Doc Loco a écrit :
GimmeShelter a écrit :
Doc Loco a écrit :
Tiens, y'a pas un truc bizarre?
Que de mystère ce soir Doc... allez crache le morceau
Allez, j'ai assez fait durer le suspense
. En fait, ce petit switch est la seul modif' apparente sur l'ampli:
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Et pourtant ... y'a eu du ménage!
- commentaire général préalable du technicien qui l'a "nucléarisé":
The Donor Amp here is the New Harley Benton GA15. The Stock Factory Amp is Very Poor Design with a HUGE Voltage Mismatch - 385 Volts DC on EL84 Valves - That's Insane - There is almost NO Gain, It Buzzes Like a Bumble Bee and Sounds Dreadful like it is Submerged in a Tank of Water. Even the Harley Benton Badge on the Front of the Amp does not Fit correctly, leaving Sharp edges exposed. In Standard form, it is NOT a Nice Amp.
The Cabinet is Nice. Cream Colour Covering and Woven Grille Cloth with Metal Corner Protectors and a Brown Leather Carry Handle.
I Initially thought the Amp was a Terminal Basket Case but decided to see what I could do to Save it. Im Glad I did because with a lot of work, it has turned out to be a Fantastic little Amp.
The Hours of work Paid off - The Amp Sounds Great - It Has a Beautiful Clean, Vintage Sound at Lower Volume Settings - and - At Higher Settings a Sweet, Smooth, Rich Tonal Harmonic Distortion. It is Extremely Articulate and Detailed. You can hear every Touch and Movement of your Fingers on the Strings of the Connected Guitar.
Le pire, c'est qu'il ne ment pas, pas plus qu'il n'exagére!
Mais qu'a t'il fait au juste? Voilà:
Valve Heaters are Now DC and there is NO Heater Buzz at all - The Amp is Silent Except for some Very Slight 'Hiss' at Full Gain.
I have Corrected the Excessive HT Voltage, Re-Biased Both Sides of the Preamp Valve, Added a 3 Stage Gain Switch and Set the Correct Bias for the Output Valves.
If the Output Valves are Changed, No Re-Bias is Required Providing a Matched Pair of EL84 Valves are Fitted. This is Because the Amp Output Stage is 'Cathode Bias' and NOT 'Fixed Grid Bias'.
The 'Gain' Switch. - Set to the 'Centre Position' the Amp is Clean. Switch it 'On' to Position 1 (Up) or 2 (Down) and the Amp Sparkles and Comes to Life. The Depth, Dynamics and Detail are Superb - Beautiful Smooth Creamy Sustain just Flows.
A. - Position '1' is Medium Gain.
B. - Centre Position is 'Normal Gain'.
C. - Position '2' is 'High Gain'.
The 'Volume' Control is a 'Master Volume' - The Gain on the Preamp is set with the 'Boost' Switch.
The 'Treble', 'Middle' and 'Bass' Controls are 'Active' and offer both 'Boost' and 'Cut' of the the Input Signal.
I Have Corrected the Headphone Output (It was Dull and Distorted) - The Main Speaker is Muted when Headphones are Connected.
The 'Line Out' Socket has been changed from 'Preamp Signal' (useless) to 'Speaker Emulation' - From the Output Transformer.
The Send/Return Effects Loop is 'Serial' and works Well. There are No Level controls but the Levels can be set on the Connected Effects. The 'Return' Socket can be used for Direct access to the Valve Power Amp if Required.
I Have Fitted a New Celestion 'Tube 10' Speaker (10 inch) - The 'Tube 10' is Loads Better than the Standard Speaker.
I Fitted an Electro Harmonix EH12AX7 Preamp Valve and a New Matched Pair of EL84EH Output Valves.
There are Several 'Other' Modifications that I do to All of my Amps that are Exclusive to me and both Enhance Performance and Help to Keep the Noise Levels Way Down. The Background 'Hiss' from this Amp is so Low, you may not notice it is Switched on. The Amp Sounds INFINITELY Better than a Standard Unit.
Except for the 'Boost' Switch Located above the 'Input Socket' - and - Removal of the 'HB' Badge, the Outside Cosmetics of the Amp are the Same as a Stock factory Unit. The Layout of the Controls seem fine to me and everything now works as it Should.
The Size of the Amp is 39h x 42w x 26d (cm) and it Weighs 15 Kg.
Oui ... y'a eu du boulot
.
Mais le résultat est là: une bombe d'ampli pour 300€ tout compris:
- il est silencieux comme une tombe, même à fort volume: pas un parasite, pas un souffle
- plus aucune trace de "boxyness", le son est ample et précis, costaud
- le son est aussi très détaillé, et l'égalisation trois bandes fonctionne à merveille
- le switch trois positions du préampli fait qu'on a quasiment trois canaux : un clean chaud , un crunch léger et un crunch appuyé - et je ne vous dit pas quand les lampes de puissances sont mises à contribution!
- le son est réminescent d'un vieux Marshall style Bluesbreaker/mini bluesbreaker
- branché dans un baffle ... oh ma mère! n'étant rentré qu'à 19H, je n'ai pas pu l'essayer longtemps dans cette config' mais c'est énorme (baffle 1xG12H30 fermé), certainement suffisant pour la scène
- le HP Celestion Tube 10 est très chouette pour un 10", avec un rendement assez pauvre (comme tous les 10", qui affichent au mieux 97 dB là où beaucoup de 12" en font 100; le Tube 10 tourne autour de 94 dB) qui fait qu'il est utilisable à "relatif" bas volume
- et je n'ai pas encore essayé la sortie casque, la boucle, le line out ... au secours!
Bref, enchanté, c'est exactement ce que je voulais; le gain maximum va jusqu'à AC/DC, au-delà il faudra booster et mon petit doigt me dt qu'il adore ça.
Cependant, il est fort probable qu'à terme, je lui fasse cadeau du nouveau Celestion Greenback G10 ou du G10 Vintage.
Depuis, j'ai remplacé le bon Tube 10 par l'excellent Greenback.
