Metropoulos Forum

Here are the inside pictures of the Roccaforte HG100 Amp, if someone can make correct schematic, please do.

What's the schematic symbol for a wire tie LOL... You'll need A LOT of those!

all i can say is that the yellowish rectangular caps seem to be 0.1ufs , i've seen one of those type of caps in rockstah wrecked 68 plexi build ....but as it is appearent that orange drops are from the 715p type i cannot tell about their value though got clearer pics ? is there an orange drop expert in here ?

Nice build, but could use a few more tie wraps. Actually that is a very, very nice job.

What's the purpose of the shield around the input jacks? I mean I assume it's for noise abatement. It would be easy enough to fabricate one and I wonder if it would be helpful in a Super Lead?

Very nice job on that amp!

jfhudak wrote:What's the purpose of the shield around the input jacks? I mean I assume it's for noise abatement. It would be easy enough to fabricate one and I wonder if it would be helpful in a Super Lead?

Very nice job on that amp!

it's only helpful when you wan't to put a master volume next to the input jacks ....but it's always cool to have a master volume on the front rather than on the back of the amp ....i think this shield is a great device !

frenchie wrote:

jfhudak wrote:What's the purpose of the shield around the input jacks? I mean I assume it's for noise abatement. It would be easy enough to fabricate one and I wonder if it would be helpful in a Super Lead?

Very nice job on that amp!

it's only helpful when you wan't to put a master volume next to the input jacks ....but it's always cool to have a master volume on the front rather than on the back of the amp ....i think this shield is a great device !

Merci mon ami!

mensur wrote:

Roccaforte HG100 4.JPG

Here are the inside pictures of the Roccaforte HG100 Amp, if someone can make correct schematic, please do.

My going reverse-engineering rate is $50/hr. Do you think someone is going to take that job on for FREE .

Nice work, for the most part. But is that junction of the PI tail-R, the PI Rk, and the two 1M PI grid-R's just a blob of solder? Is there a terminal in there somewhere ?

I had a HG100 years ago. Was a beautiful amp. Wish I still had it!

That said...I'm wanting a Metro 12 series right now.

its a blob of solder. i have a roccaforte custom 20.

mensur wrote:Here are the inside pictures of the Roccaforte HG100 Amp, if someone can make correct schematic, please do.

The schem is very close to a Rocco modded 2203, means four stages w/o a CF to the tone stack - and very low voltages to the preamp tubes. Supply voltage to V1 is IIRC about 190V, to V2 about 210V

I've had such an amp from one of my British Purist Customers on my bench for "taming", not for modding. I even haven't drafted only a quick hand schem of the amp, because I've been shocked of the orig. amp's sound! It wasn't worth it IMO, to spend time for this. Insane gain - yes! But noisy as hell, hard and ice picky - and I've missed the typically 'British Growl'!

I've tamed it to somewhat like a 'refined' 2203 w/ CF, but nonetheless the customer then has sold the amp a while later. Said, that all he's getting from this amp he already has just w/ the Rough sound of his British Purist, but with more beef & perfection in the tone.

frenchie wrote:all i can say is that the yellowish rectangular caps seem to be 0.1ufs , i've seen one of those type of caps in rockstah wrecked 68 plexi build ....but as it is appearent that orange drops are from the 715p type i cannot tell about their value though got clearer pics ? is there an orange drop expert in here ?

The yellowish rectangular caps are .68/100V - the Orange Drops are indeed 715P w/ one exception, what is a 225/200V as the 'lower' coupling cap into the PI - the blue ceramics are 470p/3kV Murata's.

frenchie wrote:

jfhudak wrote:What's the purpose of the shield around the input jacks? I mean I assume it's for noise abatement. It would be easy enough to fabricate one and I wonder if it would be helpful in a Super Lead?

Very nice job on that amp!

it's only helpful when you wan't to put a master volume next to the input jacks ....but it's always cool to have a master volume on the front rather than on the back of the amp ....i think this shield is a great device !

No! The shield is inevitable in this layout, otherwise the amp wouldt be squealing like a pig and I'm shure, that Roccaforte run into this problem at the first prototypes - hence the shield now

Oh sorry! You all certainly want to know, why ?

The input jack is placed exactly there, where the tone stack caps are located on the board. The phasing difference between the (sensitive) input signal and the (strong) signal in the tone stack is 720° !!! 360° already is enough for a hefty squeal, if you bring input & output too close together. Due to the amplification of two additional stages (two stages = 360° phasing diff. / 4 stages = 720° phasing diff.) this case is about 60 times worse than the 360° situation mentioned above. Without a shield there presumably only a half or maybe only a tenth of a picofarad capacitance between the tone stack caps and the input's hot tip is enough, to get the 'oscillator' on - to get the pig squealing.

So finally it turns out, that this what you regard as: "this shield is a great device" is nothing else than an inevitable technically crux! Sorry for the straight words, Doug! But the truth not always is comfortable. You probably already run into this prob by modding Marshall JTM's in the past, I've had the prob by modding Marshall JMP's in the early 90' as well - and other well-known modders from the past, who now have their own amp line have had this prob as well.

Larry

Nice review Larry. Thanks!

Wow, that's some more kind of of wire tie art!

novosibir wrote:

mensur wrote:Here are the inside pictures of the Roccaforte HG100 Amp, if someone can make correct schematic, please do.

The schem is very close to a Rocco modded 2203, means four stages w/o a CF to the tone stack - and very low voltages to the preamp tubes. Supply voltage to V1 is IIRC about 190V, to V2 about 210V

I've had such an amp from one of my British Purist Customers on my bench for "taming", not for modding. I even haven't drafted only a quick hand schem of the amp, because I've been shocked of the orig. amp's sound! It wasn't worth it IMO, to spend time for this. Insane gain - yes! But noisy as hell, hard and ice picky - and I've missed the typically 'British Growl'!

I've tamed it to somewhat like a 'refined' 2203 w/ CF, but nonetheless the customer then has sold the amp a while later. Said, that all he's getting from this amp he already has just w/ the Rough sound of his British Purist, but with more beef & perfection in the tone.

frenchie wrote:all i can say is that the yellowish rectangular caps seem to be 0.1ufs , i've seen one of those type of caps in rockstah wrecked 68 plexi build ....but as it is appearent that orange drops are from the 715p type i cannot tell about their value though got clearer pics ? is there an orange drop expert in here ?

The yellowish rectangular caps are .68/100V - the Orange Drops are indeed 715P w/ one exception, what is a 225/200V as the 'lower' coupling cap into the PI - the blue ceramics are 470p/3kV Murata's.

frenchie wrote:

jfhudak wrote:What's the purpose of the shield around the input jacks? I mean I assume it's for noise abatement. It would be easy enough to fabricate one and I wonder if it would be helpful in a Super Lead?

Very nice job on that amp!

it's only helpful when you wan't to put a master volume next to the input jacks ....but it's always cool to have a master volume on the front rather than on the back of the amp ....i think this shield is a great device !

No! The shield is inevitable in this layout, otherwise the amp wouldt be squealing like a pig and I'm shure, that Roccaforte run into this problem at the first prototypes - hence the shield now

Oh sorry! You all certainly want to know, why ?

The input jack is placed exactly there, where the tone stack caps are located on the board. The phasing difference between the (sensitive) input signal and the (strong) signal in the tone stack is 720° !!! 360° already is enough for a hefty squeal, if you bring input & output too close together. Due to the amplification of two additional stages (two stages = 360° phasing diff. / 4 stages = 720° phasing diff.) this case is about 60 times worse than the 360° situation mentioned above. Without a shield there presumably only a half or maybe only a tenth of a picofarad capacitance between the tone stack caps and the input's hot tip is enough, to get the 'oscillator' on - to get the pig squealing.

So finally it turns out, that this what you regard as: "this shield is a great device" is nothing else than an inevitable technically crux! Sorry for the straight words, Doug! But the truth not always is comfortable. You probably already run into this prob by modding Marshall JTM's in the past, I've had the prob by modding Marshall JMP's in the early 90' as well - and other well-known modders from the past, who now have their own amp line have had this prob as well.

Larry

Damn Larry Glad I sold my HG100 and bought a Diezel VH4---can't afford a Dino yet!

novosibir wrote:

mensur wrote:Here are the inside pictures of the Roccaforte HG100 Amp, if someone can make correct schematic, please do.

The schem is very close to a Rocco modded 2203, means four stages w/o a CF to the tone stack - and very low voltages to the preamp tubes. Supply voltage to V1 is IIRC about 190V, to V2 about 210V

I've had such an amp from one of my British Purist Customers on my bench for "taming", not for modding. I even haven't drafted only a quick hand schem of the amp, because I've been shocked of the orig. amp's sound! It wasn't worth it IMO, to spend time for this. Insane gain - yes! But noisy as hell, hard and ice picky - and I've missed the typically 'British Growl'!

I've tamed it to somewhat like a 'refined' 2203 w/ CF, but nonetheless the customer then has sold the amp a while later. Said, that all he's getting from this amp he already has just w/ the Rough sound of his British Purist, but with more beef & perfection in the tone.

frenchie wrote:all i can say is that the yellowish rectangular caps seem to be 0.1ufs , i've seen one of those type of caps in rockstah wrecked 68 plexi build ....but as it is appearent that orange drops are from the 715p type i cannot tell about their value though got clearer pics ? is there an orange drop expert in here ?

The yellowish rectangular caps are .68/100V - the Orange Drops are indeed 715P w/ one exception, what is a 225/200V as the 'lower' coupling cap into the PI - the blue ceramics are 470p/3kV Murata's.

frenchie wrote:

jfhudak wrote:What's the purpose of the shield around the input jacks? I mean I assume it's for noise abatement. It would be easy enough to fabricate one and I wonder if it would be helpful in a Super Lead?

Very nice job on that amp!

it's only helpful when you wan't to put a master volume next to the input jacks ....but it's always cool to have a master volume on the front rather than on the back of the amp ....i think this shield is a great device !

No! The shield is inevitable in this layout, otherwise the amp wouldt be squealing like a pig and I'm shure, that Roccaforte run into this problem at the first prototypes - hence the shield now

Oh sorry! You all certainly want to know, why ?

The input jack is placed exactly there, where the tone stack caps are located on the board. The phasing difference between the (sensitive) input signal and the (strong) signal in the tone stack is 720° !!! 360° already is enough for a hefty squeal, if you bring input & output too close together. Due to the amplification of two additional stages (two stages = 360° phasing diff. / 4 stages = 720° phasing diff.) this case is about 60 times worse than the 360° situation mentioned above. Without a shield there presumably only a half or maybe only a tenth of a picofarad capacitance between the tone stack caps and the input's hot tip is enough, to get the 'oscillator' on - to get the pig squealing.

So finally it turns out, that this what you regard as: "this shield is a great device" is nothing else than an inevitable technically crux! Sorry for the straight words, Doug! But the truth not always is comfortable. You probably already run into this prob by modding Marshall JTM's in the past, I've had the prob by modding Marshall JMP's in the early 90' as well - and other well-known modders from the past, who now have their own amp line have had this prob as well.

Larry

thanks for your very precise input larry ...no hard truth ,i don't take it bad at all, i just love truth as she is ......it's always cool to be corrected by someone who clearly knows his shit .....i linked this shield in my mind with the lot of guys i read of who were saying that when you put a master near the inputs noises occur ....i was just trying to enlight approximately the whole thing with the tiny bit of knowledge i had ....though the yellowish caps are exactly the same on rockstah's wrecked plexi which are 0.1u without any doubt, only judging by their size i find a bit weird that 0.68uf are exactly the same size than 0.1uf ...perhaps they have" the standardized wima size syndroma" no