Paul and Bascom,
Thanks again for such a fabulous amp. I have been investigating different types of tubes for use in the BHK 250. I have tried various 7308’s, 6DJ8 (ECC88) and 7DJ8 with various levels of satisfaction. I must say the 7DJ8 seem to my ears to be the most resolved, best ambient info conveyed and the most seductive and accurate tonality of them all. The tube just sounds real. Today a package arrive with a pair of GE5670 with customer-made 6922 adapters. These are referred to as a direct drop-in replacement for all current production 6922 Valves. They are manufactured by IFI Audio, the actual tubes are General Electric 5670 that have been thermally treated to rejuvenate the valves. Do you have any concerns with using these in the BHK 250?
Paul and Bascom,
I’m certainly not Paul or Bascom or even one who has any business giving advice but everything you said after “today a package arrive…” sounds a bit scary. Why take a chance?
Harry, please let us know how they sound in your bhk250. Thx!
My only concern with be the height of the adapter and tube. I looked in my amp and it looks like it might have enough space for it. Let us know how they sound!
I’ve got 2 pairs of these and have tried 1 pair in 1 of my BHK-250s. They worked ok. In my system and to my ears, they didn’t beat the stock tubes during my admittedly limited trial (which might not have been sufficiently long for the tubes to break in). I need to try them again.
AND I’m curious what you’ll have to say.
Greg in Mississippi
P.S. I should add that IF one is running their BHK-250 through one of the recent PS Audio regenerators (P5 / P10 / P12 / P15 / P20), try various levels of Multiwave. Again, to my ears and in my setups, I prefer a moderate amount of Multiwave with these amps, about 2-3 on the P10s and so far, 3-4 on the just received P15s. I had tried Multiwave on my previous amps, either Hypex NC400 or IcePower-based ones and none of them sounded better with Multiwave.
On the BHK-250, I hear a nice little bump in bass impact and dynamics, along with a smidge more midrange body. BUT don’t overdo it!
Thanks for the replys from everyone, I plan to do some burn-in and listening over the next few weeks and will report.
I also made some measurements of the typical tubes I have been using, in relation to tube overall height.
IFI Audio GE5670 first two tubes from the left in photo. Tube base to top 2.014".
E188CC/7308 Third tube from left. Tube base to top 1.9140".
Genalex E88CC (stock tube) Fouth tube from left. Tube base to top 1.9140".
Tungsram PCC88/7DJ8 Fifth tube from left. Tube base to top 1.9120".
So it looks like the GE5670’s are a bit taller but should fit.
I used the ifi in the BHK250 for about a month with no problems , I took them out as the tubes made the power amp sound very laid back , softer with a bit less punch in the bass .
I then tried them in the pre and same again after 4 weeks I removed them the mids were nice clear but the bass was a little to soft for me the forward dynamic range had dropped . Now my friend he much preferred the sound when I asked to listen and give me views so it is down to you to try them you may like what you hear .
Thanks for your insights shihan
Can I ask about the heater current capability of the amp, 6922 require 300mA for the heater, how much can the amp support? Would 600mA be possible? or more?
Falling_leaves, that would be a question for Paul or Bascom, a 6DJ8/6922/7DJ8 requires 300mA and the 6570’s [edit: GE5670] require 370mA not sure what the BHK 250 heater current max is?
Paul or Bascom
I’ll try and joggle Bascom
If my memory serves me correctly, The heater supply regulator drops out with a 120V line at about 1.2A and sooner for a lower AC line voltage. This theoretically would allow for a pair of 600 mA tubes in the limit.
However, your mention of a 6570, that is a photo tube! And not workable as a twin triode like the 6922 genre.
So why don’t you look again at the number of the tube you want to know about.
The tube type was mistyped its GE5670 which require 370mA.
Checking the characteristic curves for the 5670 for a supply voltage of 120V and 10K plate loads and a plate current of 5 mA indicates a grid bias of about 0 volts. This would work but could draw some grid current causing the input impedance to drop. You could try it and see, who know, it could sound OK.