G2 diss. 0f the 6cb5a is 3,6 watts. As the anode doesn't produce heat this can be increased to about 6 w. You can check this using a variable neg. grid supply of say 70v, 250v on g2 . Take Rk=10 ohms and adjust -Vg1 until you get 0,24v across the 10 ohms- this corresponds to 24 ma. Do this in a dark room so you can see whether or not g2 turns red. If so, increase the neg. grid voltage until there's no red glow any more.
I think 2 6cb5a's are comparable to 1 EL 504 regarding g2 dissipation.
I think 2 6cb5a's are comparable to 1 EL 504 regarding g2 dissipation.
Found this thread when I was looking for something different.
If you talk about sound you obviously should mention the type
of output transformer.
Thanks.
If you talk about sound you obviously should mention the type
of output transformer.
Thanks.
I've used several ot's first the u72 a Dutch ot from the sixties (5k primary) a Vortexion (5k) a Toroidy (3k5) and a Iwistao from China (3k5). Then there were reactions from Germany, Sweden, Belgium, Kroatia and of course the US (Jonathan Weiss marketed this amp - look for parallax amp- at first for $11.500 and later for $31.500). I don't know what ot he used. The character of the 519 g2 as anode was obvious for everyone and all reactions were quite positive apparently irrespective of the ot that was used
Hi,
After a visit to Kees (thanks again for the friendly welcome) I was able to get a personal impression of this rather unusual operating mode.
A worn EL/PL519 and a 300B transformer are quickly found or already available.
Stick to the circuit at the beginning of this thread with the split cathode resistor and a Ub of 250-300V.
The driver and the tubes matching the circuit are decisive for the sound.
Pretty much anything that will drive a 300B will work and it's purely down to personal taste what gives you the best result.
Fortunately, I was able to use all the iron from my 6CB5A project by T.M. which can't hold a candle to the el519 mesh in any way, or as Kees and I summarized it so nicely:
It has something you wouldn't want to be without.
I tested it for several months with a wide variety of end tubes.
The 6CB5A was not convincing, the el5000 (five thousand) was the finest, but weak in the bass.
The 519 is the perfect partner and will not disappoint.
Sorry for my bad english
Christian
After a visit to Kees (thanks again for the friendly welcome) I was able to get a personal impression of this rather unusual operating mode.
A worn EL/PL519 and a 300B transformer are quickly found or already available.
Stick to the circuit at the beginning of this thread with the split cathode resistor and a Ub of 250-300V.
The driver and the tubes matching the circuit are decisive for the sound.
Pretty much anything that will drive a 300B will work and it's purely down to personal taste what gives you the best result.
Fortunately, I was able to use all the iron from my 6CB5A project by T.M. which can't hold a candle to the el519 mesh in any way, or as Kees and I summarized it so nicely:
It has something you wouldn't want to be without.
I tested it for several months with a wide variety of end tubes.
The 6CB5A was not convincing, the el5000 (five thousand) was the finest, but weak in the bass.
The 519 is the perfect partner and will not disappoint.
Sorry for my bad english
Christian
Did anybody try to connect anode to screen grid instead of grounding it to check, if without anode connected it sounds indeed better? 😉
I tested the different tubes in this mode and the PL519 gave the worst result.
The Ra is not perfekt for 519 Triodmod but i see on the sound that's the wrong way.
My transformers are double M102 with 5kg and a Ra of 4.4k and for this I was looking for the best partner and found it with the 519 G2 mesh
The Ra is not perfekt for 519 Triodmod but i see on the sound that's the wrong way.
My transformers are double M102 with 5kg and a Ra of 4.4k and for this I was looking for the best partner and found it with the 519 G2 mesh
Those wanting a bit more power could try a russian GU72 at 4-500V, it is a comparable cheap, nice looking, sturdy build tube and without needing the difficult to get anodecap it would be easy to use. Screen dissipation is nominal 15W and heater current only around 1A from a 24V transformer (26V nominal but 24V is mostly ok), so no burned sockets problems.
Last edited:
Somone mentioned using one of those 4CX... ceramic transmitter tetrodes, small, anode could be mounted to a grounded heatsinck, low mu...only downsides i could thinck of is, if they are pricey, or someone would not like the looks..
Other than that, a VERY good idea, thanks to the one bringing it forward, if i where younger, i would have jumped on it, i always liked those little critters 😉
Other than that, a VERY good idea, thanks to the one bringing it forward, if i where younger, i would have jumped on it, i always liked those little critters 😉
I was only referring to the types of the previous posts and wanted to encourage those who have not yet found the holy grail in their 300B to try something different with a very small financial outlay. I got a few noname end of live 519 from Kees and they sound exactly like my NOS Telefunken.An acquaintance who does this hobby professionally is impressed by the spatiality of the G2 mesh mod in the driver stage. My first amplifier that makes it from the building board into a housing after years. After many hours of listening, there is still nothing to complain about, im happy to go this way.
Hi everybody,
A year ago I have heard from a friend (Vance) about Kees his PL519 with the G2 as an anode. Something which triggers me and and finally decided to build the amplfier. Before I started I have contacted Kees and he sent my some new schematics which he was listening too, at that time and find to be an upgrade to the original schematic. Find attached the schematic. You will find that this schematic has as a second stage a " the White Cathode Follower".
I have build this amplifier and must say it's a great sounding amplifier. Which triggers me, is this the combination of the two first stages? Will it work with every end stage? Listening to it you will find a great 3D soundstage, great separation of instruments a really Live effect. Is this an effect from the G2 sounding like a mesh end tube? It doesn't only sound great is measures also great also. Something to add to your PL519. It's worth it.
A year ago I have heard from a friend (Vance) about Kees his PL519 with the G2 as an anode. Something which triggers me and and finally decided to build the amplfier. Before I started I have contacted Kees and he sent my some new schematics which he was listening too, at that time and find to be an upgrade to the original schematic. Find attached the schematic. You will find that this schematic has as a second stage a " the White Cathode Follower".
I have build this amplifier and must say it's a great sounding amplifier. Which triggers me, is this the combination of the two first stages? Will it work with every end stage? Listening to it you will find a great 3D soundstage, great separation of instruments a really Live effect. Is this an effect from the G2 sounding like a mesh end tube? It doesn't only sound great is measures also great also. Something to add to your PL519. It's worth it.
Wow, you did a great job. Also with tube rectifier right? Beautiful colour of the housing. Could you discribe the sound as it comes to you?
The amplifier of a friend of mine had 4 519's in parallel, used it 7 hrs a day in his workshop for 3 yrs. I had measured the tubes before I gave them to him and after 3 yrs they measured the same. So after thousends of hours there was no wear. That's how strong these tubes are.
He had g2 on 14w dissipation and no failures. Besides, these tubes that had been used for yrs in colour tv's so they already had a life behind them. Both the 504 and the 519 are designed as impulse tubes and are therefore much stronger than ordinary audio tubes.
He had g2 on 14w dissipation and no failures. Besides, these tubes that had been used for yrs in colour tv's so they already had a life behind them. Both the 504 and the 519 are designed as impulse tubes and are therefore much stronger than ordinary audio tubes.