Dual Rectifier question (NAD) - New question added!

Maynehead

I have recently become the proud owner of a new (used) Dual Rec 3ch non-multiwatt!

Just got it up and running last night after reading the extensive manual and after some testing I've got a couple of questions about things I noticed...

If I put both ch2 and ch3 in vintage mode, with all the controls at 12 o'clock, then according to the manual, I should hear a lot more presence in ch3 than ch2, as the ch3 presence control "picks up where ch2 leaves off".

However, I find the opposite is true. ch2 sounds a lot more present than ch3 at those settings, and even increasing the presence in ch3 doesn't help much. In fact the presence control in ch3 hardly does anything until you get to around 8 or 9 (out of 10), and then it suddenly takes off.

So in summary, in vintage mode, all controls at 12, ch2 has more presence than ch3, and this remains the case until ch3 presence is turned past 8 (out of 10). But with presence maxed out on both channels then ch3 does have more presence than ch2.

Can some Dual Rec owners please tell me if this is normal or does it indicate an issue with the pots (need cleaning?) or the valves (need changing?)

Oh and another thing, the output volume control doesn't do anything between 0 and 2, but then the volume suddenly kicks in big time, like turning it 0.1 degrees will increase the volume significantly. Again, normal or does the pot need cleaning?

Thanks in advance!

ICBM

The presence sounds like a pot taper variation, but probably just down to manufacturing tolerance rather than a fault. It won't be valves.

If it's a problem at all… Mesa manuals are often a bit strange, some of the things they say are either not entirely accurate or even sometimes plain wrong. The thing about the 'mid control acting like a gain' which most of them say is wrong, It doesn't, it's simply a mid control with more range than normal. The differences between different modes of the same channel (which Ch 2 and Ch 3 are, even though they have different controls) can sometimes be different ways round at different volume settings as well - my Trem-o-verb is like that, at some settings the two modes on each channel can seem to reverse their volume difference as the overall volume goes up.

The step in the output volume control is also normal and is a pot taper quality issue. You may be better to set the channel masters lower so the Output Level is closer to the mid-point - there will be a tone improvement as it gets further above the 'step' as well.

These are very fussy amps to dial in, as you will find - the controls are all highly interactive. Worth persevering though, and also explore the 'unusual' ends of the ranges as well, particularly gain - you can get some great sounds both on the clean channel with the gain up and on the dirty channels with it down.

Fiftyshadesofjay

I also find that vintage mode is in general a lot darker than modern mode. Do you still have the issue with all controls set at noon in modern mode?

fretmeister

Stunning amps, but do need learning!

I have the Multi-watt version and I'm still finding loads of great settings

Maynehead

Thanks for the reassurance ICBM. I've gone and ordered myself a full set of preamp tubes anyway as the previous owner had never changed them I like to make sure it's running at its best.

Fiftyshadesofjay said:

I also find that vintage mode is in general a lot darker than modern mode. Do you still have the issue with all controls set at noon in modern mode?

No in modern mode ch3 presence control works fine, and there is an audible difference as I turn it from low to high, and it does add more presence than ch2 which is what the manual states.

It's just that in vintage mode the ch3 presence control suddenly stops responding.

I know they use different tapers between the channels for the presence pot, but I just assumed that in any mode the ch3 should sound brighter than ch2 at the same settings...

Maybe it's a problem with the manual rather than the hardware....

guitarfishbay

Maynehead said:

If I put both ch2 and ch3 in vintage mode, with all the controls at 12 o'clock, then according to the manual, I should hear a lot more presence in ch3 than ch2, as the ch3 presence control "picks up where ch2 leaves off".

However, I find the opposite is true. ch2 sounds a lot more present than ch3 at those settings, and even increasing the presence in ch3 doesn't help much. In fact the presence control in ch3 hardly does anything until you get to around 8 or 9 (out of 10), and then it suddenly takes off.

Totally normal.

The presence taper for Ch3 is optimised for modern mode, which gives different results in vintage mode.  The Ch2 presence pot is optimised for vintage.  The latest Multiwatt revision switches the presence value per mode, so that it is 'correct'.

Maynehead said:

It's just that in vintage mode the ch3 presence control suddenly stops responding.

Turn it to 10 - it should get brighter right towards the end of the taper, IIRC.  Or maybe I'm thinking of ch2 modern...  I've not owned a Recto in months now.

Maynehead

@guitarfishbay Yes in ch3 vintage the presence consistently lower than ch2 vintage at the same settings until you get to near the end when it suddenly overtakes the ch2. Sounds like this is the same for all Dual Recs then? That's good to know, thanks. 

I've just thought of another question, so I'll ask it here while we're at it. On my Engl, I have a "Level" volume control to balance the lead channel against the clean and also a "Master" volume across channels. If I want to overdrive the power tubes I crank up the Master. 

 On the Mesa however there seems to be a Master per channel and an "Output" volume control across all channels. 

My question is, which one do I crank if I want to overdrive the power tubes?

guitarfishbay

Maynehead said:

@guitarfishbay Yes in ch3 vintage the presence consistently lower than ch2 vintage at the same settings until you get to near the end when it suddenly overtakes the ch2. Sounds like this is the same for all Dual Recs then? That's good to know, thanks. 

The most recent Dual Rec Revision, called 'reborn' or multiwatt, switches to the Ch2 value for vintage and the Ch3 value for modern, regardless of whether you're on ch2 or ch3, if that makes sense.  All the older 3 channels including the 4 channel Roadster/Road King, don't switch.

Maynehead said:

I've just thought of another question, so I'll ask it here while we're at it. On my Engl, I have a "Level" volume control to balance the lead channel against the clean and also a "Master" volume across channels. If I want to overdrive the power tubes I crank up the Master. 

 On the Mesa however there seems to be a Master per channel and an "Output" volume control across all channels. 

My question is, which one do I crank if I want to overdrive the power tubes?

With regards to this I don't think I could speak accurately given my own knowledge.

But I think you can 'crank' the master volumes on the channel and turn down the output level - but it won't necessarily sound good if you run the masters very high on the gain channels, from memory... but again I'm not sure.  I don't think this is the same as pushing the output tubes, someone like @ICBM could tell you.

Personally I found I got the best tone just switching the loop off, if you don't use a loop it is worth experimenting with that but be well aware that you might want to turn down the channel masters before disengaging the loop, otherwise it could get very loud!

Maynehead

Good point about the loop... I do want to use it but I haven't tried switching it off yet to see what the difference is.

I just want to make sure there isn't anything wrong with the amp basically. A full re-valve is on the way but I was just wondering if these kind of problems are caused by faulty/dirty pots. Guess I can spray them out anyway for good measure once I have the chassis out for the re-valve.

ICBM

guitarfishbay said:

Personally I found I got the best tone just switching the loop off, if you don't use a loop it is worth experimenting with that but be well aware that you might want to turn down the channel masters before disengaging the loop, otherwise it could get very loud!

You can't overdrive the power valves at any sensible volume setting. The only way to do it is to turn up *both* the channel masters and the Output Level, and then you will need an attenuator if the result is too loud. (It probably will be!)

The definitive tone of a Rectifier does not come from overdriving the power section anyway, quite the opposite. It needs to be pushed hard enough for it to introduce the rectifier sag which is part of what gives it its great loose feel and dynamics, but not hard enough to overdrive it or it will turn to mush. The rectifier sag starts at surprisingly low volume - not bedroom volume, but you'll get there with a moderately loud band.

If all the knobs work smoothly over their full range and don't crackle then there isn't anything wrong with the pots. Don't clean them unless you need to, it can wash the grease out of the bushing.

Maynehead

That's good advice about the pots @ICBM. I did think if they're not crackling then they're probably OK, but I (perhaps foolishly) thought maybe it would help with things like the output pot dead zone. In reality all I'd do is probably destroy that smooth resistance they've got and make them turn too easily.

As for the master volumes, I did play with them and thought the best tone was when they're past 12 o'clock. As I crank them I can hear a smooth breakup that sounded to me like power tube breakup, whereas if they're below 9 o'clock the sound gets really thin and fizzy. That's where I originally got the idea that they may be the "real" master volumes from.

However I had to perform these experiments with the output turned right down (on the cuff of the "step") so I'm not sure if that had any adverse effects on what I heard.

ICBM

If the Output Level is turned down, you can't be hearing power valve breakup at all. What you may be hearing is overdrive from the FX loop gain stages, which are before the Output Level. You can get some quite fat sounds like that, although it tends to mess up any effects you have in the loop if you're actually using it for that.

The 'fizz' at low master volume settings is more usually caused by the way the circuit interacts with the resistance of the pot itself, it's quite normal and nothing to do with the valves.

Maynehead

Ah, that makes sense. It's probably either the FX loop valve or PI valve breaking down. I did order a new long plate valve for the PI specifically for this reason but I hadn't considered the FX loop valve, which is going to be a spare ECC83S JJ I had lying around as I thought this position wasn't particularly important. I hope it will be up to the job.

Fiftyshadesofjay

As has been mentioned, you'll already be deaf / dead by the time you achieve power amp breakup on a Dual Rectifier. 

I can also say from experience (I've cranked one in a studio in an isolation booth, heard via a mic in the control room) that it sounds rubbish, the sweet spot is around three on the volume for me. 

Maynehead

Fiftyshadesofjay said:

As has been mentioned, you'll already be deaf / dead by the time you achieve power amp breakup on a Dual Rectifier. 

I can also say from experience (I've cranked one in a studio in an isolation booth, heard via a mic in the control room) that it sounds rubbish, the sweet spot is around three on the volume for me. 

Is that the channel master or the output level? Because my output level doesn't even do anything until it's turned up past 2!

Fiftyshadesofjay

For me it was the channel master with the loop bypassed.

ICBM

Maynehead said:

Ah, that makes sense. It's probably either the FX loop valve or PI valve breaking down. I did order a new long plate valve for the PI specifically for this reason but I hadn't considered the FX loop valve, which is going to be a spare ECC83S JJ I had lying around as I thought this position wasn't particularly important. I hope it will be up to the job.

It won't be the PI either as that's part of the power section and comes after the Output Level .

A decent PI does improve the tone though.

You could try in different positions and see where it sounds the best - but you shouldn't try it in V3 or V4 really, since these are cathode-followers and some Russian-made (assuming this is a Sovtek LPS) 12AX7s don't like that.

The order of the valve stages is:

V1 - input gain stage (both channels) and clean channel stage 3

V2 - second gain stage (both channels) and dirty channels stage 3

V3 - dirty channels stages 3 and 4

(channel masters at this point)

V4 - FX loop send and return

(Output Level at this point)

V6 - phase inverter

Power valves

So the valve that will have the most effect on the overdrive you get when you turn the channel masters up and the Output Level down is actually V4, the FX loop valve.

Maynehead

@ICBM

I have to say, this board is a lot more helpful than the Boogie Board where I posted the same question and still no replies... Don't know why I bothered joining that really.

Anyway, I've read somewhere that the JJs are very resistant to breakup even though they are short plates. I'm hoping it will be a good fit.

FYI the valves I ordered for v1 - v3 are ECC83-HARMA RETRO

Cheers. :-B

Deijavoo

I bloody love the Dual Rec tone so much.

Nerine

I don't remember the output control having a strange taper on either of the Dual Rectifiers I had.

Maynehead

Nerine said:

I don't remember the output control having a strange taper on either of the Dual Rectifiers I had.

Played around with it more last night. It's not as dramatic as I describe, although it still does very little until you get to a certain point (8 - 8:30). It's probably unnoticeable unless you're trying to play at very low volumes.

On a related note I discovered a little trick to allow me to turn the volume controls up a little more. I just enable the FX loop and turn down the send pot at the back a little. This allows me to turn up the masters and output controls so that I've got more fine control over the volume.