Boogie MKIIA Rev Eq 60/100W
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mark2boogie
Well-known member
Hi McBarry,
Un Australien qui parle le Français... C'est pour le moins étonnant ! Félicitations... Même après vingt ans !
An Australian who speaks French... That's nothing more than surprising ! Congratulations... Even after twenty years !
OK - I will prepare offline a description of the work I have done on my MKIIA assorted with pictures and stick it there - in English, of course !
Hi igfraso,
1 - I borrowed an Ernie Ball and tested the volume pedal plugged in the PreAmpOut/PowerAmpIn jack, as you suggested : it works, and I must confess that it would be a very practical feature for me. Unfortunately, there is 2 drawback : a volume loss(circa 6dB) remains when pedal is maxed, and a treble loss at any setting (due to the pedal cable acting as a capacitor which draws the treble to GND). Both are sensitive, but it's a first trial which may be improved before discarding that interesting feature.
2 -
I noticed with no surprise that plugging in the 4 ohms while in 100W changes the sound : more bass, less treble, jazzy-style. But Trial after trial, he 417-8H withstands the 8ohms full power, but I think that I prefer the EVM12L as the main speaker, and would put the nonetheless excellent 417-8H in an additional 1x12" cab. I finally found the ALTEC a bit more "hype" and not able to compete with the EVM12L's performances... But it's my taste & my needs here.
Here are some pictures of the my MKIIA installed in the "aftermarket SUS-4" hardwood cab (with the ALTEC here). Nice but potentially fragile, I'm afraid... So I wonder if I won't return to the tolex cab...
A+!
Un Australien qui parle le Français... C'est pour le moins étonnant ! Félicitations... Même après vingt ans !
An Australian who speaks French... That's nothing more than surprising ! Congratulations... Even after twenty years !
OK - I will prepare offline a description of the work I have done on my MKIIA assorted with pictures and stick it there - in English, of course !
Hi igfraso,
1 - I borrowed an Ernie Ball and tested the volume pedal plugged in the PreAmpOut/PowerAmpIn jack, as you suggested : it works, and I must confess that it would be a very practical feature for me. Unfortunately, there is 2 drawback : a volume loss(circa 6dB) remains when pedal is maxed, and a treble loss at any setting (due to the pedal cable acting as a capacitor which draws the treble to GND). Both are sensitive, but it's a first trial which may be improved before discarding that interesting feature.
2 -
I noticed with no surprise that plugging in the 4 ohms while in 100W changes the sound : more bass, less treble, jazzy-style. But Trial after trial, he 417-8H withstands the 8ohms full power, but I think that I prefer the EVM12L as the main speaker, and would put the nonetheless excellent 417-8H in an additional 1x12" cab. I finally found the ALTEC a bit more "hype" and not able to compete with the EVM12L's performances... But it's my taste & my needs here.
Here are some pictures of the my MKIIA installed in the "aftermarket SUS-4" hardwood cab (with the ALTEC here). Nice but potentially fragile, I'm afraid... So I wonder if I won't return to the tolex cab...
A+!
mark2boogie
Well-known member
Hi McBarry,
Here is the description of what I have done on my MKIIA to make it work correctly... For the very few technically minded, indeed !
A+!
Here is the description of what I have done on my MKIIA to make it work correctly... For the very few technically minded, indeed !
A+!
McBarry
Well-known member
Cést plus, plus bien!
That is really brilliant Mark2Boogie!
A request if I may...the pics were a little small in places - maybe U could post the links to the file-hosting so we can see them a little larger.
With the hum and relay power-supply modifications, did the channel-switching popping resolve?
It's the last thing on mine, (and present also to a lesser extent on my MkIIB and MkIII), that I'd like to solve, though I readily admit a lack of extensive experience in valve amp and switching systems design to really tackle said issue with any great seriousness.
David
That is really brilliant Mark2Boogie!
A request if I may...the pics were a little small in places - maybe U could post the links to the file-hosting so we can see them a little larger.
With the hum and relay power-supply modifications, did the channel-switching popping resolve?
It's the last thing on mine, (and present also to a lesser extent on my MkIIB and MkIII), that I'd like to solve, though I readily admit a lack of extensive experience in valve amp and switching systems design to really tackle said issue with any great seriousness.
David
mark2boogie
Well-known member
Hi McBarry,
I know that the images are small - but I do not have a better solution, sorry...
It's only attenuated, but not eliminated as the "hum factory" is, unfortunately. But Better relay supply = prompt relay movement = faster contact and discontact = less pop noises. I also cleaned the relay, which can usefully and very easily be opened (!), and I think it helped to diminish pops also - note that it is close to watchmaker's job...
Ah, interesting : I would agree with popping noise on the MKIIB as it uses the same relay scheme as the MKIIA, but I am surprised with pops on the MKIII, since it uses VACTROLs optoisolators to make the Rhy/Ld switching instead of a relay... This solution, introduced with the MKIIC, is reputedly known to have solved that channel pop switching issue... ??? :?:
Nonetheless, about the MKIIA/B relay, I think that no great improvement is to be waited. I often used it in commutation and with low audio signal, pops are difficult to avoid, even with special design relay, it not unknown... I was tempted to "Vactrolize" the switching (way less now, reading your MKIII's concerns !), but the pops only occurs in fact when you switch while hitting a note, not on silences, even if the reverb is sounding, so it is not a major issue for me, as I always "take the time" to switch...
A+!
I know that the images are small - but I do not have a better solution, sorry...
It's only attenuated, but not eliminated as the "hum factory" is, unfortunately. But Better relay supply = prompt relay movement = faster contact and discontact = less pop noises. I also cleaned the relay, which can usefully and very easily be opened (!), and I think it helped to diminish pops also - note that it is close to watchmaker's job...
Ah, interesting : I would agree with popping noise on the MKIIB as it uses the same relay scheme as the MKIIA, but I am surprised with pops on the MKIII, since it uses VACTROLs optoisolators to make the Rhy/Ld switching instead of a relay... This solution, introduced with the MKIIC, is reputedly known to have solved that channel pop switching issue... ??? :?:
Nonetheless, about the MKIIA/B relay, I think that no great improvement is to be waited. I often used it in commutation and with low audio signal, pops are difficult to avoid, even with special design relay, it not unknown... I was tempted to "Vactrolize" the switching (way less now, reading your MKIII's concerns !), but the pops only occurs in fact when you switch while hitting a note, not on silences, even if the reverb is sounding, so it is not a major issue for me, as I always "take the time" to switch...
A+!
mark2boogie
Well-known member
Hi,
Now I have one amp and two cabs : one HDW (aftermarket hardwood) and one TOLEX (the original vinyl covered).
How to switch from one to another quickly and without issue, one being "direct old-style" mounting, the other "SUS-4 mounting" ?
I read many advices saying that it's just not possible... Que de tribuns improvisés et peu habiles de leurs dix doigts... Si ce n'est de leur cervelle !"
Here's my solution : the mark2boogie Multicab Adaptor TM
It mainly consists in 4 aluminium little blocks conveniently drilled to the chassis/HDW/TOLEX spacings :
Of course, some drilling of the chassis is necessary to mount the blocks :
Here is one block installed, with the 2 models of screws both presented, one for HDW, one for TOLEX :
Of course, you simply choose the screw set according to the cab you will use. The blocks are installed once for all :
And I made a new shielding screen (0.5mm aluminium plate) glued under the HDW's top cab, instead of the aluminium foil. For perfect grounding to the chassis, there is a removable cable screwed on chassis and shield :
If the cabs are fitted with reverb unit and speaker (they will be, soon), an instant swap is now possible...
A+!
Now I have one amp and two cabs : one HDW (aftermarket hardwood) and one TOLEX (the original vinyl covered).
How to switch from one to another quickly and without issue, one being "direct old-style" mounting, the other "SUS-4 mounting" ?
I read many advices saying that it's just not possible... Que de tribuns improvisés et peu habiles de leurs dix doigts... Si ce n'est de leur cervelle !"
Here's my solution : the mark2boogie Multicab Adaptor TM
It mainly consists in 4 aluminium little blocks conveniently drilled to the chassis/HDW/TOLEX spacings :
Of course, some drilling of the chassis is necessary to mount the blocks :
Here is one block installed, with the 2 models of screws both presented, one for HDW, one for TOLEX :
Of course, you simply choose the screw set according to the cab you will use. The blocks are installed once for all :
And I made a new shielding screen (0.5mm aluminium plate) glued under the HDW's top cab, instead of the aluminium foil. For perfect grounding to the chassis, there is a removable cable screwed on chassis and shield :
If the cabs are fitted with reverb unit and speaker (they will be, soon), an instant swap is now possible...
A+!
mark2boogie
Well-known member
OK - Here's the end of my Boogie MKIIA 60/100 Rev Eq Saga...
- 2 cabs available at an instant swap : hardwood and tolex,
- each cab with it's own speaker and reverb unit,
- exit the ALTEC 417-8H, welcome the EVM12L Black Shadow in the hardwood cab,
That works...
Some pictures for the end :
A+!
- 2 cabs available at an instant swap : hardwood and tolex,
- each cab with it's own speaker and reverb unit,
- exit the ALTEC 417-8H, welcome the EVM12L Black Shadow in the hardwood cab,
That works...
Some pictures for the end :
A+!
mark2boogie
Well-known member
Thanks Daniel for the ad on the MKIIA +++
A+!
A+!
brion
Well-known member
Cool thread. Bookmarked for future reference.
Hi mark2boogie
great thread, a truckload of information and ideas. thanks for sharing.
I think about getting the reverb signal more balanced on my Mk IIB too, but I am unsure about your description:
you wrote, you changed the lead series resistor from 62k to 100k. On my schematics of the Mk IIA I cant find any 62k resistor. For the lead channel it is 47k and for the clean channel it's 330k.
On the MK IIB the lead channel resistor is 330k and the clean channel resistor is 470k.
my question: why does the reverb get stronger by raising the resistor to 100k?
My other question: how did you rewire the master 1 pot? did you put the 22k resistor and the middle lug of the lead master on the the top lug of the master 1 and the middle lug of master 1 goes to EQ?
thanks for helping
great thread, a truckload of information and ideas. thanks for sharing.
I think about getting the reverb signal more balanced on my Mk IIB too, but I am unsure about your description:
you wrote, you changed the lead series resistor from 62k to 100k. On my schematics of the Mk IIA I cant find any 62k resistor. For the lead channel it is 47k and for the clean channel it's 330k.
On the MK IIB the lead channel resistor is 330k and the clean channel resistor is 470k.
my question: why does the reverb get stronger by raising the resistor to 100k?
My other question: how did you rewire the master 1 pot? did you put the 22k resistor and the middle lug of the lead master on the the top lug of the master 1 and the middle lug of master 1 goes to EQ?
thanks for helping
mark2boogie
Well-known member
Hi TiPiMods & Thanks,
A+!
Look again at your MARK II schematic. Just along the 47K resistor, at the right, you find another resistor connected at one side at .05, 2.2M, 30pF, 330K, and at the other side at .02. This resistor was 62K on my amp and 56K on others, and is probably labelled 56K on your schematic (62K on mine). I changed it from 62K to 100K.
When the amp is in lead mode, this resistor takes the place of the 2.2M//30pF assembly. If you increase it, you increase the predominance of the reverbered signal (coming from the REV 100K pot) vs the dry signal in the lead mode at the entry of V3A - and conversely if you decrease it - without affecting in any way the reverb level in clean mode. 100K offered the best balance compromise to my taste. I hope I am clear !
At the same place where you find the 56 or 62K we spoke about for the MKIIA, you find a 470K resistor in a similar arrangement on the MKIIB schematic. So modifying this value may have the same effect - but it's to be checked, therefore.
Exactly.
A+!
Thanks again,
@reverb resistor: I understand, you either make the "dry signal" resistor higher instead of lower the "wet"resistor. Is there any disadvantage to do it the other way round? My first thought would have been to make the 47k ( or 330k for MK IIB) lower to let more reverb signal go to the mix.
@master 1: I wired the master 1 pot like this and it is really a big improvement. I played about half an hour now and have to say it works and feels great. Much more usable now.
Before I had full volume between 2 and 3 on the pot, after that it didnt get any louder, only power tube saturation got more. And as you described, the balance between clean and lead stays the same. I didn't hear any loss of highs, and if there is, you could easily raise presence or treble a tad to compensate.
btw:another idea for peoplo who dont want to change the master 1 and lead master series arangement: to put a volume pedal or another pot in the send-return loop also works great as an overall master volume, even better as the MK IIB has a cathode follower tube buffered loop, so long cables and low resistance volume pedals are no problem. I also thought about rewire the slave pot and use it as an master volume, since I never ever used the slave output.
greetings TP
@reverb resistor: I understand, you either make the "dry signal" resistor higher instead of lower the "wet"resistor. Is there any disadvantage to do it the other way round? My first thought would have been to make the 47k ( or 330k for MK IIB) lower to let more reverb signal go to the mix.
@master 1: I wired the master 1 pot like this and it is really a big improvement. I played about half an hour now and have to say it works and feels great. Much more usable now.
Before I had full volume between 2 and 3 on the pot, after that it didnt get any louder, only power tube saturation got more. And as you described, the balance between clean and lead stays the same. I didn't hear any loss of highs, and if there is, you could easily raise presence or treble a tad to compensate.
btw:another idea for peoplo who dont want to change the master 1 and lead master series arangement: to put a volume pedal or another pot in the send-return loop also works great as an overall master volume, even better as the MK IIB has a cathode follower tube buffered loop, so long cables and low resistance volume pedals are no problem. I also thought about rewire the slave pot and use it as an master volume, since I never ever used the slave output.
greetings TP
mark2boogie
Well-known member
Hi TiPiMods,
But why do you need to rewire the slave output as a master volume ? Where would you connect it, then ?
Like you, I didn't use the slave output, so I am studiying a solution to use it as BOOST mode reverb level control. When on lead mode, the (footswitching) boost mode is a very interesting feature, as you probably noticed it : it boost the sustain, just a bit the volume level, but NOT the agressivity. But it also boosts the reverb level - it's not a major drawback on MKIIA/B as you know why and how good is the reverb on these amps - but it may be sometimes too deep, and an additional adjustable reverb attenuator would be welcome when the boost mode is on. I didn't found something simpler than using an additional relay for the moment...
... And it's pleasant to discuss and share with a tech-minded guy, indeed !
A+!
That was also my 1st idea, and my 1st trial, just to eliminate it... As I guessed it, it proved useless. In fact, this 47K is more like an "insulation/damping" resistor intended to avoid parasitic oscillations when settings are maxxed, but doesn't give significant attenuation to the reverbered signal, as it is not here for this purpose. I remember reducing this 47K to zero with no audible improvement in level balance, but finding instability at high reverb settings, as far as I remember. But it is on a MKIIA, where the resistor value (47K) is lower than on the MKIIB (330K), so on the later one, there may be an influence - ? - A trial would tell, of course, if there is an improvement and/or instablility.
Exactly !
I agree. I tried the volume pedal as an external master control on my MKIIA : it works but it is not satisfactory, as there is a loss in the highs due to cable capacitances, simply because the cathode follower facility of the MKIIB (effect SEND) doesn't exists on the MKIIA here (pre OUT power amp IN). A solution would be to displace that jack on the top lug of MASTER1, which is connected to the cathode follower V2B. I am not sure that it would work as good as on a MKIIB, because of the higher Rk value (150K) - again, a trial to check !
But why do you need to rewire the slave output as a master volume ? Where would you connect it, then ?
Like you, I didn't use the slave output, so I am studiying a solution to use it as BOOST mode reverb level control. When on lead mode, the (footswitching) boost mode is a very interesting feature, as you probably noticed it : it boost the sustain, just a bit the volume level, but NOT the agressivity. But it also boosts the reverb level - it's not a major drawback on MKIIA/B as you know why and how good is the reverb on these amps - but it may be sometimes too deep, and an additional adjustable reverb attenuator would be welcome when the boost mode is on. I didn't found something simpler than using an additional relay for the moment...
... And it's pleasant to discuss and share with a tech-minded guy, indeed !
A+!
Quote:"But why do you need to rewire the slave output as a master volume ? Where would you connect it, then ?"
What I meant: to use the existing Slave pot instead of a volume pedal and rewire it between send and return. No long cables, only disadvantage: its on the back of the amp. Would been interesting for people who want to leave the original arrangement of master 1 and lead master like it is.
But anyway I am happy now with the changed master 1, so another master volume makes no sense.
What I meant: to use the existing Slave pot instead of a volume pedal and rewire it between send and return. No long cables, only disadvantage: its on the back of the amp. Would been interesting for people who want to leave the original arrangement of master 1 and lead master like it is.
But anyway I am happy now with the changed master 1, so another master volume makes no sense.
McBarry
Well-known member
quote:>>TiPiMods>>how did you rewire the master 1 pot? did you put the 22k resistor and the middle lug of the lead master on the the top lug of the master 1 and the middle lug of master 1 goes to EQ?
Can I just confirm, the master 1 top goes to 22k and lead master pot middle lug, and the master 1 middle lug to eq.
Thus now the eq only gets it's feed from the master 1 pot middle lug, whereas before it was from the master 1 middle, the lead master middle and the 22k resistor.
Cheers, Dave
Can I just confirm, the master 1 top goes to 22k and lead master pot middle lug, and the master 1 middle lug to eq.
Thus now the eq only gets it's feed from the master 1 pot middle lug, whereas before it was from the master 1 middle, the lead master middle and the 22k resistor.
Cheers, Dave
mark2boogie
Well-known member
Hi McBarry,
Here a schematic showing how I rewired the master1 pot on my MKIIA :
I am also in search of a 100K LOG push-pull CTS Pot for the Lead Master, instead of the 1M, for more spread in the lead master adjustment - and I must confess that 's an hard-to-find part...
A+!
Here a schematic showing how I rewired the master1 pot on my MKIIA :
I am also in search of a 100K LOG push-pull CTS Pot for the Lead Master, instead of the 1M, for more spread in the lead master adjustment - and I must confess that 's an hard-to-find part...
A+!
mark2boogie
Well-known member
Oh, I forgot to mention my latest addition to my MKIIA in Tolex version : a matching EVM12L 200W Thiele cab of the same era, awaiting delivery to home :
I'll post more pics when it will be here...
A+!
I'll post more pics when it will be here...
A+!
McBarry
Well-known member
Thx for that MkIIB,
Interestingly, the pot I am replacing is 250k BUT its' switch is reversed ie: gain is "on" when switch in..
but I am going to see if I can change the current switch to the 250k pot for a more even spread around the dial, although I'm not sure if the 250k pot is taper/log etc etc..
If it helps, it's codes are:
596821 137/8831 ROC
I can't decipfer them, except the 137 CTS code..
Dave
Interestingly, the pot I am replacing is 250k BUT its' switch is reversed ie: gain is "on" when switch in..
but I am going to see if I can change the current switch to the 250k pot for a more even spread around the dial, although I'm not sure if the 250k pot is taper/log etc etc..
If it helps, it's codes are:
596821 137/8831 ROC
I can't decipfer them, except the 137 CTS code..
Dave
