Peavey VMP2 Mod / Upgrade

[gomet]

First Post ever here! Hello!

I'd like to upgrade the Peavey VMP2 with new, better caps and while searchin the internet I found a comment from Jim Williams on Gearslutz, saying:

"Other benefits are to replace the smaller .1 uf coupling caps with Wima MKP-3's or MIT MultiCaps. The larger mylar film caps can be bypassed with MIT .01 uf PPMFX 630 volts. The HF EQ caps are mono ceramic, 180 pf. Two are used in parallel. Use a Wima FKP-2 330 pf."http://www.gearslutz.com/board/geekslutz-forum/314845-peavey-vmp-2-full-retube-job.html

I'd like to do what he suggests, but my problem is to indentify the according caps on the board. I took some photos of the most prominent caps and an overall picture of the VMP. My hope is, that someone can tell me, which caps can be replaced by better ones.
If you have any other ideas or suggestions, please feel free to comment.

Thank you
Simon

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[gemini86]

Welcome!

Questions like this are best posted here in the lab. The preamplifier section isspecifically for Groupdiy projects that have their own support or troubleshooting thread.

When you set off to mod something, it helps to have a goal in mind.
What is it you're trying to accomplish?

But to answer your question, the yellow and cream colored are what he's calling Mylar film. You might just yank those all together and pop in some poly caps, maybe Mallory 150 series. It's really all personal preference at some point, so you're going to have to experiment a bit. The .1uf psu caps may be replaced for wimas, but again, personal preference. For the hf cap, (330pf) I would tend to use a silver mica, I like how they sound.

 

[gomet]

Thank you for directing me to the right place!

My goal is to make the sound of the preamp more open and more precise. It' a bit mushy now.

About the values of the caps, could someone please help me to identify these:

The yellow Mylars are labeled .78A250P. 
Jim says to use 0.01uF on this place, can this be done without problems?

The creamy ones are labeled 1.5A250P

Thanks
Simon

 

[maxwall]

I have found the output transformers to be a little dark and unfocused.

I threw in a pair of Edcor WSM 15K/600 on the outputs and was impressed by the improvement
in clarity and over all iron color. Its a cheap upgrade too.

The stock input transformers are pretty worthy.

It certianly does'nt hurt to loose the cheap tubes that come stock in those either.
try ECC83's and ECC81's. Or if your really want a good sound ECC803s and ECC801s

the mods above can do wonders for running FET microphones thru this VMP unit.

 

[gemini86]

Those film caps are .78uF 250v (probably easier and cheaper to find 1uF) and 1.5uF 250v... Jim is saying to place a .1uF cap in parallel with them, but I would sooner just pull them out and replace with some nice poly caps. Some different tubes would help, i'm sure. Chapter Chinese ones can tend to lack clarity.

 

[JohnRoberts]

I have found the output transformers to be a little dark and unfocused.

If you find the output transformer out of focus and dark (?) i had them provide a high Z output before the output transformer, so it should be neutral and completely un-transformered. Just won't drive low Z. 

JR

PS: My favorite features are the gain knob that goes to 11 and the EQ boost/cut knobs that don't (so it's hard to make it sound bad with too much). 

I threw in a pair of Edcor WSM 15K/600 on the outputs and was impressed by the improvement
in clarity and over all iron color. Its a cheap upgrade too.

The stock input transformers are pretty worthy.

It certianly does'nt hurt to loose the cheap tubes that come stock in those either.
try ECC83's and ECC81's. Or if your really want a good sound ECC803s and ECC801s

the mods above can do wonders for running FET microphones thru this VMP unit.

 

[Treelady]

From my experiences with that Pre as an owner and at Peavey (boots on the ground at corporate) I can tell you that the VMP and the VC/L were made under the directive that "cost is no object" from Hartley himself. 

So, when we talk about replacing caps that are not blown, I have to ask "Why?"

If you want a different sound and are willing to tear open your unit and experiment, then go for it.  But to replace the caps because someone on gear-wedontactuallyeverrecordantyhing-slutz suggested so, is something I find questionable.

 

[idylldon]

But to replace the caps because someone on gear-wedontactuallyeverrecordantyhing-slutz suggested so, is something I find questionable.

Jim Williams is far from what you describe.  He's one of the most knowledgeable electronics people you'll find these days on the net.  Folks might not agree with his suggestions because he's into the "clean" side of things, but there's no doubt he knows his stuff inside and out.

Cheers,
--
Don

 

[retrogradeorbit]

Those film caps are .78uF 250v (probably easier and cheaper to find 1uF) and 1.5uF 250v... Jim is saying to place a .1uF cap in parallel with them, but I would sooner just pull them out and replace with some nice poly caps. Some different tubes would help, i'm sure. Chapter Chinese ones can tend to lack clarity.

When you mention 'poly caps' here, with regards these vmp-2 caps, which poly are you meaning? Polystyrene? Polypropylene? Polyethylene? Any of them?

thanks.

 

[okgb]

John Roberts should have more info to add , but I thought I heard that earlier models had Jensen
transformers , and although I don't believe it was the chinese bait & switch , I think it is common
for peavey go for better parts deals in subsequent runs .
I recall liking the hi pass filter  [ 4 pole ? ] not sure if it was that dual section that made it feel better
but I keep thinking I should implement that HP filter on other pres .
They still have good resale value , so that says something

 

[JohnRoberts]

John Roberts should have more info to add , but I thought I heard that earlier models had Jensen
transformers , and although I don't believe it was the chinese bait & switch , I think it is common
for peavey go for better parts deals in subsequent runs .
I recall liking the hi pass filter  [ 4 pole ? ] not sure if it was that dual section that made it feel better
but I keep thinking I should implement that HP filter on other pres .
They still have good resale value , so that says something

This is an old thread and I have posted here and around about this before.

The input transformer is not a Jensen but similar in design, perhaps not same core metallurgy, but a good transformer.

I did not design this but influenced the feature set and design targets...  EQ was kept modest in max amount of boost/cut so it would be hard to make it sound bad.

yes IMO the VMP is still a good value. If someone wants a more precise preamp, perhaps don't look for that in a tube preamp, while one of my concerns was that the VMP was too clean (I literally had the designer include a jumper so we could alter the amount of loop gain margin and make it less linear). Thankfully the marketplace was very happy with the clean sound and later versions removed the jumper that could dirty it up if desired. (this was never mentioned in the owners manual, I don't know about other documentation).

I don't expect huge sonic differences from parts substitutions but some people with too much money and time, replace the input transformer with a real Jensen, and use more expensive components through out. I haven't heard a single case of somebody changing the design. Just hot rodding parts.  8)

JR

 

[okgb]

Now's that's interesting  news  , jumper ?
do you think a switch in that spot  or trimmer [ if applicable ]
is worth while  ? Do tell how does one find this spot  ? [ not that I have one myself ]
And though I saw it was an old thread  , revived by low count poster 
I wondered what you would have to say about peavey changing parts grades
during production [ was this regular , standard , or imagined ? ]

 

[JohnRoberts]

Now's that's interesting  news  , jumper ?
do you think a switch in that spot  or trimmer [ if applicable ]
is worth while  ? Do tell how does one find this spot  ? [ not that I have one myself ]

No, I only added it because I was concerned that the VMP was too clean.. If you want a tube distortion effect, there are many of them already in the market.

The VMP is good preamp as is.

And though I saw it was an old thread  , revived by low count poster 
I wondered what you would have to say about peavey changing parts grades
during production [ was this regular , standard , or imagined ? ]

Mostly imagined, while there was some nonsense surrounding the VMP about input transformer used during design/development, and actual production parts. The premium transformer community is small and followed this product's development. First prototype is about proof of concept. Production uses economic parts that consumers will pay for. The VMP was already an expensive product for Peavey/AMR dealers so using a Jensen was pretty much out of the question.

There was always an ongoing tension between purchasing to reduce parts cost and win cost saving rewards, and engineering to keep the products working properly.

I lost only a handful of battles over parts cost, one i recall with the guy who's name was on the buildings about the fader I specified for a big recording console. After the fader I was forced to use by the boss, revealed it's crapiness (Korean Jung Poon), by literally breaking and falling apart in use, I was rescued by Alps who made their own version of that korean fader, but the Alps one  didn't suck. Perhaps if I was allowed to use the several times more expensive Alps fader originally, they would have never tooled up the cheaper one. .. or not.

Peavey uses a very sharp pencil wrt buying components, because their customers are so price sensitive. As a design engineer, you can get good performance from using mylar and decent cost effective parts without breaking the bank by using them intelligently.  At one point I wasted some of my too scarce political capital. to help an engineer in the transducer group specify a more expensive polypropylene cap in a passive loudspeaker crossover. His boss was not so dumb as to argue for a several cent cost increase with the big boss, but i was, even though it wasn't even my engineering area. When in doubt do what is right.. so i signed the engineering change order, his engineering manager wouldn't.  Polypropylene is a superior dielectric that could actually make a sound difference in a passive speaker crossover due to the current and terminal voltages involved. I wasn't willing to give up sound quality for a few pennies per unit. i never made an engineering design decision that wouldn't make for my own use. 

That is just one of several things i don't miss about having a boss....  but now my current boss (me) is angry because i'm wasting too much time on the WWW...

JR

 

[dissonantstring]

...  but now my current boss (me) is angry because i'm wasting too much time on the WWW...

JR

ha, ha!  but we like it when you waste time, expound with your knowledge and heresy JR. 
-grant

 

[keeeth]

Hi guys

I have one of these that I mainly use as a "colour box". I tend to pad down a line level signal and feed it through the mic inputs adding a bit of gain and then back in. It does change the sound a bit bit not as much as I might like.

I'm looking for a really coloured sound that you might associate with tubes. Airy, soft, smooth etc

Could anyone suggest mods or types of tubes I could use in there to get closer to that sound?

Cheers