Hi James,
I did not build a KT88 Baby Huey. It can be daunting to read through this long thread to find the corrected values for components. But the recent GB by Algar-emi of the EL34BH PCB Mk2 and PSU Mk2 did a good job to collect most changes that evolved over time. You can find that BOM for both Amp and PSU here:
GB: EL34 Baby Huey Amp and PSU MK2 PCB
Amp:
There are a few additional changes proposed by gingertube which I would check against the above BOM. See post #755-757.
https://www.diyaudio.com/forums/tubes-valves/326920-el34-baby-huey-amplifier-76.html#post6151577
Personally I would try a R13 value of 16k-24k for KT88s (preferably adjustable by adding parallel resistors), but I hope someone who built a KT88 BH would chip in here. I believe a BH using EL34 and one using KT88 tubes use essentially the same component values, only difference is the power supply that needs to proved more current and possibly higher voltage, and the bias adjustment for the power tubes.
PSU:
If you have the corrected (MOSFET leads) PSU PCB Mk2 you are fine, else heed the fix discussed a few posts earlier here. Same for the values of R1, R2 and R6.
Hope this helps. Good luck.
P.S. Did I forget something BH people? Probably did. Please help.
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Bfpca suggested not to chase power per se, but to keep an eye to the tone, and in his experience 400V gives less power but better tone than 450 or 500V.
If you are still interested in absolute power, higher voltages (or parallel another pair of tubes) is the easiest way.
Be aware that 550V and 630V PSU caps are more rare and expensive, and most probably won't fit in the standard board, so you'll need to arrange an off-board setup.
IIRC with KT88 and 500V B+ it is needed around 55V for bias, -150V and +50V for the driver and a 4 kOhm Raa transformer. Again, maximum power can be obtained if you reduce UL from 40 to something less.
But IMHO maximum power only, is not the best goal to chase.
If you are still interested in absolute power, higher voltages (or parallel another pair of tubes) is the easiest way.
Be aware that 550V and 630V PSU caps are more rare and expensive, and most probably won't fit in the standard board, so you'll need to arrange an off-board setup.
IIRC with KT88 and 500V B+ it is needed around 55V for bias, -150V and +50V for the driver and a 4 kOhm Raa transformer. Again, maximum power can be obtained if you reduce UL from 40 to something less.
But IMHO maximum power only, is not the best goal to chase.
Thank you for the reply and information.
My response was probably not the best since I was in a hurry with it.
I look at this as “almost” a guitar amplifier in the build faze. What obviously changes it the frequency range need for music reproduction. So to that end, to me that is where the difference comes in. So I am going to shoot for the highest wattage without compromising on overall sound quality.
As for the needed parts, I like to build things I can be proud of, work as they should, last a long time and not need to go back in changes components later down the road. So for that if I have to spend the money on say Vishay MKP’s or anything like that, that will be the road I take.
I completely agree with you on the parts layout, as in the parts I want to use may not fit the board. So if that is the case mine might be a hybrid of a point to point and PCB. I have both versions of the board on the way and have point to point boards in my office that can be used.
Thanks again, James
My response was probably not the best since I was in a hurry with it.
I look at this as “almost” a guitar amplifier in the build faze. What obviously changes it the frequency range need for music reproduction. So to that end, to me that is where the difference comes in. So I am going to shoot for the highest wattage without compromising on overall sound quality.
As for the needed parts, I like to build things I can be proud of, work as they should, last a long time and not need to go back in changes components later down the road. So for that if I have to spend the money on say Vishay MKP’s or anything like that, that will be the road I take.
I completely agree with you on the parts layout, as in the parts I want to use may not fit the board. So if that is the case mine might be a hybrid of a point to point and PCB. I have both versions of the board on the way and have point to point boards in my office that can be used.
Thanks again, James
Which of the experts has the time and the desire to work on a wiki for EL34 Baby Huey in which the most important changes / assembly tips are summarized? also about shopping tips and reference for OPT in USA / Europe etc., adaptation when using different types of tubes, technical mods, etc.,
I think that will help many DIY enthusiasts and save a lot of inquiries and search in the forum that continues to expand!
I've already started but my english is bad, I mostly use the translator
the beginning has been made: ;-)
Header:EL34 Baby Huey Amplifier
Instructions for the wiki can be found here:
Main Page
I think that will help many DIY enthusiasts and save a lot of inquiries and search in the forum that continues to expand!
I've already started but my english is bad, I mostly use the translator
the beginning has been made: ;-)
Header:EL34 Baby Huey Amplifier
Instructions for the wiki can be found here:
Main Page
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I did it partially time ago on my thread for my own version of BH Slowly building three Baby Huey EL84 - with notes
Zintolo,
I just took a quick look at your thread and yes indeed it has a lot of notes. I subscribed to it, so I can go back and read through it.
As for me using KT88's; that is now up in the air since I cannot find 4 NOS tubes without spending a tom of money. So I am going to keep searching for some, but if I cannot find any within a month or so I will find a different tube to use and plow forward.
I just took a quick look at your thread and yes indeed it has a lot of notes. I subscribed to it, so I can go back and read through it.
As for me using KT88's; that is now up in the air since I cannot find 4 NOS tubes without spending a tom of money. So I am going to keep searching for some, but if I cannot find any within a month or so I will find a different tube to use and plow forward.
mlackey,
I noticed that you also posted in Algar_emi’s group buy.
GB: EL34 Baby Huey Amp and PSU MK2 PCB
That is the most recent GB concluded but Algar_emi mentioned in that thread that he may do a repeat if enough interest is evident. You may want to send him a PM.
Or do a WTB in the Swap Meet forum. There are some folks with unused PCBs that might be willing to sell.
I noticed that you also posted in Algar_emi’s group buy.
GB: EL34 Baby Huey Amp and PSU MK2 PCB
That is the most recent GB concluded but Algar_emi mentioned in that thread that he may do a repeat if enough interest is evident. You may want to send him a PM.
Or do a WTB in the Swap Meet forum. There are some folks with unused PCBs that might be willing to sell.
I run a pair of Mullard XF2 duel halo getters in my Marshall 50 clone I made and love them. And yes, they are a lot easier to find.
Is it the Mk2 Rev 1.5-1 that needs the fix? The Mk2 Rev 2.0 is the fixed version? Trying to determine which one I have for sure, but I think it needs the “fix” Gingertube detailed.
it is easier to turn gate and source on the mosfet,
https://www.diyaudio.com/forums/tubes-valves/351919-oh-baby-huey-el84-build-23.html#post6675749
https://www.diyaudio.com/forums/tubes-valves/351919-oh-baby-huey-el84-build-23.html#post6675749
Attachments
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Yes, I did post in the aforementioned thread, , but did not have much hope as that seemed to have occurred earlier, not current. Thank you very much for the reply, I will pursue those options.
I just recently ordered 2 sets of these boards, one set is the original PCB with the power supply on the board (if you so choose) and a set of the newest version.
If you are interested in the original PCB's I can sell them to you for what I paid for them.
Are in CONUS? This reason I ask is I would prefer to sell them to someone in CONUS.
James
If you are interested in the original PCB's I can sell them to you for what I paid for them.
Are in CONUS? This reason I ask is I would prefer to sell them to someone in CONUS.
James