luvdunhill

that's what doublers are for lol, very cool though!

seems reasonable. I was thinking about something like a 12AY7 driver tube into a pair of 6BX7s. Just curious, do you actually mean the 6BL7GT or perhaps the GTA? If the former, then you're probably the only person I've met that has recommended these tubes. I love 'em, no one else will try them

so, they might work. I'll share my experience... There was no way in hell those screws would move with a normal Allen key type wrench. In fact, I'm pretty sure I stripped one trying, so this could be interesting... Also, a few more concerns. Depending on if it's a P2P wired or PCB MPX3, drilling holes for new jacks may be a PITA, as everything is top mounted and the whole enchilada is quite heavy at that. It may be easier to convert one of the jacks, assuming he has two with source selector knob on the front. This is what I'm planning on doing.

definitely not a security bit.. don't forget there are SAE hex and fractional hex as well.

nate: perhaps, but remember tkam is suggesting a 1/16" bit, so it will be quite small, and the screws are black and the chassis is glossy black. I'm going to pick up one of those 100pc security bit thingys at harbor freight (it's on sale!) this weekend and I'll report back

They are exactly has tkam described, they require a very small (I had no idea how small, or even torx, fractional hex, metric hex, etc. because it's so small and hard to ascertain the shape) hex key. Something like this: Honestly, I don't think a camera will get an accurate picture.

two other helpful links for obtaining parts, etc... http://www.diyaudio.com/forums/showthread.php?s=&postid=1374762#post1374762 http://www.diyaudio.com/forums/showthread.php?s=&threadid=110654

http://www.firstwatt.com/downloads/f4_om.pdf

thanks! I looked at some point at Lowe's / Home Despot and they didn't have anything. Perhaps I need something like this:

my plans exactly... I have about 50 lbs of Plitron toroids and four sets of PCBs ready for the dual dual mono version (can I coin a term? basically, bi-amping each speaker)

Too much gain you say? Perfect for a pair of these: http://www.firstwatt.com/products/f4.htm and a 0.24mV output moving coil cartridge.... Nate: Please keep me posted on this, as I'm going to do the same thing. First things first, how do you get those damn screws off? Honestly, this is what's been holding me back from doing this.

fair enough. I'd be curious what you finally end up with If you like the above, I think the North Star comes awful close, considering the price.

any comparisons between the vinyl rigs? I'm partially biased to the Nott, but I'd be curious what you thought (yup, just call me a "rimester")

yeah I've heard them too I agree with KG, they need double the voltage (at least).

so, all the voltages would scale up in the output stage, so I can keep the 100V zener, the 50K at the bases of the 2sa1156 (soon to be 2sa1413/2sa1968) .. looks fun

me too great tube, especially the RCA and Brimar tubes.

seems to me to be more complex that just swapping out the transistors. Won't I have to recalculate the resistor values for the vbe multipliers in the second stage, or will they still create the 13 v bias for the third stage? The 2sa1156 is a new one for me, I guess the fact that it is surface mount really isn't of any concern, as I wouldn't have to heatsink it anyways? Thanks for the heads up! will the power dissipation for the FETs remain about the same, or will I need to look into some extra heatsinking for them as well?

The uprated 6BG6 are $6 each... them's US dollars... that's basically free My guess is without upping the bias, the difference in transconductance will be too great to be able to accurately judge the new tubes. That's why I have two 16" pieces of this due to be here on Friday

spritzer: A standard 6BG6 is an 807 with an octal base on it, so perfect for dropping into the BH. There have been reports of Philips/ECG 6BG6GA tubes that can be run at (a minimum) 500VDC plate voltage, 75ma plate current (35W) with screen voltage set at 450 VDC and can replace an EL34 where the cathode is connected to the suppressor grid, like in the BH. This will be the first place I'll start, as these are cheap and reportedly sound great. KG: I don't see any reason I cannot also increase the voltage of the positive rail (as well as increasing the current through the programmable current sources) for more power? My psu can easily accommodate raising just the +400 V rail... I figure maxing out what my psu can deliver voltage-wise and then varying the current sources until I get 35W and seeing what happens then... KG: do you have an opinion on DC heaters employing things like hum balancers or cathode biasing? I found someone selling little PCBs to do the trick: http://www.tubeaudiokits.com/LIBRARY/heater-balancer.htm

well, if you ear leans towards the NOS "sound", check out the two DACs I posted a few days back in this thread (www.ecdesigns.nl). A pretty innovative approach IMHO...

granodemostasa: have you ever heard a non-oversampling DAC?

this is a rather ambiguous statement. do you mean: a.) the EL34 is the best sounding pentode b.) the EL34 is the best sounding pentode in the BH circuit c.) the EL34 is the best sounding pentode in the BH circuit that is pinout compatible with the original circuit

can circuit can handle only having half the transconductance of the EL34? This is the only spec that I cannot meet easily. see my concerns above. none of the tubes I listed are drop-in replacements. That would be too easy... I agree about kt88, 6l6, etc... I won't be trying those. EL360 are getting hard to find, but I have some sources. Again, not my first choice, but they look promising. <flame suit on>I'm more tempted to play with the 3D21A after hearing these in Mikhail's ES amps (in direct comparison to the Mullard EL34 actually). Amazing tubes and the 3D21WB are pretty much indestructible... perfect for the BH + big heatsinks + IXYS current sources.</flame suit on> Looks like there is only one way to find out...

need a top-flight DAC with USB input? I'd recommend either of these designs: http://www.ecdesigns.nl/ NOS using direct interpolation ==