All about electronic valves and hi-fi
It’s been a while indeed. Mostly busy with my day job and family. However, spare time is dedicated to synthesisers – I’m designing and building modules for Eurorack – and playing and listening to music.
I’ve been asked about the GU-50 triode curves. I have misplaced them, however I have something even better to share which is the accurate model created for this great valve.
It’s been a long and weird year with COVID-19. This evidently has kept me a bit distracted and changed priorities (as probably has done to you as well). Anyhow, here are the belated curves I was asked to publish.
The SRS-551 is a lovely powerful transmitting pentode from RTF. Similar (or close enough) to RS1003 and F3a. Much more accessible in price is the SRS-551. I have a nice stash of NOS valves somewhere lost in my attic storage. Either way, they sounded nice and could definitely live in my setup. The valve was intended for audio modulation in FM transmitters so it’s very reliable and linear device. Distortion was extremely low when I measured it but most importantly it could work really well with local feedback to squeeze out 14W in Single-Ended at nearly 490V/100mA bias point with an LL1623 OPT. The distortion was below 0.7% predominantly H2.
Some time ago I got hold of a nice stash of Telefunken EL152. These German pentodes are amazing. After playing with the RL12P35P and then obviously GU-50 (which is a copy of the LS-50), the EL152 was a nice valve to have at hand as it’s actually the LS-50 in a different bottle.
The B-10V socket is quite tricky as it seems like it was designed for the EL/FL-152 and similar Telefunken valves. Anyhow, managed to get some new ceramic ones to trace the curves and generate a Spice model. Hope you find this useful.
I really love the Ba DHT preamp, if you need the gain in your system, is likely to be one of the best sounding DHT preamps in my experience. As received many requests for the SPICE model for the Ba DHT, here it is:
**** Ba TRIODE Composite DHT *****************************************
* Created on 10/13/2017 18:33 using paint_kit.jar 2.9
* www.dmitrynizh.com/tubeparams_image.htm
*
* Traced and model by Ale Moglia valves@bartola.co.uk
* (c) 2017 Ale Moglia and Bartola Ltd. UK
* www.bartola.co.uk/valves
*———————————————————————————-
.SUBCKT DHT_Ba 1 2 3 4 ; P G K1 K2
+ PARAMS: CCG=1P CGP=3.8P CCP=1P RFIL=7
+ MU=14 KG1=8940 KP=84 KVB=5232 VCT=-3.5 EX=1.47 RGI=2000
* Vp_MAX=350 Ip_MAX=10 Vg_step=1 Vg_start=0 Vg_count=11
* Rp=4000 Vg_ac=55 P_max=1.5 Vg_qui=-48 Vp_qui=300
* X_MIN=75 Y_MIN=51 X_SIZE=492 Y_SIZE=530 FSZ_X=1192 FSZ_Y=679 XYGrid=false
* showLoadLine=n showIp=y isDHT=y isPP=n isAsymPP=n showDissipLimit=y
* showIg1=n gridLevel2=n isInputSnapped=n
* XYProjections=n harmonicPlot=n harmonics=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 32 0 1G
RE12 42 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
D3 5 3 DX ; FOR GRID CURRENT
D4 6 4 DX ; FOR GRID CURRENT
RG1 2 5 {2*RGI} ; FOR GRID CURRENT
RG2 2 6 {2*RGI} ; FOR GRID CURRENT
.MODEL DX D(IS=1N RS=1 CJO=10PF TT=1N)
.ENDS
*$
You can download the file here: Ba spice triode model
I’ve got hold of a NOS quartet of UX-120 Radiotron valves made in 1925. These are 95 year old beauties. Unbelievable how well conserved they are and operate.
This valve developed by RCA was the first output valve intended to be used with dry-cells (3 No. 6 cells in series). See the data sheet extract below:
There is no much data available on this valve, if you have some please share and let me know. Here are the curves I traced from a sample which measured 114%:
Here is a nice sharp cut-off RF pentode with low capacitance, high gm and nice curves: 6AG5.
I’ve got a set of teflon sockets from Jakeband. These are fantastically made to order. Luciano from Jakeband sent me in addition some samples which I will use in the eTracer which I will bring along to ETF.19.
Honestly, these are fine pieces of craftwork. For example, you can measure and let Luciano know the diameter of your 845 (or any other transmitting valves) when ordering these valves so they fit perfectly.
I’ve used these sockets on my projects for years and am very pleased have to say. Of course you pay a premium price as these are hand-made with fine materials. In my opinion, these are worth every cent.
Also I had a pair of RCA sockets, look at them:
They are made on a single piece of tellurium copper. First coating in pure silver 99.99% thickness 18 microns and the second coating Gold 24 K 3 micron thick. Sterling job!
You can contact Jakeband directly to order your sockets. Just use the form I posted years ago here.
Received the ER801a today back from Thomas. They were working fine, it was a faulty UX-4 socket pin of my tracer which annoyingly made the grid to appear faulty and open at certain voltage level. I need to replace it.
Either way, they are now in my system and I can only say how much I was surprised with the sound of these. They take the detail and timbre of the VT-25 to a next level. Amazing result, happy to have these as part of my driver stage. The preamp is the 201a feeding the ER801a into the 4P1L PSE.
Highly recommended valves, worth the price indeed.
Since my early days of valves and DIY audio, I developed an obsession around testing and tracing valves. This led me to design and build my analogue curve tracer which I used for many years successfully until I build my uTracer, which was a great innovation in curve tracing. I do have many valve testers (some which I made myself) so why building another one?
Well, Chris Chang from Essues Technologies developed a fantastic new digital curve tracer for valves, the eTracer. There are a few things which will grab anyone’s attention on this curve tracer. Firstly, the power supplies can accommodate a large range of valves which the uTracer can’t. HT can go as high as 750V @ 300mA and the grid supply down to -170V! This is exactly what you need to test your transmitting valves or even a 300B. Secondly, the tracing speed is surprisingly fast. This is a nice feature, specially when you want to trace pentodes at various screen voltages to develop a Spice model for example.
A quick trace of a NOS Tung-Sol 6GE5 measuring around 113%:
Derived the Spice models using Dekker’s ExtractModel tool. The uTracer has a limit of 200mA so it’s not possible to trace the extended set of curves for this valve. However, this is not a limitation to produce a good model.
Here is the triode matching:
I run a set of curves at various screen voltages from 100V up to 200V at 25V steps to generate the pentode model The saturation effect is visible on higher currents above 140mA as you can see below:
Below is the triode model, you can dow Continue reading “6GE5 Pentode Model”