# Gizmo 1.0 input voltage limits? Mod help pls!



## imported_m-fine (Mar 15, 2008)

I remember Craig said the Gizmo 1.0 was limited to an input voltage of 3 volts. Does anyone know if this is peak to peak 3 volts, or is it 3 volts RMS?

Reason I am asking is I am seriously considering building in a USB DAC using the bantham board with has a 5 volt p to p output. That is equal to 1.77 v RMS, so the answer determines whether or not I need to build in a 4.5 db attenuator. 

Thanks!


----------



## Mike_WI (Feb 26, 2009)

m-fine said:


> I remember Craig said the Gizmo 1.0 was limited to an input voltage of 3 volts. Does anyone know if this is peak to peak 3 volts, or is it 3 volts RMS?
> 
> Reason I am asking is I am seriously considering building in a USB DAC using the bantham board with has a 5 volt p to p output. That is equal to 1.77 v RMS, so the answer determines whether or not I need to build in a 4.5 db attenuator.
> 
> Thanks!


m-fine -

No idea.
However, I'm curious as to how much the built in USB DAC will cost.

Mike


----------



## imported_m-fine (Mar 15, 2008)

If you have to tools, it can be done for $25-$35 depending on what parts you buy and where. If you need to buy a good soldering station and other tools, it will push you to the $100 range where you can buy a completed DAC or a fully assembled board. 

Besides being cheap, the Bantam is super small so it will easily fit inside the Gizmo for an uncluttered desk. I am not sure yet, but I think doing it internal may require disabling the RCA's or at least putting in a switch since I think the DAC chip would be unprotected from any voltage from another analog input. I would probably be fine with a USB only Gizmo, but you can also build a bantamcableDAC where it sits in a small box with a USB cable on one side and RCA's on the other. It would be a fraction of the size of the power brick for the Gizmo, so not too bad for clutter.


----------



## Mike_WI (Feb 26, 2009)

*Bantam DAC / bantamcableDAC*



m-fine said:


> If you have to tools, it can be done for $25-$35 depending on what parts you buy and where. If you need to buy a good soldering station and other tools, it will push you to the $100 range where you can buy a completed DAC or a fully assembled board.
> 
> Besides being cheap, the Bantam is super small so it will easily fit inside the Gizmo for an uncluttered desk. I am not sure yet, but I think doing it internal may require disabling the RCA's or at least putting in a switch since I think the DAC chip would be unprotected from any voltage from another analog input. I would probably be fine with a USB only Gizmo, but you can also build a bantamcableDAC where it sits in a small box with a USB cable on one side and RCA's on the other. It would be a fraction of the size of the power brick for the Gizmo, so not too bad for clutter.


m-fine -

I don't have tools, but would consider buying them (recs?).
It's been a long while since I soldiered something -- likely H.S. electronics class -- but as long as I can get some free moments away from th kids, I'd try it.

If you are so inclined, would you take pics and make a how to guide? :yes:
Given the DAC MAN is on hold a Gizmo DAC-mod sounds very cool.:scratchchin:

I wonder if more Gizmo's would sell to that DIY enthusiast community?



Mike


----------



## imported_m-fine (Mar 15, 2008)

There are some good pictures and guides for the Bantam already. If (BIG IF) I decide to go ahead with it as an internal mod, I'll post pictured and instructions, but it will be pretty basic once you have the DAC board. The big hurdle is the DAC board is tiny and uses miniscule surface mount components which are a biatch to solder.

Other than a case mod to get the USB cable in, the steps to connect the DAC to Gizmo will be as follows:

Assuming the Gizmo can accept 3v RMS

1) Connect the + and - from the DAC output to the + and - from the Gizmo RCA ports.

Assuming it only can take 3v Peak

1) Add a pair of resistors to each of the DAC outputs to attenuate the signal
2) Connect to the + and - from the DAC output to the + and - from the Gizmo RCA ports.

In other words, once you have a DAC, getting it connected will be a snap.


----------



## Mike_WI (Feb 26, 2009)

*TooleAudio Bantam DAC*

m-fine:
Cool.

Some links for interested people...

- TooleAudio Bantam DAC
- PCM2702 stereo DAC
- TooleAudio BantamCableDAC
Interesting that the DAC is about $10 (file).
Some pics...


Mike


----------



## imported_m-fine (Mar 15, 2008)

Looks like I am not going to do the bantam DAC. For the price plus labor, I have too many concerns about it's robustness without any output stage. Hate to spend a weekend building it only to see the chip get fried when I power off the Gizmo. 

There are some decent options though. For $30 there are several USB audio devices that can be used as is, or mounted in the Gizmo with little effort. 

Hotaudio has the DAC destroyer on sale for $65 which I think will have a performance edge over the bantam and it is ready to use. I suspect you could pull the card and mount that in the Gizmo as well. 

At $100 there is the Hotaudio straight DAC, the super pro, the HRT streamer and a host of other attractive options. 

Depending on the speakers and your SQ targets, I seems like you can step up from a built in sound card to a USB interface with noticably better sq for less than bantam parts, and you can beat the bantam sq without the labor for justna little more. 

I still would like to know the Gizmo input limit so I can select a DAC the matches well.


----------



## Mike_WI (Feb 26, 2009)

m-fine said:


> Looks like I am not going to do the bantam DAC. For the price plus labor, I have too many concerns about it's robustness without any output stage. Hate to spend a weekend building it only to see the chip get fried when I power off the Gizmo.
> 
> There are some decent options though. For $30 there are several USB audio devices that can be used as is, or mounted in the Gizmo with little effort.
> 
> ...


Bummer.

I looked at the HRT Music Streamer, but the S/N ratio (~82) didn't seem that impressive. 
Link
Review

Still gets away from a laptop integrated DAC.

HRT Music Streamer+ is $299 (Review), so at that price someone could consider the Music Fidelity V-DAC ($299) or similar products.

Mike


----------



## Mep (Jan 28, 2009)

Now that dac-man is dead I was thinking about doing something similar. I do believe it is 3 volts max input. There are plenty of small usb dacs for sure. Twisted Pair Audio has a small simple one with a TI chip but doesn't give the output voltage. At the very least gizmo needs a true off switch.

I do think you would have to kill the RCA inputs or through it on a switch which will get things cluttered. Otherwise some type of mixer circuit that will protect the dac is needed.


----------



## imported_m-fine (Mar 15, 2008)

I doubt the SN ratio would be much of an issue with a Gizmo WAF setup and less so even with the ELT's. I think I am leaning toward a hotaudio, but they have different output voltages so I will wait on an answer.


----------



## alphaiii (Nov 30, 2007)

Overdriving the input causes a distortion problem, right?

So am I correct in saying - if the Gizmo input is 3V max (peak to peak), then you should not use the HRT MusicStreamer or the Hot Audio Straight DAC, since both have RMS voltages that would be too high for the Gizmo?

EDIT: Actually the Hot Audio Straight DAC is 3.1V peak-to-peak. But the musicstreamer is 2.25V RMS, which would be too high if the Gizmo is limited to 3V peak-to-peak, right?


----------



## HAL (Sep 22, 2009)

3.0 volts peak to peak is 1.06 Volts rms. So yes, that would be to high an input if the maximum input is 3vp-p.


----------



## imported_m-fine (Mar 15, 2008)

Bingo. That is why it is fairly important to know. 

I might get the Hotaudio bitperfect though which has a volume control that affects the RCA's as well as the head phone out. That eliminates the max voltage concern and I question how much the SQ difference will be audible in any setup I would use the Gizmo for.


----------



## dvenardos (Sep 27, 2008)

Surprised dweekie hasn't chimed in here, he did extensive mods on the gizmo.


----------



## imported_m-fine (Mar 15, 2008)

dvenardos said:


> Surprised dweekie hasn't chimed in here, he did extensive mods on the gizmo.


Dweekie bypassed the built in crossover, and in the process bypassed the problem. He probably does not know since his modified units don't have the problem.

That does not help me much since I want to keep the crossover and use a sub.


----------



## dvenardos (Sep 27, 2008)

It will probably have to be Doug to answer your question then.
Are you planning on regulating the voltage if you need to?


m-fine said:


> Dweekie bypassed the built in crossover, and in the process bypassed the problem. He probably does not know since his modified units don't have the problem.
> 
> That does not help me much since I want to keep the crossover and use a sub.


----------



## dweeke (Oct 30, 2006)

m-fine said:


> Dweekie bypassed the built in crossover, and in the process bypassed the problem. He probably does not know since his modified units don't have the problem.
> 
> That does not help me much since I want to keep the crossover and use a sub.


What you will want to do is implement the 1.0M mod that Craig posted. Then you can bypass the input opamp wthout any issues. That will leave the highpass and lowpass intact. Let me know if you need any specifics. 

You're right about the rest though; I chose to take the easy way out by bypassing the problem instead of addressing it :biglaugh:


----------



## imported_m-fine (Mar 15, 2008)

dweekie said:


> What you will want to do is implement the 1.0M mod that Craig posted. Then you can bypass the input opamp wthout any issues. That will leave the highpass and lowpass intact. Let me know if you need any specifics.
> 
> You're right about the rest though; I chose to take the easy way out by bypassing the problem instead of addressing it :biglaugh:


Cool, I was planning on doing the 1.0M mod to fix the sub out volume tracking anyway. I'll take a look inside later this week (busy week ahead) and see if I can figure out how to bypass the input opamp.


----------



## imported_m-fine (Mar 15, 2008)

dvenardos said:


> It will probably have to be Doug to answer your question then.
> Are you planning on regulating the voltage if you need to?


Sent a PM to Doug. If I need to I can build an attenuator into the Gizmo inputs, or follow dweekies suggestion and bypass the input opamp. (how much will that reduce the overall gain?)

I have to figure out how much money and time I really want to spend on it though. I have no plans to use it in a super high quality critical listening setup, just looking at get a decent desktop setup that can be fed from my laptop.


----------



## wesley63 (May 25, 2008)

m-fine said:


> Sent a PM to Doug.


Please rely his response about the input voltage.

Thanks,
Jim


----------



## alphaiii (Nov 30, 2007)

Did anyone get an answer to this?


----------



## imported_m-fine (Mar 15, 2008)

No.


----------



## alphaiii (Nov 30, 2007)

It'd be nice to get an answer on this...

I'm considering buying a HRT Music Streamer DAC, but it has a 2.25V RMS output....

And since the Gizmo v1.1 seems to be waaaayy off...I am strapped by the voltage input limitations of the v1.0 for now - I'm just not exactly clear on what they are....


----------

