jose

Thanks Dr. Gilmore. My ampli sounds amazing in both SE and Balanced, but as I can change the THAT by another solution. I have several Jfets in my "warehouse" so I'm tempted to make a small mini-plate for them.

I have been reviewing the entire pcb and I have not encountered any problems. Solder is OK, resistors, sand seemed intact too. So I installed the board and decided to change the THAT340 as it´s the easiest component to replace and the most prone to make noises and ... Bingo! Totally silent. Fortunately, I placed these components on the bases. This is the third THAT340 that I change by different noises. Has anyone else had problems with them? I've bought it at Mouser so they are original.

This old XRCD: Reiner and Chicago Symphony Orchestra, Tchaikovsky: 1812 Overture

Sorry Pars, I have dismantled the channel and I am checking the solders but for the moment I have not found anything strange. I asked you about TRS gorund because with this ampli I worked hard to avoid the ground loops.

It's a gift from my wife. She bought it at David Gilmour's official store. Comes a pack of 4 vinyls and 2 CDs.

I have checked the wiring and there aren´t problems but since I am doing things, I have a XLR 4 pin output conector and a TRS. What is the most appropriate way to connect the TRS ground? From the TRS to ground of any Sigma22 or join the cold outputs into TRS ground. ¿?

I´m working on input wires and tomorrow I check both boards in search of some problem with solders. I wish it were just that! The sound is so low that my oscilloscope can not detect it so I can´t show you any measure. However, at the moment I am also looking for a couple of boards (see 1.4 on board) in case I have to replace any.

Bias at 370/365mVolt. Offset is most stable, arround -10~30 mVolt. Now I only have noise on R channel. Noise is like a crackling and you can hear very low . With bal or SE I have the same kind of noise and with the same level. I'm sure it's not a ground noise.

Thanks Rumina. I have reviewed my documentation but only find the reference at 0.75 Volt but I'm regulating the Bias at 0.375 Volt and in a while I can tell something.

Well I like to think that with Héroes he were different.

Héroes del Silencio

I did not remember that my input board bridges the Cold channel with ground when I select the a SE channel. So that's not the problem.

Thanks for the answer boys Yes, I also think that having SE and balanced inputs brings a lot of versatility. In my Stax amps I always bypass the cold channel (I use input selectors with relés) in SE inputs, but in the dynahi I hadn't through necessary... remember that I heard the crackling noise yesterday and I have this amp for a long time. For the outputs, SE and balanced is also necessary by the different types of headphones that I have. Yes, I understand that it's a waste of energy and that even results in the longevity of the components but we aren't talking about using a Grado. In my case use my Dynahi with high impedance and/or an disgusting sensitivity.

Thanks spritzer. I'm working on it now. Let me check.

Because at the moment I haven't had problems with that. If it's the problem it's easy to solve but I doubt it's my problem. As for the output device (hope you like it more...), you're right I'm wrong they aren't mosfet.

Yesterday I was listening to my amp and I noticed a small sound coming from both channels, it's not constant and it's not perceived while listening music. It's a sound like "fried". I was listening SE input and SE output and I don't bridge the cold input to ground. I have been taking some measurements and BIAS is symmetric on both sides; 750/760 mVolt on R channel and 720/735 mVolt on L channel. On the contrary, offset drift a lot and I've never been able to keep it on 0 volt. It's always between -100~40 mVolt and 120~60 mVolt (without servo). With servo, the offset never exceed 20 mVolt. It has always seemed to me that Mosfets run too hot for an on-board assembly (Mosfet reach 90°) although I know that the maximum temperature is 150° but even so, components and the PCB also get very hot. I'm not sure where to start since I've changed the THAT and OPAs too and I still have the same noise. Can Mosfet be damaged? Or can the problem be elsewhere? Thanks

I always use this on trafo lines, from EIC to trafo. Usually I use a solid state relay and you can use T2 soft start design for do it.

I wouldn't put anything on the out put. To have a soft start I put a relay in the trafo or HV part (between amp and PSU). With 10 seconds is sufficient for the heating filaments to have some temperature.

Eric Johnson "Venus Isle"

Hum problems are a b***h. You only need patience. My SRX-P is dead silent now but I needed weeks of work to find the cause of the problem. Basically trial and error. Edit: Laowei put this layout on "Technical Assistance/Advice Thread" maybe It can help you too.

I recommended the new Tung-sol 6SN7GTB

Porcupine tree "in absentia" with my F5ha and HD600

Flat stage with final Sprint [emoji23] [emoji23] [emoji23] :