Modified Laney VH100R lacks mids

[Reeltarded]

Umm.. he had to post things we still don't understand so we could help him remove them. Ehh..

[Gaz]

So Mr. Davis, that 47K in series with the .47uf bypass cap had to be mistake, right?

[Reeltarded]

We need a baby monkey eating a banana emoticon.

[Trace]

Well hello Mr. Trace, nice to hear from you, in the attachment you can see screen print of my E-mail that was sent out to you on 04/01/13. But off course I'll take your word that for some reason you did not receive it, and that your attention to this forum thread, after several days of discussion, was drawn just after I posted the mod photo. Not a problem, I understand you are busy and/or Hotmail for some reason did not deliver. As for calling over the phone, well that is impossible because phone calls from Serbia to USA are ridiculously expensive, so I had no choice but to ask for help from the community on forum. Anyway I will respect your wish, will not post pics here and I am sending you an Email to trace@voodooamps.com will not ask you any questions here.
Thanks

Good Monday morning to you. I was not doubting that you sent an email, unfortunately we did not receive it. I was unaware you were from Serbia. I do have Skype and you can add me, my screen name is "Voodoo Amps". We can message and/or talk free-of-charge.


I received the email you just sent and I sent you an in depth reply with a great deal if information I look forward to helping you increase the mids and to helping you resolve this to your satisfaction.


All the best to you and yours;
Trace

[Emetal]

VacumVoodoo you graphs gave me great insight and understanding of tone shift involved with those resistor values. Thanks a lot All I can say now is that I believe that secret to the sound I want lies simply in tweaking the C6 and/or C7 components values. I will leave pretty much all the other mods in, and play around with C6 and C7, just as jelle sugested . Just out of the curiosity how would this graph, that VacumVoodoo posted, look like if there is only original Laney cap 680nF in C7 position? Any guesses? Where would the curve be?

[Reeltarded]

The hump would move down to the left with the curve centered more toward the low 100Hz range.

[VacuumVoodoo]

Only the left slope of the hill would move towards the Y-axis. It might muddy up the sound, 1uF is as far as I would go in a metal machine.

[Reeltarded]

Yes! I should have said the hump will GROW or EXPAND towards the left.

[Emetal]

Hey guys, I just discovered that grid stopper from V1A G. is not 10K it is actually only 820 Ohms I took the measurement with my meter, is that unusual? As far as the sound I did not notice any difference either that or default Laney 68K, any comments?

[Emetal]

I was reading about grid stoppers and Miller capacitance, RF roll of... Nice article here:
http://www.valvewizard.co.uk/gridstopper.html

I love this part: "For those afraid of the capacitor failing and placing a high voltage on your guitar strings, the capacitor could be placed between grid and cathode instead, although it will need to be a higher value since it won't be subject to the Miller effect. In this case:
796 - 100 = 696pF
The closest standard would be 680pF."

New thing to try

[Emetal]

Ohh I have quick a question, why is 22pF placed between grid and plate in the B side of V1 and grid stopper reduced on the A side of V1? Shouldn't both actions (increasing Miller capacitance and reducing grid-stopper) be taken in the same stage (first stage) ?

[Emetal]

at first glance the two pairs of 4n7 caps in series would cut mids to a degree... jumpering one cap (C10, C2) on each pair would be a mid boost (you could put it on a switch too)

Also returning C7 to a 680n cap without the 47k in series would boost mids...

Not familiar with this amp but it's a start...

TT

Jumpered C2 and got great results, got boost exactly in the frequency range I needed, best result of any other experiments so far I just have a question are you shore the other cap I could jump is C10? Did you mean C3? Because C10 is far away, C3 and C2 are next to each other.