Put EL 34's in my MT-15!!

Gustavo Posada

New Member
Joined
Apr 15, 2019
Messages
17
Location
Stuttgart, Germany
Thank you @bodia ! I’ll take that as a win based on my current reading.
I’ll wait on PRS about the questions I asked; they are in another thread.
Does your MT15 happens to emit a sound/noise to the speaker while in standby? And when you switch the standby on/off emit a “bump” sound?
Thank you in advance!
 

bodia

Authorities said.....best leave it.....unsolved
Joined
Jan 21, 2015
Messages
29,871
Location
Suburban Chicago
Thank you @bodia ! I’ll take that as a win based on my current reading.
I’ll wait on PRS about the questions I asked; they are in another thread.
Does your MT15 happens to emit a sound/noise to the speaker while in standby? And when you switch the standby on/off emit a “bump” sound?
Thank you in advance!

Negative to both. Whisper quiet while I had it.
 

DreamTheaterRules

My friends call me The Cruiser
Joined
Nov 20, 2013
Messages
11,924
Location
Cincinnati area
Hi!
Yes, usually it is between 25 and 30mV.
What I mean is, if you have a chance to read the voltage from both bias points, could you share both results?
There is only 1 adjust screw, but there are 2 read points. In my case, one reads 25.1 and the other 27mV.
I wonder if that is why it makes that weird noise... because factory tubes are not matched.
I should get myself a match pair of NOS Mullard made in USA. I only see Russian versions available in tube stores.
Those are matched tubes. No two tubes are identical, and they will drift over time. That would not create noise, or any issue with tone. If the PI stage is perfectly symmetrical, this will just make it slightly assymetrcial, which is no big deal and might even sound better than if they were dead on perfect match. The more important thing is making sure what PRS suggests, and setting the two as close as possible to that. I know what they recommend for the Archon, but not the MT15.
 

Gustavo Posada

New Member
Joined
Apr 15, 2019
Messages
17
Location
Stuttgart, Germany
Got back from Thomann

Here are the answers:

Hello Mr. Posada,


thank you very much for your patience.
In this amplifier the standby switch works differently than in other tube amplifiers. The power tubes are under high voltage even when the standby is in "off" position. That´s why small amount of noise is hearable.
The click during switching on or off is also completely normal, there are few amps which doesn’t make any noise by powering on or off.
Good to know: This has nothing to do with true bypass switching on guitar pedals. It is caused by transient voltage spikes in the power supply electrolytic capacitors and although it can be unpleasant, it is safe for speaker and will not cause any damage.
25mV and 27mV means that one tube runs slightly warmer than the other. Although this is still acceptable - there is always some small difference between power tubes. More than 3mV would already be too much.

Kind regards

Sebastian Held, Kundenservice
Tel: +49 9546 9223-68 | Fax: +49 9546 9223-8399 | E-Mail: [email protected]
 

DreamTheaterRules

My friends call me The Cruiser
Joined
Nov 20, 2013
Messages
11,924
Location
Cincinnati area
Did you ask PRS what it was supposed to be set at? I know the Archons, H and Custom 50 I've had were all to be set a bit higher than that.
 
Top