Build suggestions please

[titser_marco]

Hello! I got a chassis that I'm looking to use for a build project and it has 4 punchouts for preamp tubes. One's definitely going to be used for the PI, and I was wondering if you had any suggestions for a build. I'm thinking of the following options (all of them reverb and effects loopless):

1. ODS-style build with two extra gain stages after the OD section
2. ODS-style build with two switchable OD channels (one non-HRM and one HRM)
3. ODS-style build with a CF driver after the PI

Any thoughts?

[Phil_S]

4 tubes is 1 more than the typical 3. Subtracting one for the PI leaves 3 preamps. It is impossible to know what your attraction is to the OD amps so no comment on that as it is a matter of personal taste.

You've got enough tubes to build one with reverb if the chassis has enough space.

You could do a 2 channel amp, giving 3 triodes to each channel. There's a lot you can do with 3 stages. Or you can go simple with something like the AA763 which only needs 2 triodes before the PI, and use the other 4 triodes with something more high gain. I'm thinking this gives you two good amps in one package. I think I'd go for something on that order.

[titser_marco]

Thanks! Been toying with the idea of Wreck and ODS in one box and here's the closest idea I came up with. Thoughts?

[titser_marco]

OK been doing some reading and it appears that a key factor in the Wreck sound is power amp distortion. Am I right in assuming that putting in a Wreck preamp section into a Dumble style output section is pretty much just going to be a Dumble OD channel minus one gain stage?

[Firestorm]

OK been doing some reading and it appears that a key factor in the Wreck sound is power amp distortion. Am I right in assuming that putting in a Wreck preamp section into a Dumble style output section is pretty much just going to be a Dumble OD channel minus one gain stage?

That's an oversimplification of the "Wreck" sound. Certainly the power tubes are driven hard, but there is a "cascascading" voltage reduction as the output draws more current. The screens drop, the PI voltage drops (which reduces output), the preamp voltage drops (which narrows clean bandwidth "browning" the sound). The "key" to the Wreck is the third stage: biased cold, it reduces gain to a barely manageable point and clips the signal asymmetrically. (There is some near-scholarly analysis of this on TAG if you search hard enough.

Dumble are mostly clean PA with preamp modulation. I'm not sure the two can be blended. There may be a way. Keep us posted.

[titser_marco]

Will do, but I would need to find that detailed description of what happens in a Wreck. Based on what you have said, it does seem near impossible but hey, this is the fun part of DIY!

OK been doing some reading and it appears that a key factor in the Wreck sound is power amp distortion. Am I right in assuming that putting in a Wreck preamp section into a Dumble style output section is pretty much just going to be a Dumble OD channel minus one gain stage?

That's an oversimplification of the "Wreck" sound. Certainly the power tubes are driven hard, but there is a "cascascading" voltage reduction as the output draws more current. The screens drop, the PI voltage drops (which reduces output), the preamp voltage drops (which narrows clean bandwidth "browning" the sound). The "key" to the Wreck is the third stage: biased cold, it reduces gain to a barely manageable point and clips the signal asymmetrically. (There is some near-scholarly analysis of this on TAG if you search hard enough.

Dumble are mostly clean PA with preamp modulation. I'm not sure the two can be blended. There may be a way. Keep us posted.