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NEW D3a equivalent on market?

Dear Friends,

I wonder if there is a equivalent new D3A tube on marked?
It´s difficult and expensive to get an original D3A tube. There seemed to be nice NOS 6J52P tubes for which some people say that they are quite near the legendary D3A. I love NOS tubes but it´s not predictable to get them in reliable condition and price.

I would like to use the D3A as the first stage in a Phono preamp.

best regards
Karsten
 
dear billshurv,

Thanks a lot for the link!
Yes, you are right. The major parameter is low noise and high gain for which I want to use a pentode in triode mode. The starting schematic ist these wonderfull arrangement from SY described in his amazing article "His master.."

regards
Karsten
 

Koonw

Member
2013-04-09 9:37 pm
Some say you can use 6f12p instead of DA3. I just almost completed sim with 2 models, one painted myself and one from the net. The overall gain is 1700X or 17dbs, cathode fully bypassed. Here are the models, if you're interested to sim futher and share the result noise level etc, I can upload the source asc. I have clean up floor noise in FFT sim result as attached.

A) Pentode Section
**** 6F12PI_P ******************************************
* Created on 02/07/2016 22:40 using paint_kip.jar
* Model Paint Tools: Trace Tube Parameters over Plate Curves, Interactively
* Plate Curves image file: 6f12pi-p.png
* Data source link: <plate curves URL>
*----------------------------------------------------------------------------------
.SUBCKT 6F12P-P 1 2 3 4 ; P G K G2
+ PARAMS: CCG=6.6P CGP=1.4P CCP=1.9P RGI=1030
+ MU=112 KG1=101.8 KP=361.1 KVB=1.92 KVC=1.6 VCT=0.00863 EX=0.664 KG2=12
* Vp_MAX=320 Ip_MAX=37.5 Vg_step=0.5 Vg_start=0 Vg_count=8
* Rp=1600 Vg_ac=23.5 P_max=5 Vg_qui=-23.4 Vp_qui=240 UL=0.43 EG2=120
* X_MIN=102 Y_MIN=74 X_SIZE=699 Y_SIZE=646 FSZ_X=1359 FSZ_Y=856 XYGrid=true
* showLoadLine=n showIp=y isDHP=n isPP=n isAsymPP=n isUL=n showDissipLimit=y
* showIg1=n gridLevel2=n isInputSnapped=n
* XYProjections=n harmonicPlot=y harmonics=y
*----------------------------------------------------------------------------------
RE1 7 0 1G ; DUMMY SO NODE 7 HAS 2 CONNECTIONS
E1 7 0 VALUE= ; E1 BREAKS UP LONG EQUATION FOR G1.
+{V(4,3)/KP*LOG(1+EXP((1/MU+(VCT+V(2,3))/V(4,3))*KP))}
G1 1 3 VALUE={(PWR(V(7),EX)+PWRS(V(7),EX))/KG1*ATAN(V(1,3)/KVB)}
* Alexander Gurskii screen current, see audioXpress 2/2011
RE2 8 3 1G ; Dummy
G2 8 3 VALUE={(PWR(V(7),EX)+PWRS(V(7),EX))/KG2*(KVC-ATAN(V(1,3)/KVB))}
E2 8 4 VALUE={0} ; Dummy
RCP 1 3 1G ; FOR CONVERGENCE
C1 2 3 {CCG} ; CATHODE-GRID 1
C2 1 2 {CGP} ; GRID 1-PLATE
C3 1 3 {CCP} ; CATHODE-PLATE
R1 2 5 {RGI} ; FOR GRID CURRENT
D3 5 3 DX ; FOR GRID CURRENT
.MODEL DX D(IS=1N RS=1 CJO=10PF TT=1N)
.ENDS
*$

B) Triode section

.SUBCKT 6F12P-T 1 2 3 ; P G C (Triode)
+ PARAMS: MU=112.5 EX= 1.66 KG1= 94 KP=760
+ KVB=12100.0 VCT= 0.00 RGI=4500
+ CCG=4.6P CGP=1.6P CCP=0.26P
E1 7 0 VALUE=
+{V(1,3)/KP*LN(1+EXP(KP*(1/MU+(V(2,3)+VCT)/SQRT(KVB+V(1,3)*V(1,3)))))}
RE1 7 0 1G
G1 1 3 VALUE={(PWR(V(7),EX)+PWRS(V(7),EX))/KG1}
RCP 1 3 1G ; TO AVOID FLOATING NODES IN MU-FOLLOWER
C1 2 3 {CCG} ; CATHODE-GRID;
C2 2 1 {CGP} ; GRID-PLATE;
C3 1 3 {CCP} ; CATHODE-PLATE;
D3 5 3 DX ; FOR GRID CURRENT
R1 2 5 {RGI} ; FOR GRID CURRENT
.MODEL DX D(IS=1N RS=1 CJO=10PF TT=1N)
.ENDS
 

Attachments

  • 6F12P RIAA FFT-1.png
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Last edited:
Hello euro21, Koonw.

Thanks for your answers.

Well, mainly I search for NEW, means actual manufactured "replacements" of a D3A. I know, there is no exact replacement but which small signal pentode will do the best replacement job in case of noise and amplification?

One of the current issues about new manufactured tubes seemed to be that there are only rough data are released. No one will give you information about tolerance of published data or noise. You can buy "selected" tubes from manufactors like JJ. But they said only "selected by anode current" what ever this means.

Regards
Karsten
 

kevinkr

Administrator
Paid Member
Might want to have a look at the 6J9P, 6J9P-E - they differ in significant ways from the D3A, (lower transductance) and offer a little more than half the mu when triode connected, however they are quiet and quite linear. They're also plentiful and cheap.

I got a bunch of 6J52P and found them to be an extraordinarily inconsistent tube with quality all over the place. I was not able to get consistent traces from tube to tube with my uTracer, and the results in circuit were not good either. And yet some people have reported very favorable results using them, apparently there were several makers and quality was very inconsistent. I guess I could have gotten bad tubes.
 
vibrational mode of the C3m

I was alarmed at the vibrational mode of the C3m as noted on the tavishdesign pages.
It reminds me of a preamp I had for years with a 6J6 in the front stage. It would ring when turning my 22-click/position potmeter - but at end-of-life it would even start metallic ringing for up to 5 or ten seconds on loud/dynamic passages. So this means: the C3m gets a big Nay from me . . . :eek:

I have used 6SJ7 with good results in a moving coil amplifier. Adding this tube to the comparison would be nice.
 
Last edited:
C3g and C3o can work, and I forgot another one, all cousins of the D3a

C3m should not ring , it was probably a defective tube, same for 6j6.

I don't think there will be the technology and money to develop a similar tube, the tube which sold for a lot of money in the times, now obsolete, could be sold for around 500US$ if produced now, equivalent of the price when produced with inflation.

The good news is that you don't need a pentode, there are similar triodes which are as good if you buy a couple and choose the less noisy you could excel the performance of the D3a in a phono first stage. 6922 and all the variations, I use a variation of the 6922. cannot complain with 0 feedback and perfect sound