Blackheart BH5H Mod

[Colossal]

Thanks for the advice Colossal.
You've been a great help.

No problem!

On C2 increase, since I am placing an order was just wondering on this for the future if it was justifiable and if my line of thinking was correct that if lowering C2 made it brighter than higer values would make it darker. Your response allowed me to understand that C2 changes aren't that simple and more is going on behind the scenes.

Check the tonestack graph again (post above). Making C2 smaller lowers the gain slightly, shifts the mid "scoop" and will let a bit less treble through. Making C2 larger gives a boost in mid and treble frequencies so you hear a bit more of a mid focused shimmery kind of tone; maybe more complexity is a good description. Of course this depends a lot on the amp, where the tonestack is in relation to the other gain stages, etc. So if by darker you are meaning a bit of treble cut, this is one way you could realize some. But yes, the landscape is multivariate here so brightness doesn't just come from one place. You can attenuate at the input or in other places as well or a bit of both.

So it looks like I will be ordering parts again in the future possilby so I will hold off on C2 for now.

Lowering that 100k mid slope resistor down to 33k will have a nice treble cutting effect so listen to that one first before judging C2. I would go with 33k/500pF or the other plexi standard is 56k/250pF.

I like the looks of the Mod you have drawn up and will be something to add a bit more complexity to the overall tone of this amp. In the future of course.

Yep, something to consider. For now I'd concentrate on just getting the tone closer to what you are after then add the bells and whistles. You might really like the effects of bumping the output tube's cathode bypass cap up from 22uF to 1,000uF (or even higher). Something to keep in mind after you go through the first round of tweaks.

Well have a good weekend, the wife is dragging me out to an SCA event. It's the Ceilidh weekend, (pronounced Kaylee's or so I think) so much for a quiet weekend at home.

Well, there should be some good ale around so hopefully that will provide some solace for the loss of the weekend. Play some Down By Dun Ringill by Tull and sip some fine ale!

[John_P_WI]

Jerry,

I have used Kevin's stuff for many years and own most of his books. He is very open with advice over at powerscaling.com (It seems to be down these last several days...) You need to register to participate in the powerscaling discussions.

I do not know the SB84 kit, but have used other SB power scaling kits. Could it be possible that the suggested use of the 100k master volume pot was in a "bootstrapped" circuit making it look larger than 100k?

We all need to remember that his business is selling his technology, therefore if he would "freely disseminate" all of his info, he would be giving the farm away so to speak.

Good luck with the mods....

John

[jmohr58]

Thank,
Colossal,
Good Advice.
So you are famailar with the SCA?
Yes, a great Tull song, still got it on vinyl.
And a bit a Ale is always a good thing.
Jerry

[jmohr58]

Thanks John for the reply,
Kevin definatly knows his stuff and I would love to be able to afford his TUT series, and I am very careful not to post any info of his information as to give away his farm where just anyone can see it. Because I do understand this is his bread and butter.
My main issue is when I have requested information from him, which yes he will provide on a one to one basis. He speaks way above my knowledge level on the subject and says reference TUT xx which I don't pocess. So even though he provides info, just kind of makes my head spin. Other people have been able to answer questions for me in a manner that is logical and at a level I can follow. Such as Colossal who has been great at helping me, not only let me know what mods I can make but explains the reasons behind the change. I have had no trouble understanding and following his advice.
I am not trying to put Kevin down at all, just saying that I have known some people that have such a high level of knowledge in a given subject that it is hard for them to bring it down to the level of a novice.
I did join the Power Scaling forum, but very little is on the subject of the style of my amp so it really hasn't helped alot, at least not until I have a better understanding of whats really ticking inside the circuitry of tube amps.
I do think Colossal's approach to the Master volume at R9 instead of R10 has merit, and is worth trying. The R10 method I followed from Kevin just doesn't seem to sound quite right. (I mean at an audio level)
And also thank for wishing me well on my mod.
Really appreciate that very much.
Jerry

[Colossal]

Hi John,

The SB-84 is the "super budget power scaling kit for EL84 amps". From everything I can tell it is voltage scaling the plates and the ratio of anode voltage to screen voltage is held constant as the plate voltage is scaled. The Drive Compensation pot is set up as a pre- or post-PI master volume. In Jerry's case it is just taking the place of the grid leak. From everything I can tell, the Drive Comp (MV) pot is operating independently of the voltage scaling kit and is just supposed to be used in tandem with the Power Scaling to dial down the signal the power amp is seeing (if desired).

Jerry,

No, I am not familiar with SCA but I did just polish off a Guinness. I know that's Irish, but it's still good ale!

[John_P_WI]

Colossal and Jerry,

Yes, the SB84 sounds similar to the SB's that I have used. The major reason of the master volume or drive comp is to limit the size of the drive signal as the output tube voltage is dialed down to limit the grid from being driven positive. Of course, this is not needed if the whole amp is scaled. There is a larger tonal difference from scaling the whole amp than scaling just the output tubes.

Sorry I can't help you more Jerry with your amp, I'm a high gain guy from the 80's and love to cascade a lot of stages plus a real PI. If you are looking for more distortion I think I would try to strap a couple of diodes somewhere along the line. I used to do that to my plexis for late night practicing back in the 90's.....

Colossal..... a Jose Black Heart

Man, all this talk of beer, I'm thirsty... yeah yeah, I'm from WI.

Have a Good weekend guys.

[Colossal]

Colossal..... a Jose Black Heart

John, that's hilarious! I was actually thinking about suggesting that after Jerry got done with his initial mods...

Jerry, I hope you haven't placed your order yet...you'll need some zeners LOL. (just kidding).

Man, all this talk of beer, I'm thirsty... yeah yeah, I'm from WI. Have a Good weekend guys.

Cheers!

[jmohr58]

Thanks John and Colossal,
Once the 250KA pot and resistor arrive I will try the change Colossal has suggested at R10 and see what differences it makes opposed to the original MV coming off R9.
Thanks Guys,
I will have an Ale or two, maybe ? for both of you.
SCA stands for "The Society of Creative Anachronism"
It's kind of a club for a Midieval Renaissance fair, only with year round events.
The SCA exists around the globe and has been around for quite a long time.
There are fighters that do the entire armour thing and wield swords, Ladies in waiting, the whole realm of possibilties. An escape from the ties of the modern world. http://www.sca.org/
In case anyone is interested.
So everyone have a good weekend and as of tomorrow I will be Duncan of a Celt Clan, still not sure of what century, but as Richard Lewis declares as Prince John in Robin Hood Men in Tights: "Tell everyone that when the day is out we shall have a wedding. Or a hanging. Either way, we're gonna have a lot of fun!"

[Colossal]

SCA stands for "The Society of Creative Anachronism"
It's kind of a club for a Midieval Renaissance fair, only with year round events.

Ah yes, SCA, now I remember. Yes I have heard of it.

So everyone have a good weekend and as of tomorrow I will be Duncan of a Celt Clan, still not sure of what century, but as Richard Lewis declares as Prince John in Robin Hood Men in Tights: "Tell everyone that when the day is out we shall have a wedding. Or a hanging. Either way, we're gonna have a lot of fun!"

'Tis true fair Duncan. And as Mel Brooks said:

King: Hump or death?
Maiden: Humperdink?
King: Not humperdink! <i>Hump or Death</i>!
(King chanting) Hump. Death. Hump. Death. Hump. Death.
Maiden: Hump!
King: It's good to be the King!

[jmohr58]

I thought you might have the same warped and twisted sense of humor as I.
When you grow up listening to Firesign Theatre, kind of does a number on your thought process.
You know: "There is a whole dead cat is every bar of Dead Cat Soap"
(Disclaimer: I do like cats and wish them no harm!)
Probably a local chapter of SCA around you, they seem to be everywhere.
Yes, there is usually always at least one Brewmaster in every chapter as well.

[jmohr58]

I can see myself now after a long night of drinking Ale.
(No Cats where harmed in them making of this post)
Duncan of the severly hungover Clan.

[Colossal]

With a loud snort, he awoke in a terrible stupor in a pile of straw, head foggy with meat and mead from the evening's festivities. Standing over him were Men from the AmpGarage Clan. One kicked him in the back with a laugh and said, "You shall now be henceforth known as Duncan Blackheart, Clan of the Aftermath!".

This thread is degenerating rapidly...

[surfsup]

R5 shifts the midrange frequencies. 33k is classic plexi. You could bump it up to 47k if you want more of modern type tone (hot rodded Marshalls, Slawn, Friedman, Cameron, etc). 33k sounds really good though and is classic Marshall. Check out the enclosed tonestack simulation.
100k = Green trace
47k = Red trace
33k = Yellow trace
Notice where the "trough" is. Decreasing the R value shifts the mids up.

Or he could put in a 33k and 68k in series with the 68k on a switch that could be bypassed to get 33k or 101k.

I am considering this as one of the mods to the X10 amp I'm about to start building. Considering a few mods, and will probably update the layout for all of them and just not wire in what I decide not to do so the layout/drillplan supports it at least.

[jmohr58]

Colossal and to all else,
Hope everyone had a good weekend.
I'm back from the past and the wife is out so I am going to try to get some work accomplished on my Amp today.
Colossal, even in jest you have once again helped me.
I have been working on an SCA name for over a year, and only recently decided on Duncan, and with no point of reference beyond that.
But Duncan BlackHeart, and the Clan Aftermath. Colossal YOU ARE A GENIUS! It is perfect! Even my wife was estactic. No small feat there.
So once again. You have my thanks.
Jerry / Duncan BlackHeart

[jmohr58]

Surfsup,
A good idea, after I get my tone mods done it sounds like something to try.
Thanks for the concept,
Jerry