Modding a Laney VC-30

TomCat

We have scored a VC30-210 amp for church that was going for a song.

I'm itching to get my hands on it and do a couple of mods.

My goal is to:
1. Warm up the tone as it is a little glassy stock.....very bright. My thought there is to change some of the cathode bypass caps as the stock ones seem a little small in value.
2. Work the OD channel a bit. I see it is not too different from my own design and am thinking of modifying to get it to be more three dimensional..... :-\
3. I see the effects loop buffering is op-amp based and am wondering whether it will be worth putting in a tube buffer CCT, or at least a loop bypass switch to switch out the buffer cct.
4. Retube the Pre tubes to JJ's to generally warm things up.
5. Recap the audio path caps to higher grade caps.

Interesting thing I see is that the PS tube is a ECC83 and not a 12AT7

Any experience.....thoughts.......suggestions.....anything...... ? ?

aja

In my expert opinion, I would paint it blue

Karel-Mars

I had to improve the sound on a VC-30 some while ago. I pulled the first pre-amp tube and replaced it with a 12AU7. That fixed the glassy/hissing sound. Next I bridged out the solid state fx etc. (leaving the send connected for line out etc. function) to have only tubes in the signal chain. That seemed to make the amp sound a bit better.

I would upgrade the output transformer for a warmer sound, but as I remember there is not much space on the chassis.

TomCat

Thanks Karel...I'll definitely look at those mods and see how it goes.

guidothepimmp

Tomcat.. hows this going?.

curious to hear whether the mods helped. id also like to tame the clean glassy tone i have. overdrive is grand though. just clean i could take off heads

TomCat

guidothepimmp wrote: Tomcat.. hows this going?.

curious to hear whether the mods helped. id also like to tame the clean glassy tone i have. overdrive is grand though. just clean i could take off heads

Been busy with other stuff at the moment...i.e. work.... >☹ so I've not had the chance to have a go at the amp yet.

I'm hoping to get to it in about a week or two.....I'll let you know how it turns out.

guidothepimmp

yeh let me know when you get around to it..

I know its a difficult call to make but would replacing caps, transformer and speaker and tubes significantly change/ improve tone?

I currently have TAD's in my amp and speaker is a celestion 70/eighty.

obviously the caps etc are stock but i don't know enough technical lingo to know what i am talking about there... :-[

Gearhead

guidothepimmp wrote: I know its a difficult call to make but would replacing caps, transformer and speaker and tubes significantly change/ improve tone?

You would leave little else in the amp to influence tone...

guidothepimmp

right.

Im starting to grasp the magnitude of the job involved after seeing you post. Logical now that I think about it. :-[

Gearhead

Tubes are easy, speaker is quick, caps take a little longer and more skill. Trannies can be downright hard to replace, just forget about doing that for the time being.

TomCat

Here is to reviving an old Thread..... :-\

I finally got my grubby mits on the VC-30 to see what I can do. First off, here are a few things I noticed when I stripped the chassis out of the Cabinet.
1. No Choke and SS rectification.
2. V1a has a 47uF (C50) Cathode bypass capacitor across a 1k5 Resistor - V1A has a fair bit of gain.... :-\ :-\
3. V1b has a 330K resistor in series with a 220K on the output of V1b as a potential divider. There is a 100p Cap (C41) in Parallel with the 330k - Fixed Top Boost cct on the Clean Channel

So I did the following Mods:
1. Dropped the 47Uf Cathode Bypass down to 1Uf to dial out some of the gain in V1a.
2. Removed the 100pf Top-Boost Cap at the output of V1b

BTW.....working with double sided PC boards in a Tube amp really sux......total pain to change or remove components... >☹ >☹...Snot Fun at All.... >☹ >☹

Powered up for a test.......Clean Channel lots more manageable in terms of Gain.....Amp only starts to break up at 8-9 out of 10.......nice control now instead of breakup at 4.....
Amp still has lots of highs but some of the glassiness has now gone. Bass control has lots more tonal range than before....Good so far......

SNAG......!!!!
Switched to the OD channel and all went papper than soggy toilet paper......all the overdrive was virtually gone.....the amp obviously required the gain of V1a to drive the OD channel properly......Hmmmmm....back to the schematic........
Further inspection revealed that:
1. The cathode bypass cap in V2a and V2b is only 1uF each (C3 & C5)....not much real gain there.....
2. Voltage divider between V2a and V2b....2 x 470K resistors......Level suck there....Although probably only about 3dB
3. No Grid Stopper Resistors on the grids of V2a or V2b

So...What I did was......
1. Replaced V2a Cathode bypass with a 10uF Cap to up the gain
2. Dropped the first 470K resistor to 10K to increase the signal voltage to V2b.

Put it all back together to find the amp go into oscillation when the drive was turned up......Forgot to put in Grid Stoppers......Take the amp apart again..... >☹
Fitted Grid Stoppers (10K...probably a bit low in value but was all I had) to both V2a and V2b....Reassembled amp and tested.......Still oscillation...... ? ☹......
After some head scratching.......wait, maybe that voltage divider between V2a and V2b is there for a reason...... :-\ :-\.....Reverted back to the 470k Resistor again......reassemble.....Test...oscillation gone and much better OD.....can push the drive to 10 without any instability.....Lot more and bigger distortion than before the mods.....

In Summary

Clean Channel is much more usable....Fuller cleans with less glassiness to the tone.....Tonetsack seems to be generally more responsive......
OD channel has more gain than before with V2a driving much harder and breaking up nicely......

Cost....Parts no more than a couple of rand......Experience Gained....priceless......

BTW...all the pre and power tubes are Sovtek...Looking at chucking a couple of JJ's to hopefully warm things up a little more......

Nicholas-L

Oh how I love these threads.... I feel like going into complete nerdynessness

Styles

Cool thread and great info. almost makes me wish i hadn't sold my VC100 ?

arjunmenon

Styles wrote: Cool thread and great info. almost makes me wish i hadn't sold my VC100 ?

? Thanks Styles. Cool thread Tom - lots learned.

TomCat

We're going to use the amp at band practice tonight to see how the changes worked out.....

I'll post and update to let you all know how it went....

TomCat

TomCat wrote: We're going to use the amp at band practice tonight to see how the changes worked out.....

I'll post and update to let you all know how it went....

Update....

Ran the VC-30 on stage tonight and definitely a difference in tone......Glassiness is almot gone with the cleans almost Fender like now..... 8) 8)

The amp just sounded Bigger without it getting too loud.....Also picking dynamics seems to come through a lot more......

The general feeling was that the amp was a lot more playable and sounded better.......so I'm chuffed......

OD channel was also nice and grainy....although not as sweet at the Twin Tube Classic hooked onto the amp...That just sounded unbelievable..... :dance: :dance:

Mission accomplished....... 8) 8)

Nicholas-L

Hey Tom, quite interested to know why you didn't touch your tonestack

TomCat

Nicholas L wrote: Hey Tom, quite interested to know why you didn't touch your tonestack

That was to have been my next port of call but we felt that the work done had done enough to improve the amp's tone and working with a double sided board is a pain in the proverbial whatsit.... >☹.... so I felt enough is enough....... ? ?

However....who is to say I might not revisit sometime in the near future...... :-\ :-\

Gearhead

PCBs are more trouble modding than P2P / turret boards. I can only imagine what it is like modding double sided boards, eish.

marcoluz

Hey Tomcat,

I just made the same mod as you did and guess what? What you have mod was simple turning off the bright switch (which the amp already has). Removing the cap C7 (you said C41) but it is C7 does not affect the tone controls and its range at all, mantains exactly the same.

The most interesting change that you might make in amp is simple put a EQ pedal in front of this amp and take out some of the high freq or simple boost the lows.

it works like a charm.

And of course, changing the speaker it might help also in having a little bit more accurate sound.

Cheers,
Marco