Help/advice voicing DLite 22?

[markmalin]

Hi guys,

I'm still not satisfied with the D'lite 22 I built. I used Normster's schematics and layout as a starting point and sourced my own parts, then have tweaked it. It's pretty much tweaked to the attached schematic. I'm using an Eminence Delta Pro 12A, but would like to try a Celestion. I'm running JJ Tesla 6V6's, and have tried various JJ and EH preamp tubes. Eveything functions fine, I just find the amp to be sort of lifeless and uninspiring. That's probably a harsh way to put it -- it's just not lively, dynamic or "touch sensitive". Seems compressed on clean and OD settings. The OD sounds good, just not very dynamic.

As a comparision, if you check out Gregor Hilden's "Dumble 69/70 Les Paul" clip on youtube, you can hear the dynamics in that Dumble he's playing. That's what I'm after. Also, I've been checking out this Rivera amp at a local music store, which my amp does sound similar to, but this thing had so much more dynamic range and touch sensitivitiy (I hate that term but I can't think of what else to call it .

Here is a list of the voltages I'm measuring. Any thoughts? Per Normster's suggestion I added a switch to disconnect the NFBL in V1, which makes a difference, but it's not very noticable.

Any thoughts? It's frustrating because I know in my head what I'm looking for, but I don't know how to tweak the amp to get there, or where to look for something that's not right.

Thanks for any thoughts you have on this.
Humbly,
Mark.

V1a plate: 205V
V1a cath: 1.77V
V1b plate: 210V
V1b cath: 1.67V

V2a plate: 214V
V2a cath: 1.77V
V2b plate: 218V
V2b cath: 1.67V

PI pin 1: 297V
PI pin 3: 54.5V
PI pin 8: 54.5V
PI pin 6: 307V

6V6 plates: 442V
6V6 pin 4: 442V
bias set at 21.8 ma

Power supply voltages:
446V at standby switch
441V at "HT + B"
419V at "HT + C"
336V at "HT + D"
328V at "HT + E"

[markmalin]

here's the power supply section of the schematic...

[odourboy]

Mark,

Since I've just done a build that is virtually identical to this one, I'll toss out some ideas for you. By coincidence, I was noting how similar my build was sounding to some of Gregor's recorded material.

My V1 and V2 plate voltages are about 15V or so lower than yours across the board. There seems to be a voltage threshold, above which these things seem to get stiff and harsh. I'd mess with your dropping string to try and bring them down and see if that helps.

You might try a 500 ohm WW in place of the 300 in the first PS string spot to get a little more sag and squishyness.

The 4K7 NFB resistor seems low to me for a 6V6 power section. The D'Lite uses 8K1 doesn't it? I've got something even higher in mine - I think 15K (though embarassingly, I didn't document it after my last change and I don't recall for sure). So you might have too much NFB in the power section which might ne imparing the responsiveness as well.

Just some ideas. Hope these help.

[markmalin]

Mark,

Since I've just done a build that is virtually identical to this one, I'll toss out some ideas for you. By coincidence, I was noting how similar my build was sounding to some of Gregor's recorded material.

My V1 and V2 plate voltages are about 15V or so lower than yours across the board. There seems to be a voltage threshold, above which these things seem to get stiff and harsh. I'd mess with your dropping string to try and bring them down and see if that helps.

You might try a 500 ohm WW in place of the 300 in the first PS string spot to get a little more sag and squishyness.

The 4K7 NFB resistor seems low to me for a 6V6 power section. The D'Lite uses 8K1 doesn't it? I've got something even higher in mine - I think 15K (though embarassingly, I didn't document it after my last change and I don't recall for sure). So you might have too much NFB in the power section which might ne imparing the responsiveness as well.

Just some ideas. Hope these help.

Thanks for the input, odourboy. That's totally bizzare that you built the same schematic and it sounds like what I want mine to sound like... go figure I'll try some of the things you suggested, maybe starting with dropping the voltages on V1 and V2. They seemed high to be compared to what other people have talked about.

Funny you should mention the NFB resistor over the power section -- I was talking with another amp builder about the situation and he also suggested increasing this. He said try something real high just to see if it changes anything and work from there. I think this is certainly an area I'd like to try to play with.

Re the dropping resistor, I have a 500 Ohm cement type, but not wire wound. Is WW better tonally? I'll see if I can scrounge one up.

Again, thanks for the input. I've got to try some of these things. That "Gregor tone" is haunting me

Mark.

[odourboy]

By all means, go with the cement type. I doubt there's any significant sonic difference - it's been suggested that a WW would have a small inductance that may have a subtle effect, but I'm sure it's subtle.

Getting back to the NFB resitor value. As I think about it, I may have that one messed up. I had to go higher in my own build because the OT I'm using only has a 8 ohm tap.

[markmalin]

By all means, go with the cement type. I doubt there's any significant sonic difference - it's been suggested that a WW would have a small inductance that may have a subtle effect, but I'm sure it's subtle.

I'll try the cement type first. If I were to use a choke instead of a resistor, do you know what size choke I would use?

Getting back to the NFB resitor value. As I think about it, I may have that one messed up. I had to go higher in my own build because the OT I'm using only has a 8 ohm tap.

Would you suggest I leave it alone then? Actually, I'm using a Heyboer 7,000 primary with 8/4 Ohm taps, running at 8 Ohms. If I understand this correctly, if I lower the size of the NFB resistor, I'm applying more negative feedback to the poweramp, squashing the signal some, right? I'm thinking if that's the case and I want to "liven" up the amp some, I'd go with a larger value. (someone correct me if I'm wrong)

All in all, it's encouraging that you built to the same schemo. as me and you're getting the sound I want Now to get my amp right. Honest, I was ready to completely dismantle the thing and start over.

Mark.

[odourboy]

Would you suggest I leave it alone then? Actually, I'm using a Heyboer 7,000 primary with 8/4 Ohm taps, running at 8 Ohms. If I understand this correctly, if I lower the size of the NFB resistor, I'm applying more negative feedback to the poweramp, squashing the signal some, right? I'm thinking if that's the case and I want to "liven" up the amp some, I'd go with a larger value. (someone correct me if I'm wrong)

All in all, it's encouraging that you built to the same schemo. as me and you're getting the sound I want Now to get my amp right. Honest, I was ready to completely dismantle the thing and start over.

Mark.

You're correct in your interpretation of what's going on with the NFB. The 4K7 works in conjunction with the 390R (they form a voltage divider, so it's the ratio of the two which determine the NFB) - increasing the 4K7 means feeding back less voltage, thus less feedback into the PI. You could actually put a pot in there wired as a variable resistor and 'dial-in' what you want.

For sure don't scrap the amp. That values in that schemo are fundamentally sound. I'm sure you're ust a few tweeks away from nirvana

[Fischerman]

Mark,
FWIW, the 8 ohm tap will have more voltage (so more NFB) than the 4 ohm tap...but not double. A 16 ohm tap would have double the NFB of a 4 ohm tap. I think that's what odourboy was getting at (RE: why he had to increase his NFB resistor).

EDIT: ooops, was posting at same time as odourboy.

[markmalin]

Mark,
FWIW, the 8 ohm tap will have more voltage (so more NFB) than the 4 ohm tap...but not double. A 16 ohm tap would have double the NFB of a 4 ohm tap. I think that's what odourboy was getting at (RE: why he had to increase his NFB resistor).

EDIT: ooops, was posting at same time as odourboy.

Thanks, Fisherman and odourboy. This is really helpful info.

For sure don't scrap the amp. That values in that schemo are fundamentally sound. I'm sure you're ust a few tweeks away from nirvana

Thanks. You're right, I just needed to hear that. I'm pretty stoked to know your amp sounds so good with these values. I hope to get some time in tweaking this weekend. Good idea on the NFB pot, by the way!

Mark.

[markmalin]

Mark,
FWIW, the 8 ohm tap will have more voltage (so more NFB) than the 4 ohm tap...but not double. A 16 ohm tap would have double the NFB of a 4 ohm tap. I think that's what odourboy was getting at (RE: why he had to increase his NFB resistor).

EDIT: ooops, was posting at same time as odourboy.

Guys, I was about to swap out the 4.7k NFB resistor with something bigger, but I thought that I noticed the NFB resistor was connected to the 8 Ohm tap rather than 4 Ohm as on the schematic. I was mistaken, it was connected to the 4 Ohm tap (as it should), but I thought it was wrong and switched which tap the NFB was connected to and put it (mistakenly) on the 8 Ohm tap. The amp started sounding more lively. I thought I had fixed something(!), until I realized I had moved the NFB to the wrong tap. Anyhow -- I think I'll play around with NFB values, but does this make sense??

Mark.

[odourboy]

Somewhat unexpected since going to from the 4 ohm to the 8 ohm will increase the amount of negative feedback (by a factor of X 1.41 I believe). But what's right for this build will depend a lot on the transformer, so experiment!

Question: Is your output tranformer common referenced to your signal ground? (Just checking... if not, the NFB is floating and could be doing wacky things).

Getting back to the issue at hand - I'd focus on the V1 and V2 plate voltages - I suspect they are having a more significant impact on your tone.

[Bob-I]

Anyhow -- I think I'll play around with NFB values, but does this make sense??

Mark.

Makes a lot of sense. I like to put a pot into the circuit and adjust by ear. Once I find tha value I put in a fixed resistor. Your mileage may vary.

[markmalin]

I wound up installing a 100K pot in series with the NFB resistor to dial in some values. At what point do you call it good? It seems in general that the > the resistance, the punchier and livelier it gets, but it's hard for me to hear the trade-off. Is it a balance between just enough punch but not too harsh of a tone?

I also temporarily wired in a decade box in series before the 330 Ohm "choke" replacement resistor to drop the voltage across the entire dropping string. I have it where the voltages now read:

(I've got to go measure them again, but from what I remember...)

V1 plate1: 195 V
V1 plate2: ~202 V
V2 plate1: 205 V
V2 plate2: 211 V

the PI plates are around 288 and 298

I think these are all within a better range now, right? The thing is, the 6V6 plate voltages are now at 424 V. Is that sufficient for 6V6's? Before they were like 444 V, which I thought seemed high.

If this spread is good, I have the decade box at 100 Ohms, so I'll remove it and solder in a high wattage B+ droppring resistor right off the standby switch. If this spread isn't good, I'll ditch the decade box idea and play around with values across the string.

I sure could use some input on this. The amp is sounding better, but maybe a little on the harsh side. Much more life to it, though.

Thanks, guys.
Mark.

[phsyconoodler]

Mark,
you are fast approaching a meltdown of your PI with 298v on the plates.
A 100 ohm resistor at the standby switch induces sag,not really what you want.I would ditch the 330 ohm resistor and use a choke.I did and now use them in all my builds.The amp sounds smoother in OD with a choke IMHO.
I use a Hammond PT and use 430v on the plates.I prefer the lower voltage throughout the amp.
Are you still using that 200 watt speaker?I find a good speaker choice makes or breaks these amps.

[markmalin]

Mark,
you are fast approaching a meltdown of your PI with 298v on the plates.
A 100 ohm resistor at the standby switch induces sag,not really what you want.I would ditch the 330 ohm resistor and use a choke.I did and now use them in all my builds.The amp sounds smoother in OD with a choke IMHO.
I use a Hammond PT and use 430v on the plates.I prefer the lower voltage throughout the amp.
Are you still using that 200 watt speaker?I find a good speaker choice makes or breaks these amps.

Hi Keith,

Actually the PI plates had a higher voltage on them before. When you say approaching meltdown, are you saying because the voltage is too high at the PI plates? What should those plate voltages be? If I remove the 100 Ohm resistor at the standby switch the plate voltages on the PI are 304 V and 309 V (and the power tube plates are up around 440 V).

Also, if I go with a choke, what value choke do I use?

Re the speaker, yes, I'm still using that high wattage Eminance Delta Pro 12A. I'd like to try a Celestion G12-65, but would need to sell the Eminence and this 16 Ohm G12T-75 to have enough cash (shoestring budget...)

Mark.