5E3M Deluxe Micro Prototyped Using Merlin B9A Boards

[robrob]

Did some more comparison playing today. I ran my H&K Tubemeister 5 (single 12BH7 power tube) through my Weber 12A125A alnico 12" and JBL E130 hemp cone 15" speakers along with the Deluxe Micro.

The biggest difference in tone is the Deluxe Micro's low end. It's always there no matter how hard you shred the little amp, while the Tubemeister screams with modern higher pitched accuracy. You could really hear the difference between the two amps through the big 15" JBL E130 but the Deluxe Micro blows away the Little Hoffbrau when playing clean through a Weber 12A125A 12" alnico.

[robrob]

I'm beginning the design stage of my next project amp, the 5F6A-M Bassman Micro. It uses three 12A*7 tubes and features the 5F6A Bassman's preamp paired with the earlier 5E6A Bassman's cathodyne phase inverter which feeds a true push-pull power amp using 12AU7 or 12BH7 power tubes.

You can follow the project here: http://robrobinette.com/Bassman_Micro.htm

[Riffraff]

I did some more tweaking to the amp design and the little Deluxe Micro sounds fantastic. It's absolutely killer tweed with a 12AY7 in V1 and it gets snarly mean with a 12AX7. I made four design changes during the test and tweak phase. The first was to drop the Master Volume pot from 1M to 500K to attenuate the signal from the driver stage to the power tube. The second change was to increase the power tube grid stopper resistor from 330K to 470K, again to attenuate the signal from the driver stage and reduce power tube blocking distortion. The third change was to add a Master Volume Bright Cap to add some brightness to lower Master Volume levels. This really made the Master Volume more useable. The final tweak was to drop the power tube cathode resistor from 2.2K down to 870 ohms which boosted the clean power output from 135 milliwatts up to 720 and max power with distortion climbed to 1.33 watts. The amp sounds a little more lively too. I also changed my recommended power transformer to the ClassicTone 40-18027. All the diagrams on the Deluxe Micro webpage reflect these changes: http://robrobinette.com/Deluxe_Micro.htm

NICE!!

I have most of these parts on hand. I might need to order a couple of caps but other than that I'm good to go. I'll be trying this one when I get a little time.

[robrob]

If you plan to use a tube rectifier then a power transformer with slightly higher HT voltage is recommended like the ClassicTone 40-18028 with 300-0-300V. This compensates for the voltage drop so you end up with a power tube plate voltage around 400V.

[robrob]

We finally have our first clip of the Deluxe Micro (hopefully more to follow). Keep in mind it was recorded using an iPhone but it still sounds really good. This is from Deluxe Micro #3's builder:

https://www.youtube.com/watch?v=aD42Z26Ua3A&feature=youtu.be

[Zozobra]

I've just ordered a bunch of these boards and I'm finding your layout creator template very useful, so thanks for that

I've made layouts for an OR/OD120 and the lead channel of a Splawn Nitro thus far. Can't wait for the bits to come in the post!

[KCTigerChief]

Absolutely LOVING what you are posting. Welcome to the forum man. Hell, this is the correct place for this, but you should really post some of these in the Amp forum on here.

Love the labeling you did on the schematic...Will help some people out.

Welcome...Good to have you here! I'm going to try and build one of these!

[hardvalve]

VERY cool

[JerEvil]

I've just ordered a bunch of these boards and I'm finding your layout creator template very useful, so thanks for that

I've made layouts for an OR/OD120 and the lead channel of a Splawn Nitro thus far. Can't wait for the bits to come in the post!

THIS I want to hear! To the OP, that little guy sounds great!

[Zozobra]

I've just ordered a bunch of these boards and I'm finding your layout creator template very useful, so thanks for that

I've made layouts for an OR/OD120 and the lead channel of a Splawn Nitro thus far. Can't wait for the bits to come in the post!

THIS I want to hear! To the OP, that little guy sounds great!

First I'm making a 20W OrMAt based design but the nitro will follow as a rack mount pre.

[Zozobra]

So I hacked up the first amp I ever built (MadAmp A15 Mk2 kit) to fit the B9A boards in. Circuit is a PPIMV OrMat type thing. It needs a bit of work to get sounding right as there is certainly frequency doubling occurring in the cathodyne PI when overdriven so the next port of call is to add a big grid stop. There might be a bit of blocking distortion occurring too as the bass is a bit weak and farty. Time to dig the O-scope out...

[robrob]

Very cool amp, let us know how the tweaking goes. The blocking distortion may be occurring in the power tubes so you may also need to add or increase the value of the power tube grid stoppers or lower the value of their grid leaks for some signal attenuation.