My first build - AB763 Deluxe Reverb clone - opinions please

[Greg_L]

Hello guys, my name is Greg. I've recently built my very first amp, as the title says, and overall I'm very pleased with it and all of it's functions work as they should. It's a Weber 6A20 kit - built as a head unit. I'm using a ClassicTone 40-18087 OT. Otherwise a stock type build.

My only issue is a bit of "brittle" break up right at the attack of a note, it sustains for a sec, then the brittleness goes away as the note sustains out.

I've heard this sound on other AB763 type amps, but mine seems more brittle and a little more pronounced.

It happens on either channel, normal or vibrato, reverb on or off, tremolo on or off, no matter the mic or speaker used. It's always there.

Here is a soundclip running through the amp volume, guitar volume, reverb, and tremolo. You can clearly hear the brittle breakup, it almost sounds like a faint static on the attack of the notes. Sorry for the length and size of the clip, but I wanted to provide a high-quality example with lots of variation. Please download the wav file and listen and comment on what you think this may be.

This sound clip was done using a Gibson SG with a P90 bridge pickup through a Marshall 4x12 cab with vintage Celestion G12-65s.
https://jmp.sh/KXmIVIV

Other than that, I'm very pleased with the amp and happy with the outcome for it being my first build. It sounds great overall, it's just got that hint of brittle breakup all the time.

Any pics or specs you may need to help decipher this issue will be readily available upon request. I have tons of pics and pin voltages and all that stuff. I even have a scope at the ready - I'm not very good with it, but I'll give it a shot. Haha.

Thanks for your time and I genuinely appreciate any guidance you can give me.

[g1]

Can you post your power tube DC voltages at idle (no signal). Do you have a means of checking idle current of power tubes?

[Greg_L]

Can you post your power tube DC voltages at idle (no signal). Do you have a means of checking idle current of power tubes?

Sure thing.....

Power Tubes
Tung Sol 6V6GT


V7
1: NA
2: H
3: 435
4: 435
5: -42.0
6: 436
7: H
8: 19.5 mv - measured at 1 ohm resistor to ground

V8
1: NA
2: H
3: 435
4: 436
5: -42.2
6: 436
7: H
8: 19.5 mv - measured at 1 ohm resistor to ground

[dstrat]

Hi, first I will say congrats that amp sounds pretty good to me, much of what you hear IMO is those speakers.
try it with some real greenbacks you will be surprised.

[Greg_L]

Hi, first I will say congrats that amp sounds pretty good to me, much of what you hear IMO is those speakers.
try it with some real greenbacks you will be surprised.

Thank you very much. I have some Greenbacks, it's pretty much the same thing no matter what speakers or mics I use.

The sound doesn't really bother me too much because it doesn't show up in a mix or live, but it's eating at me because it just doesn't seem right. I've done everything in my power to do this build right. Everything else is great. Just that little brittleness has me scratching my head.

[dstrat]

um ya could be some slight oscillation which would come down to layout, grid wires (p2 - p7) on ax7 tubes can be fussy about how close they are to other higher level signal carrying wires. but I can only guess at this point. maybe a clear picture of the tube wiring etc may help.
there are lots of knowledgeable folks here that will likely have better ideas then me. only spoke about the G12-65 speakers because they always seem brittle to my ears. crank it up and play it will smooth out over some time playing it also.

yeah I do like the P90s!

[Greg_L]

um ya could be some slight oscillation which would come down to layout, grid wires (p2 - p7) on ax7 tubes can be fussy about how close they are to other higher level signal carrying wires. but I can only guess at this point. maybe a clear picture of the tube wiring etc may help.
there are lots of knowledgeable folks here that will likely have better ideas then me. only spoke about the G12-65 speakers because they always seem brittle to my ears. crank it up and play it will smooth out over some time playing it also.

yeah I do like the P90s!

Thanks. My 65s are from 1980, so they should be broken in by now. Haha. The amp is brand spanking new though. I've been beating on it, but it still has that "new amp smell". I just finished it a few weeks ago.

I suppose oscillation is a possibility. I've had it on my scope and the signal path looks normal to me from input all the way to speaker output, but I admit I'm not very well-versed with using oscilloscopes. I just got it pretty recently.

As for the grid wires, I *think* they're pretty good. My heaters are done "Marshall style" with a bit of Valve Wizard thrown in, so there's no criss-crossing with signal and heater wiring. The layout of the board in relation to the tube sockets means I can't avoid a few wires crossing here and there. But over all the amp is very very stable and quiet. It's quieter than any of my Marshalls. And original Fenders looked like pure hell inside, so I feel okay about mine. Hahahaha.

Anyway here are some pics.

[dstrat]

over all everything looks ok , I didn't look real close , this time of night my eyes are shot.
give it some time it will mellow over time if played it regularly.

are those tubes new ones or are like this real tung-sol? just curious
.

I have tried to cook this tube but it just keeps kicking.

yeah you did a very nice job with that amp. I would be very happy!

[Greg_L]

over all everything looks ok , I didn't look real close , this time of night my eyes are shot.
give it some time it will mellow over time if played it regularly.

are those tubes new ones or are like this real tung-sol? just curious
[ATTACH=CONFIG]49551[/ATTACH].

I have tried to cook this tube but it just keeps kicking.

yeah you did a very nice job with that amp. I would be very happy!

Thanks a lot!

Mine are new production Tung Sols. Honestly, I'm not that into NOS vintage tubes. *Ducks for cover*

I know they're nice and all, I have a few nice old 12AX7s, but my amps get ridden hard and for me new stuff seems to be fine....and cheaper. I blew up some TAD EL34s in a 50W Plexi cranked to the moon - like really blew them up. It was quite the light show. But overall I've had good luck with regular production tubes.

[Chuck H]

Looks and sounds right to me If you wanted a darker sounding amp you should have built a different model. DR's aren't known to be "mellow"

Here's a trick I use to kill the glassies on one model I build. Connect a 4.7pf/1000V ceramic cap from the plate to the grid on each input triode. Don't go larger or you will hear the affect on the overall EQ. Try it on one channel first (obviously) to see if it gives you what you want. It shaves off the shards without really killing the top end. Further, the effect is relative to gain. So the more you attack the more it works. Worth a try.

It's worth noting that most really good players like that glassy top end and they alter their attack to suit what they're trying to do. Removing it for such players is limiting. YMMV. And FWIW I have the 4.7pf cap on my own amp (I'm not a really good player )

[dstrat]

oh I just have a few old ones laying around I really like the sound of (compared to newer ones) but hey we have to use what we can get now days , I say don't worry be happy!

[Greg_L]

Looks and sounds right to me If you wanted a darker sounding amp you should have built a different model. DR's aren't known to be "mellow"

Here's a trick I use to kill the glassies on one model I build. Connect a 4.7pf/1000V ceramic cap from the plate to the grid on each input triode. Don't go larger or you will hear the affect on the overall EQ. Try it on one channel first (obviously) to see if it gives you what you want. It shaves off the shards without really killing the top end. Further, the effect is relative to gain. So the more you attack the more it works. Worth a try.

It's worth noting that most really good players like that glassy top end and they alter their attack to suit what they're trying to do. Removing it for such players is limiting. YMMV. And FWIW I have the 4.7pf cap on my own amp (I'm not a really good player )

Hey thanks for the tip!

I like bright. That's no problem. I do not want "dark". I just wasn't sure if that little bit of brittleness in my sound is supposed to be there or not. I'm a life-long Marshall guy and this is actually my first Fender type amp. I played a lot of Fenders in stores before I decided the Deluxe Reverb is what I wanted to build.

This amp will primarily be used for semi-aggressive surf/rockabilly type tones. There will be lots of reverb and tremolo action happening with this thing!

So for those caps, I will give it a try and see what happens. I've done something similar with high-gain mods on Marshalls to kill oscillation. Do they really need to be 1000v though? There's only ~200v on the plates. Just curious.

[Chuck H]

500V would be fine. I suggest 1000V because you REALLY don't want that cap to ever fail short and apply HV to the input grid (which is connected to your guitar!!!).

[Greg_L]

500V would be fine. I suggest 1000V because you REALLY don't want that cap to ever fail short and apply HV to the input grid (which is connected to your guitar!!!).

Ha right. Okay thank you.

I'll go pick up some caps tomorrow and see what happens.

[Steve A.]

Mine are new production Tung Sols. Honestly, I'm not that into NOS vintage tubes. *Ducks for cover*

If you search around the forum here you will learn that no one still makes 6V6s anymore... the current supply are basically military tubes that have been tested and do work in Deluxe Reverbs, etc. You might see what is recommended here for DRs these days.

While NOS tubes can be very pricey there are some sellers on eBay that sell used and tested old stock tubes, usually with a 30 day exchange period.

Steve A.

P.S. The head cabinet for your DR looks really cool. I wonder if it would fit my 2006 DRRI chassis...

P.P.S. So how many hours have you run your amp? It seems to me that they mellow out a bit with time... perhaps the caps? Or maybe I just get tuned in and pick softer...

You got this covered with your original from 1980 but Warehouse Guitar Speakers makes an ET65 Celestion clone that sells for $80. GC & MF sell the 8 & 16 ohm varieties with free shipping which is really cool since WGS's shipping charges have always been a deal killer for me.

Not that I tend to go overboard (I do! I do!) but I've ordered 4 of them since discovering them last year — best.speaker.ever!