Findings on implementing some tweaks

[greiswig]

Christmas day gave me a little time to tweak!

I have a Stock D'Lite that I'm running with 6L6's and an 8k OT. I thought it might be helpful to log some of what I hear as I try out some tweaks. Probably not, as I get the feeling that I am a high school student amidst Ph.D. candidates on this board! But...

I primarily use a Tele, but I have a Strat and a PRS with Harmonic Designs Z-90's as well. I am running this amp into a single Celestion G12-65 in a small semi-open back cab for the time being.

I started with putting the Skyliner midrange values in. I actually think this is less "sweet" sounding than stock, and will probably go back. The stock setup sounded like there was too much in the low mids (near bass), and I had hoped this mod might change that. I don't think this mod is the place to look for that.

Then I tried a couple of kleinm's modifications that he has helpfully outlined and described elsewhere.

I tried putting a 4.7k FB resistor off the 4ohm tap. This results in a significant drop in volume, and a tighter feel and sound to the amp. The amp reacts more stiffly to digging into the strings, and it lost some of the sweetness. Some of the harmonic complexity disappeared, too. If I were playing primarily rock on the bridge pickup and had a half stack, this might be a good thing. But for blues and jazz, I prefer it without this loop.

I tried the pre-OD network (10M/.05uF). This one puzzled me: I *might* hear a tiny drop in the bassy/woofy quality of the OD section, but it was very subtle. I'm not sure what this network is actually designed to do.

I tried severing the jumper between wiper and outside terminal on the bass pot. Interesting! Lost a lot of bass there...too much. Okay, jumpered is too much bass and not a lot of usable sweep of the bass control, open is not enough bass. I put a 100k resistor across it instead, and this seems to be a good compromise. Time will tell.

I'll try to jot down more findings as I stumble across them. Meanwhile, I've asked some questions elsewhere about the theory behind some of the tweaks used by kleinm and others, and I'm hoping to learn from that.

Merry Christmas!

[phsyconoodler]

Do you have the Brownote OT? If so,doesn't it have a dual primary?6L6's to start with should have a 4k or 4.2k primary.
8k is better with 6v6's.
That would be a good styarting place on the quest for tone.

[greiswig]

Do you have the Brownote OT? If so,doesn't it have a dual primary?6L6's to start with should have a 4k or 4.2k primary.
8k is better with 6v6's.
That would be a good styarting place on the quest for tone.

I got the 8k BrownNote OT. Looks like it doesn't have the 4k primary. When I bought this from BrownNote, I explained that I would likely be using 6L6's, and I was told that this transformer would do just fine, but to run it at 16ohms for an 8ohm load with 6L6's. What kind of effect would you expect the different transformer coil to have?

[dogears]

Why not try 8 ohm into 8 ohm??? Typically these amps can sound nice when mismatching 8 into 4 or 16 into 8. You are going thre opposite way. Therefore, try 8 into 8. Should be much smoother.....

[greiswig]

Why not try 8 ohm into 8 ohm??? Typically these amps can sound nice when mismatching 8 into 4 or 16 into 8. You are going thre opposite way. Therefore, try 8 into 8. Should be much smoother.....

Cool...I'll give that a try. Thanks, dogears!

[JimiB]

with an 8K pri into 4-8-16 ohm secondarys, wouldnt using them as 2-4-8ohm secondarys be reflecting 4K back to the primary?

[talbany]

I had an in depth conversation with Paul @ Mercury Magnetics the other day and he had some comments about output transformer impedance matching.
First it is not critical that you match Impedances, (like Scott suggests.) However he recommends that with a multi tap output tranny you try to use as much of the winds as possible. The more winds you use the thicker more harmonically rich the tone. Basically the same as a guitar pickup. Makes sense to me. Amplifies more of those fragile harmonics.. LOL!!




Tony A VVT Amps

[greiswig]

I had an in depth conversation with Paul @ Mercury Magnetics the other day and he had some comments about output transformer impedance matching.
First it is not critical that you match Impedances, (like Scott suggests.) However he recommends that with a multi tap output tranny you try to use as much of the winds as possible. The more winds you use the thicker more harmonically rich the tone. Basically the same as a guitar pickup. Makes sense to me. Amplifies more of those fragile harmonics.. LOL!!




Tony A VVT Amps

Interesting...so which tap would one use to use all of the winds...the 16 ohm tap?

[talbany]

That is correct. Try it with let's say a multi tap Marshall switchable 2204 or something like that and grab an 8 ohm cab. Switch between each tap you can hear the differance. The amp has to be moving a little air when you do the test but the tone will be meatier. Maybe there was a reason why Jim Marshall liked 16 ohm cabs. Hummmm!!.






VVT

[mlp-mx6]

The amp has to be moving a little air when you do the test but the tone will be meatier. Maybe there was a reason why Jim Marshall liked 16 ohm cabs.

Part of that reason would likely be that a 16ohm setup has less loss in the speaker cable - less impact (percentage-wise) from the resistance of the speaker cable itself. 0.2ohms is has less additional percent impact on a 16ohm setup than on a 4ohm setup. Especially with a head-and-cab setup where there could be some significant distance, whereas in a combo the speaker is reliably a foot or two away.

[Tdale]

Christmas day gave me a little time to tweak!



I tried severing the jumper between wiper and outside terminal on the bass pot. Interesting! Lost a lot of bass there...too much. Okay, jumpered is too much bass and not a lot of usable sweep of the bass control, open is not enough bass. I put a 100k resistor across it instead, and this seems to be a good compromise.

Merry Christmas!

What jumper is that? The schematics I'm looking at, doesn't have a jumper in that position, unless we're talking about the connection between the wiper and outside terminal, that goes through the boost and rock/jazz switches?

What am I not understanding?

Tommy

[stelligan]

Tommy,

There is a "bass mod" listed on the BrownNote forum for the D'Lite layout here: http://brownnote.net/forum/viewtopic.php?t=125

I believe that is what is referred to here.

[greiswig]

Tommy,

There is a "bass mod" listed on the BrownNote forum for the D'Lite layout here: http://brownnote.net/forum/viewtopic.php?t=125

I believe that is what is referred to here.

Correct...my D'Lite build started with this mod in place. I didn't know it was a mod!

[ampgeek]

I believe that the 4.7K in the NFB loop is a partial/incorrect implementation of the BM power section. The BM has a 4.7K across the presence pot among many other changes if you are comparing it to the standard D'lite plan.

Check out our gracious moderator's JCM800 schematic at mhuss.com for a BM launching point for the D'lite. Starting from the PI input grid through the OT if using 6L6'ish tubes. Tweak to taste from there.

Cheers,
Dave O.

[Tdale]

Thanks!

But without the jumper or resistor between center and outer terminal, the boost & jazz/rock switches still acts as a jumper between the same terminals when they are in the right position?

Won't that give me the "jumper sound" even if there is a 100K resistor there?

Tommy