Geshelli Labs NEW J2 Dac

[jmaz87]

How j2 compares with e30 … any noticeable difference?

Hard to say objectively. I switched to XLR on T5v's and use the Erish as well so too many variables.
J2 completely eliminated PC USB ground loop noise that I had with E30 but I lost pre-amp volume control which both L30 and E30 (remote) could do.
it does have 3 gain modes which i do switch to low for casual use and high for concert music (dynamic) or for using erish which has a decent pot.\

only common chain for me is E30/L30 IE300's in living room and J2/L30 IE300's which i still use for SE output and low gain. honestly both seem transparent to my casual ear.

 

[ArR]

Hard to say objectively. I switched to XLR on T5v's and use the Erish as well so too many variables.
J2 completely eliminated PC USB ground loop noise that I had with E30 but I lost pre-amp volume control which both L30 and E30 (remote) could do.
it does have 3 gain modes which i do switch to low for casual use and high for concert music (dynamic) or for using erish which has a decent pot.\

only common chain for me is E30/L30 IE300's in living room and J2/L30 IE300's which i still use for SE output and low gain. honestly both seem transparent to my casual ear.

Thanks for sharing your thoughts

 

[Macro]

Got an answer from Geno of Geshelli Labs.

"Roughly 2.5Vrms output for XLR and RCA @ 0dbfs [max input sine]."

This is in line with their measurements on the website. He also gave rough estimates for the lower gain stages but will get back to me with more specifics when he has the data in front of him.

It's the same for the single ended and balanced outputs? That's odd, I wonder why they would design it that way.

 

[jmaz87]

I recently had to send the J2 back for RMA one channel wasn't switching to lower outputs. Geno and Sherri were SUPER helpful and nice! I happened to ask Geno a similar question here are a couple snips out of context to be clear.

"We use 2.5V rms because when we tuned it, it was a perfect sweet spot for SNR/noise and sound.

What’s funny is at some point someone decided that XLR outputs should be 4Vrms? Which are not compliant with the pro audio standards [what’s left of the standards]… I think websites/forums just make things up most of the time anyway…

We generally follow our own rules and make it sound amazing without conforming to what the internet says we should do

"

Great reply, not entirely consistent with others takes but makes sense either way. to me it makes sense to have both amps in a differential circuit outputting more since 2 amps means more noise... why output same voltage if noise floor is now higher than single-ended circuit just by the nature of having 2 distinct op amp circuits.

I'm no engineer just heard a good take from the guys at schiit on a similar topic. they don't really care for balanced much either since it means more noise inherently.

 

[Veri]

"We use 2.5V rms because when we tuned it, it was a perfect sweet spot for SNR/noise and sound.

What’s funny is at some point someone decided that XLR outputs should be 4Vrms? Which are not compliant with the pro audio standards [what’s left of the standards]… I think websites/forums just make things up most of the time anyway…

Yes, pro audio outputs tends to be much hotter than 4Vrms, begs the question why one would make a DAC with XLR outs that bare produce more voltage out than the average single-ended RCA output. SNR will definitely hurt due to weak power and higher inherent noise from the balanced out, it just makes very little sense.

If they decided that on "sound tuning" yeah, sure .. Schiit also thought it made sense to have their on-board DAC cards produce a rather low voltage out. Thankfully they reconsidered and their new ESS card fixed that.

 

[MaxBuck]

I'm no engineer just heard a good take from the guys at schiit on a similar topic. they don't really care for balanced much either since it means more noise inherently.

Balanced means more noise "inherently?" That's inconsistent with nearly every measurement I've seen from @amirm.

 

[Veri]

Balanced means more noise "inherently?"

Generally, yes. In balanced dual mono constructions, the output noise will double because there are two modules instead of one. There are obvious benefits to balanced such as virtual ground loop immunity etc, but noise can be slightly higher.

 

[KSTR]

Generally, yes. In balanced dual mono constructions, the output noise will double because there are two modules instead of one. There are obvious benefits to balanced such as virtual ground loop immunity etc, but noise can be slightly higher.

The output stage noise is usually irrelevant so using two does yield the same noise wrt signal basically as the signal also doubles.
And when the actual gain stages are balanced this gives 3dB lower noise (vs signal) actually, as two uncorrelent noise sources don't simply add, they add power-based.

 

[jmaz87]

hmmm ok so if what you say is true why are so many current balanced DAC's using 4vrms vs the 2-2.5 I see on a lot of Single Ended Dacs.
and why did they choose not to in J2. also since it has 3 output levels it gets super low. its an odd setup esp with IEMS on their amps.

to me 2 output stages being noisier than one was just a no brainer. so using a higher combined VRMS also followed that logic to further improve SINAD. I personally only switched to balanced to eliminate a nasty ground loop and both J2 and Bifrost2 have done wonderful jobs in that regard.

 

[ousi]

hmmm ok so if what you say is true why are so many current balanced DAC's using 4vrms vs the 2-2.5 I see on a lot of Single Ended Dacs.
and why did they choose not to in J2. also since it has 3 output levels it gets super low. its an odd setup esp with IEMS on their amps.

to me 2 output stages being noisier than one was just a no brainer. so using a higher combined VRMS also followed that logic to further improve SINAD. I personally only switched to balanced to eliminate a nasty ground loop and both J2 and Bifrost2 have done wonderful jobs in that regard.

It’s related to the overall gain structure and what downstream device you will use. Generally you want the source to have high enough gain but not clipping the downstream so that down the chain you can have minimum gain to reach the desired output level. The further down the chain the more noise one will amplify, hence the Benchmark power amp has a low gain mode to minimise the noise. You can always attenuate the input without much penalty but boosting the signal will incur noise, it is just more flexible to have high output in this case.

Some manufacturers still put max input voltage for input (E.g. audio research). 2Vrms should have peak 2*1.414V (peak/root 2 gives you rms IIRC) so you can look up the preamp/amp input and see if that will clip.

 

[jmaz87]

I don't see how anything you said is relevant to the conversation above... the designer literally said it was the sweet spot for his design its subjective which is totally fine its not like I'm debating the sonic qualities it sounds fine to me.

Its just interesting that the J2 outputs the same voltages roughly on RCA and XLR when the latter uses potentially twice the circuits. I think its probably more a limitation of the tiny power supplies they used on all their products until very very recently. things were designed around things that's all it was an interesting decision and price was probably involved too.

 

[ousi]

I don't see how anything you said is relevant to the conversation above... the designer literally said it was the sweet spot for his design its subjective which is totally fine its not like I'm debating the sonic qualities it sounds fine to me.

Its just interesting that the J2 outputs the same voltages roughly on RCA and XLR when the latter uses potentially twice the circuits. I think its probably more a limitation of the tiny power supplies they used on all their products until very very recently. things were designed around things that's all it was an interesting decision and price was probably involved too.

The point I wanted to make is to make sure the downstream equipment will work with the output voltage. Some preamp works better with 6Vrms and on the other hand some may just clip. Some preamp has very low input impedance so this may not work as well and need more gain downstream.

They likely decide it based on the downstream they have for subjective testing and decided no more gain is needed.

 

[Lambda]

A General rule of thumb in gain staging is not to apply to mush gain and not to attenuate if not needed.

So what Amplifier relay needs 4V to reach max. output? maybe this Is not a good match for this amp.
But most amps i know don't need more then 2V.

Therefore Geshelli has a valid point in not applying to much unneeded gain.

Generally, yes. In balanced dual mono constructions, the output noise will double because there are two modules instead of one.

No
The output will double (+6db) but the noise won't because its incoherent

Adding acoustic levels summing sound levels 10 combining addition summation sum decibel levels or SPL of up to ten incoherent sound sources audio logarithmic decibel scale identical summing 1/3 octave spl full octave sum sound pressure level noise so

Sound level adding addition summing summation sum decibel dB of 10 acoustic sources sum combining decibels or SPL of incoherent sound identical pressure levels audio logarithmic decibel scale sum summing 1/3 octave spl full octave noise sound pressure acoustic pressure volts - Eberhard Sengpiel...

www.sengpielaudio.com

there fore you can gain 3dB SNR with balanced


I would like to have a trend to DACs with 21dBV or 12VRMS output and Amplifier with extremely low Gain.

 

[jmaz87]

you literally contradicted yourself in one post...
again not debating why Geshelli decided to build their Dac AND Amps around the 2VRMS area.

The point is a lot of Gear expects more power from an XLR input vs RCA here is my use case which I would think is wildly common

I use Adam T5v powered monitors and T10s powered sub in my office. initially I had an E30/L30 stack which performed fine with headphones but had a terrible audible ground loop via USB from my PC.

I started with a J2 to see if a balanced DAC would solve my Ground loop issue and it Totally but the volume was so much lower that i had to turn the gain on monitors up where typical hiss is now somewhat audible.

not an expert but is this related to J2's lower voltage via XLR than what is typical?
the input switch on back says +4dBu XLR and -10dBv RCA

I then got a Bifrost 2 and a Topping A90 which allows me to run a much hotter input without the his from excessive gain at monitor.

like u said gain staging basics... so while the J2 might be perfect for my Erish and Archel2.5Pro (which i still love and enjoy in my living room for couch listening) it was terrible for a "pre-amp" to powered monitors.

i think they upgraded power supply for the new erish with pre amp so maybe that's another limitation. or maybe its simply output impedance from pre-amp of L30 and A90 being im sure i'm wrong about something just thought it was interesting since it was a design choice.

 

[ousi]

you literally contradicted yourself in one post...
again not debating why Geshelli decided to build their Dac AND Amps around the 2VRMS area.

The point is a lot of Gear expects more power from an XLR input vs RCA here is my use case which I would think is wildly common

I use Adam T5v powered monitors and T10s powered sub in my office. initially I had an E30/L30 stack which performed fine with headphones but had a terrible audible ground loop via USB from my PC.

I started with a J2 to see if a balanced DAC would solve my Ground loop issue and it Totally but the volume was so much lower that i had to turn the gain on monitors up where typical hiss is now somewhat audible.

not an expert but is this related to J2's lower voltage via XLR than what is typical?
the input switch on back says +4dBu XLR and -10dBv RCA

I then got a Bifrost 2 and a Topping A90 which allows me to run a much hotter input without the his from excessive gain at monitor.

like u said gain staging basics... so while the J2 might be perfect for my Erish and Archel2.5Pro (which i still love and enjoy in my living room for couch listening) it was terrible for a "pre-amp" to powered monitors.

i think they upgraded power supply for the new erish with pre amp so maybe that's another limitation. or maybe its simply output impedance from pre-amp of L30 and A90 being im sure i'm wrong about something just thought it was interesting since it was a design choice.

This is the reason why I don't understand the J2 or JNOG having a low output voltage for XLR. The preamps I used (ARC LS28, Parasound JC2, ML No.52) all have default setting of +4dB for XLR and -10dB for RCA, which as you pointed out is contrary to what the J2/JNOG is providing. The Archel2.5Pro that I have seems to have "too much gain" for XLR, and I guess you are right they used that in their subjective test to tune the output level. At least they can left us the choice to use high/low output voltage, not low, very low and very very low output

 

[Lambda]

@ousi
with what amp or preamp amp combination would not get enough power if you use this dac with 2Vrms?

 

[ousi]

@ousi
with what amp or preamp amp combination would not get enough power if you use this dac with 2Vrms?

You can read the reply from jmaz87. Powered monitors mostly. For preamp, ARC LS28 that I had requires a hotter signal (I used RCA to XLR before, which I need to crank up the gain to get to the level I want).

 

[Lambda]

Powered monitors mostly

What powered monitor can't get full power with 2Vrms?

For preamp, ARC LS28 that I had requires a hotter signal

So the rated output off your tube PreAmp is the same as the DAC...
PreAmp has 18.5dB gain.
with 18db gain you need 2Vrms to get this preamp to its maximum of 17V RMS.

The preamps I used (ARC LS28, Parasound JC2, ML No.52) all have default setting of +4dB for XLR and -10dB for RCA,

+4dB is invalid it is +4dBu or dBV most likely +4dBu.

+4dBu is 1.22VRMS
So the DAC has MORE than enough voltage for everything with a +4dBu input.

https://parasound.com/pdfs/JC2Manual.pdf

So the Parsound can only handle MAX.1.58Vrms in before clipping its output at 8V

 

[jmaz87]

again if what you say is correct then I'm "overdriving" my powered speakers using any of the dozens of balanced HPA's with pre-amp output that are designed in a stack with 4vrms dacs...
but the lower output of J2 needs me to add more gain at each monitor resulting in hiss... so its audibly worse... and RCA has ground loop...

what a conundrum

do appreciate any/all insight. is it more related to the output impedance of said dac vs pre amps? A90 is designed around a 4VRMS input from a balanced dac right? what am i missing.

I will say its nice in the living room since i like to use IEM's and the super low gain makes the archel 2.5pro's volume pot usable. so your probably right its designed with that in mind only. wierd tho since it was originally designed to be behind a system not on a desk.

 

[ousi]

What powered monitor can't get full power with 2Vrms?


View attachment 171625

So the rated output off your tube PreAmp is the same as the DAC...
PreAmp has 18.5dB gain.
with 18db gain you need 2Vrms to get this preamp to its maximum of 17V RMS.


+4dB is invalid it is +4dBu or dBV most likely +4dBu.

+4dBu is 1.22VRMS
So the DAC has MORE than enough voltage for everything with a +4dBu input.

https://parasound.com/pdfs/JC2Manual.pdf

View attachment 171629
So the Parsound can only handle MAX.1.58Vrms in before clipping its output at 8V

The JC2 definitely has a different sensitivity for XLR. I don’t know which they list in that section. I had tried connecting a CD player with RCA and then switched to XLR with a converter (RCA to XLR, as I have a Cardas converter laying around) and the volume level is different.

The ML 52 preamp has menu to adjust the sensitivity per input so it’s a moot point for that preamp.

For LS28 the max input it can take is 16Vrms for balanced and 8Vrms for SE. It’s right above what you quoted above. https://audioresearch.com/product/ls28se/

The powered speaker as pointed by jmaz87 was Adam T5v. He mentioned the increased gain needed and caused hissing noise to be heard.