mwl168

Yes, the GRLV 18VDC rails are for the 2SK170 front-end.

Finally finished casing my Blue Hawaii today. Running on my "universal" PSU that also powers my HV Carbon. 400VDC and 18VDC rails, 20mA plate current. The heatsinks warm up to about 42C (108F) and stabilize, about 22C (40F) rise from ambient temperature. The chassis is a Breeze Audio 3608A, one of 5 chassis I bought from Breeze Audio at TaoBao. I requested that the front and rear panels be left plane, un-drilled. Works quite well.

Thanks congo5!

I read the Firstwatt F5 and F5 Turbo article, the capacitor is listed on the schematic as .0033uf I think. So 3.3nf instead of .33nf? Do you have a part number for the part you use? Also, the schematic is different between the original F5 and the later F5 Turbo. I assume the F5 Turbo one is the one to follow? Thanks!

Thanks all for chiming in. This is exactly what I was hoping for - to learn from your knowledge and empirical experience. The issue Craig mentioned is the problem I was hoping to solve with the thermistors - the fuse rating needed to survive power-on inrush is way above what is needed once the amp is fully energized. Sounds like I have over simplified the issue. @Bespav: sorry I don't have the knowledge to answer your question.

I was hoping to keep this discussion as a generic topic but it seems time to describe my specific case which triggered my question. I built a dedicated PSU to be used with my KG ES amps (KGSSHV, HV Carbon, Blue Hawaii and in the future, the Grounded Grid and maybe CFA) as can be seen at the Carbon Build thread. The PSU contains a GRHV, GRLV and have two Antek transformers (300VA for GRHV and 50VA for GRLV). I have a 3A slow blow fuse and a CL60 (IIRC) thermistor on the IEC. I also have one 15ohm/3A thermistor on each of the two 325v secondaries which are controlled via a second power switch. When I use this PSU to power the HV Carbon, I keep the second power switch in the "On" position and only use the main power switch to turn on and off the amp and the 3A mains fuse has no problem handling the power-on inrush. I tried using this PSU to power the Blue Hawaii this past weekend. I kept the 2nd switch in the "Off" position, turned on the main switch which energizes the GRLV and the filament supply to the 4 EL34's. After 30 seconds or so, I flipped on the second power switch which controls the 325vac secondaries to the GRHV. The 3A fuse blew within a second or so. I replaced the 3A fuse, used a variac to power on the PSU and the amp worked fine. I was really puzzled - why did the 3A fuse blow when I flipped on the second power switch? Shouldn't the inrush current be lower in this case? Anyone has a theory of what happened?

I do have either a CL60 or CL70 between the primary wiring and the IEC socket of the PSU. I added an switch on the HV secondaries and put two extra thermistors in series so together they function as a manual HV delay switch when I use the PSU for the Blue Hawaii. And going back to my questions in my first post; Is it better to use one single inrush current limiter and a higher current fuse or to use a lower current fuse and use two inrush current limiter in series when the power-on inrush current is much higher than steady draw current of the amp?

It's a 15 ohm 3 amps NTC thermistor, Mouser part number: 954-15D2-13LD. Right now I use one each on the two 325vac secondaries on my Antek AS-3T325 (rated at 300VA with 325v/450ma x2 and 6.3v/4a x2 secondaries). It energizes a GRHV PSU which I use to power my KGSSHV, HV Carbon and Blue Hawaii so I doubt the PSU ever draws more than 200mA on each rail. The thermistors are mounted on a PCB for exactly the reasons you mentioned - to give it proper cooling and prevent shorts and coming into contact with other parts and wires. The soft start circuit looks interesting. I'll need to read the article carefully. My current PSU chassis may not have room for them though...

Thanks for the replies. My question is specifically targeted at when using NTC thermistors on secondaries, in my case, 330vac secondaries. The data sheet says 110vac/250vac but I am pretty sure Mouser listed them at 400vac when I ordered them (although I am unable to find that information now). I searched quite extensively and could not find any thermistors rated higher then 110/250vac. Since the thermistor is wired in series, would it really see the whole secondary voltage drop?

Hi All: Ignorant people like myself and newbies often need various technical advices and assistance when dabble in this wonderful hobby. Many of these are general topics that do not specifically apply to one specific device. These valuable advices and suggestions are scattered in various threads over time and difficult to find. I thought it may be a good idea to have a dedicated thread where these discussions and information reside. So I thought I'll start this thread and see if it gets traction. So here goes my first question - inrush current limiter and fuse. My thinking has always been that the main fuse need to meet two main requirements; 1. provide protection to both the device and user when the device malfunctions and 2. able to survive the inrush current when the device is first powered on. To me, these two requirements are somewhat contradictory. A high current rating fuse that can survive the power-on inrush current, with the help of inrush current limiter(s), may not provide proper protection against device malfunction and vise versa. For my PSU for Kevin's ES amps, is it better to use one single inrush current limiter and a higher current fuse or to use a lower current fuse and use two inrush current limiter in series? Also, do I need to worry about the voltage rating of the inrush current limiter (in my case a NTC thermistor)? What's the actual voltage drop on the inrush current limiter during power-on? I would really appreciate your experience, thoughts and advices. Thanks!

Got my pots today. Looks good! Thanks!

VAT payment sent. Thanks!

Payment sent. PayPal address is fine. Thanks!

I had hum problem with my SRX Plus initially too. I traced the hum problem to two factors - the wiring, especially the AC filament supply, and the contact between the pins of the 12AT7's and the tube sockets. I rearranged and tidied up all the wiring and cleaned the pins on all the 12AT7's and my SRX Plus has been hum-free.

I can confirm standard parts are fine with 15VDC. Have built one and has been running fine for months.

I cannot think of a reason why I would give a flip on a comment coming from someone that thought to use 300B as output tubes on an ES headphone amp and charge $50K US for it.

All except 3 US/CA destined packages have been shipped yesterday. Of the 3 remaining packages, 2 has not responded to my inquiries and 1 has asked for package to be held and shipped later.

I bought a matched quad of NOS Winged C Svetlana EL34 from Upscale Audio in preparation for the Grounded Grid build. The 4 tubes have these spec's on their boxes: Tube 1: Bias 40.8, Transconductance 5.80, G2 mA 7.07 Tube 2: Bias 40.9, Transconductance 6.07, G2 mA 7.25 Tube 3: Bias 40.9, Transconductance 6.07, G2 mA 6.70 Tube 4: Bias 40.8, Transconductance 6.18, G2 mA 7.02 So based on the Grounded Grid circuit, how should I pair them up? Would the same pairing work for the Blue Hawaii? Thanks!

A few packages including pots and boards have been shipped to US and CA participants. MLA is waiting for the boards that I ship him about 10 days ago. There was delay on my end on figuring out how many boards to ship to MLA because I was not able to ascertain the country of residence of all the GB participants.

I saw that and they were offering 15% discount over Thanksgiving and now 10% discount over Christmas which makes their price "acceptable" for those XF2 EL34. I bought some KenRad 6SN7GT from them a few years ago and now regularly receive e-mail informercial from them. The 6SN7 I received seem fine. Cannot speak to the XF2 EL34 though. Anyone has experience with them and can vouch one way or the other? I did pull the trigger on a quad of NOS Tesla EL34 with Brent. Anyone has experience with these tubes and can share your impressions?

Only received three responses so far about shipping option. Two of these will be shipped today. I will be leaving on a long trip in two weeks and would like to process all the US/CA shipments before I leave to avoid long wait so would really appreciate prompt responses. Again, flat rate USPS priority shipping option is $6.8 USD plus $1 for each of the pots you ordered for US destined packages.

What do you all think of Charles Hansen's (of the Ayre fame) article below about PCM vs DSD? I am a big fan of his early Avalon speakers so tend to pay attention to what he has to say... http://www.ayre.com/insights_dsdvspcm.htm

Exchanged e-mails with Brent. He does not have enough XF2 Mullard EL34 on hand to make a matched quad at this time.

Anyone know and can recommend reliable sources for NOS XF2 Mullard EL34? What's reasonable price to pay for a matched quad? Have been thinking about getting a set so I don't kick myself 5 years from now...

I am ready to ship the US/Canada destined orders. $1 USD for each TKD volume pot will be added to the postage to cover the shipping from MLA to me. For Canada destined packages I‘ll need to get quotes from USPS based on weight/destination and PM each individual. For US destined orders we can either do the same or we can use the Flat Rate Priority Mail option which will be $6.8 USD per package. I can check other options but given that, except for sbelyo, everyone has one or more volume pots so order need to be sent as packages, by the time we add the cost of shipping container/envelop the saving is likely amount to 1 or 2 dollars. For those that prefer to go with the Flat Rate Priority shipping option, please PayPal me $6.8 USD plus $1 each for the pots you ordered. Please remember to include your shipping address and HeadCase ID if you have not already done so previously. My PayPal ID: If you prefer to go with the weight-and-calculate method please let me know either by responding to this post or PM me. Thanks!