Xits X10 = liverpool half power?

[azatplayer]

Im gonna put the 220k's back in my ac30 build with rthat allready has the larmar in it. Will check out what happens on the weekend. WIll answer the question in my mind anyways.
I was thinking that could be a choke resistor and not a sag R.

[Colossal]

<b>Schematic updated (see page 2) with changes based on latest intel and discussion.</b>

Any ideas for the values of the sag resistors <i>in front</i> of the rectifier diodes? Based on Stephan's sound idea that the sag resistor is actually a choke resistor between B+1 and B+2, what size do you guys think the resistors in front of the diodes could be? 100-130R will approximate the sag of an EZ81. Based on the video, how "fast" does the amp sound?

Not much to go on, but any guesses for the last two dropping resistors in the B+ rail? Typical 18W values? 2k2 followed by 8k2?

[fishy]

I'm intrigued by that Rocket build too..

I am familiar with the film caps in a power supply and also paralleled with an electrolytic but I have not seen it employed in a cathode cct. That does not mean it hasn't happened or not of value though.
If the basic principle remains, I see no reason why it cannot be a useful tool and I am inclined to think a suitably robust grounding scheme and layout should go a long way to controlling parasitics. Employing this as a mod might be a little more involving but that would not be the case here.

The only other variation I can think of is a shelved bypass using a resistor and cap; I don't see that here and that would likely be switchable.

[Colossal]

I'm intrigued by that Rocket build too..

I am familiar with the film caps in a power supply and also paralleled with an electrolytic but I have not seen it employed in a cathode cct. That does not mean it hasn't happened or not of value though.
If the basic principle remains, I see no reason why it cannot be a useful tool and I am inclined to think a suitably robust grounding scheme and layout should go a long way to controlling parasitics. Employing this as a mod might be a little more involving but that would not be the case here.

The only other variation I can think of is a shelved bypass using a resistor and cap; I don't see that here and that would likely be switchable.

Yeah, I've seen no real reason not to use films in parallel with an electrolytic and I've done this myself in a power supply right after the rectifier and before the reservoir cap at about 0.1% of the first big cap's value. I think this is good for cutting down rectifier hash. I've also seen amps where every electrolytic in the PS was paralleled with a film cap of about 1% of the e-caps value. Paralleling films with e-caps has become known as the Jedi Cap Trick on ppwatt and sewatt.com. Someone saw this done in a Valve Junior of all places and given the wild popularity of modding those amps, the idea has been explored in those circles.

Paralleling a film cap along side an electrolytic in a preamp does seems to add a bit more clarity in some cases, others it can be more subtle. I try to use films in place of electrolytics in a preamp whenever possible. I'm looking forward to trying an all-film PS in some upcoming builds.

I completely agree with you about the utility of good grounding and should not be a deterrent. In the case of the X10 amp, it looks like that 0.1uF cap may be grounded at the input jack along with a number of other grounds.

[Darkbluemurder]

Not much to go on, but any guesses for the last two dropping resistors in the B+ rail? Typical 18W values? 2k2 followed by 8k2?

Brown-Black-Red would be 10k.

[azatplayer]

Not much to go on, but any guesses for the last two dropping resistors in the B+ rail? Typical 18W values? 2k2 followed by 8k2?

Brown-Black-Red would be 10k.

oops, i think you meant 1K Stephen

My feeling on the string, from my experience trying to get an AC30 to work with a string rather than distributed supply, ( filter stages running from a single point in the AC30) is that next R after the 22k needs tio be low. I used 1K in my build to get the voltages near AC30. The next was 10K.
So, 22k - 1k - 10k was where i ended up.

[Darkbluemurder]

Not much to go on, but any guesses for the last two dropping resistors in the B+ rail? Typical 18W values? 2k2 followed by 8k2?

Brown-Black-Red would be 10k.

oops, i think you meant 1K Stephen

My feeling on the string, from my experience trying to get an AC30 to work with a string rather than distributed supply, ( filter stages running from a single point in the AC30) is that next R after the 22k needs tio be low. I used 1K in my build to get the voltages near AC30. The next was 10K.
So, 22k - 1k - 10k was where i ended up.

Oops - missed red for orange.

[Colossal]

My feeling on the string, from my experience trying to get an AC30 to work with a string rather than distributed supply, ( filter stages running from a single point in the AC30) is that next R after the 22k needs tio be low. I used 1K in my build to get the voltages near AC30. The next was 10K.
So, 22k - 1k - 10k was where i ended up.

Guys, what do you think? The X10 is a 15W amp and shares quite a bit in common with the Voxy designs. The first dropping resistor is definitely 22k and I am reasonably convinced (based on the photo and computer matching the color bands on the second R) that the next one is 1k. I have studied what I can see of the third and last dropping resistor but there is very little there except for the tail end of the last band. If it is indeed 10k, the band should be orange. Just looking at the zoomed out gut shot, it appears kind of orange to me, or at least "pale". The second resistor is hiding the first two bands of the third. Can we make a reasonable assumption that the third is 10k?

Also, I found this tidbit which is of interest:
<i>*Many of Michael's amps are tube rectified, but the X10 is silicon diode rectified although it definitely has a tube rectified feel and back end type of soft compression. The silicon diode design does a great job of keeping the low end tighter under the higher gain settings. I honesty think a tube rectifier, in this design, would cause the amp to lose definition and focus; especially at higher volume settings.</i>

[Darkbluemurder]

Can we make a reasonable assumption that the third is 10k?

I think we can assume that it is unlikely that the dropping resistor is larger than 10k given the fact that we have a dropping string and not a distributed supply string.

[azatplayer]

Well in the interest of science... i placed the 220k's back in my ac30 build, which i had fitted a PPIMV too recently.
Firstly, the PPIMV in that amp was usable. It liked some guitars more than others. was pretty good down to about 7, but below that started to lose sparkle/brightness and just kinda lost its chime.
I had a non drummer gig today, a wedding, my brother an I. He used his AC15 and I pulled 2 tubes from my AC30 build. Had acoustics too.
I did this mod yesterday, so had a brief moment with it, but used it at and below 5 on the dial.
The difference then, the amp retains its character and chime without losing ANY of the sparkle and brightness. There may be even a little more brightness, which i dont mind in this amp as i run the treble and cut up a little. But it could be a balancing act, that 100pf ? cap across the grid leaks. He may have tuned a little off the top to keep it neutral thru the sweep. Certainly feels just a hair brighter.
So. Im definitely trying this on my other amps. Its made this amp a very happy low volume unit.
Of course the circuit here, has three gains compared to 2 and a CF, so its pretty different for sure, but what i see in the video of how usable the MV is, i can certainly attest to what ive gleaned here.
Very cool!

[PlinytheWelder]

I'm intrigued by that Rocket build too..

I am familiar with the film caps in a power supply and also paralleled with an electrolytic but I have not seen it employed in a cathode cct. That does not mean it hasn't happened or not of value though.
If the basic principle remains, I see no reason why it cannot be a useful tool and I am inclined to think a suitably robust grounding scheme and layout should go a long way to controlling parasitics. Employing this as a mod might be a little more involving but that would not be the case here.

The only other variation I can think of is a shelved bypass using a resistor and cap; I don't see that here and that would likely be switchable.

Yeah, I've seen no real reason not to use films in parallel with an electrolytic and I've done this myself in a power supply right after the rectifier and before the reservoir cap at about 0.1% of the first big cap's value. I think this is good for cutting down rectifier hash. I've also seen amps where every electrolytic in the PS was paralleled with a film cap of about 1% of the e-caps value. Paralleling films with e-caps has become known as the Jedi Cap Trick on ppwatt and sewatt.com. Someone saw this done in a Valve Junior of all places and given the wild popularity of modding those amps, the idea has been explored in those circles.

Paralleling a film cap along side an electrolytic in a preamp does seems to add a bit more clarity in some cases, others it can be more subtle. I try to use films in place of electrolytics in a preamp whenever possible. I'm looking forward to trying an all-film PS in some upcoming builds.

I completely agree with you about the utility of good grounding and should not be a deterrent. In the case of the X10 amp, it looks like that 0.1uF cap may be grounded at the input jack along with a number of other grounds.

When building my Express, I decided to parallel a film cap where B+5 feeds the board at the junction of R3 and R6 to ground at R7 for local bypass. The board was empty there and it seemed like a good idea for stability and noise.
It worked out really well as mine seems pretty quiet as wrecks go..

[img:800:521]http://verosurfcam.com/TW20.jpg[/img]

On my Laney GH-100, when I recapped it, I paralleled film caps on all the board mounted PS electrolytics and it sounds good ,too.

[rooster]

azatplayer - Man that is doing some reference work! But at this point, if its working well, then the total resistance is roughly 100K (as was mentioned before). This typically tightens up the bass in a circuit and you will see this in Allyn's 80 watt Express I believe, and various SF Fender amps, too. ? It's not unheard of then, no, so why not? I guess the benefit is that if the pots go South, the 220Ks are still in place. ??? Which is to suggest that the amp builder is a very cautious fellow who perhaps like tighter bass, and not so much a crazy crack smoking Vox junky. .......Hm, I sure he appreciates that insight!

[mojotom]

Thanks for the schem Colossal.

I really thought I was done with dual
El84... You never know.
My Bruno Underground 15 is really huge
with two EL84 So why not.


About the 100n bypass I noticed Matchless
use them along with 22u too on The first Channel of the DC30.

[Colossal]

Thanks for the schem Colossal.

Sure, no problem

I really thought I was done with dual El84... You never know. My Bruno Underground 15 is really huge with two EL84 So why not.

I've always been a Marshally kind of guy but my tastes are really changing these days and I'm rather infatuated with the 2xEL84 sound. You can get some smokin' tone out of the those amps. I've got a couple of sets of 18W iron so plan to build a Marshall 1974 clone and perhaps take a stab at something like this X10 amp or a variation on that Voxy/Liverpool theme.

About the 100n bypass I noticed Matchless
use them along with 22u too on The first Channel of the DC30.

EDIT: Removal of display of stupidity...

[mojotom]

I took some time to study the schem and pictures.

10n input cap could be smaller like 4n7, Matchless uses 1n2 on the Liverpool, 2n2 on the Spitfire with a 1MA volume pot. Maybe that's why he uses 10n PI caps and lower bias resistors than the expected 220k.
100p bright cap make sense along with 100p PI cap. 47p on the tonestack could be 470p too, less Voxy.
100R screens and output tubes cathode resistors most likely.

I'm confused about the two resistors between PT secondary and diodes, never seen this kind of power supply, almost excusively sag resistor(s)after the diodes. If I look at the pictures I see 15 or 16k for the PS resistor after the 22k (brown/green(or blue)/orange) and would use a 10k for the last one. Just a guess here, close to what you would expect on a DR.