This site offers 12 months warranty and a certificate from original factory, some offers nothing beside the tube so be sure to look for these protection before you buy.
Shuguang 12BH7 Don't match new vacuum tube
Shuguang 12BH7 Don't match new vacuum tube
Here is model for TAD 12bh7a-str, and comparison with GE.
Code:
**** 12BH7A_STR ** Advanced Grid Current **********************************
* Created on 08/24/2020 14:31 using paint_kit.jar 3.1
* [URL="http://www.dmitrynizh.com/tubeparams_image.htm"]www.dmitrynizh.com/tubeparams_image.htm[/URL]
* Plate Curves image file: 12bh7a-str.png
* Data source link:
*----------------------------------------------------------------------------------
.SUBCKT 12BH7A_STR 1 2 3 ; Plate Grid Cathode
+ PARAMS: CCG=2.9P CGP=2.5P CCP=0.5P
+ MU=18.02 KG1=945.75 KP=185.4 KVB=1247.69 VCT=-0.6206 EX=1.181
+ VGOFF=-1.03 IGA=8.2E-4 IGB=0.162 IGC=6.624 IGEX=1.3
* Vp_MAX=500 Ip_MAX=16 Vg_step=2.5 Vg_start=5 Vg_count=12
* Rp=4000 Vg_ac=55 P_max=3.5 Vg_qui=-48 Vp_qui=300
* X_MIN=279 Y_MIN=106 X_SIZE=857 Y_SIZE=593 FSZ_X=1618 FSZ_Y=918 XYGrid=true
* showLoadLine=n showIp=y isDHT=n isPP=n isAsymPP=n showDissipLimit=y
* showIg1=y gridLevel2=y isInputSnapped=n
* XYProjections=n harmonicPlot=n dissipPlot=n
*----------------------------------------------------------------------------------
E1 7 0 VALUE={V(1,3)/KP*LOG(1+EXP(KP*(1/MU+(VCT+V(2,3))/SQRT(KVB+V(1,3)*V(1,3)))))}
RE1 7 0 1G ; TO AVOID FLOATING NODES
G1 1 3 VALUE={(PWR(V(7),EX)+PWRS(V(7),EX))/KG1}
RCP 1 3 1G ; TO AVOID FLOATING NODES
C1 2 3 {CCG} ; CATHODE-GRID
C2 2 1 {CGP} ; GRID=PLATE
C3 1 3 {CCP} ; CATHODE-PLATE
RE2 2 0 1G
EGC 8 0 VALUE={V(2,3)-VGOFF} ; POSITIVE GRID THRESHOLD
GG 2 3 VALUE={(IGA+IGB/(IGC+V(1,3)))*(MU/KG1)*(PWR(V(8),IGEX)+PWRS(V(8),IGEX))}
.ENDS
*$Attachments
I wouldn't say they don't put their name on it because they are so bad. I bought multiple tubes from China (quad matched set EL34B matched pair EL34L matched pair 6L6GC matched pair KT98 (essentially 88) 6SN7 and a 12AX7 none of the tubes were horrible and or incredibly out of match...infact all the power tubes including the EL34L which I bought as "no print Mullard replica" have been tortured and they still work great
I did see KT90, KT94 and KT99 (from the numbers from 90 to 99) before, but I never saw a KT98. Could you post a photo of yours, or a link to one on the web?
I found it: RS PRO Pentode Thermionic Valve, Octal Base, 42W, 6.3V, 52 (Dia.) x 125mm | RS Components
Number somemany in the KT series.
Number somemany in the KT series.
Shuguang KT88-98 Audio Tubes - www.thetubestore.com
Please keep to the topic.
Anyone has an idea what would be the ideal plate load for the 12BH7 in PP ? (Single tube PP)
And if 12bh7 won't cut it I'm sure the ECC99 will
Please keep to the topic.
Anyone has an idea what would be the ideal plate load for the 12BH7 in PP ? (Single tube PP)
And if 12bh7 won't cut it I'm sure the ECC99 will
Have a look at Tube-Town Store - TT Kit Molly
It uses a single ECC99 in a PP connection delivering 4w
I actually build one ( just for fun of it) see : Bygg en Molly for
pictures and a glimt of schematics.
It was finally donated to a upcoming young guitar hero.
Tubetown has transformers if you need a source
It uses a single ECC99 in a PP connection delivering 4w
I actually build one ( just for fun of it) see : Bygg en Molly for
pictures and a glimt of schematics.
It was finally donated to a upcoming young guitar hero.
Tubetown has transformers if you need a source
As usual for triode PP power stages, 2*(3..5*Rp)
Rp is about 5.5k for 12BH7, 3k for 5687, 2.3k for ECC99, 1.8k for 6N6P, 1.6k for E182CC, 1.2k for 6N30P
I wouldn't be quite as concerned about an unbranded tube as one that had no tube type printed on it.
Tube manufacturers often sold tubes that had other companies names on them if they were a large customer. But, those manufacturers also sold the same tube with their own name on it and they always had the tube number, regardless of branding. Even the unbranded Chinese 12AX7s I bought years ago had the tube number on them.
Perhaps Shuguang made these for another company and the order was cancelled. We'll probably never know.
But why no tube number? That's just weird.
The only other similar size tube with similar amplification factor I can think of would be a 6CG7 / 6FQ7 but the pinouts are different so that doesn't make sense either.
If the ideal primary for a single 12BH7 with the sections in parallel is 10.75k it would seem that each section would like to see 21.5k.
Have you measured your prospective OTs? What is the turns ratio / primary impedance per plate with your intended speaker load?
I've read that the ECC99s are very similar to the 12BH7 but I haven't compared them closely. I did come across this statement about them, in relation to using them in a guitar amp . . . but who knows if it's accurate:
"JJ ECC99s . . . make a great power tube in push pull or parallel SE with a primary around 11k per triode."
That would seem to indicate that they are not that similar, though, if they like 11k per triode vs 21.5k for the 12BH7.
Attached is the output impedance for 12bh7a-str and various quiescent point with HT 270V. I noticed that Z is higher when compared to another model. But you can use these operating points as guide and go follow the steps in トランス結合 １２BH７A パラ PP アンプ （３） : まほろば 写真俳句 as it has PP model to design your own loadline to suit your OT.
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Yeah that one looked promising.. Is it really the ideal plate load tho? My only concern is the output transformer. Im srue it will work no doubt but I want to wind something for myself and that gives me an opppurtunity to really make into something more precise
I wish I could read chinese.. I have no idea what the site is about I just see a couple interesting looking graphs.
Triodes don't have "ideal" load, unlike multigrid tubes.
Anything above 2*Rp (4*Rp for push-pull) will do. The higher the load, the more linearity and damping you gain and the more power you loose. It's your choice where to stop.
You can Google to translate foreign language. Anyhow hope you can read other article to boost your knowledge which is advantage to yourself. You can just wire up a PP amp even you don't fully understand how it works. I have put together a circuit using Hammond 125B OT, it has 22500 Ohms anode to anode resistance (Ra-a=22500) when the secondary load is 8 Ohms. The 2 tubes in PP bias at -10V (which is lower Z than 22500), the output is shown as attached. For maximum power output the combined tube output Z should be at least equal to Ra-a/4 for Class B amp or Ra for Class A of the OT (loadline), Read: Plate load for push-pull
https://www.mouser.com/datasheet/2/177/125a-125e-1389927.pdf
https://www.mouser.com/datasheet/2/177/125a-125e-1389927.pdf
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Use published datasheets to draw and optimize your load lines.
EDIT:
That´s Japanese 🙂
EDIT 2: and as koonw suggested, you can google translate it.:
Google Translate
Not surprisingly , they solve it using the graphic method I suggested earlier ... simply because it´s the most straightforward one.
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TG,
Post # 35.
Thanks!
What a nice kernel of truth you put up.
What does the designer most want:
Lowest distortion at lowest power, highest damping factor?
Highest Power, highest distortion, lowest damping factor?
Or somewhere between those extremes?
The simplicity of no negative feedback?
The complications of negative feedback?
"All Generalizations Have Exceptions" - Me
Post # 35.
Thanks!
What a nice kernel of truth you put up.
What does the designer most want:
Lowest distortion at lowest power, highest damping factor?
Highest Power, highest distortion, lowest damping factor?
Or somewhere between those extremes?
The simplicity of no negative feedback?
The complications of negative feedback?
"All Generalizations Have Exceptions" - Me
Post 35 sure does clear things up
Post #38
I am looking for mostly power. The distortion won't really be a big deal in the bind of stuff I want to use this in. Maybe something nice for a headphone amp but who know..maybe that distortion will end up sounding "nice". But for a headphone amp I sure don't need a couple of watts...that would be more like deafening factor than anything else.
I'm sort of leaning towards the ECC99 option right now than the 12BH7.
Post #38
I am looking for mostly power. The distortion won't really be a big deal in the bind of stuff I want to use this in. Maybe something nice for a headphone amp but who know..maybe that distortion will end up sounding "nice". But for a headphone amp I sure don't need a couple of watts...that would be more like deafening factor than anything else.
I'm sort of leaning towards the ECC99 option right now than the 12BH7.