D-type cathode biased

[10thTx]

I wanted to do something a little different. So this amp is cathode biased and uses a GZ34. I used a paralleled terminal layout. Some of the component values and layout are different.

I tend to use front panels on my cab heads that attach with velcro, so I put the OD tone controls on top for easy access.

It is the quietest amp at idle I have ever built or owned which surprised me with the wiring so messy. I'll start tweaking it this wkend. Hopefully will get the cab head built within a few wks.

With respect, 10thtx

[phsyconoodler]

Not that bad looking.
I just finished one with 4 -6CA7 phillips tubes,cathode biased and so far it's pretty nice sounding.I need to tweak the treble and bass pots as the treble comes on too quick and the bass is too late.
This one might benefit from the bass mod wire and leave it at that.
The overdrive is really nice.
I'm using an old set of Traynor Transfomers and they are HUGE.
I decided to cathode bias it when the plate voltage ended up at 430v(416v from cathode to plate).
I have the tubes at about 17.8ma at idle.I can easily bump that up quite a bit but for now I like it as is.
Certainly no lack of clean headroom with 4 bottles and 2-12's!

[Structo]

Clever build!
I see you used the 470K/47pf on the input of the OD.
What does that bring you?

[10thTx]

I see you used the 470K/47pf on the input of the OD.
What does that bring you?

Not sure I understand the question accurately? It reduces signal to the input of the OD but allows some high frequencies to bypass.

I just got the thing built and I'm very impressed with the tone particularly the smoothness of the OD and sustain. However, I typically tweak amps I build and plan to do so with this one also.

With respect, 10th

[M Fowler]

Looks like a great project do you like how its working out so far?

Mark

[10thTx]

I like it alot. It needs some tweaking but it has nice harmonics and does the blooming thing somewhat decent on the mids but not as well as I'd like on the higher frequencies (yet).

I'll tweak it some this wkend and repost once I get it where I want it. I'm not used to so many adjustments available and I think it might take awhile to dial this in.

I picked up some nice sapele wood and AAA quilted maple for a cab head. It'll be a couple of wks before I get it finished.

With respect, 10thtx

[Structo]

What did you use for your relay?

[10thTx]

I used a Weber relay board. Easy to install and not expensive. It was my first venture in using a relay.

With respect, 10thtx

EDIT: 6-27-10

The amp is now tweaked to where I want it. The clean channel is a little brighter and the OD channel has more mids & bass. However, the OD channel is still slightly bright than the clean channel. It blooms very nicely with these component values.

[10thTx]

Finally got the cab head done. Wood is sapele with quilt maple front panel. Half blind dovetails.

With respect, 10thtx

[M Fowler]

The cabinet looks great. Did you get all the tinkering done and finalize your schematic?

Mark

[Structo]

Whoa!
That is nice.

Is it just the speaker cab that makes the head cab look so big?

I know that most D style amps are tubes down so maybe that is what is throwing me.

Did you make the speaker cab as well?

Looks a lot like a Bob Burt cab.
I like how the baffle slants back.
What do you have in it?

[10thTx]

The 6-17-10 schematic represents what I'm anticipating being the final version. In other words, I don't see/hear a reason to change anything currently.

Yeah the speaker cab is pretty small. Close to Princeton Reverb or 5E3 Deluxe size. And yes the chassis is pretty big. 20" x 2.5" x 8". It hangs over the speaker cab on both sides by @ 1". Cab has a Red, White and Blues in it.

I have another head that is same length as the speaker cab. It has a pentode going into a CF then switchable D-type OD with HRM into a cathode biased D-type LTPI and poweramp. And it has VVR also.
http://s28.photobucket.com/albums/c216/ ... ketcab.jpg

I built both the head and cab out of sapele.

With respect, 10thtx