Do the 3C24/35T sound any good at less than half their rated anode dispersion?

toshiba_nz · 2024-07-18 12:55 am

I read here some peeps running 3c24 at 400V / 15ma - less than half of the rated anode dispersion...would these tubes:

1. Sound any good there?
2. Live very long there?
3. Be all good

Fuling · 2024-07-18 1:16 am

I've never been in the same room as a 3C24 so I can't say anything about the sound but post #13 in this thread mentions the need to run the plates hot:
https://www.diyaudio.com/community/threads/3c24se-amp.119368/

jan.didden · 2024-07-18 8:08 am

You mean dissipation, not dispersion?

Jan

andyjevans · 2024-07-18 9:17 am

Sometimes the unexpected works. I'm running my 6C4C (2a3 type) driver tube at 15mA, where it sounded better than at 18mA. I guess just try it and listen.

Zoran · 2024-07-18 9:47 am

toshiba_nz said:
I read here some peeps running 3c24 at 400V / 15ma - less than half of the rated anode dispersion...would these tubes:

1. Sound any good there?
2. Live very long there?
3. Be all good

1. not lightly as power amplifier
2. yes
3. Not
.
this is power DH triode. Ususaly run as A2 class with grid current.
3C24 has very high Ri, and needs good output transformer with high primary inductance to have close to decent bass... 🙁
.
As preamplifierm it could be used BUT then high amplification factor of about 25 could be the problem. Because sources has about 2Vrms outputs, that is about 6Vp-p to the grid of 3C24.
In that case -3V is minimum value for the bias point...
Again High output resistance of about 10K ohms from preamp because of high Ri. maybe it is too week to drive alone next stage?
And 6vp-p x 25 = 150Vp-p on the output of preamp when pot is in max with 2Vrms input...
.
As a driver, again high output resitance could be the issue to drive next input capacitances...
.
here are the spice models based on diy audio members. Could be useful for further steps?
2 spice models are in code window, one model for DHT and same for classic triode.
cheers

Code:

****  ** Composite DHT with Advanced Grid Current **************
* Created on 07/18/2024 10:05 using paint_kit.jar 3.1
* www.dmitrynizh.com/tubeparams_image.htm
* Plate Curves image file: /Users/zoran/Desktop/Model_Paint_Tools/Graph/
* Data source link:
*----------------------------------------------------------------------------------
.SUBCKT 3C24_DHT 1 2 3 4 ; P G K1 K2
+ PARAMS: CCG=2.8P  CGP=2.1P CCP=1P RFIL=2.1
+ MU=26 KG1=7038.69 KP=200 KVB=1140 VCT=-1.25 EX=1.53
+ VGOFF=-1.772 IGA=0.0025 IGB=0.0935 IGC=0.35 IGEX=1.823
* Vp_MAX=600 Ip_MAX=27 Vg_step=0.5 Vg_start=0 Vg_count=11
* Rp=30000 Vg_ac=3 P_max=25 Vg_qui=-3 Vp_qui=400
* X_MIN=77 Y_MIN=119 X_SIZE=645 Y_SIZE=742 FSZ_X=1573 FSZ_Y=978 XYGrid=true
* showLoadLine=y showIp=y isDHT=y isPP=n isAsymPP=n showDissipLimit=y
* showIg1=y gridLevel2=y isInputSnapped=n
* XYProjections=y harmonicPlot=y dissipPlot=y
*----------------------------------------------------------------------------------
RFIL_LEFT    3  31 {RFIL/4}
RFIL_RIGHT   4  41 {RFIL/4}
RFIL_MIDDLE1 31 34 {RFIL/4}
RFIL_MIDDLE2 34 41 {RFIL/4}
E11 32 0  VALUE={V(1,31)/KP*LOG(1+EXP(KP*(1/MU+V(2,31)/SQRT(KVB+V(1,31)*V(1,31)))))}
E12 42 0  VALUE={V(1,41)/KP*LOG(1+EXP(KP*(1/MU+V(2,41)/SQRT(KVB+V(1,41)*V(1,41)))))}
RE11 34 0 1G
G11 1 31 VALUE={(PWR(V(32),EX)+PWRS(V(32),EX))/(2*KG1)}
G12 1 41 VALUE={(PWR(V(42),EX)+PWRS(V(42),EX))/(2*KG1)}
RCP1 1 34 1G
C1 2 34 {CCG} ; CATHODE-GRID
C2 2 1 {CGP} ; GRID=PLATE
C3 1 34 {CCP} ; CATHODE-PLATE
RE2 2 0 1G
EGC1 81 0 VALUE={V(2,31)-VGOFF} ; POSITIVE GRID THRESHOLD
GG1 2 31 VALUE={0.5*(IGA+IGB/(IGC+V(1,31)))*(MU/KG1)*(PWR(V(81),IGEX)+PWRS(V(81),IGEX))}
EGC2 82 0 VALUE={V(2,41)-VGOFF} ; POSITIVE GRID THRESHOLD
GG2 2 41 VALUE={0.5*(IGA+IGB/(IGC+V(1,41)))*(MU/KG1)*(PWR(V(82),IGEX)+PWRS(V(82),IGEX))}
.ENDS 3C24_DHT
*$

 
****  ** Advanced Grid Current **********************************
* Created on 07/18/2024 10:06 using paint_kit.jar 3.1
* www.dmitrynizh.com/tubeparams_image.htm
* Plate Curves image file: /Users/zoran/Desktop/Model_Paint_Tools/Graph/
* Data source link:
*----------------------------------------------------------------------------------
.SUBCKT 3C24 1 2 3 ; Plate Grid Cathode
+ PARAMS: CCG=2.8P  CGP=2.1P CCP=1P
+ MU=26 KG1=7038.69 KP=200 KVB=1140 VCT=-1.25 EX=1.53
+ VGOFF=-1.772 IGA=0.0025 IGB=0.0935 IGC=0.35 IGEX=1.823
* Vp_MAX=600 Ip_MAX=27 Vg_step=0.5 Vg_start=0 Vg_count=11
* Rp=30000 Vg_ac=3 P_max=25 Vg_qui=-3 Vp_qui=400
* X_MIN=77 Y_MIN=119 X_SIZE=645 Y_SIZE=742 FSZ_X=1573 FSZ_Y=978 XYGrid=true
* showLoadLine=y showIp=y isDHT=n isPP=n isAsymPP=n showDissipLimit=y
* showIg1=y gridLevel2=y isInputSnapped=n 
* XYProjections=y harmonicPlot=y dissipPlot=y
*----------------------------------------------------------------------------------
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 3C24
*$

Zoran · 2024-07-18 9:48 am

3C24 is totally different tube than 2A3 types. By parameters and construction. Cant be compared in any way...

Zoran · 2024-07-18 9:56 am

For positive grid current You can use this models for 3C24

Code:

****  ** Composite DHT with Advanced Grid Current **************
* Created on 07/18/2024 09:45 using paint_kit.jar 3.1
* www.dmitrynizh.com/tubeparams_image.htm
* Plate Curves image file: /Users/zoran/Desktop/Model_Paint_Tools/Graph/
* Data source link:
*----------------------------------------------------------------------------------
.SUBCKT DHT__A2 1 2 3 4 ; P G K1 K2
+ PARAMS: CCG=2.8P  CGP=2.1P CCP=1P RFIL=2.1
+ MU=22.77 KG1=7650.75 KP=1500 KVB=1140 VCT=0.05 EX=1.515
+ VGOFF=-1.772 IGA=0.0025 IGB=0.0935 IGC=0.35 IGEX=1.823
* Vp_MAX=700 Ip_MAX=250 Vg_step=10 Vg_start=100 Vg_count=13
* Rp=4000 Vg_ac=55 P_max=25 Vg_qui=-50 Vp_qui=300
* X_MIN=85 Y_MIN=103 X_SIZE=516 Y_SIZE=613 FSZ_X=1701 FSZ_Y=852 XYGrid=true
* showLoadLine=y showIp=y isDHT=y isPP=n isAsymPP=n showDissipLimit=y
* showIg1=y gridLevel2=y isInputSnapped=n
* XYProjections=y harmonicPlot=y dissipPlot=y
*----------------------------------------------------------------------------------
RFIL_LEFT    3  31 {RFIL/4}
RFIL_RIGHT   4  41 {RFIL/4}
RFIL_MIDDLE1 31 34 {RFIL/4}
RFIL_MIDDLE2 34 41 {RFIL/4}
E11 32 0  VALUE={V(1,31)/KP*LOG(1+EXP(KP*(1/MU+V(2,31)/SQRT(KVB+V(1,31)*V(1,31)))))}
E12 42 0  VALUE={V(1,41)/KP*LOG(1+EXP(KP*(1/MU+V(2,41)/SQRT(KVB+V(1,41)*V(1,41)))))}
RE11 34 0 1G
G11 1 31 VALUE={(PWR(V(32),EX)+PWRS(V(32),EX))/(2*KG1)}
G12 1 41 VALUE={(PWR(V(42),EX)+PWRS(V(42),EX))/(2*KG1)}
RCP1 1 34 1G
C1 2 34 {CCG} ; CATHODE-GRID
C2 2 1 {CGP} ; GRID=PLATE
C3 1 34 {CCP} ; CATHODE-PLATE
RE2 2 0 1G
EGC1 81 0 VALUE={V(2,31)-VGOFF} ; POSITIVE GRID THRESHOLD
GG1 2 31 VALUE={0.5*(IGA+IGB/(IGC+V(1,31)))*(MU/KG1)*(PWR(V(81),IGEX)+PWRS(V(81),IGEX))}
EGC2 82 0 VALUE={V(2,41)-VGOFF} ; POSITIVE GRID THRESHOLD
GG2 2 41 VALUE={0.5*(IGA+IGB/(IGC+V(1,41)))*(MU/KG1)*(PWR(V(82),IGEX)+PWRS(V(82),IGEX))}
.ENDS
*$



 
****  ** Advanced Grid Current **********************************
* Created on 07/18/2024 09:45 using paint_kit.jar 3.1
* www.dmitrynizh.com/tubeparams_image.htm
* Plate Curves image file: /Users/zoran/Desktop/Model_Paint_Tools/Graph/
* Data source link:
*----------------------------------------------------------------------------------
.SUBCKT TRIODE_ 1 2 3 ; Plate Grid Cathode
+ PARAMS: CCG=2.8P  CGP=2.1P CCP=1P
+ MU=22.77 KG1=7650.75 KP=1500 KVB=1140 VCT=0.05 EX=1.515
+ VGOFF=-1.772 IGA=0.0025 IGB=0.0935 IGC=0.35 IGEX=1.823
* Vp_MAX=700 Ip_MAX=250 Vg_step=10 Vg_start=100 Vg_count=13
* Rp=4000 Vg_ac=55 P_max=25 Vg_qui=-50 Vp_qui=300
* X_MIN=85 Y_MIN=103 X_SIZE=516 Y_SIZE=613 FSZ_X=1701 FSZ_Y=852 XYGrid=true
* showLoadLine=y showIp=y isDHT=n isPP=n isAsymPP=n showDissipLimit=y
* showIg1=y gridLevel2=y isInputSnapped=n 
* XYProjections=y harmonicPlot=y dissipPlot=y
*----------------------------------------------------------------------------------
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
*$

Zoran · 2024-07-18 10:10 am

with this spice model for A2
some fast determinate working point for about 4W output
.
BUT plesae note thet RI is very very high value about 8.5K ohms
needs very complicated OT with huge number of turns for primary...
(2A3 has 0.6K ohms cca.)

toshiba_nz · 2024-07-18 10:13 am

Thanks everyone.

Was thinking of trying it (35T) in A1 with a CCS (10M90) , anode 300V, direct coupled to a mosfet Phase Inverter.

Zoran · 2024-07-18 11:42 am

Page link for measured chrs of 3C24
https://www.diyaudio.com/community/...ut-tube-for-lundahl-ll9202-50ma.369428/page-5

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Do the 3C24/35T sound any good at less than half their rated anode dispersion?

toshiba_nz

Fuling

jan.didden

andyjevans

Zoran

Zoran

Zoran

Zoran

toshiba_nz

Zoran

Do the 3C24/35T sound any good at less than half their rated anode dispersion?

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