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Blue Hawaii Special Edition

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

 

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

Edited by wink
clarification

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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. 

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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?

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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.

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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?

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

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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!

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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.

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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?

     

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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.

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

Thank you gentlemen for your help.

PS Damn gooood amp!

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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

 

 

 

 

 

 

 

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