[hpamdr]

Got a new amp at home... Just a plain old design full of transformer CAP, and tubes 2 GZ34 + 2 6SL7GT + 2 x 2 EL34 Push Pull 20W.. Full of juice
Hand made in 2016 by local builder (retired 2 years after the build )
Powering STAX L500 with SRD-7 MK2 and HeedFone using speaker out.

 

[Designsfx]

Got a new amp at home... Just a plain old design full of transformer CAP, and tubes 2 GZ34 + 2 6SL7GT + 2 x 2 EL34 Push Pull 20W.. Full of juice
Hand made in 2016 by local builder (retired 2 years after the build )
Powering STAX L500 with SRD-7 MK2 and HeedFone using speaker out.

That amp looks like a beast! Reminds me of a Jadis JA mono block!

 

[OctavianH]

Got a new amp at home... Just a plain old design full of transformer CAP, and tubes 2 GZ34 + 2 6SL7GT + 2 x 2 EL34 Push Pull 20W.. Full of juice

Looks brutal. Is it yours or you have borrowed it? Tell us more about it.

 

[hpamdr]

That amp looks like a beast! Reminds me of a Jadis JA mono block!

Yes, it is build like a tank ! But what makes the impression of "being so big" is the placement of transformers in the side instead of in the back... The box is a large rectangle instead of a square with 25Kg of metal
The chrome-plated transformer cover is similar to Jolida but the transformer are not the same
It is not a dual monobloc as tubes transformers are shared but rectifier and Big CAPs are allocated to one side only.

@OctavianH It is mine, I purchased it near my home for 600€, I made an audition with huge JBL Speakers and literally fall.....

 

[Designsfx]

Yes, it is build like a tank ! But what makes the impression of "being so big" is the placement of transformers in the side instead of in the back... The box is a large rectangle instead of a square with 25Kg of metal
The chrome-plated transformer cover is similar to Jolida but the transformer are not the same
It is not a dual monobloc as tubes transformers are shared but rectifier and Big CAPs are allocated to one side only.

@OctavianH It is mine, I purchased it near my home for 600€, I made an audition with huge JBL Speakers and literally fall.....

Awesome!

 

[OctavianH]

@OctavianH It is mine, I purchased it near my home for 600€, I made an audition with huge JBL Speakers and literally fall.....

You were lucky, at that I price I would have also bought it. Not sure why since I'm dwelling into the tubes of 30s. I have a few quads of EL34 I never use. What's the situation with the bias / plate voltage on that one? I think you can put a lot of others on it.

 

[OctavianH]

Monday morning reading time. This is interesting.

Excerpt:

These (n.r. Philips "red" series") are really special, in my opinion. Especially the early side-contact series. When operated correctly these valves have a very energetic sound which is very pleasing for almost all music varieties. Downside is the side-contact socket, not very safe and it relies on the spring effect of metal to make contact. However I do like the fact that the valve base is tucked away in the chassis and that the metal contact strips in the sockets are of modest dimensions (no thick lumps of metal). The Philips red-series are all of the highest possible quality of that time and certainly applied as a reference to other valve manufacturers both then (and now).. Dutch engineering at the top!

I tend to disagree with him regarding the socket, such a socket makes almost impossible to remove the tube from the socket without touching the glass. So, you know... It was made to put the tube in it and forget it there, not for us replacing tubes often.

EBC3 will be a part of this thread soon. A triode from the "red" series which we will try as input tube in Eternity, if all goes well. Mu of 30 makes it very interesting. Bias has to be around -4V somewhere. Looking forward to this. Some nice literature from 1940.

 

[hpamdr]

You were lucky, at that I price I would have also bought it. Not sure why since I'm dwelling into the tubes of 30s. I have a few quads of EL34 I never use. What's the situation with the bias / plate voltage on that one? I think you can put a lot of others on it.

I got it without any information nor documentation.. I'm trying to get a bit more.
I was able to open it and using what i see it is autobias and plate voltage should be around 350V but did not experimented too much nor did some measure. it was delivered with a quad of RSD from early 80s, a pair of Sylvania VT229, and a pair of GZ34 Dario.. I made a try with siemens EL34 (not a perfect quad) and it is almost same sound as RSD ???

-- edit correct RSD instead of RFD

 

[OctavianH]

I got it without any information nor documentation.. I'm trying to get a bit more.
I was able to open it and using what i see it is autobias and plate voltage should be around 350V but did not experimented too much nor did some measure. it was delivered with a quad of RFD from early 80s, a pair of Sylvania VT229, and a pair of GZ34 Dario.. I made a try with siemens EL34 (not a perfect quad) and it is almost same sound as RFD ???

As far as I remember from the times I was studying the EL34, Siemens never produced EL34 but rebranded. In my collection I have these:

And then these:

If I remember correctly both are produced by RFT in East Germany. In short, you might have 2 quads made by RFT and branded differently. A guide to these are the stappled plates, but here there are some Telefunken which also have stappled plates, but the dimension of the hole is different, mine are like these:

 

[hpamdr]

I would like have RFT , but it is just RSD.

If i can get more info, i will try to run with 6M6 if not out of range to reduce output power. I do have too many Watt for my level of listening...

 

[OctavianH]

Switched back to RT 4654. These tubes gave me some headache today because one of them stopped working during operation. Well, after some retries and checks works fine.

I observed that these do not like to be started/stopped often. If you want to listen to them, you'd better leave them untouched in those adapters on the amp. If you play with them they start to act strange. And not only RT, also Philips are acting in the same way. For sure, not made for rolling.

 

[Isaacc7]

Have pulled out a tube I haven’t used in a long time. I was originally impressed with the Brimar when I first tried it but going back to it was disappointing. It was dry and flat sounding. Hmm. Then I remembered that another well regarded tube, the RCA grey glass 6sn7, also struck me the same way. With the RCA I decided to let them cook a while since their reputation was for the opposite of what I was hearing. Sure enough they broke in and gave me more of what people talk about with RCA.

So I did the same thing with the 13d1 and have been rewarded. They actually remind me of the GEC b36 a lot. Mostly neutral, good bass, nice presentation of the soundstage. These are a bit more mid forward I think. They work well with the Sylvania 6bg6ga.

Speaking of which, I had noticed a bit of distortion during peaks with them set at 400v on ultralinear so I dialed them back to 350v and all is well. Will leave these in for a few nights and then I think I will resume my experiments with the 2c50 on the input.

 

[Isaacc7]

Switched back to RT 4654. These tubes gave me some headache today because one of them stopped working during operation. Well, after some retries and checks works fine.



I observed that these do not like to be started/stopped often. If you want to listen to them, you'd better leave them untouched in those adapters on the amp. If you play with them they start to act strange. And not only RT, also Philips are acting in the same way. For sure, not made for rolling.

Such is the life with adapters. Several times I have had tubes just not light up. Take them out, reseat them in the adapter and then they are fine. I have also had some noise issues from time to time that can be solved with reseating them. I wonder if I am shying away from single triodes because of that lol. Been using twin triodes for the last little while.

 

[hpamdr]

If you play with them they start to act strange. And not only RT, also Philips are acting in the same way. For sure, not made for rolling.

For me it was the same with EL3N and FDD2 and i just concluded this was due to the socket/tube junction when you move/twist a bit the tube you can have a strange connection. The way to secure it is to cleanup the tube base "copper plate" and even make them a bit flat to prevent twisting.
My friends from Radiofil said the same for their radio saying that it could be even hazardous to insert/remove old tube from the glass too much. It can damage the tube base internal soldering as the force on the socket is too big.

 

[OctavianH]

The problems I sometimes have with these tubes (by the way the problematic RT never light up again today even if I haven't touched it since yesterday, remained on the amp) are more complex than what we know at the moment. First of all, the quality of soldering and side contacts on the french tubes is not as good as on the Philips red series. I have observed this type of side contacts with a different shape, some of them shorter and the neglijent soldering on RT EL2 and also RT 4654. The Philips ones are different, longer and in my view this is why I rarely have contact problems with the Philips red series. Of course, I might be wrong, but a photo makes more than 1000 words:

Now, imagine that this kind of tube socket has to make proper contact with a P8A adapter we can find nowadays and most probably everyone is using it:

And I looked also at the famous Yamamoto here and I am unsure those will be completely non problematic.

Now, besides these problems, these very old pentodes might be also not very pleased about fixed bias and gyrator loaded anodes.

A solution would be to resolder these tubes and also to solder directly the tube on the adapter.

Later edit:

Similar side contacts also on Valvo (like RT):