Want Pre500 tone? Here's how to get it!

[APEMAN]

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[rpurdue]

Hi,
I'm confused with the mods suggested on the last pages, please help!

I totally belive you that it might sound better/tighter, but please help me to understand....

- the 82p/2,2Meg Pre-Gain-Filter was part of the Rectos since at least (?) the Past500 Models, removing this filter will kill your raw(3CH)/blues(2CH) mode, or not (maybe I'm completely wrong here...)?

[- early 2CH Models used a 475k instead of an 680k resistor in the resulting Pre-Gain-Filter for vintage and modern. ...which will bring you a little bit more mids in the preamp.]

- jumping the 100 Ohms will help - completely agreed...

- removing the 20p cap in front of V2 - wasn't that cap part of the circuit since ever? Of course it will bring you more brightness, but are we hunting for the original recto voice or something else? Or is this maybe comming from a pre500???

- Have you seen the 10p (dullness-cap) on the 3CH master pot (only non-multiwatt)? My suggestion is to remove it...

- that 1Meg Gain pot thing - completely agreed (even if I prefer 500k....)

[- take a closer look at the preamps power supply cap values]



Wow, 24 pages :shock: but I have the feeling we are close to THE solution. (Is it possible to have more than 99 pages for this topic, or should we go for something like "www.Want Pre500 tone? Here's how to get it!.com ?) :lol:

Are you talking the over all output master or the 3rd channel master? Where is this cap located? I have a 3 channel and see no actual cap on the pot.

 

[kramerxxx]

Hi,
I'm confused with the mods suggested on the last pages, please help!

I totally belive you that it might sound better/tighter, but please help me to understand....

- the 82p/2,2Meg Pre-Gain-Filter was part of the Rectos since at least (?) the Past500 Models, removing this filter will kill your raw(3CH)/blues(2CH) mode, or not (maybe I'm completely wrong here...)?

[- early 2CH Models used a 475k instead of an 680k resistor in the resulting Pre-Gain-Filter for vintage and modern. ...which will bring you a little bit more mids in the preamp.]

- jumping the 100 Ohms will help - completely agreed...

- removing the 20p cap in front of V2 - wasn't that cap part of the circuit since ever? Of course it will bring you more brightness, but are we hunting for the original recto voice or something else? Or is this maybe comming from a pre500???

- Have you seen the 10p (dullness-cap) on the 3CH master pot (only non-multiwatt)? My suggestion is to remove it...

- that 1Meg Gain pot thing - completely agreed (even if I prefer 500k....)

[- take a closer look at the preamps power supply cap values]



Wow, 24 pages :shock: but I have the feeling we are close to THE solution. (Is it possible to have more than 99 pages for this topic, or should we go for something like "www.Want Pre500 tone? Here's how to get it!.com ?) :lol:

I think we are possibly chasing the Dragon on some of this. I believe some of the orginal posts were targeted at the 2ch Rectifiers and those specific instructions were to get the later Revs to sound closer to the Pre500s.

The last few pages, folks like myself, have been more specifically interested in removing the 'blanket off the amp', specifically with the 3ch Rectifiers. I didn't mean to derail the thread because some of the mods seemed to overlap the 2ch/3ch amps. I cannot be so bold as to state the mods offered up will make my 3ch sound like a Pre500, but I can say the mods have taken the amp to the best I've ever heard it sound. I would also like to offer I have an upgraded OT in it and it has been modded by a respected builder on the East coast. I still wasn't totally satisfied with it, but as I'd spent a bunch of money, I resigned that that was the best it was going to get, but I was wrong. Enter the Gain Pot Mod and the V1, V2, V3 resistor jumps and I think I'm pretty close to having the Rectifier I always wanted it to be. It is not as Bright as a Marshall, it has better 'Touch/Feel' than other Recs I've played, I can actually turn up the Bass pot and not have complete MUD for tone AND it works VERY well for Lead playing without having an OD pedal in front of the amp. I was always put off with this last part as the name on the amp said Solo Head, but it didn't sound good, to me, for anything but Rhythm playing.

There are a few quirks that these mods result in that are not ideal, but the overall tone of the amp is much improved and the Red channel is Stellar, if you like High Mesa tones.

Just my 2cents.

 

[rpurdue]

I just did the above changes with jumpering the resistors and removing the cap/resistor and cap. I did the jumpers first and then removing the cap/resistor. I noticed a great change with just jumpering the resistors. More open and a little more bite. I removed the other circuit and the presence knob ceased to function and RAW in channel 3 was very flubby. I re soldered the caps and resistors and left the others jumped. I'm not sure what a pre 500 sounds/feels like even but this made a world of difference thanks.

 

[rpurdue]

So now i notice that in vintage or modern on both channels there's a strange noise i've never noticed before. Almost an oscillating with morse code type taps in it. It's not near as noticeable with the gain below 5. It's also on RAW but hard to hear as the gain is quite low. It also seems that it hums louder if i touch the gain knob on channel 2. I replaced the missing caps and only have the 100 ohm resistors jumpered. Any ideas.

 

[kramerxxx]

some more observations on my 3ch Dual Rec:

I have the resistors replaced with jumpers and the cap and cap/resistor removed.
I swapped out the EL34s that I had in the amp and popped in a set of 6L6s. These are not fresh and might be some of what I'm hearing, so I'll need to go back to the EL34s to be sure.

I'm not having the Oscillations but there are compromises with these 'changes'.

I noticed the Red Channel, Modern Mode sounds Fantastic, but the other modes on that channel are just OK. The 250k Presence Pot doesn't add the same Mojo to each Mode.

The Orange Channel might have more gain with the 1M pot, but the overall tone is not as clear on any of the modes.

The Green Channel is fine, I can live with it either way.

If the Cap/Resistor and Cap is what makes the Presence control work correctly across all channels but causes the oscillation without the preamp resistors maybe there is a compromise that could be used to accomplish a little of both.

If 100ohms 'puts a blanket' on the preamp tone and jumpered is NO resistance, maybe somewhere in the middle gets the compromise. Say 50ohm or 25ohm for the resistors?

Or possibly changing the Cap values to keep it from oscillating?

 

[Anonymous]

Hi,
I'm confused with the mods suggested on the last pages, please help!

I totally belive you that it might sound better/tighter, but please help me to understand....

- the 82p/2,2Meg Pre-Gain-Filter was part of the Rectos since at least (?) the Past500 Models, removing this filter will kill your raw(3CH)/blues(2CH) mode, or not (maybe I'm completely wrong here...)?

[- early 2CH Models used a 475k instead of an 680k resistor in the resulting Pre-Gain-Filter for vintage and modern. ...which will bring you a little bit more mids in the preamp.]

- jumping the 100 Ohms will help - completely agreed...

- removing the 20p cap in front of V2 - wasn't that cap part of the circuit since ever? Of course it will bring you more brightness, but are we hunting for the original recto voice or something else? Or is this maybe comming from a pre500???

- Have you seen the 10p (dullness-cap) on the 3CH master pot (only non-multiwatt)? My suggestion is to remove it...

- that 1Meg Gain pot thing - completely agreed (even if I prefer 500k....)

[- take a closer look at the preamps power supply cap values]



Wow, 24 pages :shock: but I have the feeling we are close to THE solution. (Is it possible to have more than 99 pages for this topic, or should we go for something like "www.Want Pre500 tone? Here's how to get it!.com ?) :lol:

Let's tackle this!

- I'd leave the 82pF || 2.2M pre-gain filter intact. This circuit is used in conjunction with .002uF || 680k network to form a nearly equivalent circuit of the pre500's .0022uF || 475k.

- Again, although there is a 680k resistor in the pre-gain filter, it is always used with the 2.2M resistor. This gets you an equivalent resistance 520k. Now, if you want to really get accurate, put a 5M5 (or as close as you can get) in parallel with the 680k resistor. This will replicate exactly the pre500 circuit.

- I can't honestly tell the difference with or without the 20pF cap in front of V2. I thought I could, but upon further testing, I've found it to be totally irrelevant to my amp's tone.

- 10pF is an extremely small value. I doubt very much this is here to alter tone. Probably has more to do with oscillation control. That said, maybe someone can try removing it and describe their findings.

- 1M gain pot is - IMO - an awesome mod. Even if most pre500 tones aren't derived from here, I really like the response of the amp with a 1M gain pot.

- Preamp power supply caps is the difference everyone associates with old 3ch Rectifiers sounding different from 2ch.

 

[Anonymous]

So now i notice that in vintage or modern on both channels there's a strange noise i've never noticed before. Almost an oscillating with morse code type taps in it. It's not near as noticeable with the gain below 5. It's also on RAW but hard to hear as the gain is quite low. It also seems that it hums louder if i touch the gain knob on channel 2. I replaced the missing caps and only have the 100 ohm resistors jumpered. Any ideas.

Not sure. This could be happening for a multitude of reasons, but I guarantee it's not due to the 100 ohm resistors being jumped. Retrace the steps you took when modding and see if you left a ground off or in the wrong place somewhere.

 

[Anonymous]

some more observations on my 3ch Dual Rec:

I have the resistors replaced with jumpers and the cap and cap/resistor removed.
I swapped out the EL34s that I had in the amp and popped in a set of 6L6s. These are not fresh and might be some of what I'm hearing, so I'll need to go back to the EL34s to be sure.

I'm not having the Oscillations but there are compromises with these 'changes'.

I noticed the Red Channel, Modern Mode sounds Fantastic, but the other modes on that channel are just OK. The 250k Presence Pot doesn't add the same Mojo to each Mode.

The Orange Channel might have more gain with the 1M pot, but the overall tone is not as clear on any of the modes.

The Green Channel is fine, I can live with it either way.

If the Cap/Resistor and Cap is what makes the Presence control work correctly across all channels but causes the oscillation without the preamp resistors maybe there is a compromise that could be used to accomplish a little of both.

If 100ohms 'puts a blanket' on the preamp tone and jumpered is NO resistance, maybe somewhere in the middle gets the compromise. Say 50ohm or 25ohm for the resistors?

Or possibly changing the Cap values to keep it from oscillating?

Which cap/resistor value are you referring to?

 

[rpurdue]

So now i notice that in vintage or modern on both channels there's a strange noise i've never noticed before. Almost an oscillating with morse code type taps in it. It's not near as noticeable with the gain below 5. It's also on RAW but hard to hear as the gain is quite low. It also seems that it hums louder if i touch the gain knob on channel 2. I replaced the missing caps and only have the 100 ohm resistors jumpered. Any ideas.

Not sure. This could be happening for a multitude of reasons, but I guarantee it's not due to the 100 ohm resistors being jumped. Retrace the steps you took when modding and see if you left a ground off or in the wrong place somewhere.

It actually ended up being a tube. Although they are new, the Tungsol in V1 was faulty. After replacing it all the noise was gone. I found the amp way more responsive and a nicer , open midrange character by jumping the 3 resistors but I think i'll still try to change the presence pot's just to see the effect. It's an easy mod afterall. I'll order a few from ebay.

 

[Anonymous]

So now i notice that in vintage or modern on both channels there's a strange noise i've never noticed before. Almost an oscillating with morse code type taps in it. It's not near as noticeable with the gain below 5. It's also on RAW but hard to hear as the gain is quite low. It also seems that it hums louder if i touch the gain knob on channel 2. I replaced the missing caps and only have the 100 ohm resistors jumpered. Any ideas.

Not sure. This could be happening for a multitude of reasons, but I guarantee it's not due to the 100 ohm resistors being jumped. Retrace the steps you took when modding and see if you left a ground off or in the wrong place somewhere.

It actually ended up being a tube. Although they are new, the Tungsol in V1 was faulty. After replacing it all the noise was gone. I found the amp way more responsive and a nicer , open midrange character by jumping the 3 resistors but I think i'll still try to change the presence pot's just to see the effect. It's an easy mod afterall. I'll order a few from ebay.

Nice; definitely let us know!

 

[2CDR]

ok just a quick clarification,and i cant find the post for it.can someone please re cap which cap/resistors get jumped?
this is in a revG 2.either list them or if one still has a gut shot with them circled?
much appreciated guys.

 

[kramerxxx]

some more observations on my 3ch Dual Rec:

I have the resistors replaced with jumpers and the cap and cap/resistor removed.
I swapped out the EL34s that I had in the amp and popped in a set of 6L6s. These are not fresh and might be some of what I'm hearing, so I'll need to go back to the EL34s to be sure.

I'm not having the Oscillations but there are compromises with these 'changes'.

I noticed the Red Channel, Modern Mode sounds Fantastic, but the other modes on that channel are just OK. The 250k Presence Pot doesn't add the same Mojo to each Mode.

The Orange Channel might have more gain with the 1M pot, but the overall tone is not as clear on any of the modes.

The Green Channel is fine, I can live with it either way.

If the Cap/Resistor and Cap is what makes the Presence control work correctly across all channels but causes the oscillation without the preamp resistors maybe there is a compromise that could be used to accomplish a little of both.

If 100ohms 'puts a blanket' on the preamp tone and jumpered is NO resistance, maybe somewhere in the middle gets the compromise. Say 50ohm or 25ohm for the resistors?

Or possibly changing the Cap values to keep it from oscillating?

Which cap/resistor value are you referring to?

82pf cap/2m circuit from V1.

 

[APEMAN]

-

 

[kramerxxx]

OK, I accidentally broke the 82p cap in the 82p/2,2Meg circuit when I removed it. Does this need to exactly match this value? I wanted to try putting that one and the other 82p cap back in to see if it brings the control back for Raw for the Presence control

I have a bunch of little caps but the markings on them do not say 82pf on them, what should I be looking for?

thanks.
Steve

 

[Anonymous]

OK, I accidentally broke the 82p cap in the 82p/2,2Meg circuit when I removed it. Does this need to exactly match this value? I wanted to try putting that one and the other 82p cap back in to see if it brings the control back for Raw for the Presence control

I have a bunch of little caps but the markings on them do not say 82pf on them, what should I be looking for?

thanks.
Steve

Which presence pot value are you using? Is this raw mode you're referring to on the orange channel?

As for cap value, you'll want to look for something pretty close, but it doesn't have to be exact. I'd look for a 100pF. Ceramic caps might have the label 101 (Here's a guide to cap values).

 

[kramerxxx]

I am using a 250k presence pot.

Thanks for the response, I will see if I Have a 100of 1kv cap.

Try the amp sounds pretty good like this, I would just like it to be as functional,as possible.

When I made these changes I only had a linear pot to try, but I have an audio taper ordered

Thanks again for the help and all of your posts. These changes made a pretty good sounding amp do much better, for the way I use it.

Steve

 

[2CDR]

guys, i killed the green cap that goes on the gain pot.would jumping the lugs on the pot do anything?

 

[Anonymous]

guys, i killed the green cap that goes on the gain pot.would jumping the lugs on the pot do anything?

Wouldn't recommend doing that; you'll get a lot of muddy gain. Just grab a new 1nF cap.

 

[2CDR]

Thank You.
what caps/resistors are the ones that can be jumped?