300b's for Kaiju
- Thread starter drewh1
- Start date
drewh1
New member
Ain't that the truth!
So I just put my order in. One more question.
Knowing I'll be using the EML Mesh Plates, I did not order tubes. I assume I will need to make sure the Filament Voltage and current are correct prior to using the tubes. Can I measure this without tubes, or will I need a cheap set of tubes to set things up?
thanks again, when does it ship? ;D (joking of course)
So I just put my order in. One more question.
Knowing I'll be using the EML Mesh Plates, I did not order tubes. I assume I will need to make sure the Filament Voltage and current are correct prior to using the tubes. Can I measure this without tubes, or will I need a cheap set of tubes to set things up?
thanks again, when does it ship? ;D (joking of course)
drewh1
New member
It is amazing how well 44.1 sounds through this DAC. I keep going through my old CD rips and it is like hearing them for the first time. I have downloaded comparison DSD and 192 PCM files. I couldn't hear any audible differences. J-River (which I use) converts DSD to PCM anyway. Charlie Hanson prefers PCM so the DAC probably does a better job with it anyway!
Provided the instructions are followed in the manual for measuring your AC line voltage and selecting the appropriate power transformer wiring, no additional testing is necessary.drewh1 said:
drewh1
New member
Got my kit! It includes the DC Regulated filament kit - Given that I will be using EML's from the start do you still recommend building the kit stock and then adding the DC circuit board? l
I won't have my tubes for a couple of weeks, so I could probably get everything done prior to the arrival of the tubes. I can't measure voltages before getting the tubes and would prefer to have the circuit in place prior to firing up the tubes.
thanks for the advice.
drew.
I won't have my tubes for a couple of weeks, so I could probably get everything done prior to the arrival of the tubes. I can't measure voltages before getting the tubes and would prefer to have the circuit in place prior to firing up the tubes.
thanks for the advice.
drew.
fullheadofnothing
Moderator
Read p. 10 of the DC manual.
drewh1
New member
Well, of course I did read that page. The reason I am asking is that Paul J. recommended that I utilize the DC Filament circuit for use with the EML's. So I am just making sure it is reasonable to start using the EML's safely with the AC then switch over.
I also need to modify the circuit after getting some measurements. So, I also imagine the measurements won't be accurate until I have the DC circuit in place.
I also need to modify the circuit after getting some measurements. So, I also imagine the measurements won't be accurate until I have the DC circuit in place.
Paul Joppa
Moderator
In the best of all worlds, I myself would use cheap, worn tubes until everything is running correctly and the filament voltages look perfect. I can do that, because we have plenty of tubes lying around. The only reason for such care is that the EMLs are really expensive, and I have a substantial portion of Scottish DNA. My grandfather used to say we were descended from the finest horse thieves in Scotland - also the reason my ancestor moved to America... :^)
But I'm assuming you don't have a spare pair of used 300Bs. So yeah, build it stock, take it slow and careful, and do all the tests. Be extra careful about the power transformer input voltage (starts on page 29). If there are any questions, this is the place to bring them up. We will be paying special attention to any confusion or problems, until there are a few successful builds.
A few hours at a slightly wrong filament voltage will not harm most tubes, but EML specifies a very tight +/-4% on the filament voltage, and conforming to that spec is important to retain their warranty.
But I'm assuming you don't have a spare pair of used 300Bs. So yeah, build it stock, take it slow and careful, and do all the tests. Be extra careful about the power transformer input voltage (starts on page 29). If there are any questions, this is the place to bring them up. We will be paying special attention to any confusion or problems, until there are a few successful builds.
A few hours at a slightly wrong filament voltage will not harm most tubes, but EML specifies a very tight +/-4% on the filament voltage, and conforming to that spec is important to retain their warranty.
Just to give a little of our rationale here, what we can give competent tech support for is an amp assembled by the method we describe in the manual. Which is to say assemble it with the AC supply first, make sure it is functioning properly, and then install the DC upgrade. If the amp is built with the DC supply from the get-go, our tech support advice in the case of it not working is to tell the builder to complete the amp with the AC supply first, make sure it works right, and then install the DC supply. When part or assembly changes are made to a first run kit you will have to wear your pioneer hat.
drewh1
New member
Thanks Doc and Paul - I am definitely taking this one slow and will be careful about the voltages through every step. When I get to putting the tubes in, I'll take all the measurements and check in with you Paul about any needed changes.
yeah, it would be great if I had a crap pair of 300b's to test with, like most of us, I am extravagant in some ways and really cheap in others. The kit looks great and I am really excited to be building it.
drew.
yeah, it would be great if I had a crap pair of 300b's to test with, like most of us, I am extravagant in some ways and really cheap in others. The kit looks great and I am really excited to be building it.
drew.
Paul Joppa
Moderator
That is a bit on the high side. It will drop a bit when the transformer is drawing full current, but probably not enough.
However, the EML mesh 300B draws 1.4 amps, greater than the 300B spec of 1.2 amps. This will pull the filament voltage down further than normal.
If you are lucky, these two effects will cancel each other. So I suggest you proceed with the stock build, and add an AC voltage measurement across the filament (socket pins 1 and 4) before proceeding with the other voltage measurements. If you still have a voltage outside the EML spec of 4.8 to 5.2vRMS, you can adjust the 0.51 ohm resistors to refine it. (See these resistors in the photo on page 35 of the manual.)
Incidentally, you may wish to mark the setting of the hum pot before installing the DC heater circuit. It will otherwise be difficult to determine the best setting.
However, the EML mesh 300B draws 1.4 amps, greater than the 300B spec of 1.2 amps. This will pull the filament voltage down further than normal.
If you are lucky, these two effects will cancel each other. So I suggest you proceed with the stock build, and add an AC voltage measurement across the filament (socket pins 1 and 4) before proceeding with the other voltage measurements. If you still have a voltage outside the EML spec of 4.8 to 5.2vRMS, you can adjust the 0.51 ohm resistors to refine it. (See these resistors in the photo on page 35 of the manual.)
Incidentally, you may wish to mark the setting of the hum pot before installing the DC heater circuit. It will otherwise be difficult to determine the best setting.
drewh1
New member
Great minds think alike! I was wondering if the additional voltage would bring it closer to spec.
BTW, I did manage to get my hands on a pair of 300bs to set up and test with, so I am good to go. I'll just keep checking in with details as things move along.
I really appreciate all your time and help Paul, but what are you doing working on a Saturday!
drew.
BTW, I did manage to get my hands on a pair of 300bs to set up and test with, so I am good to go. I'll just keep checking in with details as things move along.
I really appreciate all your time and help Paul, but what are you doing working on a Saturday!
drew.
