mwl168

Finished building the first one of the DAM1021. This is the .05% resistor version. Runs on +/- 9VDC rails. Amanero USB/i2s receiver. It's hard to beat for the money.

Good point. I was referring to street vendors in Taiwan. Not surprised by what you said based on things I read and heard.

Street vendors usually offer the best taesting choudofu. Easy choice !

Thanks Craig and John! This is really very helpful and critical information to have. I've followed John's KGSSHV wiring scheme on all my builds to great effect (thanks John). I am now finishing a Soekris DAM1021 DAC build and have a question: In the headphone amps with the XLR input connectors, I have the pin 1 of the XLR connectors tie to chassis, only pin 2 and 3 are wired to the non-inverted and inverted inputs of the amp board. For the DAC's balanced output, should I follow the same practice - that is, tie pin 1 of the male XLR connectors to the chassis and only wire the inverted and non-inverted output from the DAM1021 board to the pin 2 and 3 of the XLR connectors? EDIT: Also, what about RCA connectors?

Is it 30V or 30mV?

I have some of Pars’ rectifier boards made (with Pars’ permission) and can spare a few. PM me if you are interested. EDIT: just read that this board will be added to the GB in the 2018 GB thread. That’s a better option - in many cases, the shipping from me will likely equal or exceed the cost of the boards.

The value needs adjusting not the wattage. Don't remember for sure but try 3R 5W or so. In a pinch you can parallel 2 5.1R to get 2.55R but it's a good idea to replace it with a value that's more appropriate for your application. Going by memory I think the B- on the BH draws around 140mA.

Not sure this is a factor but, the Blue Hawaii draws significantly higher current than the Carbon does, especially on the B- rail. If you are using the 5.1R current limiting resistors on the GRHV you will for sure have issue with the B- and possibly the B+ rail too.

So the tubes you are using now are drawing 2.6A filament current per pair based on the measurements you provided. Since the filament supply is not regulated, subject to mains fluctuation and different tubes will likely varies a bit in their filament current draw. I suggest you make some calculation and set up the resistors to drop the filament supply under load to fall in a range you feel comfortable with. I have some high cost NOS EL34 tubes so I personally feel most comfortable having the filament be between 6 - 6.3v. And, by the way, I believe the filament current draw varies a bit from cold start to fully warmed up too.

Congratulations! I think the 5.5v is too low for the filament supply for the EL34. This is an often debated topic whether lower filament voltage is beneficial or not but I think most believe it should be within 10% of the 6.3v.

Interesting. I just received an order from Mouser and they shipped me the 2-gang potentiometer instead of the 1-gang I ordered. Now I’ve had a few orders more than $300 worth and never got any free upgrade in shipping. Have to be honest I have never checked my orders to verify everything was shipped correctly.

Has anyone built this tube unbal/bal board yet?

That makes sense. Thanks!

In my case, I also kept the 2K trim pot for the offset. It's a messy job desoldering a three pin part. It has worked fine so far just a bit too sensitive to the adjustment than I like. I don't remember the schematic much but if needed, you can always change the fixed resistor (if there is one) in series with the trim pot like in the KGSSHV.

But there is only one output for B+ on the PSU?

Why does the PSU have two sets of F+/F- output?

Yes.

Pardon my ignorance but what's the difference between this Belkin one and the ones on eBay that sells for a fraction of its price?

Does this work on MacBook Pro too or only Windows PC?

Have not played with the filters yet. Just doing some testing and getting an impression of the sound. Have been reading up on the filters on and off. I don't have a PC with serial port any more so have to figure out how to change and load different filters too. Thanks for the kind offer. Which version of buffer do you have - the SMT or the through-hole ones?

Running the Soekris dam1021 I just received through its course. This one is the V4, 0.05% resistor version I am building for a friend. I got the 0.01%/0.02% version myself which I will be building for my son. Fairly straight forward to get it up and running after reading the information on the DIYAUDIO thread and on the excellent Hifiduino site. Using +/-10VDC supply (PSU of the original Wire headphone amp, LM317/LM337 based) and simplest SPDIF connection. The 10K pot is a log pot I happen to have so it's a bit wonky when adjusting volume. Buffered balanced out to the SS Dynalo. Now I am kicking myself for not getting a few of Kevin's diamond buffer boards when these was a GB.

I think you meant the "50R" resistor in series with the 50R trim pot in the plate CCA. If so, yes, adjust the 50R trim pot so there is 1V drop across the 50R resistor will set the CCS current at 20mA. I run mine between 18mA - 20mA at different time. I know there are others that run as high as 25mA. Make sure you have plenty of heatsink - the BH runs much hotter than the Grounded Grid does.

I started out using 150R instead of the 360R for the KSA1156 emitter resistors to set the current to the 3rd stage and never tried the 360R on my build so cannot comment on the sonic difference. I believe the original BH ran 10mA current to the 3rd stage and was later reduced to 3mA to reduce the heat. I decided to go half way based on a similar adjustment I made on my KGSSHV and in that case I like the sound of the raised current much better. Do note though that if you raise the current to the third stage you need to make compensation to the offset-setting resistor and trim pot. I would suggest using 1.2K or so trim pot instead of the 2K and preset it to 600R or so. You'll need to measure and do some calculation so you do not have too much voltage drop across the offset trim pot.

My experience echo with JoaMat's. Kevin's original Blue Hawaii schematic on Headwize stated 1/4 W resistor is fine with this part. I've used 1/2W 470R resistor in this position on my Blue Hawaii (FET version) for the past few years with no issue. This is the 100V zener I use on my Blue Hawaii. https://www.mouser.com/ProductDetail/78-BZX85B100-TAP 1.3W rated and works fine.

I first suspected the special diodes I am using as well but eliminate that possibility after observing the same thing with a GRLV using the regular bridge rectifiers. In this case a GRLV configured for 15VDC regulated output and fed by a 15vac transformer. It maintains regulation under load (about 300mA) and the LEDs are all lit but I was getting only 17.7VDC rectified DC at the 1N4007 and the Vce on the MLF15030 is between 2.9 - 3VDC. I do plan to use transformer with higher secondaries in the future. Your GRLV load-testing post is what prompted me to revisit this whole issue. In another case (I built quite a few GRLVs), I could not get 28VDC regulation from a transformer with 28vac secondaries when the load is over 1A and the voltage drop here between the raw rectified DC and the regulated output is over 10VDC.