Metropoulos Forum

looks real good. nice job.

Mark

Great stuff!

Pardon my ignorance, but what are the caps and diodes on the right hand side of the amp (1000uf/25uf etc...) used for?

vlad wrote:Great stuff!

Pardon my ignorance, but what are the caps and diodes on the right hand side of the amp (1000uf/25uf etc...) used for?

Thanks, vlad. That's the 12vdc heater circuit for V1 and V2. I installed it to reduce hum and to run the relay switching that I install with this mod for channel switching.

xenrelic wrote:

vlad wrote:Great stuff!

Pardon my ignorance, but what are the caps and diodes on the right hand side of the amp (1000uf/25uf etc...) used for?

Thanks, vlad. That's the 12vdc heater circuit for V1 and V2. I installed it to reduce hum and to run the relay switching that I install with this mod to switch between 2 different sets of pre and master pots, also to switch between the vintage and modern inputs. I will update the layout with the relay switching in version 5 once I figure out how to get the input switching part quiet and smooth enough to be worth sharing with you guys.

Awesome man! I appreciate the info!

Updated the layout.

New version up!

Hi...

I'm looking to build some thing like this and i'm wondering if there might be a layout utilizing the foot switch option with the additional channel volume controls.

Hi!

I was curious as to the brand/model transformer you used for your DC Heaters & the brand/part # of the relay?

I use the Philmore 24v (12v-0v-12v) 500mA (with a full wave rectifier with capacitor), for the DC heaters on the first two preamp tubes to an LM7812 12V positive voltage regulator. For the relay switching I use an LM7815 5v positive voltage regulator from the LM7812 input node and Omron G5V-2-H1-DC5 relays.

New version up.

Hi Xenrelic, What is the effect of putting the zener on the gain instead of the volume pot ?

Your layout is breathtaking

It's an asymmetrical clipping circuit that is designed to emulate power tube distortion and works best after the final gain stage that is fed by a large coupling capacitor around .22uF to .33uF depending on how much bass response is wanted. Lower values from .022uF to .1uF, don't seem to work very well and can cause undesired results.

I notice a really cool grinding sustain that occurs, when engaged just before the pre-tonestack master volume.

If you were to experiment with diode clipping earlier in the preamp stages, I would check out the different types of clipping available as well. Possibly starting with a symmetrical clipping circuit that utilizes germanium diodes or a hybrid combination of silicon and germanium.

Maybe something like this (just for shits and giggles): http://img94.imageshack.us/img94/1068/p1040560q.jpg You can also try moving the 33k resistor between to the gain pot wiper and the input grid of V1B.

Here's some different types of clipping you can try along with a great article about it.

http://www.cubisteffects.com/images/MIY ... mmetry.jpg

http://www.effectrode.com/blackbird-vac ... -explained

Updated the Version 3 layout with the pre-tonestack master volume.

xenrelic wrote:It's an asymmetrical clipping circuit that is designed to emulate power tube distortion and works best after the final gain stage that is fed by a large coupling capacitor around .22uF to .33uF depending on how much bass response is wanted. Lower values from .022uF to .1uF, don't seem to work very well and can cause undesired results.

I notice a really cool grinding sustain that occurs, when engaged just before the pre-tonestack master volume.

If you were to experiment with diode clipping earlier in the preamp stages, I would check out the different types of clipping available as well. Possibly starting with a symmetrical clipping circuit that utilizes germanium diodes or a hybrid combination of silicon and germanium.

Maybe something like this (just for shits and giggles): http://img94.imageshack.us/img94/1068/p1040560q.jpg You can also try moving the 33k resistor between to the gain pot wiper and the input grid of V1B.

Here's some different types of clipping you can try along with a great article about it.

http://www.cubisteffects.com/images/MIY ... mmetry.jpg

http://www.effectrode.com/blackbird-vac ... -explained

Thank you so much.

Made a change to the version 3 layout, the wire from the plate of stage 4 to the 10k resistor should not be shielded like in the previous drawing.