KGSSHV Carbon Build Thread

[Kung]

43 minutes ago, gnasherrr said:

Hey guys. I'm somewhat new to diy and would like to ask some questions.

1. for the amp board. I was told to do the following modifications pictured below:

for the resistors circled in red use 75ks and for the green ones use 50ks

now I have close to 0 knowledge as far as circuits design goes, could someone tell me what they would change as a result?

2. I was told for the 450v version, the thermal might be a huge issue, also it might be pushing the limit of some of these parts in terms of voltage, currency or wattage ratings. Is any of this true? I want to ask because from what I read in the threads and it seems like people are having success on the 450v PSU.  Could someone clarify for me on that? 

 

I appreciate any time and effort in answering these questions in advance. Thanks.

 

use 2*75k in nfb loop，will change the closed-loop gain from 60dB to about 57.5dB。

the 500k resistors are used as input load to prevent oscillation when you use a shunt attenuator at minimum attenuation。

+-450v PSU is ok，just pay more attention to grounding。

[gnasherrr]

1 hour ago, Kung said:

use 2*75k in nfb loop，will change the closed-loop gain from 60dB to about 57.5dB。

the 500k resistors are used as input load to prevent oscillation when you use a shunt attenuator at minimum attenuation。

+-450v PSU is ok，just pay more attention to grounding。

thanks for answering me.

Now for reducing the closed-loop gain for the nfb loop, will that help in reducing the noise/distortion of the output?

[spritzer]

Who on earth suggested these mods?  This is DIY so you can do what ever you want but this is just a shit idea...

[Whitigir]

2 hours ago, spritzer said:

Who on earth suggested these mods?  This is DIY so you can do what ever you want but this is just a shit idea...

Especially to new folks 

[JimL]

13 hours ago, gnasherrr said:

thanks for answering me.

Now for reducing the closed-loop gain for the nfb loop, will that help in reducing the noise/distortion of the output?

Decreasing the gain can reduce noise/distortion - however, that is not a problem with this design. It can also increase the risk of the amp oscillating. In case you don't know this, oscillation is NOT a good thing. Further, decreasing the feedback resistors means more of the signal current goes to driving the feedback resistors rather than driving the headphones, which is the whole point of the exercise. 

 

In case you can't take the hint from spritzer, here's the bottom line. Unless you think the designer didn't know what the heck he was doing (in which case, why are you building his design?), I would ignore the suggested changes, and build the amp as designed. And this comes from someone who has done a fair amount of circuit modifications.

Edited February 25, 2018 by JimL

[joehpj]

STN9360 ran out of stock on mouser. Can I use STN9260 or PBHV3160Z instead?

[Blueman2]

1 hour ago, joehpj said:

STN9360 ran out of stock on mouser. Can I use STN9260 or PBHV3160Z instead?

The STN9260 is the closest I see at Mouser.  Collector/Base gain is the only thing that is off a bit.  

[Laowei]

3 hours ago, joehpj said:

STN9360 ran out of stock on mouser. Can I use STN9260 or PBHV3160Z instead?

They are in stock at Arrow. 

https://www.arrow.com/en/products/stn9360/stmicroelectronics

[spritzer]

The STN9260 will do just fine.

[Helium]

On 29.06.2016 at 5:33 PM, spritzer said:

But you just install a switch which grounds the - input for SE.  Hell, just make two XLR plugs with pins 1 and 3 tied internally. 

Can anyone confirm please that output power is the same in case of using SE inputs? Any drawbacks?

[kevin gilmore]

there is a difference in voltage gain. 6db.

[Kung]

I see Carbon removed the output buffer stage from KGSS ，So... for es amp，is the output impedance no longer important ? 

[Laowei]

Wondering if I can get some help with the front end of my Grounded Grid (same as the Carbon). 

What are the correct voltages or design currents across R50 and R44, circled in red. 

Thanks

Edited April 12, 2018 by Laowei

[kevin gilmore]

about 1V

 

[JoaMat]

Voltage cross the resistor is LED voltage minus base-emitter voltage - roughly 1.9V – 0.6V = 1.3V.

 

So approximately current through R33/Q17 2.5 mA (RV2 centered) and R50/Q20 4mA. Those values will depend on the individual components.

[mypasswordis]

It's usually much closer to 1V as KG said as he uses 1.7V LEDs and Vbe is closer to 0.7V. If using higher voltage LEDs I would compensate with resistance accordingly.

[JoaMat]

The first electrostatic amplifier I built was the first version of  KGSSHV with onboard  heat sinks and I used LTL-4213 LED forward voltage 2.1V. At that time the suggested LED was LTL-4213 which also was used in the DIY T2. I’m aware of that some builders stick to LED with lower voltage. My experience is that you very well can use the “higher voltage” LED without changing resistors.

Edited April 12, 2018 by JoaMat

[mypasswordis]

Maybe you need to edit your post again, after you look through any KGSSHV BOM as well as read Kevin's above post. 

[Laowei]

Appreciate all the helpful replies offered. Gives me a better understanding how to get a handle on this. 

This started by my replacing the 1.7V Vf LEDs in my working GG with supposed lower noise and impedance 1.6V Vf LEDs. Installed and powered up, the forward voltages measure 1.512V (D13) and 1.500V (D10). In circuit, they are biased at ~1mA, pretty low for these new LEDs. 

I can solder parallel resistors to R51 and R42/R43 to supply 5mA total to each the LEDs to get to the 1.6V Vf. To exactly match the original operating points of Q20 and Q17/Q18, I can play with R50 and R44/R45 values. I’d like to get these changes addressed to fully consider if these LEDs actually offer a positive audible change. On first listening over the last few days, IMO it’s worth the effort to continue with this. So far, I am liking what I hear. 

 

[JoaMat]

2 hours ago, mypasswordis said:

Maybe you need to edit your post again, after you look through any KGSSHV BOM as well as read Kevin's above post. 

Here is a link to a post. In that  post there is a link to a BOM. In that BOM you find LTL-4213.

I’ve two different BOMs on my computer from the same topic, both with LTL-4213.

[Rodeodave]

I'm looking for two STN9360 transistors to complete my amp. They seem to be sold out at every major online vendor...

I can offer shipping+beer money as compensation.

[Blueman2]

1 hour ago, Rodeodave said:

I'm looking for two STN9360 transistors to complete my amp. They seem to be sold out at every major online vendor...

I can offer shipping+beer money as compensation.

Use the STN9260.  I did on my amp and it works just fine.  

 

 

Edited July 4, 2018 by Blueman2

[Rodeodave]

Oh, I thought that one was sold out too, but it looks like digi-key has a few thousand in stock. Thanks!

[penmarker]

Regarding GRHV, is there a drop in replacement for C2M1000170D? They're on backorder on most major sellers.

 

**Edit

Never mind guys, found out they get out of stock every few months. SCT2H12NZGC11 is also on backorder now and still don't know if FQFP8N80C is a good replacement.

I guess I'll just wait.

Edited August 29, 2018 by penmarker

[PICaudio]

I can not finish my Carbon either because I cannot find the C2M1000170D and STN9360 anywhere ?

Can I use TSA1765 instead of the STN9360?

EDIT: I found some C2M1000170D in RS with a bit high price IMHO, but they only sell a minimum quantity of 30 units and I only want 10, if anybody want some units of this sand I can make a little groupbuy.

Edited September 3, 2018 by PICaudio