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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

Thanks for the reply guys. I'm quite happy with my Sigma/404 but in the future might try. bwck2000, how do you get a dust free environment? You have an access to a clean room or simply a thorough cleaning of the working area is enough?

A-ha! So it is possible to fit newer drivers than 404 into Sigmas? I was recently redoing my Sigmas and was told 404 is the last driver that fits.

I second Zolkis findings. Have followed his instructions, first modded original 007 pads then 009 pads and no way back. In 2 words - increased immediacy.

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

Awright, so seems there is no issue and my amp behaves like it should. Thank you gentlemen for your help. PS Damn gooood amp!

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

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.

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

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!

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

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?

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

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.

Hi guys, Sorry if this has been asked already: I rebiased a set of new tubes as per Justins instructions in a 4h session. Then after powering the amp again after few days the gain drifted away again to -27V and stays there unless I rebias again. Is that normal? I guess I dont need to rebias everytime I power it up? Another Q: Are the 2A and 0,2A fuses fast or slow blow? I wanted to try some nice silver ones. Thanks in advance!

Thank you Spritz, but I think I'll go the Lambda route. All those older drivers seem not available anyway so finding a donor Lambda or better Lambda Sig seems the most effective way.

Looks like problem solved: "No this isn´t possible the new driver frame don´t fit in the Sigma housing. Last drivers they work was from the Lambda SR-202/303/404 series." Soeren from Inexxon.de Looks like transplantation is the only way. Anyone has a spare Lambda Signature to sell :) ? Cheers

Let me resurrect this ancient thread. Will L700 or L500 drivers fit Sigma's? Has anyone tried this mod or know someone who can do that in EU? I have a pair of NB Sigma's that I want to convert to Pro to enjoy with BHSE. Cheers, Jarek

Hahaha It's their way of quantifying when the tube starts to distort. This is what Brent Jessee says: "The hardness is actually the plate current draw of the tube when under full operating voltages for the plate, screen grid, and with negative grid bias applied at the proper voltage" What plate current correspond to their "hardness" they however do not disclose as its their commercial secret. Only the higher the "hardness" the higher the plate current. The Shuguangs I inherited my BHSE with were rated 30mA but unfortunately gave up the ghost. PS Impressively made amp, Justin! Great job!

Thank you Kerry! A follow up question: Did anyone compare different hardness of Groove Tubes in BHSE? I found only few posts of people who tried them but no mention on the hardness. I can get number 7 quad, higher seems very rare. Thanks!

Hi all, Just joined the BHSE club acquiring a nice early specimen with the serial number #34 After some research here and on head-fi started to look for a set of good tubes. Here comes a question: There is a big variation in plate current in the EL34 kingdom from specimen to specimen. Since the output tubes are current sourced and sinked, is there a risk of burning the source/sink with a tube with a high plate current? For example Groove Tubes labels their EL34M according to their hardness parameter from 1 to 10 with the highest numbers being the most linear but as far as I understand drawing the most plate current. I'm looking for them (was advised the 7-9 range) but started wondering if too strong a tube can possibly burn its current source/sink? Thank you in advance for any input!