My take on Eric Johnson's Steel String Singer #005

[bcmatt]

I was just checking out your schematic and layout today for inspiration on altering my presence and GNFB values on my MHartman layout #004? inspired build.

Anyways, I tried wiring mine like your schematic, but it seems like something is a little wrong.
When I use the presence circuit in your schematic. I notice the when I use the 4.7K GNFB resister, I get a super quiet signal. I have to bring my master volume up to about 7 to match the volume of the 100K Feedback resister choice. And I have to be in standby to change the Feedback switch otherwise it makes a big bang sound.

Then I noticed it is different from your layout as well:
Your layout has your .1uF PI grid input cap connected directly to ground through one lug of your presence pot. I was wondering if maybe your red and pink wires are mixed up at the presence pot, but that would still connect that same cap directly to ground when dialing the presence pot all the way to one side... I'm not sure what that would cause happen but I haven't seen a presence circuit like that before.

Do you know which is more accurate to what you actually have working?

[rootz]

Here's a better layout. It is only missing a 1meg resistor at the input jack AFAIK.

Feedback network consists of a 220k series resistor and a 4k7 resistor at the tail of the PI. The only thing the presence pot does, is gradually paralleling a 100n cap to that 4l7 resistor.

You can vary the 220k series resistor. I've tried 100k, 150k, 200k depending on looseness of the power amp desired and the type of output tubes. I tend to like a bit more feedback in lower power amps like a dual or quad 6V6.

[bcmatt]

Here's a better layout. It is only missing a 1meg resistor at the input jack AFAIK.

Feedback network consists of a 220k series resistor and a 4k7 resistor at the tail of the PI. The only thing the presence pot does, is gradually paralleling a 100n cap to that 4l7 resistor.

You can vary the 220k series resistor. I've tried 100k, 150k, 200k depending on looseness of the power amp desired and the type of output tubes. I tend to like a bit more feedback in lower power amps like a dual or quad 6V6.

Thanks for that link.
Is that a 91K Tail Resister?
I'm starting to grasp a bit better about how the ratios work and why there can be such wildly different values... as long as they correspond with each other.
I may try that. I've currently gone back to the MHArtman version: 2.7K, 270r to ground, and 18K PI tail with no Presence circuit.
But, I'll revisit tweaking my Global feedback and possible presence, cut, or mid contour after I get my step filters sorted out. That's what I'm currently working on.

[rootz]

No, that's a 9k1 tail resistor. But 10k would also work well. The PI bias resistor is 510 Ohm, but 470 Ohm also works. The amp is low on gnfb. I think that is a big part of the sound of 005: big, loose and spongy bass. I made an 005 with an Odyssey Deluxe power amp and it is a totally different amp. Much tighter and dryer sound. More immediate attack. And it sounds really cool when the power amp is overdriven. I think that is where the 12au7/12bh7 PI/driver is giving the goods and really starts to sing.

[rootz]

Here's the bastard son of the 005 and Odyssey power amp.

[Roe]

Here's the bastard son of the 005 and Odyssey power amp.

nice idea for EJ tone! any schematic or layout?

[rootz]

Sure Roe! It's quite easy to try this one out. Different bias arrangement, like in an ODS and an adjusted dropping string. Really not much more to it. Fun amp for sure, sounds like a monster when overdriven and loud. Although I think it needs to be super loud to get the full potential.

[rootz]

And the schematic minus all relais. I think this amp would benefit from a deep switch instead of a mid boost, though that is subjective.

No full layout. It's 90% SSS005 though.

[ElectronAvalanche]

And the schematic minus all relais. I think this amp would benefit from a deep switch instead of a mid boost, though that is subjective.

No full layout. It's 90% SSS005 though.

Hi Rootz,

Nice amp and thanks for the schematic. I noticed you implemented a LNFB on V1b in this amp which AFAIK was absent in your original 005 iteration. Can you elaborate why you choose to have the LNFB here and what it brought to the sound?

Thanks,

Electron

[rootz]

Good catch! Main objective was to lower the gain a bit. Why? The power amp has much more gain than the LTP+CF combination. The windows started to rattle with the master on 1.

The amp did lose its wilder side though. Local feedback made it even cleaner, which was not what I was looking for. It did bring out the high end a bit more though, which the amp needed. But it was an experiment.

Since I've ditched the local feedback and at the same time got rid of the cathode bypass caps on the filter recovery stage and the reverb recovery stage (c1 and c11). So that are now just 1k8 resistors. This also lower the gain of the preamp considerably but at the same time it keeps that bit of a rawer sound I lost with the local feedback. Also seems to bring out the high end a bit more compared to bypassed cathodes.

[ElectronAvalanche]

Good catch! Main objective was to lower the gain a bit. Why? The power amp has much more gain than the LTP+CF combination. The windows started to rattle with the master on 1.

The amp did lose its wilder side though. Local feedback made it even cleaner, which was not what I was looking for. It did bring out the high end a bit more though, which the amp needed. But it was an experiment.

Since I've ditched the local feedback and at the same time got rid of the cathode bypass caps on the filter recovery stage and the reverb recovery stage (c1 and c11). So that are now just 1k8 resistors. This also lower the gain of the preamp considerably but at the same time it keeps that bit of a rawer sound I lost with the local feedback. Also seems to bring out the high end a bit more compared to bypassed cathodes.

Thank you for your comments Rootz! I also feel that 005 is not as bright as 004 or 002. I currently have 25uF on the filter recovery stage an like it in my double SSS preamp. Of course now 005 is much louder than 004 so I need to dial down the 005 Master to,achieve good equilibrium between both channels. I needed the 25 uF aince the V1b 0.68uF cathode cap thinned out the sound too much in comparison to 004. A delicate thin red line to walk to tweak the two preamp sections to work good together but yet not too make them sound to alike.

Best,

Electron