Bridging F4’s for monoblocks

6L6

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Paid Member
2010-10-22 6:43 pm
Denver, Colorado
You are describing parallel. That will get you 2x the current to the load but no more voltage.

Bridging needs to be fed from a balanced source and the output taken from the two red speaker posts, this will get you the same current but twice the voltage.

The F4 manual is a fantastic read in general and has all the answers better than I can explain them :)

http://www.firstwatt.com/pdf/prod_f4_man.pdf
 
Thanks 6L6 -- I read the manual - terrific -- let me get this straight and ask a few questions:

1 - for bridging then, assuming I use RCA's only - I'd use one side to feed the positive signal, the other to feed the negative (ground) signal. At output, I'd use both positives (or negatives) as the +/_ for feeding the speaker yes?

what I've described is YES - a paralleled amp config.

NOW - what are the advantages to each? I am running low watt Lowthers and the like, and also a full range Ribbon that reacts really well to current drive (which is why I'm building F4's to begin with.)

THANKS!!!
 

6L6

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Paid Member
2010-10-22 6:43 pm
Denver, Colorado
Ok. Let’s back up a second and make sure we’re all talking about the same thing.

Do you have a preamp with balanced (XLR or TRS) outputs? If yes, you can bridge the amplifier by feeding the F4 via the XLR and take the output from the two speaker reds.

Does your preamp only have RCA? If so, then you are going to run the amp parallel and tie the speaker reds together and take output from one of the blacks (as they are connected internally) and the now tied together red.
 
My preamp is only RCA. Nelson indicated in the manual that even with only RCA's, the F4 can be run bridged (as well as parallel). I understand parallel - that's easy. For Bridged, My plan is to split the signal with a Y-cable from the preamp, run the - as the signal in 1/2 and the + as the signal in the other. Then, as Nelson says, hook the speaker up across both red speaker posts, while tying the two blacks internally. WILL THAT WORK?

And the other question is less crucial but I'd like to know -- in general, what are the advantages here to running parallel as opposed to bridged -- Sonically, or as their need for more or less gain, or their interactions with speaker types. I understand one doubles current, the other voltage. Does bridged make the amp easier to drive with less preamp gain? Sound louder/softer? more direct, compressed? Thanks so much Jim.
 
Despite of my crappy english, lack of knowledge, I feel there is some confusing in this story. Respondents, I think, didn't recognise that you are talking about this configuration:
Bridge_amp.GIF

My opinion, this will not work in your case, as you described above.

Moreover in F4 article, there are parallel mono and balanced mono operations, not bridged, if I'm right.
 
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@dbdicker - You've said "negative signal" and GND together a few times. In an RCA interconnect from your pre-amp, the GND wire does not carry a separate "negative signal" that can be separated from the "positive signal" using y-connectors. There is only one signal for each channel. Search a couple articles on balanced/differential vs. SE. No need to re-type it all here.

The manual does say that the amp can be run mono balanced using the RCA INPUTS. What you still need is balanced signal to feed the inputs. So, you need a pre-amp with a balanced output as @6L6 has said. Or, if you really must use the same pre-amp, and you really must run balanced, you can do as 2pico has suggested.

re: advantages. No way for any of us to know if you're current or voltage limited. I doubt either, but it's possible. It may not sound better or help at all over standard monoblocks or even a well-built stereo pair in one chassis. It is very system dependent.

In general - Parallel may work well for systems with lower impedance speakers. Bridged may work well for systems requiring higher voltages to get the SPL desired. If you just could not get your music loud enough before a single F4 clipped and/or before the drivers distorted to the point of making music unlistenable or your ears bled - then bridging could help :D

If you already have 2 F4s, why not try parallel? It's easy, and you can do it with your current pre-amp. If you love it - awesome. If you're not happy and have a really good reason to want balanced - cross that bridge :rofl: later.
 

6L6

Moderator
Paid Member
2010-10-22 6:43 pm
Denver, Colorado
ItsAllInMyHead - very good points, well said.

Dbdicker - you’ve touched on something in your last post, “easier to drive with less preamp gain.”

The whole gain and voltage swing thing is always confusing in regards to F4, because it has no gain, and needs the preamp to do everything. So whatever voltage your preamp can output, that’s what you’ll get at your speakers. Some preamps can spit fire, some have almost no gain. Irrespective of connecting the F4 stereo, balanced or parallel, you will get out only what you put in. (Now of course the F4 can add a bucket of current and run whatever speakers you connect to it...)

So the next question is what preamp do you have?
 
No - I refer to this picture in the F4 manual -- where Nelson specifically states that either XLR or RCA single ended connectors can be used to BRIDGE.

And I believe the schematic above will not work as it shorts the phases together......although I'm not sure, that's why I'm asking!
 

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thank you for all this -- yes, I have interchanged negative phase and ground -- sort of using both languages I know......I understand that, sorry for confusion.

As for the reason to use bridged vs. parallel - I understand the electronics as well -- but the sonics? I imagine that unless you have run both, you wouldn't know either. Maybe a question for Nelson. I think you are right, both cases will not affect the ability to drive my speakers, I use a wealth of single driver type units, ranging from Lowthers to other (even more) esoterica. My main system has a full-range ribbon from Raven, with 2 paralleled focal 10" in a bespoke cabinet design and xover from Orca design, the manufacturers of this wonderful ribbon 'tweeter' (xover at 800hz).

My question is that obviously I'm going to inevitably try both -- I will take everyone's horror at trying to run bridged and try parallel first -- yes, that is easy. But ultimately, I'm going to want to try it bridged. Is that really impossible without a balanced signal from the preamp?

do you all agree on that? Hmmmmm.....I can recall many commercial products that had switches to run bridged with a pair, using SE connectors. I think, no?

@dbdicker - You've said "negative signal" and GND together a few times. In an RCA interconnect from your pre-amp, the GND wire does not carry a separate "negative signal" that can be separated from the "positive signal" using y-connectors. There is only one signal for each channel. Search a couple articles on balanced/differential vs. SE. No need to re-type it all here.

The manual does say that the amp can be run mono balanced using the RCA INPUTS. What you still need is balanced signal to feed the inputs. So, you need a pre-amp with a balanced output as @6L6 has said. Or, if you really must use the same pre-amp, and you really must run balanced, you can do as 2pico has suggested.

re: advantages. No way for any of us to know if you're current or voltage limited. I doubt either, but it's possible. It may not sound better or help at all over standard monoblocks or even a well-built stereo pair in one chassis. It is very system dependent.

In general - Parallel may work well for systems with lower impedance speakers. Bridged may work well for systems requiring higher voltages to get the SPL desired. If you just could not get your music loud enough before a single F4 clipped and/or before the drivers distorted to the point of making music unlistenable or your ears bled - then bridging could help :D

If you already have 2 F4s, why not try parallel? It's easy, and you can do it with your current pre-amp. If you love it - awesome. If you're not happy and have a really good reason to want balanced - cross that bridge :rofl: later.
 
Despite of my crappy english, lack of knowledge, I feel there is some confusing in this story. Respondents, I think, didn't recognise that you are talking about this configuration:
Bridge_amp.GIF

My opinion, this will not work in your case, as you described above.

Moreover in F4 article, there are parallel mono and balanced mono operations, not bridged, if I'm right.

Is that what I'm describing? It could be, yes. YES, I see THAT won't work. Hmmmmmm........ Any way to convert a SE signal easily to balanced?
 
ItsAllInMyHead - very good points, well said.

Dbdicker - you’ve touched on something in your last post, “easier to drive with less preamp gain.”

The whole gain and voltage swing thing is always confusing in regards to F4, because it has no gain, and needs the preamp to do everything. So whatever voltage your preamp can output, that’s what you’ll get at your speakers. Some preamps can spit fire, some have almost no gain. Irrespective of connecting the F4 stereo, balanced or parallel, you will get out only what you put in. (Now of course the F4 can add a bucket of current and run whatever speakers you connect to it...)

So the next question is what preamp do you have?

Yes, Jim this is right. Currently I have two - a Parafeed P/P using Lundahl transformers as phase split, using only one gain stage of a 6N1P -- LOW GAIN. The other is a Shindo -- more traditional topology of tubes -- BETTER GAIN. I have a transparent kit I built back in the day somewhere collecting dust in the basement... Neither has problems driving as my room is small and I don't need much headroom -- I prefer to stick with my home brew parafeed as it has separate volume controls I use to help balance my misshapen room (why doesn't EVERY decent preamp come with separate volume controls?????? The world may never know........)
 

6L6

Moderator
Paid Member
2010-10-22 6:43 pm
Denver, Colorado
Those sound neat!

You’ll likely be fine - the actual amount of power people use is much, much less than they think.

But ultimately, I'm going to want to try it bridged. Is that really impossible without a balanced signal from the preamp?

Yes.

You’ll need something to convert SE to BAL. Transformer or an active phase inverter.
 
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Ok, thanks - I'll abandon the idea (for now)

As for neat, you have no idea. I've built a LOT of stuff, but haven't heated up the soldering iron in 12 years (until now). I expect these F4's to be worthy of the rest of the stash -- I've been a closet Pass fan for years, ever since my first 'good' amplifier (a Krell KSA-50)

Thanks to all --

Those sound neat!

You’ll likely be fine - the actual amount of power people use is much, much less than they think.



Yes.

You’ll need something to convert SE to BAL. Transformer or an active phase inverter.
 

2 picoDumbs

Member
2013-09-06 9:35 am
No - I refer to this picture in the F4 manual -- where Nelson specifically states that either XLR or RCA single ended connectors can be used to BRIDGE.

And I believe the schematic above will not work as it shorts the phases together......although I'm not sure, that's why I'm asking!

The preamp on that diagram says balanced.
Of course you can use any connection you like. You could even use BNC connectors.

There is nothing wrong with Nelson’s diagram.
 

vdi_nenna

Member
Paid Member
2000-10-10 7:27 pm
PA, USA
Mono Parallel Operation

In mono parallel operation, you can achieve up to 100 watts output into a 2 ohm
load. The amplifier is driven by a single-ended source, through the two RCA inputs
in parallel. The easiest way to do this is through a male RCA cable going into one of
the RCA inputs with a jumper between pins 2 and 3 of the XLR input connector, which
parallels the two inputs.
This jumper is supplied with the amplifier.

For parallel operation of the two channels as one, you must connect the outputs left
positive to right positive either at the connectors themselves or by “bi-wiring” the
loudspeaker with two sets of cables. Remember that the positive outputs have a red
band.