Blue Hawaii Special Edition

[wink]

You just need to be sure the fuses are inserted in in the correct direction...........

 

As for the drift. check it after about an hour wrmup, and not just after warm-up.   

Edited March 30, 2019 by wink
clarification

[phixphi]

Wink, i checked bias after some 45mins of warmup  and it was 27V off.

Fuses-yes I know,mine will be inserted by a virgin at full moon  More seriously, I had a positive effect changing to ussr silver military fuses at less resolving 717, so i expect some change here too. 

[GeorgeP]

53 minutes ago, phixphi said:

Wink, i checked bias after some 45mins of warmup  and it was 27V off.

Fuses-yes I know,mine will be inserted by a virgin at full moon  More seriously, I had a positive effect changing to ussr silver military fuses at less resolving 717, so i expect some change here too. 

Sounds like your tubes are the issue. If your tubes are within spec, you probably shouldn't have had to rebias at all. What were they measuring at before you rebiased?

[phixphi]

The tubes are Justins standard Mullards. They have only 5h on them so still very fresh. The measurings were same -27V

[GeorgeP]

1 hour ago, phixphi said:

The tubes are Justins standard Mullards. They have only 5h on them so still very fresh. The measurings were same -27V

Russian Mullards? Maybe you messed up the balance/offset process.

[phixphi]

Yes, Russian Mullards. I followed Justins video: 

1) Set balance and gain 5mins after power up

2) Corrected after 1h to below 1V 

3) Monitored for the next 3h, all was stable

4) Powering after few days I find again -27V + to gnd after 45 mins of warmup. So I corrected again to below 1V but after 10-15mins it drifted to -11V

 

Perhaps the tubes are still setting?

[Laowei]

Was the offset value measured in both channels the same @ -27V, -11V? 

[phixphi]

Yes, they re within a volt the same. I put the blame on fresh tubes still stabilizing.

[Laowei]

Best to hear from Justin on your issue. 

[phixphi]

For the time being I rebiased again (5min aftr warmup then after 1,5h then a small correction aftr 2h) and decided to ignore and just listen. The amp is amazing!

[mwl168]

It was not clear to me reading your posts if the -27V is the DC offset from one phase of the outputs and if it occurs to both channels?

If it only occurs with one channel you can rule out if the tubes are the culprit or not by swapping the tubes around.

[phixphi]

This was the R+ and L+ voltage to ground. It was the same in both channels.

[mwl168]

My Blue Hawaii without servo takes about 90 minutes for the offset/balance to stabilize. Although after 60 minutes or so they do not drift more than a few volts. I adjust offset/balance after two hours running and leave them be from there on. From power on to power on these voltage will vary a bit but usually within a volt or two once stabilized. There shouldn't be need to readjust on power-on unless the ambient temperature changes a lot or new tubes are inserted.

Does the balance, measured between L+ and L-, R+ and R-, also varies significant from power-on to power-on?

     

[phixphi]

My BHSE is an early one with serial #34. Does this duggest it’s without servo?

The +/- balance shows much smaller variation of just a few volts between power on.

[Ali-Pacha]

No servo on the BHSE. 1 hour to be stable < 10V, 2 hours to be fully stable.

Ali

[phixphi]

You mean no servo on early ones or no servo at all?

[Kung]

no servo at all

[phixphi]

Awright, so seems there is no issue and my amp behaves like it should.

Thank you gentlemen for your help.

PS Damn gooood amp!

[phixphi]

I played a bit with my BHSE. The amp is a-m-a-z-i-n-g with my O2mkI after 717! Explosive dynamics, detail, realistic complicated rendering. I must say my listening education is missing in some areas to fully understand and digest what this amp is doing.

Did some small changes:

1) Changed the Furutech Alpha power cord it originally came with to a DIY solid core

Found the right polarity

Lifted the amp ground (I know I know, I put myself at risk but the amp is grounded via the preamp and I want to avoid gnd loops)

All above in one go, I'm not particularly keen on doing all those small listening steps, that annoys me. This change was quite prominent. The sound became even more direct and intense, more dynamical (had to lower the volume by 2 points) almost like sharply etched. Freaking intense experience, at some moments a bit too much.

2) Changed the original Head-amp russkie Mullard copies (with about 10h on them only) to new GT EL-34M, grade 7. At first listen after biasing the change was in somewhat opposite direction to the above. More relaxed sound, less intense, a bit lower in volume, but with a beautiful bass. Harpsichord started to sound a bit "electronic" though and less freaking detailed. Burned them in for 12h with pink noise (burning the O2's also). This opened up the sound and gave it more edge and detail but not as much as it was in 1). Changing dynamic balance of my FR64 arm to a static one also restored some of the crazy dynamics from 1). Hard to decide which sound I prefer. Keep listening and experimenting.

The source: EMT930 +FR64S+modded FR7f + AQ Leopard 144V + DIY EAR834 with a red tip Tlf 12AX7 at the input. All pneumatically suspended.

Cheers

 

 

 

 

 

 

 

[phixphi]

Been loving and adoring my BHSE but got an itch to try vintage tubes. Right now I'm using Groove Tubes EL34. Have been thinking of going full glory Phillips metal base EL34. Any feedback on how do they perform in BHSE?

Cheers

[thebrunx]

Hello, I build the DIY Blue hawaii some months ago, and everything seems done according to the "book". but I have got a big problem. every now and then a KSA1220a Transistor goes bad randomly mostly at start ups but sometimes even in the middle of listening sessions. The KSA1220a transistor replaced the 2SJ79 from the older schematic (under the tube). I have tried different tubes, also transistors from different sellers. the problem remains! it works a few weeks than one transistor dies randomly. Has anyone experienced such a problem and know what the problem could be and how to solve it?

its so annoying.

[thebrunx]

Solved. 

[kevin gilmore]

for people building their own bh, one side of the filsment winding has to be connected to v-, not ground. also applies to all other tube output stax amp.

[CrowDaddy]

thebrunx, what was the solution?  Perhaps better heatsink insulators?

Thanks!

[thebrunx]

2 hours ago, CrowDaddy said:

thebrunx, what was the solution?  Perhaps better heatsink insulators?

Thanks!

my tube filament 6.3VAC supply was grounded with two resistors, (but too low of a resistance, only about 150ohms each) I did this to create a virtual center tap to avoid some annoying tube buzz I was getting from the beginning, it solved the buzz but I guess this added circuit also created a voltage potential that exceeded the el34 cathode to filament maximum voltage ratings and would time to time short circuit v- to gnd (arc in the tube) and pulled too much current in those moments that fried one of the KSA1220A transistors randomly. thank God I had fuses between my amp and DC power supply which probably saved my power supply every time. so with all this in mind, you got to wire the Filament correctly as Kevin has pointed out to avoid creating such a potential in the tubes.