Using E180CC / 7062

[Mucker]

I had a chance to test an E180CC in my fully upgraded (Bottlehead) Stereomour II and measured around 130 volts on the plates. My Mullard CV4024 measure just above 200+ V. The E180CC didn't sound bad but is the voltage too low to harm anything or to affect sound optimally? I tried to dig around on the forum but couldn't understand what is needed. My home voltage pushes upwards of 123V.

I am really happy with the CV4024 Mullards with Gold Lion PX2A3 or 2A3EH (both of those sound identical to me). I will just dump the E180CC if hardware changes are necessary.

Thanks!

[Paul Birkeland]

I think the amp would work better with the driver C4S R1 set to just over 100 ohms in my opinion.  This will bring the bias voltage up to more like 3V, and the plate voltage up to about where it would be with a 12AT7.  The heatsinks that are already on that board are likely adequate for this.  If you have the shunt regulated driver upgrade, that may also need some adjustment for this to work properly.

[Mucker]

Thanks for the quick response Paul. I do have the shunt regulator installed. If the change is made will the 12AT7 work without issue or is it a swap back and forth thing. If so I will just use the 12AT7 which I am very happy with.

[Paul Birkeland]

You can only really optimize for one or the other. 

Replacing the 65 ohm R1 resistors on the SR board with 50 ohm resistors will help if you want to run the E180CC permanently.

[Mucker]

Roger that. Thanks for the thoughtful reply's. I will keep it 12AT7.

[Paul Birkeland]

Roger that. Thanks for the thoughtful reply's. I will keep it 12AT7.

I would say that I think it's totally reasonable to use the 7062 and I wouldn't hesitate to make the changes.

[Mucker]

Oh interesting. I will reconsider doing that for sure especially with your encouragement. One thing I get worried with is ruining the pcb's from excessive soldering. I was doing resistor changing on the older small Speedball boards and burned the landing points out and had to reorder a kit. No big deal, I will just have to be more careful. Thank you!

[Mucker]

So, on C4S, 100 ohm resistors in R1 ?

and SR board, 50 ohm in R1 ? (is a 47R close enough? If not I can order 50's)

Appreciate the help.

[Paul Birkeland]

You can solder more R1 resistors on top of what's there.  To go from 150 to 100, solder a 300 ohm resistor across the 150.  Actually soldering a 300 ohm resistor across the other R1 value is probably close enough to get the job done here as well, so you really just need four 300 ohm resistors, and they can be installed without taking the boards out or doing any desoldering work.

[Mucker]

Ah cool. Appreciate the guidance and looking forward to trying this out!

[Mucker]

Alrighty, I was able to complete the change today and the result is excellent. I am now getting 203 and 209 plate voltage on 7062 up from 130V.

I had some of those removable pin sockets on hand so mounted them on all the R1 holes. Now I can use resistor jumpers to switch back and forth between 12AT7 and 7062. I then may make a permanent change with fixed resistors if I prefer one tube over the other. With a brief listen, yes, the 7062 sounds great. The tubes are brand new so want to break them in longer.

Currently, the C4S R1's are at 100 ohms and the SR board R1's are at 50 ohm.

I really appreciate the guidance Paul, thank you!