KGSSHV Carbon Build Thread

[mwl168]

6 hours ago, chinsettawong said:

I'm making a GG and will be using this GRHV board as well.  How can I enable the time delay HV function?  How long does it delay the HV to come up?  Do I need other circuits to work together with this function?

I know congo5 has implemented his delay switch using this module from eBay:

http://www.ebay.com/itm/DC-5V-9V-12V-Adjustable-Timing-Delay-Time-Timer-Turn-on-off-Relay-Switch-Module/191949280682?_trksid=p2047675.c100009.m1982&_trkparms=aid%3D888007%26algo%3DDISC.MBE%26ao%3D1%26asc%3D40130%26meid%3D1b0997a4bcd44fc9a34aabfdf754af52%26pid%3D100009%26rk%3D1%26rkt%3D1%26sd%3D131776109221

[JoaMat]

A delay circuit.

Similar to Stax. LED flashes during preheat and then steady. Should work with CPC1117N. Will probably cost you more than four bucks.

[mwl168]

Nice one JoaMat. 

Two questions, how is the delay time calculated and would it work with 12V supply? I am thinking about the application with Megatron where we'll have a 12VDC supply for the front end tube filament.

[sorenb]

3 hours ago, mwl168 said:

Nice one JoaMat. 

Two questions, how is the delay time calculated and would it work with 12V supply? I am thinking about the application with Megatron where we'll have a 12VDC supply for the front end tube filament.

http://www.ti.com/lit/ds/symlink/cd4093b.pdf

[JoaMat]

Here is Delay circuit.PDF schematic. R1/C1 determines the delay time and R2/C2 flashing frequency. 12 V is fine, I use this circuit in two T2 power supplies with 12  volts.

For time calculations google "R/C time calculation". Values in schematic gives me approximately a 50 seconds delay.

 

[Blueman2]

Pair of GRHV Fat PSU boards are up and running!  It feels SO much less stressful bringing these up with a variac rather than just a plug&hope approach.  All is fine, but voltages are a bit high.  +407 and -410 loaded with a 15K 10W resistor for each board.  Those test resistors get darn hot after about 5 minutes!!  I am using a 350V trafo, so not worried about going above what it can feed, so might just leave that as is.  However, the bias test point reads 590 and is still slowly climbing as the diodes heat up.  Guessing I should replace one of the 150V diodes or the 130V with something about 10V less?  Not sure what values are readily available so will have to look.  

I have also completed a pair of Carbon boards that @mypasswordis started but decided not to complete (he is going SMD route).  I have pre-set the CCSs to 17ma.  BTW, the process of using LV (in my case a pair of 9V batteries) to set the CCS was INVALUABLE.  I could not set the current for one channel and found the cause: I missed a solder joint!  Nice to find mistakes like that without having 800+ volts running through them!  

I have to wait until my 15/15 LV trafo arrives from Antek before firing up the amps  (I am using the on board LV from the GRHV board until I decide if I want to built the GRLV).   Those guys at Antek have cancelled my last 2 orders due to lack of stock.  Never even let me know this time.  I had to call and see why the order was late and they said they never shipped it.  Ah, I guess that is why!

 

Edited November 18, 2017 by Blueman2

[mwl168]

Congrats!

I would not worry too much about the bias voltage being a little higher - we are talking about 2% here.

Looks like Antek is out of 25va/15v but has 50va/15v in stock. They are $6.5 more and just a bit larger. May be an option? 

Edited November 18, 2017 by mwl168

[Blueman2]

Actually, they said today they have one 25va 15V/15V left.  Hopefully that ships tomorrow.  

Edited November 18, 2017 by Blueman2

[mypasswordis]

That sucks about Antek. Arrow did the same thing to me. Actually they didn't even cancel the item until I asked why I didn't receive it, which I checked only because they had already been spotty/uncommunicative in the past. And if you have ever ordered from Arrow before, you know it is no easy task to keep track as they split your order up into a million shipments. The Antek transformers themselves seem quite reliable in my experience. 

As to bias, I would rather err on the side of lower than higher. 

[Whitigir]

I agree about Bias voltage.  Did KG mentioned that anything over 600V will damage the Headphones ? 

[spritzer]

Not really but bias and the risk of damage is always linked to the drive voltages.  So if you push the bias too high, you have to lower the drive voltages. 

[Blueman2]

I have the bias on both my SRX-Plus's at 570v, which drifts up to about 575-580 after an hour or so.  I liked the bhultrimini psu which had a trimpot to adjust bias.  Curious what the reason was for going with fixed zener string for bias on the GRHV vs the method used in bhultramini?  In any case, I have a 120V zener in my cart for my next Mouser order.  Going down about 10V (replacing the 130v with the 120v) should provide a good enough safety margin.  Thanks for the guidance.

With regards to the rail voltages (+407, -410), tell me if this is just being too OCD, but I do have a 10M resistor that I could parallel on top of one of the 390K resistors.  By my calculations, that will bring that 390K down to 375K, so a total reduction of the 2x390 from 780K to 765K, a 2% reduction.  So on the negative rail, it would come down from -410 to -402.  Is that worth doing, or am I just being silly?      

Edited November 18, 2017 by Blueman2

[mypasswordis]

No real reason to decrease it, I think most people are running their Carbons at 450V anyway and you have a lot of extra input voltage with a 350VAC transformer. 

[mwl168]

If anything, I suggest you wait till you actually loaded the PSU with the Carbon amp before you start "fine tuneing"  your rail voltage. 

I was the same way - bugged by the "uneven" regulated voltage even though it's totally within spec of the parts' tolerance (the LT1021 and the resistors in the error amp).

Actually, with 350v secondaries you will likely be able to get the rail voltage higher if you desire as long as the parts you use are rated for it. 

[Blueman2]

OK, if it ain't broke, don't fix it.  I did spec everything to be able to do 450V.  The trafo is really putting out 370VAC because it is spec'd with 115 primary and I typically run 125V in my house, and never less than 122V that I have ever measured.  

[kevin gilmore]

so the bias circuit is constant current into a stack of zeners.  5% or so is all you are going to do with that, and its more than sufficient.

what you never want is the voltage swing to exceed the bias voltage.

a grlv just for the bias circuit would be massive overkill

[congo5]

In the Blueman2 picture above it looks to me like a metal screw in the 10m90 for the headphone bias CCS

And if so, do they make PPS washers that are white?

It looks good but for that one concern

thanks

[mwl168]

58 minutes ago, congo5 said:

In the Blueman2 picture above it looks to me like a metal screw in the 10m90 for the headphone bias CCS

And if so, do they make PPS washers that are white?

It looks good but for that one concern

thanks

7721-10PPSG is the washer part that works well for me and it's brown in color. 

[Blueman2]

52 minutes ago, congo5 said:

In the Blueman2 picture above it looks to me like a metal screw in the 10m90 for the headphone bias CCS

And if so, do they make PPS washers that are white?

It looks good but for that one concern

thanks

Thanks for taking the time to look the build over.  I appreciate ANY input and feedback still being new at this.  You are correct regarding the metal screw on the bias 10m90, but it does have a white plastic sleeve on it that came from an AVID kit.  I also have the reddish brown rectangular insulators from the BOM in post #1.  Is the rectangular insulator better?  I would use PEEK here, but my PEEKs are M3 and the heat sink was not metric threads. 

 

[mwl168]

5 minutes ago, Blueman2 said:

Thanks for taking the time to look the build over.  I appreciate ANY input and feedback still being new at this.  You are correct regarding the metal screw on the bias 10m90, but it does have a white plastic sleeve on it that came from an AVID kit.  I also have the reddish brown rectangular insulators from the BOM in post #1.  Is the rectangular insulator better?  I would use PEEK here, but my PEEKs are M3 and the heat sink was not metric threads. 

 

Yes, you want to use the one in the BOM. The idea is that the tube of the washer needs to go through the transistor tab and extends into the insulator below so the metal screw does not cause a short. 

Congo 5 just saved you from a disaster that was waiting to happen

Edited November 19, 2017 by mwl168

[Blueman2]

OK, I will replace the washer right now.  But I did do a quick test of the amp boards running at full voltage on the LV (using trafo plugged directly into the wall) and with about 45V (about 36% of full voltage) into the HV trafo using a variac.  All 4 LEDs light up, but there was a strange reading I wanted to get advice on.   The left DMM is showing the B+ rail.  The right is showing the O- offset from ground.  Both are about  150V.  Does that seem right?  Same reading on both amp boards.  I wanted to make sure there was nothing obviously wrong before going to full power.  Thoughts?  

 

mwl168, earlier you posted about your offset jumping to 170V on startup but quickly settling down after that.  Could it be that the system needs full voltage to settle down?  I have both servos off right now.  

 

Edited November 19, 2017 by Blueman2

[mwl168]

Does the offset respond to the adjustment of the trim pot?

[Blueman2]

Well, I decided since nothing was smoking or popping, I would give it 100% power.  And sure enough, the offset quickly settled down to about 3V initially, and slowly went to about 0.4V after about 10 minutes.  Great relief that everything appears to be working correctly, at least on the Left amp board.  Now on to testing the other one and getting everything dialed in.  Maybe tomorrow there will be music!!!

 

EDIT: mwl168, you posted just as I was posting.  I did not try that but should have.  In any case, it is alive!!!!!!

And if anyone noticed, I have a very strange looking header for B+/- rails on the amps.  It is from Digikey.  This item is nice because it allows the wires to be more up rather than across the board.  But the real advantage is the way it lifts up off the board where the troublesome tracer is that a couple of people have gotten arcing from.  See below how it looks.  At least it allows me to see how much solder/flux there is under there.  

Edited November 19, 2017 by Blueman2

[mwl168]

Actually, I could not tell from the pic if you have the servo engaged or not. 

You should power the amp up without the servo engaged. Adjust the balance and offset then engage the servo. From what you described above, it sounds like you have the servo engaged?

[Blueman2]

2 hours ago, mwl168 said:

Actually, I could not tell from the pic if you have the servo engaged or not. 

You should power the amp up without the servo engaged. Adjust the balance and offset then engage the servo. From what you described above, it sounds like you have the servo engaged?

No, neither servo engaged.  Just got lucky with initial setting.  I played with the offset trim and was able to go up to around 25V and then easily down to 0 with a bit of drift.  

BTW, I did not populate the IC for the opto, just the OP27.  Is the OP27 Servo 1 as labeled on the board?  And is this the one that does not require the 10V to trigger, so I can just adjust to close to 0 and let it do its work?

 

EDIT: I just finished dialing in balance and offset.  Turns out the offset was not as good as I though initially.  The balance was WAY off, at 75V.  It appears that balance impacts offset, because after getting balance to 0, the offset was then off about 20V, but easily got that down to 0 also.  On both boards,  I am able to get balance to < 100mV with a bit of drift over time, and offset to < 500mV, again with minor drift over time.  Both servos turned off (header not connected).  I am now going to re-check the 17ma setting for the 4 outputs and let it run for about an hour.  Then, depending on the thermal state, I will move up to 20ma and redial all the settings.  One thing I will say is the amps put out a LOT of heat!!  Really surprised by how much.  Massive heat sink got warm all over after just 10-15 minutes of testing.  

EDIT2: I put the jumper on Servo1, and it works quite nicely!!  The offset varies +/- 200mV around 0, but holds that range pretty well so far!  Does the servo also help with balance?  I did not think it did, but for some reason balance is also staying much more stable, going up and down within 200mV of 0.  I think I am ready to listen to music.  Finger crossed.  

EDIT3: We have music!!!  And it sounds really, really, really great!  First impression compared to the SRX-Plus is more clarity to the bass (sharper, punchier) and more clarity in the treble.  I jumped a couple times hearing some high treble parts I had not really noticed before in a few songs.  Everything just sounds sharper and more technical, if that makes any sense.  I need to listen more, but there appears to be more sound stage as well.  I am using SR-507s.  I can't wipe this smile off my face.

 

 

Edited November 19, 2017 by Blueman2