183 tweaks

[BobW]

Where did the notion that the snubbers were 25pF come from in the first place?

Ampdork originally said:
250K doesn't mean 25pF. It means 250pF, and the K means that it's got a +/- 10% tolerance

Not really. The way to read a cap that says "XYZ" (meaning there are generic numbers, not codes), is: XY are the first two digits of the value of the cap and Z is the power to which "10" is raised. Thus, 250 = 25 x 10^0. Being that any number raised to the 0 is 1, then 25 x 1 = 25pF. That's the way these things go... same rule as used to read 3-color banded resistor values. If you have, say, red-green-black (which stands for 250), that means 25 ohms and not 250 ohms -- which would be red-green-brown, or 251.

Gil

I have to check my stash of 250pf's, but I swear that are marked 250 and that is it. They are Cera-Mites.

I will verify tonight and drop a picture or two.

Gary

Unfortunately, I have seen caps under 500pF marked both ways. Not all cap manufacturers follow the EIA marking nomenclature. I agree with Gil, that is the EIA standard, where Z is the multiplier. A company that supplies MIL grade caps such as Kemet, Sprague, etc will follow the standard. Although Cera-mites may be great caps, Vishay bought out a lot of companies over the past decade and may have continued using the original OEM markings.

[makrisp]

Look, I never disputed Shad. I only said on my build I liked 250pf.

Scott,

Could you put in the 25's so that we can hear the differences?

[Chris333]

I listened to the PM and 183 clips for 20-30 seconds each, switching back and forth... there is as much variation in tone from the dynamics of the playing within each clip as there is difference in tone between the amps. Without keeping an eye on my monitor, I got mixed up about which clip I was listening to a couple times... They seem to overlap. That being said, there is something going on in the upper mids on 183 -- hard to describe, maybe a little more edge but just as smooth... Or maybe I'm just full of shit. Anyway, they certainly are close, especially considering they were played with different guitars (!) and both sound incredible.

[stevlech]

Dogears' playing is certainly more aggressive on the real 183 clip. That accounts for a slight difference in the tone, I think.

With all this confusion over the cap markings, I wonder if, perhaps, even the mighty HAD made (gasp!) a mistake. Could he have accidentally put 25pf caps where he intended to use 250pfs? I know the man is meticulous and all, but he is still human and could have been in error...

Just sayin'

[exocet]

Nice playing again Scott.

On the thorny issue of snubber cap values, not disputing anyones measurements here but if the snubber values were indeed 25pF, surely they would have next to no impact on the HF response with respect to guitar frequency spectrum? I thought that snubber values around the 250pf started to cut frequencies around 5 Khz (or there abouts)?

[glasman]

Where did the notion that the snubbers were 25pF come from in the first place?

Ampdork originally said:
250K doesn't mean 25pF. It means 250pF, and the K means that it's got a +/- 10% tolerance

Not really. The way to read a cap that says "XYZ" (meaning there are generic numbers, not codes), is: XY are the first two digits of the value of the cap and Z is the power to which "10" is raised. Thus, 250 = 25 x 10^0. Being that any number raised to the 0 is 1, then 25 x 1 = 25pF. That's the way these things go... same rule as used to read 3-color banded resistor values. If you have, say, red-green-black (which stands for 250), that means 25 ohms and not 250 ohms -- which would be red-green-brown, or 251.

Gil

I have to check my stash of 250pf's, but I swear that are marked 250 and that is it. They are Cera-Mites.

I will verify tonight and drop a picture or two.

Gary

Never mind, mine are marked 251. Gil I bow once again to you .

[wjdunham]

Has anyone posted the actual voltages measured in 183, I know Shad posted the dropping string values, but I don't recall seeing the actual voltages and specifics on the preamp tubes (brand, age etc...). Scott, what are you seeing in your pseudo clone amp for voltages? My notes say it's a Twin PT, so 330-0-330V secondary? This (preamp tube voltages) seems to be a pretty significant tweak point to get the last couple of % out of an amp/tube combination and not typically documented, no?
Thanks,
Bill

[dogears]

I get like 460-465v on the power tubes. 300v or so on PI. And 200v or so on the preamp.

I'll go record a clip with the smaller snubs in a moment. It is really good that way to. I think 250pf is small enough that it doesn't alter the base DNA of the 183 tone. It is definately zingier with the 1/10th size in there though.

[Max]

Hi Scott,

in the way both amps are presented to me in these clips and by my computer and headphones I perceive some major differences:

- the guitar timbre in the #183 clips I perceive to be more open and alive. It has a rich and juicy harmonic spectrum and opens up over the whole register from belly tones to head tones. It opens up to a singing "a" vowel like the a in after (British pronounciation). The tone is full and rich but still with a lot of high end chime. And because of the open character and high end chime I perceive more of an electric guitar sound in these #183 clips. The tone in the Glaswerks clips is a bit less "elctric guitar" and a bit more "synthy".

- the guitar timbre in the Glaswerks clip I perceive to be more muffeld, like some thin blanket has been thrown over the tone. The tone is fat, too, but not as "rich" as in the #183 clips. It has a lot of body but at the price of a reduced high end chime and charme. Because of this the singing vowel of the Glaswerks clip is more like the "ai" in air or the "i" in first. If these would be the tones of a singer I would recommend her/him to improve her/his ability to open up the resonance chambers in her/his head (one of the mental pictures for this "opening" could be to imagine that the tones leave your body from your forehead, upper head or vertex and not from your mouth).

Just my personal first glance spontaneous impression (often the most trustworthy - as far as my own experience goes - but not always of course). I wrote it down now imediately after listening and without much thinking.

Judging by only these three presentation clips I would be more interested now to be introduced to and perhaps "date" #183 to get a personal face to face impression.

That's my personal taste regarding these three clips.

Thanks a lot, Scott, for your great musical emotion and playing, the meaningful and educational recordings, the generosity of sharing and that you took all the trouble on behalf of our fun and "Dumble knowledge".

Have a nice weekend,

Max

[dogears]

I agree.

I just recorded this clip with one leg of the 250pf snubs lifted. So, no snubbers. Much much closer to the 183 clip. Do keep in mind I played a vintage 335 on the original clip! And, the mic could have been a little more cone center. Add in stack setting differences and tube differences.....

http://www.scottlernermusic.com/2010/Ph ... tweakB.mp3

Hi Scott,

in the way both amps are presented to me in these clips and by my computer and headphones I perceive some major differences:

- the guitar timbre in the #183 clips I perceive to be more open and alive. It has a rich and juicy harmonic spectrum and opens up over the whole register from belly tones to head tones. It opens up to a singing "a" vowel like the a in after (British pronounciation). The tone is full and rich but still with a lot of high end chime. And because of the open character and high end chime I perceive more of an electric guitar sound in these #183 clips. The tone in the Glaswerks clips is a bit less "elctric guitar" and a bit more "synthy".

- the guitar timbre in the Glaswerks clip I perceive to be more muffeld, like some thin blanket has been thrown over the tone. The tone is fat, too, but not as "rich" as in the #183 clips. It has a lot of body but at the price of a reduced high end chime and charme. Because of this the singing vowel of the Glaswerks clip is more like the "ai" in air or the "i" in first. If these would be the tones of a singer I would recommend her/him to improve her/his ability to open up the resonance chambers in her/his head (one of the mental pictures for this "opening" could be to imagine that the tones leave your body from your forehead, upper head or vertex and not from your mouth).

Just my personal first glance spontaneous impression (often the most trustworthy - as far as my own experience goes - but not always of course). I wrote it down now imediately after listening and without much thinking.

Judging by only these three presentation clips I would be more interested now to be introduced to and perhaps "date" #183 to get a personal face to face impression.

That's my personal taste regarding these three clips.

Thanks a lot, Scott, for your great musical emotion and playing, the meaningful and educational recordings, the generosity of sharing and that you took all the trouble on behalf of our fun and "Dumble knowledge".

Have a nice weekend,

Max

[Mac Daddy]

[quote="dogears"]I agree.

I just recorded this clip with one leg of the 250pf snubs lifted. So, no snubbers. Much much closer to the 183 clip. Do keep in mind I played a vintage 335 on the original clip! And, the mic could have been a little more cone center. Add in stack setting differences and tube differences.....



Scott if you recall , Some of the 183 were done with you playing your guitar

The last clip you posted seems to be getting further away from what 183 sounds like

[dogears]

Are you serious? No EQ used at all. Nobody would ever believe these were different amps if they did not know. In fact, I way prefer clip 2 here. There are so many variables in recording that unless we get the amps side by side in a controlled clip test, you can't draw any conclusions. You keep posting the other 183 clip, yet here is one recorded at teh same time that sounds totally different. Mic position change? Tone stack settings??

Here is 183
http://www.scottlernermusic.com/dumble/ ... AtLast.mp3
Here is the GW http://www.scottlernermusic.com/2010/Ph ... tweakB.mp3

[Max]

I agree.

I just recorded this clip with one leg of the 250pf snubs lifted. So, no snubbers. Much much closer to the 183 clip. Do keep in mind I played a vintage 335 on the original clip! And, the mic could have been a little more cone center. Add in stack setting differences and tube differences.....

Yes, indeed, much closer, just as you say. This is the right overall direction. The guitar can of course make a big difference, too. I play a late '58 ES 335 with '59 specs and a gorgeous open tone myself and like it a lot in combination with Dumble amps. Yes, guitars can make a big difference of course. In the end the amp is the "body" or "sound box" of an electric guitar, not less but not more, too.

My personal guess is anyway that because of the technical differences between current and old and aged parts as an example (differences in manufacturing procedures and materials, ROHS etc.) it may perhaps be rather difficult to recreate the current tone of an amp from perhaps the late eighties by "cloning" a schematic. Even if you use NOS parts, their specs will perhaps be rather different from the specs of parts that have been "on tour" since 20 years. So IMO a schematic can always be only the start of the quest.

And I would not be that surprised if an exact or at least very similar tonal recreation of #183 or other Dumble amps from the 80ies and 90ties done by using NOS or currently produced parts would have to be more or less different in a technical sense. But this is just a guess of course, and as you know, my technical knowlwdge is rather shallow.

Thanks again for posting, great thread, great music, great amps (all of them), lots of fun!

Cheers,

Max

[Structo]

As for the ceramic cap code, when I researched it, the old way was as described, with the multiplier then tolerance.

Not all companies did it like that but most did.

I agree that perhaps HAD thought they were 250pf when he installed them.
Although we hear he was anal about measuring things, perhaps he didn't measure the snubbers.

We haven't seen any other amps with less than 250pf have we?

Anyway, thanks for the info and clips Scott.
Nice to have these notes.

[tubedogsmith]

As for the ceramic cap code, when I researched it, the old way was as described, with the multiplier then tolerance.

Not all companies did it like that but most did.

I agree that perhaps HAD thought they were 250pf when he installed them.
Although we hear he was anal about measuring things, perhaps he didn't measure the snubbers.

We haven't seen any other amps with less than 250pf have we?

Anyway, thanks for the info and clips Scott.
Nice to have these notes.

Maybe they all had 25pf caps in them?!?!