Loving my Diavlo RD20H, questions on V1-V4 location & tubes?

  • Thread starter Thread starter GJgo
  • Start date Start date
I ordered a balanced LPS & put it in the PI, so now I have this.

V1 Mullard
V2 gain Tung Sol
V3 clean Tung Sol
V4 PI Sovtek LPS

This is definitely the best combo yet- I don't really know how to describe it, but the LPS in the PI really opened up the tone. Gave it more depth. I still need to try it cranked to make sure nothing weird happens, but I think I can call the pre tubes good with this combo.
 
Had something weird happen with the RD20 tonight. When I turned the master volume all the way down, it would still push some of my playing through the speaker- in a very cutting-in-out-choppy, crackly fashion. When I turned the volume up however it worked normally. Does anyone have any idea if this is a tube issue or possibly a hardware issue? I still have the stock Ruby power tubes in it, and the master volume dashpot has always been very crackly when turning it up from fully off.

I have ordered a matched pair of JJ 6v6 & an amp-head bias probe to set it up.
 
GJgo":1huiidgc said:
Had something weird happen with the RD20 tonight. When I turned the master volume all the way down, it would still push some of my playing through the speaker- in a very cutting-in-out-choppy, crackly fashion. When I turned the volume up however it worked normally. Does anyone have any idea if this is a tube issue or possibly a hardware issue? I still have the stock Ruby power tubes in it, and the master volume dashpot has always been very crackly when turning it up from fully off.

I have ordered a matched pair of JJ 6v6 & an amp-head bias probe to set it up.
Click to expand...

It sounds like it may just be the volume pot, it may not be of high quality or it may be flaky at the lowest setting.
Could also be dirty so even if you've got turned all the way off it's still got some contact letting a higher signal through.
By turning up slightly you're getting past the bad point.
So if it works fine turned up a bit I'd say it's the volume pot.
 
That makes sense, thanks- I'll look into it.

So I got the amp-head bias probe to install the JJ 6V6. Does anyone know if the RD20 is a class A amp like the little brother RD5 is? Or class A/B or..? Where are you guys setting your bias on the Diavlos?
 
I installed the http://www.amp-head.com/product_info.php?cPath=21&products_id=70 probes under the stock Ruby 6V6 tubes to see how it was set up at the factory, here's what I got.
-The plate voltage is 306~310v (slight float) on both tubes.
-The Bias current is 23.1mA on tube 1 & 23.2mA on tube 2.

According to the Amp-Head worksheet a 6V6 should be in the 22-28 mA range, but it makes no mention of plate voltage.

According to http://www.ax84.com/biascalc.html it says this, which tells me the factory setting is really low.
6v6 (Max dissipation 14 watts)
Results: For 308 Volts
60% 70% 80% 90% 100% 110%
27.27 ma 31.82 ma 36.36 ma 40.91 ma 45.45 ma 50 ma
Recommended Bias point for AB1 operation is 70%

So then, before I throw the JJs in should I bias up these Rubies to 60-70% & see how it changes the sound?
 
GJgo":ot2g2x9l said:
I installed the http://www.amp-head.com/product_info.php?cPath=21&products_id=70 probes under the stock Ruby 6V6 tubes to see how it was set up at the factory, here's what I got.
-The plate voltage is 306~310v (slight float) on both tubes.
-The Bias current is 23.1mA on tube 1 & 23.2mA on tube 2.

According to the Amp-Head worksheet a 6V6 should be in the 22-28 mA range, but it makes no mention of plate voltage.

According to http://www.ax84.com/biascalc.html it says this, which tells me the factory setting is really low.
6v6 (Max dissipation 14 watts)
Results: For 308 Volts
60% 70% 80% 90% 100% 110%
27.27 ma 31.82 ma 36.36 ma 40.91 ma 45.45 ma 50 ma
Recommended Bias point for AB1 operation is 70%

So then, before I throw the JJs in should I bias up these Rubies to 60-70% & see how it changes the sound?
Click to expand...

Yes.
 
My Google-fu says 23.2mA is 51% for a 6v6GT at 14v max dissipation (vs. 12v for a standard 6v6) The Rubies that came in it are a 6v6GT STR, and the JJ 6V6 S that's going in it from what I've read is also a 14v tube.

Here's another good calc I found. http://www.webervst.com/tubes1/calcbias.htm

I'll bias & report this weekend. Hope to do some more comparo vids too.
 
This is good info. It's also the closest thing I've seen to a single person thread that keeps going and going. :lol: :LOL: I'd like to try the RD20 myself IF (and that's a big IF) I ever see one in a music store.
 
LOL yeah I'm feeling that. Plus I need to get my post count up so I can post this new V30 I have to the classifieds. :P

I just think there must not be that many out there yet, and getting this all written down might help the next guy. ATM there's next to no info out there on the Diavlos. I'm super happy with mine outside of the volume pot thing.
 
So I biased up the Rubies from stock 51% to 60% & then 70% (31.6 mA in my case), no problem. As I turned it up they sounded less brown & more punchy, definitely an improvement. The tone didn't change, just the character.

Next I tossed in the JJ 6v6 S tubes. With these in the bias pots maxed out at 28.5 mA (matched), or 63%. That's kind of a bummer- I've read that the JJs should be run at least 65% & they like to be run hot in general. They are a bit louder. Tone-wise I'd say they have slightly less gain than the Ruby, but the sound is more full & tighter- I'll play with them for a while & see if it grows on me. I bet it would cut through a mix better.
 
Ok here I go again. Here's a video of the stock tubes vs. all the re-tubing. Honestly, I think for a metal amp, the stock stuff sounds better. WTF! It's easy to get caught up in upgrade-land when you're doing this stuff, I'm glad I have some videos to go back on for reference. I think I should at least step back to the Ruby power tubes & re-evaluate, the JJs I did notice lost a lot of gain.
http://youtu.be/UwY_XTPECGE
 
After playing for a few days I definitely missed the gain I lost switching to the JJ power tubes so I went back to the Rubies. Interestingly enough when I put them back in, the max bias I could dial the pots up to was 30.8 mA or 67%. I find it strange that the hardware won't allow a 70% bias on either tube type.

Anyone have opinions on what other 6V6 tube types have a good high gain sound?
 
I'm really starting to think that the G12T-75 sounds like crap with the Diavlo. It's not scooped, it's not ...And Justice For All, it's just no-tone-flat with this voicing. Thinking of going to go back to the pair of V30s, because that speaker sounds really killer with the voicing of this head. Probably why Randall picked it... It'd be fun to try some other Celestions in there but I think I'm done spending money on it.

Honestly I wish I still had the Blackstar around to try the G12T75 with that head- I *think* it could have solved a lot of why it sounded like ass (with the V30). Really interesting to see how different components really mesh or clash, you definitely can't write something off just because it doesn't work in one combination.

Also spoke with customer service today, the main volume pot definitely has issues. They're just sending me to an authorized service center to fix it. Probably just needs a new pot soldered in.
 
I've spent quite a bit more time playing this rig & changing my mind about some things. Still happy with it overall.

I decided that, even though I really wanted to split the speakers & kept messing with it, the G12T75 is just killing the tone & I can't do it. So, it's back to V30s and I have a basically new T75 to sell. Given that this amp really likes the V30 & goes way too dull with the G12T75 does anyone have a recommendation for another Celestion speaker (I want it to bolt in) that might be a good pairing?

I was really liking the dark sound of keeping a Mullard or the stock Ruby in V1. Then, I went to Riot Fest for 3 days & was reminded how the guitar really needs to cut through the mix. When I came home I went back to the Tung Sol tubes in V1-V2-V3 and with this in mind I'm liking it a lot more. The Ruby definitely has the most gain of any 12AX7 I've tried in V1, but it is quite a bit darker & lacking in tone than the TS. I think the TS combo will really cut through the mix- it has the best gain of any of the non-Rubies I tried.

Side note I was at a Guitar Center a couple weeks ago & I played a Peavey 6505+ head with a 4x12 V30 cabinet. Woof, that thing had some serious br00tz. I didn't try the clean channel but the guy told me it wasn't very good.
 
Hi. Today i changed preamp tubes to Randall RD 20 head. First i took head out from case and check the circuit board to make sure where is v1,v2,v3 and v4. I been reading these forums many days and i still didnt get the right answer:). It goes like this from input plug to right: T1,T3,T2 and T4. T1 is first gain stage, T3 is OD channel, T2 is clean channel and T4 (near power tubes) is phase inverter. I put these tubes to my amp: T1 Tungsol 12ax7, T3 Ruby 12ax7 C, T2 Mullard 12ax7 and T4 Sovtek 12ax7 LPS. The amplifier sounds so much better now, clean channel is more warm and Od channel got more punch and distortion. . Pinch harmonics <3
 
A year plus later I still have the TS in V1-V2-V3 & the LPS in the PI. It was really splitting hairs trying all these different combos, but I'm happy with it as it is. I also picked up a set of TS 6V6 for the power section but I haven't put them in yet.

Kicking around the idea of picking up a used Mesa head just because. Of everything that's out there, honestly Me$a is the only thing I like better than these new Fortin designed Randalls.
 
GJgo":14r7ckej said:
A year plus later I still have the TS in V1-V2-V3 & the LPS in the PI. It was really splitting hairs trying all these different combos, but I'm happy with it as it is. I also picked up a set of TS 6V6 for the power section but I haven't put them in yet.

Kicking around the idea of picking up a used Mesa head just because. Of everything that's out there, honestly Me$a is the only thing I like better than these new Fortin designed Randalls.
Click to expand...

I have JJ 6V6 S power tubes. Yes its very annoying trying different tubes, but allways you finally get that sound what you wanted :)
 
I tried the JJ 6V6 but took them out. They were much louder, but killed the high gain. Not my taste.

Side note out of the box it was biased very cold.
 
This weekend I stopped by a Guitar Center, and I played a Diavlo RD45 head as well as a Marshall DSL15 head, both out of a V30 cab same as I have at home. Honestly, I think I like the 6V6 sound in my RD20 better than the 6L6 sound in the RD45. It really wasn't that much "louder", and the 45 I thought sounded a little flubby compared to the evil of the RD20. No reason to trade up for me.
 
GJgo":3le5f3ff said:
I installed the http://www.amp-head.com/product_info.php?cPath=21&products_id=70 probes under the stock Ruby 6V6 tubes to see how it was set up at the factory, here's what I got.
-The plate voltage is 306~310v (slight float) on both tubes.
-The Bias current is 23.1mA on tube 1 & 23.2mA on tube 2.

According to the Amp-Head worksheet a 6V6 should be in the 22-28 mA range, but it makes no mention of plate voltage.

According to http://www.ax84.com/biascalc.html it says this, which tells me the factory setting is really low.
6v6 (Max dissipation 14 watts)
Results: For 308 Volts
60% 70% 80% 90% 100% 110%
27.27 ma 31.82 ma 36.36 ma 40.91 ma 45.45 ma 50 ma
Recommended Bias point for AB1 operation is 70%

So then, before I throw the JJs in should I bias up these Rubies to 60-70% & see how it changes the sound?
Click to expand...
Hi
 
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