Several years ago when Bob was selling his Cherry 180s on ebay, I contacted him to build me a pair with some modifications. I had Tubular Joe install V-Cap tin foil teflon output coupling caps, Furutech RCAs, Vampire copper binding posts, and OFCC power cord with Furutech tech termination over the standard "vintage" parts. More importantly, my Cherry 180s have the vintage pie wound transformer. For comparison, I also have pair of the output transformerless (OTL) Atma-Sphere M60 mk3.1 with upgraded copper V-Cap input coupling caps, power supply upgrade, and Caddock resistor package. At the time, the M60s were several thousand dollars more than the Cherry 180s. My speakers are 89 dB efficient 2-way dynamic designs with minimal impedance of 5.8 Ohms over a narrow band. The crossover is built with Dueland CAST copper PIO caps, CAST resistors, and custom 8 gauge scatter wound inductors wired with custom silver ribbon wires. They are one of best 2-way speakers I have ever heard after a 3 year search. I purchased the M60s because my speaker designer feels they are one of the two best amps for my speakers. On the contrary, I found the Cherry 180s to have more dynamics (both micro/macro), much better lower end extension and punch, and better sound staging and imaging. They just sounded more real to me. This may be in part due to the higher power of the Cherry 180s, but I listen to music in the 80 to 85 dB range with dynamic peaks in the low 90 dBs. The M60s 60 watts handles this without problem. The M60s have smoother upper midrange and high frequency extension, possibly due to their OTL design. The Cherry 180s are just as transparent, but compared to the M60s, I found the upper midrange and highs to be a little strident and timbre/tonality slightly less authentic.
However, I see the tremendous potential of the Cherry 180s. If you look inside these amps, you will not find any audiophile brand parts. This is not necessarily good or bad. However, I am convinced using higher quality parts, whether audiophile or non-audiophile parts, could improve the performance to surpass the most highly touted amps in Stereophile or TAS. I approached Bob about building my dream amp based on the Cherry 180s. I decided call it the Carver Silver Signature (CSS). With Bob's blessing and help, this is what I have come up with for the build.
1) Transformer, the heart of any transformer coupled tube amp. This is where the silver comes in. It will be a NICKLE CORE, SILVER WIRE PIE WOUND, POSSIBLY C-CORE transformer. If designed appropriately, silver can sound astonishingly real without the high frequency brightness most associate with this metal. The nickle for higher performance (aka "nickle magic" for those of you who have heard nickle core trannies) without having the transformer weigh a ton. It will be the center piece of the amp and will have clear transformer cover. Who will build them? You'll have to wait, but it will be beautiful.
2) Output coupling caps can make a significant improvement in sound. I have decided on Dueland CAST PIO copper foil caps. I have these in my speakers, and they are hard to beat. I think they are even better than teflon caps as Duelands sound more natural to these ears. The small value signal caps will be polystyrene caps.
3) Power supply caps will be polypropylene film caps. There will be NO electrolytic caps anywhere in this amp. Besides sounding more open, faster, and tighter, film caps will be more reliable and probably outlast me. However, this will increase the size of the power supply several fold. The largest 760 microF/900V caps measure 7.3 (H) x 4.6 (Diameter) inches. The reservoir capacitance will be twice that of the Cherry 180 or Black Beauty. The large value caps will be bypassed with 0.1 microF film caps. To keep the weight reasonable enough to handle by one person, the amps will be a 4 chassis design with separate amplification and power supply chassis for each channel.
4) Resistors will be mostly PRPs (very affordable with clean transparent sound). However, in key low power locations in the input/first amplification stage, I am considering the naked Vishay Z201 Z foil resistors (TX2575). Expensive so I will use them where they count. The resistors for the power tubes will likely be carbon film caps.
5) Chassis design. Other than four chassis, I don't have any more info to give.
6) Remotely controlled stepped attenuator at the input. Either DACT or Goldpoint. IME, this configuration is better than any active or passive preamp between the source and the amp, as long as the impedances are compatible.
I would appreciate your contribution to this build. I am open to any suggestions. Some of you may consider this build excessive in this economy. I do not mean to offend anyone. I have one vice in life, and this is it. I don't drink, smoke, do drugs, gamble,...or frequent strip clubs (well, may be once in a blue moon ) . So give me some freedom to enjoy my hard earned income.
As many of you may already know, Bob is one of the most cordial, enthusiastic, and giving person I have come across in audio. Over several years, I have come to consider him to be a true friend, although I have never met him in person. He is proverbial unicorn of high end audio.
I will post pictures and comments as this build proceeds. Thank you for reading my post.