luvdunhill

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 ==

I go back and forth I've owned three MPX3 SE and all sounded very different with these two tube families (three if you split the 6BL7GT/A). Seems like a solid recommendation considering Frihed89s preferences. One driver that definitely prefers the 6BL7GT/A tubes is the Amperex 7062. I can go either way on the 2c51.

no problem! I bet you'll love 'em

just curious, has anyone tried using other tubes in the Blue Hawaii than the 6CA7/EL34? I ended up with a set of boards, and was looking at some datasheets over the weekend. I started looking at the 6BG6GE, 3D21A/WB/7403, 12E1, EL360, 6146, etc.... I started looking more at the 3D21A, but noted that the one major concern is that the transconductance is about half that of the EL34 which means that the gain will probably be about 6dB lower than the EL34, and depending on headroom in the cathode drive circuit this could result in significantly higher distortion. (Also, I might not get enough voltage swing without making other changes that would raise the source impedance of the amplifier.) Other specifications seem reasonable, but I can at best make a guess as to its suitability as there are no triode curves provided for this type. Then I looked at the 6BG6GE which seems like it might work, but has some of the same concerns as above.... Both of these two tubes look like good starting points... anyways, has anyone gone down this path?

psu:

KG: sure! I'm about ready to build a preamp.... so good timing. I'm thinking about this one: Any opinions on it?

If this is the case, the 6BX7-series of tubes on the high-power setting is calling your name. If even after listening to these (they're cheap, so pick up a pair) *then* perhaps the high-voltage setting isn't for you Or maybe a trio of '51 Hytrons My MPX3 has a not-so-high voltage setting on it and it sounds wonderful with the 6BL7GT which on my other MPX3 SE with the standard high voltage setting sounded dark and surripy. I'd still look for a pair, as they're hard to find these days and worth trying (and hoarding). I could never get the 7062 driving the 7119s to really work... it sounded like something was broken, so I quickly removed them In addition to tkams idea, I'd try the 12bh7 (RCA or Brimar) driving a pair of Sylvania 5687s...

wow, sounds like a fun day! I've went though a handful of BAT preamps and I really liked them. If I had my choice, I'd go with the VTL 7.5 but I'm not sure the extra price tag is worth it these days. I really love the Ayre amps and maybe one day I'll pony up for Charles' new amps. They sounds amazing. I went through a similar journey with my Whest phono stage. At this point, it's just sitting there as I have fallen in love with another. I need to list it at some point. Anyways, it went back across the pond 3 times and finally they got rid of a few issues. At that point, several phono stages in my rig, a Klyne, Pass and an Herron. The Whest is very nice and was the first to convince me that solid-state is the way to go in a phono stage. I'd love to try the Ayre, and almost bought one a few times but I'm happy at this point. Just curious Thanks for the reply.

For output, I'd try the side getter RCA 6BL7GTA or (even better) the older CBS/Hytron 6BL7GT (non-A) tubes. For input, Tung-Sol 5670 or (even better) Ericsson 396A if you have the adapter needed for these two or pinched waist Amperex 7062. These combinations sound awesome on all headphones to me. I like detail and things a bit on the bright / hot side. edit: I thought you were looking for a recommendation Sorry, ignore the above as it looks like you have a combination that sounds great with your setup! enjoy!

Karhu: There are some "simpler" (i.e. cheaper) projects here: http://high-amp.de/html/frame.html

Tom: Just curious, did you have the Ayre phono stage at some point? I think I might have say it on the auction block a few weeks (months?) ago. What did you replace it with? I'm thinking about a SP preamp as well. I have had BAT, Ayre and VTL preamps at some point or another... at this point, I'm thinking about going back to BAT or maybe trying a Pass preamp. shrug, lots of choices. Also, does anyone know how much voltage gain the various Singlepower preamps have? Would they be enough to drive speakers through Nelson Pass's F4s (i.e. no voltage gain)?

Howdy pabbi1! I've been lurking / stalking KGs posts to see if anything cool shows up over here ... yup, I built a few JTs, I really like them. Only problem with the JT I've seen is playing the input / output impedance game with them. Haven't thrown one on the new KGSS. Nice segue though. According to Russ, the input impedance of the JT attenuator ranges from approximately 2.2K to 10K and the output impedance is 750R (this is for the 50k "version" of the Joshua Tree, this obviously is not set in stone, and there are resistor calculators on diyaudio). The original KGSS schematic has 500K input resistor for Zin. I was wondering if this combination will "work", or if I should look at reconfiguring the JT? With the relatively high Zin of 500k that the KGSS/BH uses by default, is either output offset (I assume not) or noise a problem? By noise, I mean noise due to stray capacitance between the input terminals and the board inputs? I have heard that this can be a problem when using high values for Zin and that this could have an effect on the high frequency response. Also, has anyone experimented with a RF filter (R+C) right off the jacks on headphone amplifiers such as these? Of course upstream impedance might have to be calculated and the filter "fiddled" with a bit...

I just had the option of hearing a preamp with a Alps HQPro and then it was switched out with a standard stepped attenuator using Riken resistors. Yeah, I'd take the HQPro any day... random, but I noticed that there's one for sale at diyaudio with pics http://www.diyaudio.com/forums/showthread.php?s=&threadid=112437