EL84hrm

[mat]

Sounds great Mat.

Thanks M Fowler

[10thTx]

Removed. SE 5881 with Mat's preamp and OD will not work. Not enough drive to the 5881.

With respect, 10thtx

[stiltamp]

Hi Mat,

I follow suit the words of the other replies, the MiniHRM sounds really great.
It's awesome!
I take a great interest in that amp, I intend to build the preamp section for my own.
That's exactly why I'm asking.
Is the overdrive generates in the preamp section only or is there a portion from the power stage?
What brand of pre amp tube are used?
Did you note the HRM-stack and the trim pot settings?

cheers
Manfred

[M Fowler]

I can't believe the tone you guys are getting out of these mini D amps and thanks for all the information supplied.

I would love to build one some day.

Mark

[mat]

Hi Mat,

I follow suit the words of the other replies, the MiniHRM sounds really great.
It's awesome!
I take a great interest in that amp, I intend to build the preamp section for my own.
That's exactly why I'm asking.
Is the overdrive generates in the preamp section only or is there a portion from the power stage?
What brand of pre amp tube are used?
Did you note the HRM-stack and the trim pot settings?

cheers
Manfred

Hi Manfred,

Sorry, I don't remember what brand of tubes were in when I recorded the clips of the amp. The miniHRM was a bit tricky to get it sound good. I used a stand alone tube reverb unit on the passive loop to smoothen the sound. It worked pretty good but the HRM's overdrive tone stack was really hard to adjust for a optimal sound.
My new build 86-Special uses EF86 tube for the overdrive and it is hard to get it to sound bad - much more usable sounds than from the miniHRM. Only problem is that a single 12AX7 and EL84 does not produce enough volume to match the 12AX7+EF86+EL84 overdrive channel. Actually this does not bother me much because the amp cleans nicely with the volume pot of the guitar, so I mainly use the od channel only.
Next I'm going to try the preamp with 2xEL84 push pull to get more volume.

Cheers,

[stiltamp]

Hi Mat,

thanks for the information!

cheers
Manfred

[mcrracer]

Can someone direct me to some gut shots of this amp? Thanks

[sixstringer]

I second that request, are there gut shots of the original single tube version as well as the duet (2-el84) version?
Thanks

[rp]

I'm impressed too, congrats, this is the only SE I've heard w/ a tone stack that I like. Definitely has that Dumble sound happening, I never would have thought it possible w/a little SE amp. It doesn't has that thin harshness of 1 or 2 EL84s, El84s are fun but you need 4 to get good tone IMO. For small amps the 6V6 is better for me.

I too had built a AX84, the basic P1, and hated it, any of the Champs or AC4 killed it. I built it for a friend so it's too late to convert it to this.

Colossal's drawing skills are colossal, thanks.

Love to try one of these but I've either got money and no time or time and no money - both suck

[Zippy]

I'm following this with some interest - all my experience is with classic Fender-style amps.

I have a couple transformer sets for higher power SE amps (thinking KT66).

What would I need to add to this preamp to make it better able to drive a 6L6/5881/KT66?

Thanks for the discussion.

[10thTx]

What would I need to add to this preamp to make it better able to drive a 6L6/5881/KT66?

DaGeezer and I both (on the Hoffman forum) independently tried to make this work with a 6L6/5881 and were unsuccessful. Not saying it can't be done, but we were not able to make it work.

With respect, 10thtx

[Zippy]

What would I need to add to this preamp to make it better able to drive a 6L6/5881/KT66?

DaGeezer and I both (on the Hoffman forum) independently tried to make this work with a 6L6/5881 and were unsuccessful. Not saying it can't be done, but we were not able to make it work.

With respect, 10thtx

Whoa, that's daunting. Mercy.

What did you try (is there somewhere that I can follow a thread on the attempt)? Extra drive stage or cathode follower?

Thanks (and thanks also for your other considerable contributions - I'm a big fan of your work).

[sepulchre]

That really too bad. I was thinking KT88. A CF might work but I wonder what it would do to the tone.

[10thTx]

Regarding the 5881's not working. 2nd post on this thread:

http://el34world.com/Forum/index.php?topic=9149.0

And on the lengthier thread, start on the 2nd page at post #60:

http://el34world.com/Forum/index.php?topic=9150.50

With respect, 10thtx

[jazbo8]

Regarding the 5881's not working. 2nd post on this thread:

http://el34world.com/Forum/index.php?topic=9149.0

And on the lengthier thread, start on the 2nd page at post #60:

http://el34world.com/Forum/index.php?topic=9150.50

With respect, 10thtx

HPB already did the analysis - you need to add an extra stage if you want to drive the 5881 to clipping. Alternatively, you could lower the screen/plate voltage on the 5881 a bit thereby allowing the use of a shallower grid bias, but at the expense of slightly lower output power. It's interesting to note on this thread the repeated negative comments made WRT the AX84 P1, HO, etc., as they have been pretty popular with DIY amp builders over the years...