Dario, can you share a little more info on how you are using DC-coupling? We have all been warned about the possibility of blowing up a speaker if DC gets to/through the power power amp.
Are you simply relying on DVM readings from the closest component - and is that component a pre or a DAC?
I want to try the configuration , but I'm scarred.
Nothing fancy, I simply replace C13 with a jumper, during tests.
The safe chain is:
AC coupled (with output cap so no DC on output) CD player -> pot -> DC coupled FE.
I usually risk a bit (only and just for the tests) using my DCB1 in place of the pot.
My DCB1 has 1.5mV DC offset on output.
O.K. Thanks. But if you determine that you actually like the DC coupling the best, doesn't the selection of the output cap on the CD player become as significant as the choice for C13?
How could one configure a full-on, full-time DCC system with gain? Would that require a specific style/design pre?
How could one configure a full-on, full-time DCC system with gain? Would that require a specific style/design pre?
Which came first the chicken or the egg?
Assuming DCC means DC Coupled I suppose it should be possible using DC servos and protection circuitry but possibly part of the advange would be impaired, I suppose.
Which came first the chicken or the egg?
I actually know the answer to that one, but you'll have to pay me $$BIG BUCKS$$ if you want me to share my knowledge.
Think I'll just stick with C13
We have a DC output protection circuit, what about an input protection circuit? I believe it was lehmanhill who proposed a more sensitive approach to the output circuit, could somthing like that be applied to the input?
I believe Dario and Mauro have stated that c13 is neccesary to set the current for lm318 iirc. Experts will know better.
I believe Dario and Mauro have stated that c13 is neccesary to set the current for lm318 iirc. Experts will know better.
Well, I'm certainly no expert - but the improvement in sound quality would have to be quite significant to warrant upsetting the structure of the FE and taking the risk of blown speakers. I asked the question thinking Dario was using more of a permanent setup.
Still open to ideas if Jac or others want to contribute.
Still open to ideas if Jac or others want to contribute.
I think one way to avoid DC at amp input is to use transformer volume control (TVC), as in a passive preamp. I guess you could use a 1:1 transformer between every component to eliminate DC. Might even try one in place of C13. But transformers are not sonically transparent, and ones that even come close are very expensive. It would be trading one expensive compromise for another. It would, however, end the hunt for perfect cap.
Why do you want to NOT use C13? I just don't get what the big deal is. Unless C13 is a piece of junk, the amp sounds better with it than without it. At some level of refinement, your reference should be music itself, not another configuration of amplifier.
Peace,
Tom E
Why do you want to NOT use C13? I just don't get what the big deal is. Unless C13 is a piece of junk, the amp sounds better with it than without it. At some level of refinement, your reference should be music itself, not another configuration of amplifier.
Peace,
Tom E
Hey Tom, I've seen a few comments on other threads where some people claim no input cap is their preference. Just thought Dario might have come up with something beyond what I now know is just temporary.
I honestly don't have a problem with C13, as I've been able to audition several and hear differing sonic signatures. Don't mind trying a few more. Just curious about potentially squeezing that last drop of quality sound out of these amps.
What I'm hearing is "If it ain't broke - don't fix it".
P.S. Just came back from part (football game) of my 50th High School reunion . Wow! those people look a lot older than me.
Tomorrow we'll see if any of them can still do the twist or the bugaloo - - - from the seated position
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if the "reference" uses DC coupling then the input conditions will change the bias point of the input stage.
A very small input DC offset from the Source will make a very small change to the input bias conditions. A bigger input DC offset will make a bigger change in the input bias conditions.
These different bias conditions on the input stage of that first Opamp are very likely to change the sound character due to different amplifying performance of the input stage.
I cannot accept that comparing your C13 to your "reference" is valid, unless you take extreme care to ensure your Source is not rebiasing the input stage.
Further, if there is a small input offset, then simply inserting a DC block will change the bias of the input stage. It is almost guaranteed to sound different.
A very small input DC offset from the Source will make a very small change to the input bias conditions. A bigger input DC offset will make a bigger change in the input bias conditions.
These different bias conditions on the input stage of that first Opamp are very likely to change the sound character due to different amplifying performance of the input stage.
I cannot accept that comparing your C13 to your "reference" is valid, unless you take extreme care to ensure your Source is not rebiasing the input stage.
Further, if there is a small input offset, then simply inserting a DC block will change the bias of the input stage. It is almost guaranteed to sound different.
Hi Andrew,
exactly the reason why Mauro recommends using an input cap in C13.
Yes, it's so, it sound a bit different, particularly the low frequency content, it seem.
With C13 in place bass usually seem more present, tuneful and controlled.
Nevertheless I find DC coupling useful as a reference for evaluating detail, timbre and harmonic content.
Jantzens part II
After some days of use I have to correct my impression.
Those Silver Z are fine sounding caps but their detail is not full, on the contrary they 'massage' sound hiding some detail (hight hats don't sound as metallic as the should), I think the perceived detail it's due to their timbre (a bit unbalanced toward HF).
I prefer Audyn (both Plus and True Copper) and Mundorf (Supremes).
After some days of use I have to correct my impression.
Those Silver Z are fine sounding caps but their detail is not full, on the contrary they 'massage' sound hiding some detail (hight hats don't sound as metallic as the should), I think the perceived detail it's due to their timbre (a bit unbalanced toward HF).
I prefer Audyn (both Plus and True Copper) and Mundorf (Supremes).
Oh well nothing is perfect, however.... in my system my impressions are exactly the opposite. Of course my system is different than yours. Our choice in music may be different too. I do feel though even without a sub crossed in at 120hz the audyns overcompensate the bass in an un-natural way. much like a sub in the trunk of a car passing by. So maybe it is safe to say I am not as concerned with the extreme low end of the frequency range because I use a powered sub, but...the realistic presentation of drums and guitar and vocals is what I love about the Zs. The seperation of the afore mentioned elements is to me what is so great about this amp, it is present with other caps but effortless with these. I do like the audyns but to me they make the amp sound like a tube amp (after hearing the Zs). I love the way a tube amp sounds, but part of that love is injected distortion, I can accept that. Now a guitar played through a tube amp in a song with vocals presented through a non tube amp in a live setting you would be able to tell a difference in amplification. I am just happier with the Zs presentation. again no cap war, maybe a relay based protection circuit in place of C13 would save much discussion
Oh well nothing is perfect, however.... in my system my impressions are exactly the opposite.
(...)
I am just happier with the Zs presentation. again no cap war, maybe a relay based protection circuit in place of C13 would save much discussion
Absolutely, Zs are good souding caps with a nice, relaxed presentation.
Unless you did the same, I think the main difference is not our systems or or music selection but the 'reference', I'm using DC coupling as a reference (particularly for detail and harmonic content) which could give pretty different conclusions.
Ah, yes I see what you are saying. Im not sure if I have the guts to duplicate your experiment though.
Dario
I have now changed to Black Gate as C9 and Mlytic in the powersupply.
This is by far the biggest change for the better IMHO and now I tend to agree with you on the SAL capacitors in the shuntregs. I can hear the dryness and a little syntethic effekt with them in and the ekstra focusing is almost not there anymore.
The Rhopoint , on the other hand , stays in and I still prefer no cap as C13.
Andrew:
Why do you think a little dc would change the sound?
Is it because it is a Howland pump?
A normal Opamp would not care. The only thing that happens is if you have +50mV and unity gain that clipping would be 50mV before in the positive half.
I can, at the output from my DAC that goes directly to My_ref via a Lightspeed att., change the DC presentet at the input of My_ref.
So I trimmed the output to 100mV and there was no change in the sound.
I still cannot understand people are so worried about DC coupling the My_ref.
My_ref has unity gain @ DC and even a DC protection at the output.
Even a couple of volts at the input would not harm any speakers and hopefully nobody has equipment that puts out so much DC.
Anyway just check your DAC/Preamp´s output with a multimeter and if the DC is less than 100mV (it should be far less though) you are ok.
Just my 25 c.
Ps. Got som 100n polystyrene caps from E-bay and tried them instead of the 100n MKP4 decoupling and they stay there...
Koldby
I have now changed to Black Gate as C9 and Mlytic in the powersupply.
This is by far the biggest change for the better IMHO and now I tend to agree with you on the SAL capacitors in the shuntregs. I can hear the dryness and a little syntethic effekt with them in and the ekstra focusing is almost not there anymore.
The Rhopoint , on the other hand , stays in and I still prefer no cap as C13.
Andrew:
Why do you think a little dc would change the sound?
Is it because it is a Howland pump?
A normal Opamp would not care. The only thing that happens is if you have +50mV and unity gain that clipping would be 50mV before in the positive half.
I can, at the output from my DAC that goes directly to My_ref via a Lightspeed att., change the DC presentet at the input of My_ref.
So I trimmed the output to 100mV and there was no change in the sound.
I still cannot understand people are so worried about DC coupling the My_ref.
My_ref has unity gain @ DC and even a DC protection at the output.
Even a couple of volts at the input would not harm any speakers and hopefully nobody has equipment that puts out so much DC.
Anyway just check your DAC/Preamp´s output with a multimeter and if the DC is less than 100mV (it should be far less though) you are ok.
Just my 25 c.
Ps. Got som 100n polystyrene caps from E-bay and tried them instead of the 100n MKP4 decoupling and they stay there...
Koldby
Rhopoints are a good, but expensive, alternative, since you have them I see no reason for not using them.
In fact they're probably more neutral for low frequancy content.
Can you post a pic/ebay auction?
Hi Dario
Here is the e-bay link:
Polystyrene Capacitor 100nF 0 1uF 100VDC 63VAC Sty 104 | eBay
They are a little big, but they can be sqeezed in.
After hearing them I have mounted them under the PCB.
Koldby
Here is the e-bay link:
Polystyrene Capacitor 100nF 0 1uF 100VDC 63VAC Sty 104 | eBay
They are a little big, but they can be sqeezed in.
After hearing them I have mounted them under the PCB.
Koldby
