Hybrid build in progress

[Luthierwnc]

I am accumulating parts for my next “D” amp. The first was a ’97 HRM which I have over an open-back 2X12 with Red, White and Blues. It came out really well. At the same time I built a Reverbolator along the Glasman lines but using a traditional Fender 6k6 driver. It also came out really well and compliments the HRM beautifully.

The upcoming amp will be a little more experimental. On paper now is a Hybrid A 1X12 combo with a switchable internal D-lator using a pair of 7591 outputs. It is pretty close to the posted schematic with these exceptions:

Switchable fixed/cathode bias
Switchable choke/resistor to the screens
Switchable 22m/none/44m NFB loop on CL2
No Rock/Jazz or Deep switches
4 or 8 ohm switch in case I add an extension cab.

I’m using a Tremolux-style PT which should be good for about 430 on the plates. The D-lator supply comes off the choke with two separate nodes. The OT is a Marshall JTM45 style from Weber which suits the impedance of the 7591s. I chose the higher overhead version. The Boost and OD will be controlled by footswitch (same one I use on the HRM). RN65’s, OD’s and a couple oil/paper caps in the PI. Right now, the plan is to get a little digital reverb to Velcro on top or inside – maybe a Picoverb.

The amp will be used for live playing, jamming, etc. The HRM has the jazz/rock/fusion stuff covered nicely. The idea with this amp is to be the portable cross between the HRM and a more of a Deluxe Reverb sound for warmer, bluesier tone. That and to not be so loud that I can’t get near the sweet spot. Guitars use low-output single-coils and humbuckers. Few (if any) pedals. Nothing gainy or metal.

The biggest dilemma I have now is what speaker to use. Before deciding I can test the RWBs, Tonespotters, AlNiCo Blue Dog, Cannabis Rex, Celestion Blue (for comparison sake but not too loud) and a couple of 2X10’s if I don’t like anything to that point. In my mind, the sound is 2/3 American and 1/3 British. The Wizard seemed like a good choice but a number of people I respect on this forum haven’t been able to make them work as single 12’s. Same story with the G12H30. Other options seem to be the Swamp Thang, Texas Heat, G12-65 and the EVM 12-L. AlNiCo Tone Tubbies and a big magnet Weber 1265 are also in the mix. I’d sacrifice a little top end for a bigger bottom (comments limited to tonal parameters).

If you have any comments, suggestions or witty repartee, fire away.

Thanks, Skip

[skyboltone]

Hi Skip:
I haven't even started my first D yet, but I'm planning the second. I have a couple of Fisher OT's. One needs repair/rewind (I haven't opened it yet to see if it's something simple) and the other is in good shape. I didn't realize that the 7591 had that kind of z out. Looks like a fine project, and will take 6V6s too. THD is listed at 1.5% fixed and 2% cathode bias. Man that's clean.

As far as a speaker, I wonder about the Jensen P10-12 R or N. Is that what was in the Deluxe to begin with?

Dan

[Normster]

It's good to hear another brave soul willing to risk a little experimentation. I'm building a little experimental ODS as well...5AR4 rectifier, 6V6 output, and 1-tube reverb. I'm using toneslut (Moose's) trannys (designed for a Trainwreck, but I liked the specs on them). What I'm hoping for is Deluxe Reverb style cleans with ODS style gain, hopefully with a bit more top end and bloom.

I like your approach, but I use the deep switch too much to be without it. I find it softens the tone a bit when I want a little less bite. I'm also curious to try the values in the '80s ODS that Gil posted...100k plate/1.5k cathode with 10uF bypass. Not sure about the .002uF treble cap though. I'll probably go with a 270pF treble and .047uF mid to get the Deluxe cleans.

[Luthierwnc]

Dan, make one first. You'll be surprised at how it effects everything else. Stuff like where do you put the bolts to attach it to the cab, layout, how much space a cap actually uses...the list goes on. Deluxes usually had a ceramic Utah or Oxford. Really old ones might have a Jensen.

Normster; I had a good hard look at your set up. My layout borrowed a couple ideas although about half of the D-lator is on terminal strips to keep it close to the pots and jacks (rear panel). The CL triodes are going to get 100k/1.5k resistors with 10uf caps. Thanks for the tip about the deep. I don't especially like tube screamers so it is nice to have the OD built in. I like the cleans through the D-lator on the HRM build. Highly recommended project!

Expect progress reports.

Skip

[Pete]

Skip , you may like the Emnce Tonker (I do), very nice low end and plenty of it (but not too much)IMHO.
I have them in my 2X12 open back and 1X12 ported closed back. I use these with 100 watter nearly identical to the "Gill '82".
And, also in my 50W combo (same style amp as the 100), and I use 99% humbucker guit.
Are you planning to try various speakers after you complete the amp? (would be best)

The biggest dilemma I have now is what speaker to use. Before deciding I can test the RWBs, Tonespotters, AlNiCo Blue Dog, Cannabis Rex, Celestion Blue (for comparison sake but not too loud) and a couple of 2X10’s if I don’t like anything to that point. In my mind, the sound is 2/3 American and 1/3 British. The Wizard seemed like a good choice but a number of people I respect on this forum haven’t been able to make them work as single 12’s. Same story with the G12H30. Other options seem to be the Swamp Thang, Texas Heat, G12-65 and the EVM 12-L. AlNiCo Tone Tubbies and a big magnet Weber 1265 are also in the mix. I’d sacrifice a little top end for a bigger bottom (comments limited to tonal parameters).

If you have any comments, suggestions or witty repartee, fire away.

[Luthierwnc]

I'll wait to choose a speaker (and make the baffle) until I have a chance to air out the speakers I already have. If one of them isn't a natural, I can get back on the forum and say what I liked or didn't like about each. It will have a lot to do with the amp itself. Reading the schematic and listening to the clips tells me this amp will favor the fundamental with less separation on the highs than the HRM. That's an educated guess based on lots of wrong guesses so it is better to hold off.

The wild card will be the 7591's. That would seem to be the perfect tube for bridging the gap between 6V6's and 6L6's but they were still pretty new when solid state killed the tube business. Probably like the cool new dinosaur just before the meteor hit. My only other 7591 amp is a Gemini I and it is cathode biased for maybe 20 watts. Very sweet tone and it stays clean just long enough. I was dithering between EH and JJ's and will probably go with the latter since I can use bear traps to hold them in. Opinions are welcome here too (hint)

The Marshall JTM45 trannies on the market are really versatile since they are made for either KT66's (or 7591's) at 6600 Z or half that for El34's. Weber has 'em for fifty bucks and the Mojo wholesale price is comparable.

I kept a photo diary of the HRM build and will probably do the same for this amp. Since it is in the early stages, I might just post the occasional pic for viewers at home.

Skip

[dogears]

Cause it has a traditional treble cap. That is the midboost.

I'm also curious to try the values in the '80s ODS that Gil posted...100k plate/1.5k cathode with 10uF bypass. Not sure about the .002uF treble cap though. I'll probably go with a 270pF treble and .047uF mid to get the Deluxe cleans.

[Luthierwnc]

Just got the chassis back from the welders. You can't see it from this view but the front is angled like a Fender. The corners are a little bumpy so I'll probably get some thin Garolite for the faceplate decal. sh

[Bob-I]

..... thin Garolite for the faceplate decal. sh

I had really good success with a Kinkos laminated printout of my faceplate, glued to the thin gargolite. It cost $5 and looks very good. I'll go with the matte finish if I do it again, the gloss reflects light too much.

[Luthierwnc]

Thats what I do too. I just send the printer the Corel drawing full sized and they put it on the kind of vinyl used for car signs. They also put an extra coat of laminate on it to protect against abrasion. Works great and only costs about $15. I just ordered the front and back for this 5 minutes ago. Here's a pic of the first HRM

[Normster]

Man, that TW-style head looks absolutely elegant sitting on the Burt V-front!

[Luthierwnc]

Actually, I built the cabs too. That one is made of khaya and has a couple of RWB's. The head is oak with a Spanish cedar faceplate. Most of the time I make guitars. Amps are a hobby within a hobby.

[Luthierwnc]

I'm still waiting on the faceplates so the front and rear components aren't in yet. Everything else is ready. sh

[Luthierwnc]

These are the graphics for the face and rear of the amp. They are adhesive-backed vinyl which has been laminated for abrasion resistance. I'll stick it on some 1/32 garolite to be as smooth as possible and then contact cement that to the aluminum. These were designed on Corel 8. sh

[Normster]

Looks great so far. BTW, I dig Arion pedals!