montesquieu
13-04-2014, 23:20
AVAILABLE AGAIN NOW I'VE SORTED OUT WHAT I'M DOING WITH SPEAKERS..... ALSO OFFERED FOR SALE AT £950 including the Psvane 300bs.
I've been experimenting with drivers for my new Canterburys, and after trying 12in Golds, settled on 12in HPDs. What I'd like to try next is a high power valve amp to drive them seeing as that's what recommended for them.
So offered for trade ... original WAD 300b push pull interstage amp - bit of a legend in DIY circles. The original design was done by Tim de Paravicini in the early 90s, and modified by a young Andy Grove (who soon afterwards became Audio Note UK's in house amp designer). It's a zero negative feedback push pull amp, and sounds absolutely wonderful - hear this and never again will anyone say the 300b is lovely and refined but lacks energy and backbone. No less than seven high-quality transformers go into this - a truly massive mains transformer, two chokes, two output transformers, and two interstage transformers (which do away with a driver stage and replace the necessary coupling capacitors with a substantial transformer). A very gutsy 28w output.
Tons and tons of info online on the WAD 300b interstage, needless to say it's head and shoulders above the current kit designs from World Designs or Glasshouse - they a kit like this just wouldn't be affordable to bring to market any more.
This amp the personal amp of John Caswell (official UK service tech for various high-end brands such as Unison Research and Pathos), he built it for his own use quite a few years ago and only recently replaced it with a pair of KT88 monoblocks, to match some fairly power-hungry Proarc speakers he'd just acquired. The Andy Grove design was ultra-sensitive (at least, when used in no negative feedback mode) and essentially incompatible for use with active preamps. Rather than introduce NFB, John replaced the WAD input stage with the original one SP Wound (makers of the transformers) recommended, using single 6C45P input valves (readily available). It now has a sensitivity of about 1.2V, works well with active preamps and remains without negative feedback.
John also made an improvement to the HT rectification which is by a pair of 6D22S plus fast diodes in a hybrid Graetz circuit, so warmup is slow (good for tube and component life). According to John who owns all the right kit to measure these things, frequency response is flat within 0.5dB from 10Hz to 34Khz. All valves are auto biasing and there are trim pots to remove hum if the power valves used are not perfectly matched pairs each side.
Comes with all valves including a freshly installed quad of PSVANE 300b (UK sourced) and a spare set of driver and two spare sets of rectifier valves (including a pair of NOS Telefunkens EY500A equivalents). Twin speaker outputs for easy biwiring. The original connections and sockets are all there for restoration to the 5087/6072 double tube input stage if required for any reason - but I doubt anyone would want to after hearing it.
This amp sounds truly spectacular with early Tannoys, also with Quad ESLs. Should actually suit most speakers above about 90db sensitivity.
Anyway I'm offering this for trade or trade+cash on my side for something high power, like a pair of EAR 509s, an EAR 890, McIntosh MC275, or something along those lines.
No great rush, will just wait and see what comes in.
http://i1181.photobucket.com/albums/x440/montesquieu61/300binterstage_zpsf15dd92f.jpg (http://s1181.photobucket.com/user/montesquieu61/media/300binterstage_zpsf15dd92f.jpg.html)
I've been experimenting with drivers for my new Canterburys, and after trying 12in Golds, settled on 12in HPDs. What I'd like to try next is a high power valve amp to drive them seeing as that's what recommended for them.
So offered for trade ... original WAD 300b push pull interstage amp - bit of a legend in DIY circles. The original design was done by Tim de Paravicini in the early 90s, and modified by a young Andy Grove (who soon afterwards became Audio Note UK's in house amp designer). It's a zero negative feedback push pull amp, and sounds absolutely wonderful - hear this and never again will anyone say the 300b is lovely and refined but lacks energy and backbone. No less than seven high-quality transformers go into this - a truly massive mains transformer, two chokes, two output transformers, and two interstage transformers (which do away with a driver stage and replace the necessary coupling capacitors with a substantial transformer). A very gutsy 28w output.
Tons and tons of info online on the WAD 300b interstage, needless to say it's head and shoulders above the current kit designs from World Designs or Glasshouse - they a kit like this just wouldn't be affordable to bring to market any more.
This amp the personal amp of John Caswell (official UK service tech for various high-end brands such as Unison Research and Pathos), he built it for his own use quite a few years ago and only recently replaced it with a pair of KT88 monoblocks, to match some fairly power-hungry Proarc speakers he'd just acquired. The Andy Grove design was ultra-sensitive (at least, when used in no negative feedback mode) and essentially incompatible for use with active preamps. Rather than introduce NFB, John replaced the WAD input stage with the original one SP Wound (makers of the transformers) recommended, using single 6C45P input valves (readily available). It now has a sensitivity of about 1.2V, works well with active preamps and remains without negative feedback.
John also made an improvement to the HT rectification which is by a pair of 6D22S plus fast diodes in a hybrid Graetz circuit, so warmup is slow (good for tube and component life). According to John who owns all the right kit to measure these things, frequency response is flat within 0.5dB from 10Hz to 34Khz. All valves are auto biasing and there are trim pots to remove hum if the power valves used are not perfectly matched pairs each side.
Comes with all valves including a freshly installed quad of PSVANE 300b (UK sourced) and a spare set of driver and two spare sets of rectifier valves (including a pair of NOS Telefunkens EY500A equivalents). Twin speaker outputs for easy biwiring. The original connections and sockets are all there for restoration to the 5087/6072 double tube input stage if required for any reason - but I doubt anyone would want to after hearing it.
This amp sounds truly spectacular with early Tannoys, also with Quad ESLs. Should actually suit most speakers above about 90db sensitivity.
Anyway I'm offering this for trade or trade+cash on my side for something high power, like a pair of EAR 509s, an EAR 890, McIntosh MC275, or something along those lines.
No great rush, will just wait and see what comes in.
http://i1181.photobucket.com/albums/x440/montesquieu61/300binterstage_zpsf15dd92f.jpg (http://s1181.photobucket.com/user/montesquieu61/media/300binterstage_zpsf15dd92f.jpg.html)