Denon DR-M4

derek92994 · Dec 30, 2014

I'm very sorry for your loss Sam, have been there myself, but have not had as many pets as you due to real estate rules (no pets allowed). It has been 7 years since I lost my last kitty and am considering breaking the rules to get another, as I am kitty sitting my friend's cat and it has improved my mood considerably having company.

Great info there, thank you. I will do the following things:

1. Order a new belt/pinch rollers/idler tire from Marrs but it will be some time before I can raise the cash, am jobless and financially screwed right now. Postage cost is quite high for just 1 belt kit.

2. I have a service manual for the DR-M2/M3, but its not the same back tension setup as those models use an arm for tension like you described (my DR-F7 is like this). The DR-M4 however does not have a tension arm so back tension must be applied by some other method. I will have to investigate further to find out how it does this.

3. I will check and oil the reel table shafts. The rotation is sensed by optical sensors (no belts), the reel tables have a wheel with notches on the outside of them.

4. Check capstan flywheels for end play and re-lube.

This thing is a bitch to pull apart, so I will tackle it when I've had a good rest and am not so agitated, am dealing with some personal issues at the moment, all should be settled in a day or two.

Thanks so much for your detailed reply. I will update you on progress.

derek92994 · Jan 20, 2015

Been using this deck as a playback only lately. I notice that it tracks Dolby C better than my DR-F7 and Harman/Kardon TD 420, so it good for playing back those tapes. I still plan on doing the work on it to try and fix that flutter problem. Listening to rock you don't seem to notice it that much, so overall its still a nice machine. Will post more updates when I decide to work on it again, however for now I have many digital transfers of vinyl to process for a friend.

derek92994 · Mar 8, 2015

Finally got around to servicing this unit again to see if I can improve it.

Pulled mechanism apart again, re-lubed capstan shafts and bearings. Cleaned belt, I don't think the belt is 100% but it is not slack, just doesn't look brand new. Cleaned reel idler (looks brand new, has been replaced in the past). Took off reel tables and relubed, they needed to be done as were not 100%. Cleaned idler contact surfaces on reel tables.

This unit uses a spring loaded arm arm with a brush felt on it for back tension which rubs on the supply reel, this needed cleaning, felt is still ok and not excessively worn down. The usual head clean and demag was also done.

It seems to be much improved in the wow and flutter department. I have not heard any with my bare ears during playback or record monitoring. Still not 100% with the test tape but it I'd say its around 90% which is much better than before. Quartz lock circuit is working fine and speed stable. Sounds great through the WOPL.

Tried recording on a That's MRX-P90 (Type IV), BASF Chromdioxid II and Maxell XL-II Epitaxial, all producing great results.

The only other things that should be replaced is a capstan belt and pinch rollers. The Pinch rollers are in good condition for their age and no tape skewing or frilling is occuring. I'd be inclined to get a Tension arm with new felt as well in the future.

Thanks for the advice Sam, was worth the effort doing the work on this machine.

Skywavebe · Mar 8, 2015

Apparently you are doing well and the felt on the tension arm can just be replaced by you with a small piece of like felt and some rubber cement. I do this all the time in Teac reel tables and watch the takeup torque go from 90 sometimes to 35g/cm.
The one thing is unless you have a way to measure this you never know how far off you are. That is why any Tape deck Technician should try to get a MTT160 cassette gauge or the like. There were many of them out there and they have to be selling them somewhere.
The belt can be easily obtained from Consolidated Electronics where a lot of thin type cassette belts can be had for low cost. The right size belt in a thin material will help wow and flutter figures better that a thicker belt that is applying too much pressure to the bearings. I think there are machines with original belts that were .019" thickness and I found much greater sized belts on from E bay seller that just were not the right fit- people get the idea that you only need a belt and that any belt will do.
Well from all you have written above we know that is far from the truth. So the funny thing is that Consolidated may not have every open reel belt I need and I go to Marrs for those but cassette deck wise you are in good shape to find this supplier.
To help out- This is Consolidated:
http://www.ceitron.com/passive/belt.html

Steve Coy gets products out fast and he advises you of all the steps- I wonder where he finds the time but maybe he has it automated. Marrs should contact Steve to find out how he does this and he could double his sales I am sure.

NastyTapes · Mar 30, 2016

Hi. I'm new to the forum, but was very interested to read about Derek's experimentation with the Denon DR-M4 deck - true dedication and very informative (although a lot of the technical info was over my head as I'm a novice in the world of tape decks).

Anyway, I run a tiny underground tape label and record and release tapes in small batches. I've been using a DRM-555 for my recordings but recently it developed problems which my local audio repairs/tape deck specialist couldn't fix.

Today I picked up a Denon DR-M4 for a decent price, so my plan is to go ahead recording tapes with this machine. So when Derek mentioned having to open up the deck to alter the biasing I immediately pricked up my ears, being used to the DRM 555's manual bias control dial on the front of the deck.

Can Derek, or anyone else, advise me how to go about altering the bias inside this deck? Also, what kind of bias setting should I change it to?

Bearing in mind I'm using mostly ferric/normal type tapes (although occasionally chrome tapes as well when I can get them), and the type of music I'm recording is mostly pretty blown out hardcore punk or heavy rock type music with generally a lot of noise/fuzz, very little dynamics (pretty much loud all the time), and a down-tuned, bass heavy sound. I'm also not recording using any Dolby/NR settings thus far, as it seems likely to me that a lot of my customers won't have Dolby B or C enabled decks. Is this foolish or wise? I'm basically aiming for my recordings to come out pretty bright sounding. Does this mean I want slightly higher than normal bias?

I'm going to listen to some stuff and fiddle about of course, but any advice would be marvellous! :albino:

Skywavebe · Mar 30, 2016

NastyTapes said:

Well to adjust the bias with a three head deck you need to know what the tapes that are going to be used on the machine will be or get a sample of them. I have had Ferric tapes that could not be made to record at 0 VU no matter what without mods to the machine. I told my customer also a duplicator, to get rid of that tape. He brought me some Chrome tape from NAC that very closely match the Maxell XL II tapes. This is what I told him to use. It is called 799 tape.
The tapes that people make that are not labeled in the slightest are usually garbage. I have a bunch here but do not know what they are. I was told they were NAC tapes. They are junk.

It is not hard to rebias a deck but first you need to make sure the play alignment is correct nd then you can put in a tape and with the right equipment can bias the deck for that tape at -20 dB.
Setting up a deck usually involves setting record levels and then bias and they interact so you may have to go through it a couple of times. The required equipment is AC Millivolt meter with dB scale- I use the Leader LMV181A most the time. A scope for setting azimuth with a good test tape. A sine wave oscillator with attenuator as levels have to be changed to set operating level and then bias. The service manual for the deck you have. Too many people think the front bias is of great use but they very often only change bias a bit which is not all that helpful and they do both channels at the same time which is a joke. The better machines like the Tascam 122 Mk II have all kinds of adjustments inside and even a 4th choice on the outside with a oscillator built in. In this deck you can adjust to almost any tape from the front panel without all the other fancy equipment. This is a very wanted deck right now.
If you record Metal music or RAP I don't see any reason to worry about a quality factor as the music itself is nothing but distortion and noise. Striving for a quality product and tape for this purpose just results in a waste of money and time.

orange · Mar 30, 2016

And I'm slightly envious of Derek for actually having some TDK SD 90 when all I have are two 46s and two DS-X 90s left in my stash

derek92994 · Mar 31, 2016

NastyTapes said:

I did have a go adjusting bias settings internally, but I did it purely by ear. I lack the knowledge and equipment to do it properly. I got some good results out of this deck, but it needs more work done to it internally. The mechanism and such is fine, but other components like capacitors and maybe the heads themselves may need replacing. It still makes a good recording even in its current state, but it doesn't compare with my JVC TD-V661 which has HXpro and adjustable bias and level settings on the front panel. It biases up nicely to any tape. I found the denon a little hit and miss with its auto biasing but that could be just age and the need for more advanced restoration.

All in all I still enjoy this deck, but use it mainly for playback these days. I'll have to re-read the thread as well as I can't remember what I posted previously. I'd like to put a picture guide up to show you where the bias adjustments are, but have little time after work and my mental health is not too good.

From what I can remember the bias adjustment pots are up the back of the deck behind the vertical circuit board, but not 100% sure. I adjusted them while in record mode. Still encountered channel imbalance though, which is to be expected when trying to do it by ear and not using an oscilloscope.

As for dolby, that's a tough one. Recording with dolby B and playing it back without dolby will increase the brightness. I did this for many years when I obtained my first semi decent deck, the Yamaha K-600. These days I prefer to use dolby on playback if the tape has been recorded with it, but prefer to make non dolby recordings most times.

derek92994 · Mar 31, 2016

orange said:

I have used all my chromes and metals and don't have new ones anymore. So I'm down to TDK B's, D's, old Maxell UR's, and even Teac CDX-90's when I'm desperate. Dolby is a must on TDK B's and Teac CDX-90s as they are a low grade ferric tape. D's and UR's I can just bare the hiss, they sound quite good in the car which is where they mainly live.

NastyTapes · Apr 1, 2016

Thanks for the info Derek, appreciated.

Elite-ist · Apr 1, 2016

It's great to have you join our forum, NastyTapes.

Nando.

BlazeES · Apr 1, 2016

Welcome to the Phoenix Nasty !

... now if I could only get Janet Jackson out of my head ...

orange · Apr 4, 2016

derek92994 said:

Dammit, Derek, why didn't you say so earlier? I'll be in touch...

orange · Apr 4, 2016

BlazeES said:

derek92994 · Apr 4, 2016

Elite-ist said:

Yo Nando! how are you travelling bud? Sorry for lack of contact, I'm in another world lately. Work taking up the majority of my time. Give me an update, cheers.

derek92994 · Apr 4, 2016

orange said:

Steve is going to help me get some chromes and metals in my stash, this has made my day. Thank you Steve.

Elite-ist · Apr 4, 2016

derek92994 said:

Hi Derek,

Also busy at work. I had my system apart for cleaning and rejigging of a few components. Bought a couple of decks and a few accessories and I have two of my components up for consignment sale at Innovative Audio. Haven't done any taping for the past month, or so, except for three tracks for the Tapeheads Musical Chain Travelling Tape project that's currently underway.

I can give an update, later on, with more particulars.

Nando

orange · Apr 4, 2016

derek92994 said:

I'd better hustle my corpuscles to the post office hasta manana and get the shipping estimate. Same deal as Nando, all chrome and metal with a few of the unmarked CrO2s and a C-0 or so, shipping only.

I'm continuing the Payback Tour, giving back for all I've received in nearing the end of my 5th year on Phoenix.

I've kinda got a sh!tload of blanks and not blanks right now anyhow, and not enough storage units. I wanna get more sheving toward the fall.

PS I got another CT-F750 with the local Sanyo RD-5350 I was given, it finally got here from my mom after 2 months and when I got to looking at it I saw the cord was cut and she said the guy she sent it to said everything was busted...which was BS as it looks pretty non-busted inside and I was trying to see if the belts were shot and it seems to have a similar setup to my first Sanyo deck from 1980 with short, non pianp key control and a huge flywheel.

Now I have to patch a cord to it (it's non-polarized) and carefully bring it up.

But the cord was cut.

derek92994 · Apr 5, 2016

orange said:

Some second hand blanks would be good too if you can do that as well. I am willing to pay for them. Thank you for being so kind.

Flat out at work and trying to stay healthy to get the momentum to beat these psychotropics.

orange · Apr 5, 2016

There were a few unmarked blanks that may have come from either here or wherever, but I ran out of packing tape packing that thing.

Wait until you get the shipping estimate and then see what you can afford, not charging for the tapes is going to be a godsend.

Denon DR-M4

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