The Amp Garage

Impressive work!
I just wonder whether the lack of a bias resistor at the + input of the opamp may cause problems.
See e.g. https://www.physicsforums.com/threads/v ... mp.788018/ or https://northcoastsynthesis.com/news/on ... -analysis/

cgmason1986 wrote: ↑Sun Aug 15, 2021 2:46 pm *EDIT* no idea what happened - didn't change anything but now it seems to be working?? Maybe there was a short somewhere?

Great!
Most likely there was a short, considering that voltage dropped from 6V to 0.2V.

Removing the tube all the voltages look right. The power supply says 20mA "This power supply PCB can supply 150VDC to 250VDC at approximately 20 milliamps. This is enough high voltage power to run 2 or 3 12AX7 or equivalent tube pre-amplifiers. It also can supply regulated 6 volts DC to power 2-3 t...

cgmason1986 wrote: ↑Sun Aug 15, 2021 2:22 pm

Yea removed the 4/5 to 9 connection. Now it's just pin 9 to 6V, 4/5 jumper together to ground.

How are the voltages if you remove the tube?
How many mA can you power supply provide?
Edit: Can you post the schematics of the heater power supply?

Gave that a shot - Somehow threw off all my voltages? Not getting any 6V - even right at the 6V pad connection on the power supply (reading 0.2V), pin 1 and 6 only reading about 70V and not responsive to the power supply trimmer. Switched it back to the wrong wiring and all the voltages are back to...

Looking at the layout heater pins 4/5 are missing a connection to GND. Regards, Markus Thanks Markus - I'm 100% sure I've wired these heaters wrong. Right now I've actually got 6VDC connected to Pin 4, then jumper pin and pin 5, then wire from pin 5 to pin 9. To complete this circuit do I need a wi...

I went ahead and tried to build the preamp. The [first noticeable] issue I'm having is that the tube is not heating up. I'm getting 6V at the heaters, is there something else that I should check? I tried with a different tube as well. This is my first time trying to building something with a tube s...

That's a good catch... thank you. I will have a think about the attenuation required. On the mixing side, V3 in the schematic, we have a 1M resistor taking that role. I have a suspicion that I can look to the OD for a suggestion of the usable values. The OD first triode used the 220k+350k trimmer+6...

Hi Stephen, that bigger chassis sounds like a very good choice! This makes room for a whole lot of other ideas, also a reverb that is much more like the one in the 002. However, you can’t implement the 002 reverb like you did afaik. Normally in a 002 the reverb would be taken from the volume pot wi...

Finally I managed to do the labels. :wink: For ECC83-type and 6L6/EL34-type tubes I've hard-wired sockets since these are the tubes I play around with most. I've added a regulated heater supply that can be switched to 6.3V or 5.67V (90%). The USB-TTL cable Martin suggested works nicely! Thanks for t...

In the meantime I've replaced the DR127 inductor of the negative supply. However, it did not really lower the noise level. Since replacing the inductor with the same type (DR127) did not help, I decided to go for another type, the DRA127. At https://uk.rs-online.com/web/p/wire-wound-surface-mount-in...

martin manning wrote: ↑Wed Feb 24, 2021 11:58 pm

markusw wrote: ↑Wed Feb 24, 2021 5:56 pmAny hints on how to unsolder the inductor with just a plain soldering iron?

Two regular soldering irons and an extra pair of hands?

Good idea!
Thanks!!

I works nicely. I just worry about the noise. It is really annoying :? Since the enclosure is vented there is barely any reduction in noise if I put the PCB into the box. Maybe I will try to replace it. Unfortunately, this is not a fun job. Guess I will at least need to remove a diode... Any hints o...

...during operation the negative supply of the µTracer produces a produce a high pitch sound (approximately 10 kHz). I know is indicated in the construction manual that "During operation the negative power supply can produce a high hissing sound". Is there a way to circumvent this. It is pretty lou...

Almost done with boxing. I just have one issue: during operation the negative supply of the µTracer produces a produce a high pitch sound (approximately 10 kHz). I know is indicated in the construction manual that "During operation the negative power supply can produce a high hissing sound". Is ther...