[rolotube]

Quote:

Originally Posted by funch /img/forum/go_quote.gif My 270DAX also gets hot enough that I can only leave my hand on it for a couple of seconds. It's also mounted on top of the case. I've done the Regal and Amphead mods, and use a separate heater tranny for the EZ81. I'm running 6H30's on the input, and ECC99's on the output. The other day, I fired it up with no signal and let it run for a few minutes. Then I checked the voltages on the amp boards. All were very close except at the junction of C2, R2, and V1 which should read 3V. Mine was at 6.4V. Then I connected my source and listened at a moderate volume level for most of a CD. The tranny was still barely warm. Then I turned up the volume one step. By the end of the CD, the tranny was hot again.

The transformers may be designed to run fairly warm, but I question how long they will last at the highish temp you describe. Here in Oz we have no choice, it has to be the 370 DAX (240V mains) & this seems to be a different beast altogether. I'm running an EZ81, choke PS, 6H30 & ECC99's with regal's & amphead's mods & it never gets much above lukewarm. You can certainly leave your hand on it, even after several hours. I tend to listen at a more or less constant volume (fairly low) & haven't noticed any variation in transformer temp. All voltages are within 10% of "book" values.

Shinkoh tantalums & Blackgates arrive tomorrow from PcX. Plan is to replace all amp resistors & use Blackgates at C2 (amp) & C3 (PS). I know this is probably overkill but tinkering is fun & may even yield some subtle changes or improvements.

 

[rolotube]

Quote:

Originally Posted by adamus /img/forum/go_quote.gif havent compared them, but the bugleboys are ahead of anything i have tried, which includes Jans, 8416, 6n1p.

The bugleboys get great reports. I've been considering lashing out on some, but they aren't exactly inexpensive. I'd be interested in your comments describing the sound, particularly in comparison with other types. Have you tried any of the 6H30 variants? The DP's in particular are highly regarded by some but are also very expensive. I'm running EH 6H30EB's (gold pins) which are re-badged Sovteks. Very nice, but I now think they produce a sound that is too laid back for my taste. IMO, the Bijou/HD650 combo needs a front end tube with more "punch".

 

[jkroon]

I'm going to build the Bijou as my first DIY amp. I'm waiting for a kit I ordered from GlassJarAudio.com. I was thinking about adding a DIY DAC and DIY phono preamp in the same chassis. I would be concerned with noise, and also the power supply. I have to figure out a good way of doing the power supply layouts. Just thinking about it. I only ordered parts for the Bijou so far. Any thoughts?

 

[pabbi1]

Quote:

Originally Posted by jkroon /img/forum/go_quote.gif I'm going to build the Bijou as my first DIY amp. I'm waiting for a kit I ordered from GlassJarAudio.com. I was thinking about adding a DIY DAC and DIY phono preamp in the same chassis. I would be concerned with noise, and also the power supply. I have to figure out a good way of doing the power supply layouts. Just thinking about it. I only ordered parts for the Bijou so far. Any thoughts?

Look at the Millett Max in my signature - the OPUS DAC resided in the same case, with no noise whatsoever. The NABU case has a shielded compartment for the psu, except the DAC psu was in the case as well. No problems at all with any noise.

Now, the Bijou is picky with it's wiring, so you might also look at the various wirings in this thread, including mine in my sig - dead quiet, no noise at all.

 

[jkroon]

I read this entire thread before purchasing the Bijou kit. That's what got me thinking about possible noise problems if I were to add other components. After reading about the ordeal you and Amphead went through, it seems to me that the main things to watch out for are shielding and ground loops, right? Well, I also want to add a source selector, maybe a 3 wire 4 position? I'm not sure. I was going to run shielded twisted pair cables from each input to the selector. Then I would have the left, right, AND shield switched from 4 different inputs. I wanted to wire a DAC to one of those, and have a usb input mounted to the chassis. Then wire a phono preamp to another, and have two more inputs for a CD player and one spare. Another shielded twisted pair would go from the selector to the volume pot, and that's where I start getting confused with the shields and grounding. Maybe I'm overthinking. Would I take the shield to the ground on the volume pot, to the amplifier boards, or to the star ground? I saw your Bijou in previous posts and its insane. I like it.

 

[jkroon]

I haven't even SEEN a tube since about 1985. I can't wait to hear this amp.

 

[runeight]

jkroon could you possible draw a wiring diagram for what you're trying to do?

The best way to proceed would be to build just the basic Bijou without the selector or other electronics and make it quiet. You're correct that noise is usually ground problems or shielding problems.

Once you get a quiet amp you can add the other pieces one at a time. Then you'll know, if noise appears, what the cause is. I think this will be a more pleasant experience than ripping things apart to find a problem.

You've probably already thought of this . . .

 

[adamus]

Quote:

Originally Posted by rolotube /img/forum/go_quote.gif The bugleboys get great reports. I've been considering lashing out on some, but they aren't exactly inexpensive. I'd be interested in your comments describing the sound, particularly in comparison with other types. Have you tried any of the 6H30 variants? The DP's in particular are highly regarded by some but are also very expensive. I'm running EH 6H30EB's (gold pins) which are re-badged Sovteks. Very nice, but I now think they produce a sound that is too laid back for my taste. IMO, the Bijou/HD650 combo needs a front end tube with more "punch".

a very 3d presentatain, punchy bass that also drops deep. big mids, and extended highs.

They are the most '3d' sounding tube i have tried.

Again, looking at the operating point of the amp, even with regals mod, you would expect the 6dj8 to sound better than the russians mentions, we are in a more linear region.

 

[balderon]

Hi Alex. I am enjoying the Bijou however I wanted to get your opinion on enhancement I am considering. I am siphoning about 20ma from the B+ and each channel is drawing ~38ma each for a total of ~96ma. I am finding the supply cannot deliver sufficient power for this load. With a 90ma 270DAX transfo (w/EZ81/Regal mod) my B+ is dropping to < 238v@96ma. P1 had little effect past midpoint. Once I reduce the current load, P1 once again adjusts the output voltage. Also the transfo is running very hot. I wanted to upgrade to a 270FX (275-0-275@150ma) to provide additional current and to reduce the heat (I hope).

It looks like the MOSFET/EZ81 can accommodate the additional power but would you recommend changing Q1/Q2 bias points? Any suggestions you have will be greatly appreciated.

TIA

 

[balderon]

I googled this problem and it seems to be very common with the hammond transfo. One of the posts I read on one of the other sites indicated using several Hammond transfo for the last 10 years. They run very hot and was used in different amps without problems.

Quote:

Originally Posted by funch /img/forum/go_quote.gif My 270DAX also gets hot enough that I can only leave my hand on it for a couple of seconds. It's also mounted on top of the case. I've done the Regal and Amphead mods, and use a separate heater tranny for the EZ81. I'm running 6H30's on the input, and ECC99's on the output. The other day, I fired it up with no signal and let it run for a few minutes. Then I checked the voltages on the amp boards. All were very close except at the junction of C2, R2, and V1 which should read 3V. Mine was at 6.4V. Then I connected my source and listened at a moderate volume level for most of a CD. The tranny was still barely warm. Then I turned up the volume one step. By the end of the CD, the tranny was hot again.

 

[pabbi1]

On reflection, most of my noise problem was the TUBES, the 6n1p and 6n6p - after burning for about 150-200 hours, they settled down, and are dead quiet. The attenuators were a different problem (very small lead pads), and switching to the TKD helped there as well.

Oh, and new builders (or anyone, for that matter): Shoot me a PM if you want Rubycon photoflash caps - I still have plenty - and, grattis.

 

[pabbi1]

just a heads up...

There are some smoking deals on ez81 on eBay at the moment.

I have no knowledge nor affiliation with this seller - and have plenty of EZ81 put back - for at least 4x what these auctions might go for.

 

[MoodySteve]

Thanks for the heads up pabbi1, been looking for a good price EZ81

 

[jkroon]

Runeight, you're absolutely right of course. I'm getting impatient and jumping the gun. I would draw a picture of what I'm talking about but I have no idea how to draw a 3 pole 4 position switch. I'll do like you say and start with the original design. Once I have a working Bijou, I'll bring it up again. For now, since I'm still waiting for my parts to get here, I'll start on a chassis. I bought some maple wood and 1/4" aluminum plate today. And I have a steel drawer from an old desk I think I could use.... What a fun hobby this is! I can see this easily getting out of hand.

 

[runeight]

Quote:

Originally Posted by balderon /img/forum/go_quote.gif Hi Alex. I am enjoying the Bijou however I wanted to get your opinion on enhancement I am considering. I am siphoning about 20ma from the B+ and each channel is drawing ~38ma each for a total of ~96ma. I am finding the supply cannot deliver sufficient power for this load. With a 90ma 270DAX transfo (w/EZ81/Regal mod) my B+ is dropping to < 238v@96ma. P1 had little effect past midpoint. Once I reduce the current load, P1 once again adjusts the output voltage. Also the transfo is running very hot. I wanted to upgrade to a 270FX (275-0-275@150ma) to provide additional current and to reduce the heat (I hope). It looks like the MOSFET/EZ81 can accommodate the additional power but would you recommend changing Q1/Q2 bias points? Any suggestions you have will be greatly appreciated. TIA

Yes, you can use the bigger transformer without changing the op points for the mosfets.

However, watch out for the heater voltage. The bigger transformer probably has a large current heater winding. Since it will be more lightly loaded it will have a higher voltage.