work and sound great - its worth persevering.