OLDER DECWARE GEAR SUPPORT >> SE84A, SE84B, SE84C, SE84C+,SE84CKC >> Mono operation

Message started by TerribleTed on 01/27/09 at 15:40:56

Title: Mono operation
Post by TerribleTed on 01/27/09 at 15:40:56

Trying to find out how to hook these up in mono.  I don't see any details in the manual but as I recall, a Y connector is installed and connected to both inputs while a jumper wire is placed from the positive on one speaker connector to the common on the other side to make a series connection.  Is this correct?  The two amplifiers are a SE84CS and a SE84C+ which I assume are both connected in the same fashion, correct?  What should I expect other than increased power?

Title: Re: Mono operation
Post by Steve Deckert on 01/28/09 at 14:16:03

Hi Ted,

Yes, that is correct.  You'll get an additional 6dB before clipping and a greater sense of weight.


Title: Re: Mono operation
Post by TerribleTed on 02/23/09 at 21:00:22

Yes, it does have significantly more weight and volume.  Sounds very good and handles inefficient speakers quite well in mono.  Is it just my imagination or do the amps run a little warmer in mono?

Title: Re: Mono operation
Post by Miles on 02/24/09 at 01:50:04

Ted I recently bought a second SE84C and now run them as monoblocks wired in series to drive Decware MG944 speakers. This change was a huge improvement to my system. Yes, more weight and control. You can easily modify your amps yourself by opening the case and soldering in a shorting wire between the inputs thereby obviating the need for "Y" interconnects.

Can't say they run hotter than before but did notice a significant increase in hum (approx. 2X) though I do not hear it from the listening position.

Regards, Miles

Title: Re: Mono operation
Post by Gary Anderson on 01/27/10 at 03:14:38


I just got my new SE84C+ with CCE and so far it's great!  More comments on that in another post.

I may get another and put them in series.  Could you put some detailed instructions in the manual on how to do that?  Not only informational, but perhaps a selling point, for new owners who might want to do that.

Thanks!   :)


Title: Re: Mono operation
Post by Gary Anderson on 01/27/10 at 03:48:46

Hi again,

A comment about "more weight".  My current system consists of my new-as-of-yesterday SE84C+, a Pioneer Elite SACD/DVD player, Paul Speltz anti-cables, Paul Speltz anti-interconnects, and Klipsch Forte II speakers (99dB efficient).  

I have one particular CD I like for string sound - Igor Kipnis playing Scarlatti Sonatas on the harpsichord.  When I played that CD yesterday it sounded small, even at full volume (CDs are recorded at different levels I guess) and the sound didn't hit me nearly like it did when I had hooked up my CJ PV-12 preamp and Adcom GFA-565 monoblocks.  

However the Forte IIs are 8-ohm speakers and the SE84C+ loves 2-ohm speakers according to the manual, and not 8-ohm so much.  What to do?  I hooked up my trust Paul Speltz Zero Autoformers between speaker and amp, wired so as to *reduce* the impedance by a factor of 3 - essentially changing 8-ohm speakers into 2.66666 ohm speakers.  

What a difference!  The SE84C+ puts out more power at lower impedances, and the weight is back in the sound and I'm very happy with what I'm hearing now - and the amp has barely been broken in.  I asked Steve about the Zero Autoformers before I got my amp, and he advised me to try it without the Zeros first.  I did and then tried with the Zeros, and they work wonders.  At the current price of $450 a pair they are not cheap, but you might consider it if you have higher impedance speakers.  They can be used to either lower or raise speaker impedance, with lots of different multiplying factors, depending on how you hook them up.  No, I don't work for Paul but I really like his stuff.

After a while I'll switch them around so they are only a 2/1 drop in impedance, making my Forte IIs like 4-ohm speakers to my SE84C+ and hear what that sounds like.  Kind of like tube swapping - the new hookup really has a different sound and feel.  

BTW, I have owned Atma-Sphere OTL tube preamp and monoblock amps, and I sold them because I didn't "feel" the music.  Clean and nice, but not all there.  I have to say that already, after only a day Decware blows them away.  

I also have a ClearAudio Emotion turntable with Benz Ace MC cartridge, which I'm not playing now because I need a good phono preamp (My CJ PV-12 preamp has a built-in phono pre), so of course I'll need a Decware ZP3 with MC step-up transformer.  And then perhaps a ZCD CD player, as well as full range speakers (eventually), but for now I'm really liking what I'm hearing, a LOT.

Thanks Steve!


Title: Re: Mono operation
Post by Gary Anderson on 01/28/10 at 05:17:08

Hi again,

A follow up - I just switched my Zero autoformers so that my 8-ohm Klipsch Forte IIs look like 4 ohms to my now 3-day old SE84C+ and it's even better than when I had the autoformers set to 3/1 (2.6666 ohms).  I think the 3/1 reduction in impedance wasn't quite the right combination but now the 2/1 ratio seems a good balance between more weight and smoother, solid sound.  The 3/1 was a bit grainy and forced compared to what I'm hearing now.  I noticed this difference right away when I switched connections so it's more than just the amp being another day broken in.  Instead of just tube swapping, speaker swapping hehehe.

Again, kudos to Steve and all the Decware crew.


Title: Re: Mono operation
Post by ski bum on 02/27/10 at 21:11:40

Steve (or anyone else)-

When strapped in mono is it still considered 'single ended'?  This is kind of academic, I guess, but I'm curious.  

Also, how do the extra output trannies and tubes affect the amp/speaker relationship?  I know that the amp will see half the rated impedance, but is damping factor or other aspects changed?  Why does series wiring of output 'maintain transparency' over parrallel, as per the manual?  

Relatedly, if your amps are seeing half the impedance, does that also mean that any peaks or dips in the impedance are also reduced, thus giving a smoother, easier impedance curve?  Does this benefit the sound?

Just how much do impedance irregularities affect response?  Using my rudimentary test gear, my wacky impedance speakers driven by zens produce remarkably flat in room response (once above the bass node zone, ~150hz or so, pretty freakin flat to beyond 16k, where I stopped).  I have been told that single ended amps always produced a response that reflected the impedance of the speaker being driven.  What's really going on here?

Do you really get more noise when the amps are bridged?  (I don't in my system, but perhaps I'm just lucky...speakers aren't ultra efficient so may mask residual noise.) 

Thanks in advance for any answers to these questions!

Title: Re: Mono operation : how to?
Post by Lord Grumble on 06/21/12 at 17:14:08

I have ordered 2 SE84+ amplifiers to use them as monoblocks.  I am very anxious to receive them (probably in August).  I have read the posts in this topic and others  but I am really a novice in this area.  The first poster wrote :

Trying to find out how to hook these up in mono.  I don't see any details in the manual but as I recall, a Y connector is installed and connected to both inputs while a jumper wire is placed from the positive on one speaker connector to the common on the other side to make a series connection.

The first part about getting a Y connector seems easy to realise.  Should I get however good quality connectors or will ordinary ones suffice?

The second part is a mystery to me (sorry if this makes me an amateur but that's the truth).  What kind of jumper wire should I use?  Are these jumpers available on the market or should I make them myself?  Are there any instructions in the actual user's manual related to this?

Thank you for your input on this.

Lord Grumble

Title: Re: Mono operation
Post by Lon on 06/21/12 at 17:17:33


Couldn't you ask Steve to wire them as monoblocks? Should be easy.

Title: Re: Mono operation
Post by Lord Grumble on 06/21/12 at 17:43:57

Yes I thought about it but, in a way, it will definitely transform the SE84+ into a monoblock.  I will not be able to use each one as a stereo amplifier.  I am still undecided about that.

If customizing each amplifier into a monoblock is a better technical (and musical) solution, then I'll probably do it.  I would have to be certain that it is the best solution (musically speaking).

Thank you for the suggestion.

Lord Grumble

Title: Re: Mono operation
Post by Lon on 06/21/12 at 17:51:16

To my way of thinking it would be the most musical solution, as even the highest quality interconnect is still a few more pieces in the chain that wouldn't be there if the internal wiring were used. Whether you could hear the difference with the highest quality might be debatable, but I bet you could with lower quality, and you could save yourself that expense. Steve would have the best advice.

It would mean you'd have to have them rewired for stereo, yes. I think if you plan to use them as monoblocks that may not be a big issue, and you could probably sell them rather easily as a pair of purpose built matched amps as well if you decide to, or have them rewired as stereo and warranty revamped. . . .

Title: Re: Mono operation
Post by ZYGI on 06/21/12 at 22:58:45

Seeing as it only take shorting the two positive leads at the inputs, a switch could be installed, switching between mono and stereo operation would be a simple task.

As far as wires at the speaker terminals, I'd use what you plan to use for speaker wires, keeping that all the same.

Just a thought....


Title: Re: Mono operation
Post by Lord Grumble on 08/31/12 at 21:41:57

As previously mentioned in this topic, I have ordered 2 SE84C+ in order to use them as monoblocks or to bi-amp my loudspeakers.  I feared that one SE84C+ would not be powerful enough for me.

Well I was wrong...  I have received both amps and have yet to use them at the same time.  One is more than enough to "power" my loudspeakers (Triangle Antal SE, 92 dB sensibility).  I listen to classical music, jazz and quite a bit of rock (Beatles and Beach Boys mostly, but also punk music circa 1978, that should indicate my age... :)) and, when I decide to listen to loud music, the SE84C+ is up to the task.  I have yet to hear it clipping (whatever that is).

Now what do I do with my spare SE84C+?

Title: Re: Mono operation
Post by sberger on 09/01/12 at 04:56:15

First thing I'd do is try that second amp out in the system. You may end up finding that combining them bring extra dynamics with the added power. In any event doesn't make sense to order them, endure the wait, and then not at least try them both before making any final decisions.

Title: Re: Mono operation
Post by Lord Grumble on 09/01/12 at 05:25:23

You are quite right and I intend to do that.  It was a rhetorical question.

But I am also wondering how exactly I should use my second SE84C+ : each as a mono-block, which implies some manipulations, or bi-amping which implies more runs of speaker cables.  For some reason, I already have too much cable behind my system.  Adding more does not seem a good idea but changing a stereo amp into a mono block is not easy (at least for me, who have already difficulties with a screwdriver :)).

But I will try and find the solution that suits me best.

Thank you for the advice.

Title: Re: Mono operation
Post by Steve Deckert on 09/01/12 at 06:17:16

If you have 8 ohm speakers, bridging the zen will make the amp see 4 ohms which it REALLY likes, hence you will have more weight and control.

The neat thing about bi-amping the speakers is that you can then use the volume control on each amp to effectively control the highs and lows.  If a song comes on that is too thin sounding, you turn down the amp on the highs or turn up the amp on the lows.  It's a nice way to respond to the different frequency balance in various recordings.

Triangle are a bit bright as I remember, but at 92dB or less they would probably sound the BEST if you simply mono'd the amp.

Using a simple radioshack Y-cable is fine for now.  It's so short it can't kill the deal completely and you'll still have good enough sound for a few months minimum until everything dials in at which point you can then explore better options...  One is to solder the two inputs together or have us do it.  The other is to have me make you a pair of silver/teflon Y-cables.    The output is easy to bridge with a simple piece of 16 gauge stranded copper wire hooked between the positive post of one channel to the negative post on the other channel.  The remaining two posts will power the loudspeaker.


Title: Re: Mono operation
Post by Lord Grumble on 09/01/12 at 20:42:28

Thank you for the advice, Steve.

That is the next step in my discovery of your amps.  I have already bought the Y-cables (though not at Radio-Shack...).  

You suggest 16 gauge wire for the bridge.  Is it important to use the same gauge as the one I use to "power" my loudspeakers?  I went a little overboard with those cables and use 10 gauge wire.

Sorry if that sounds silly to you, but it's actually more of a hobby to me than a full time job.  I am kind of new to this (and I still find it fun)

Title: Re: Mono operation
Post by Steve Deckert on 09/03/12 at 02:28:18

16 gauge is the minimum thickness.

Title: Re: Mono operation
Post by Lord Grumble on 09/06/12 at 02:24:47

OK I've obtained Y-connectors and I have actually bridged both my SE84C+ in mono and, guess what, it works...  up to a point.  The Y-connectors are so cheap that one of them is actually half-functionning.  I get half the sound... in one speaker.  I alternated Y-connectors, and it is really the connector that is at fault.  I'll get another one during the week-end.

Steve, you offered to build me a pair of silver/teflon Y-cables.  Would it be possible to have a pair of such cables about 2 and a half feet to 3 feet long, with two male RCA connectors at one end (the amplifier end) and one male RCA connector at the other end (the end of the pre-amp)?  And how much would that cost?  I cannot seem to find the info on the website.

Thank you for the suggestion.

Title: Re: Mono operation
Post by KobeeDog on 09/01/13 at 15:49:53

I'm experimenting with using 2 SE84C+ amps as monoblocks and I'm noticing something interesting.

The two amps sound vastly different from eachother. They are both (I believe) the same revision - the white chassis. One was made in 2009 and one was made in 2011.

The biggest difference is the newer one has much more detail in the treble and just sounds clearer. It is also a bit louder. I have turn the older one up about 5% louder to some balance.

I tried swapping the power tubes between the amps, and the differences remain. I haven't tried swapping the driver tubes, this is my next experiment.

Is is possible that it is not the tubes, and these amps just plain sound different?

Title: Re: Mono operation
Post by Lon on 09/01/13 at 15:57:18

I would not at all be surprised if there are some differences from model to model. And. . . one may have been modified even slightly by another owner. These amps are like works of art, hand-built one at a time, doesn't at all surprise me that there may be small differences.

Title: Re: Mono operation
Post by KobeeDog on 09/01/13 at 17:50:05

Thanks for the reply Lon.

That's sort of what I figured.

Title: Re: Mono operation
Post by Lon on 09/01/13 at 18:14:58

Do you know the history of them? I would guess one thing to do would be to send them back to the mothership to see if there's any way they can be made to sound closer to the same. .. but I know it's not easy to send things back (myself I suffer from separation anxiety!) :)

Title: Re: Mono operation
Post by KobeeDog on 09/01/13 at 18:32:31

I know the history of one well, since I got it from a good friend of mine. The other one I bought from another Decware forum member, who seems like a good chap, so I'm sure getting the history of it would be quite easy.

Yes, sending them back to Decware to have them inspected and bought to closer spec would be the sensible thing to do, but like you, I don't want to live without my audio :-)

I tried an experiment today. Instead of running them mono, I bi-amped my speakers with them. The newer amp driving the bass, the older one driving the high end.

This actually sounds much more balanced, and more like the spacious Zen sound I've come to love. The imaging and soundstage is back! But  at the cost of power and a bit of weight.

Sometimes I guess the audio game is all about trade offs.

Title: Re: Mono operation
Post by Lon on 09/01/13 at 19:46:43

OH It is always about trade offs. Like most of life.

Bi-amping makes sense with that disparity of sound.

I now have the luxury of having at least one Decware amp as a back up amp. I know how fortunate that is. . . . I hate to come to this conclusion, but I think a trip to Peoria may be in order, but calling Steve is a good idea.

Title: Re: Mono operation
Post by KobeeDog on 09/01/13 at 22:02:18

It does make sense in this case, but I can't help but think the solution is a bit convoluted. I have splitters, and IC's and speaker wires all over the place. Probably can't be conducive to purity of sound, right?

Title: Re: Mono operation
Post by Lon on 09/01/13 at 23:22:20

Well, "purity of sound" is one of those things that sounds really good in practice, but the more I've gotten into this hobby I've realized that there are many ways to skin the "cat" and often what I had thought before is turned on its head.

I keep going back to two things that I have gotten from things that Duke Ellington said, one being basically any time you have a problem you have an opportunity, and the other is basically if it sounds good it IS good.

So you have an opportunity and anything that gets you into great sonic territory is okay. :)

Title: Re: Mono operation
Post by KobeeDog on 09/01/13 at 23:36:35

"...  if it sounds good it IS good."

Yes, I have to agree with that.

Title: Re: Mono operation
Post by Guy13 on 08/10/14 at 09:11:46

Hi all.
A few years back, when my bag of money was full to the rim,
I bought a SE84C+ but I also thought of buying two units to get more power, but I read somewhere that I might loose the magic of SET, so I decided to go for one SE84C+
Well, with my combo SE84C+ and my Omega 7F Open Baffle Dipole arrangement, I am not really short of power.
Depending on the recording (CD) for normal listening level, not discoteque listening, I am usually around 12 o'clock on the volume control and for some lower recorded CD can can go up to 3 O'clock, therefore limited the dynamic of the music, but that does not happen often.
If one day, when my bag of money is replenish I might go with a SE34I.4 instead of two SE84C+ I will have more power, but also more options and the replacement tubes will still be a lot less expensive than 2A3 tubes.

Guy 13

Forums » Powered by YaBB 2.2.2!
YaBB © 2000-2008. All Rights Reserved.