Bob Carver Tube amplifiers upgraded to VTA305M+ Pair Monoblocks in Mint Cond.

Description

PLEASE READ BELOW VERY CAREFULLY !!! .... (Thank you :-))
These amps were brand new VTA180M Cherry Red Monoblock's using KT88 power tubes that I had Bob Carver upgrade and re-spec using the uber-powerful KT-150 power tubes. He also modified the circuits to work with my Martin Logan "Spires" Electrostats, with an impedance of under 1 ohm @ 20KHz.
These amps are in effect better than his VTA305M amplifiers with 305W per channel in 8 ohms, 440W in 4 ohms, with capability to work with less than 1 ohms loads. These amps are the pre-cursors to his Crimson RED 350 amps with less than 1 ohm load capability.
The power specs of these amps are similar to the more powerful Crimson RED 350 amps, where both amps produce 440W and 400W in 4 and 2 ohms respectively.
In essence, with my Bob-Carver modified VTA-305M (+plus+), you are getting 87% of the power in 8 ohms and 100% of the power of the
more powerful and expensive Crimson 350 RED amplifiers (~K) at a significant fraction of the cost.
My
Crimson RED 305M+
uses more powerful and musical KT150 tubes ...
Regular amp uses less powerful KT120 tubes.
These amps are
individual hand-signed by Bob Carver himself
(see pics above)!
Specs are shown below. Bob Carvers measurements shown in
BOLD
. The rest are the same as his stock VTA-305M monoblocs.
Number of Line Inputs: 1
Input impedance: 100 k ohms
Input Stage: 12AX7 current sourced long tailed balanced pair
Pre-driver Stage: 12AT7 current sourced long tailed balanced pair
Automatic DC Restoration: 6AL5
Nominal Voltage Gain: 30 dB (into 8 ohms)
Output Stage Configuration: 3 complimentary Sets of
KT150s
in a push pull configuration (6 total)
Regulated Screen Supply Voltage: 390V
Output tube plate voltage: 785V
Output tube Idle Power: 9.8W
(stock VTA-305 is 14W)
Bias Adjustment: Rear panel pot, front panel meter, set and forget...
Bob Carver recommends a 70mA bias setting
.
Bob Carver's Custom Power Specs:
- 305 watts into
8
ohms
(
Cherry RED VTA350M spec'd slightly higher @ 350W into 8 ohms.
S
ame as stock VTA305M
)
- 438 watts into
6 ohms
(no spec given for stock VTA305M
)
- 440 watts into
4 ohms
(
Same as more powerful Cherry RED VTA350M!
. A stock VTA305M was rated @
330 watts into 4 ohms).
- 400 watts into
2 ohms
(
Same as more powerful Cherry RED VTA350M!.
A stock VTA305M was rated @290 watts into 2 ohms).
- 350 watts into
1 ohms
(stock VTA305M not rated for 1 ohm operation).
Noise:
> 123 dB A-Weighted
referenced into 305W watts ...
Bob carver says "better than solid state"
.
I can confirm that these amps are dead silent and thus number is better than the best and quietest DACs out there...almost 21-bit performance. Full HD/Ultra-HD audio performance!
Frequency Response
: 2 Hz to
180 kHz!!!
(
More than doubled frequency response @1W !!!
... stock VTA305M spec'd at 2 Hz to 85 kHz)
Full Power Bandwidth: 22Hz to 46KHz
(
Extended full power response by almost 20kHz !!!
...stock VTA305M spec'd at 24 Hz to 28 kHz)
Feedback Control Switch: 20dB for Vintage Amplifier Sound, 11 dB for Contemporary Amplifier Sound
Distortion
: Less than 0.5%
(...
0.32% for these modified amps at rated power.
Though its an o
rder of magnitude less (10X or more) at normal listening volumes
)
Output Impedance: 0.5 ohms
(...stock VTA305M spec'd 1.3 ohms)
Output Transformer
: Interleaved windings,
super wideband low leakage inductance design
Bob Carver says of this custom design "
This amp is going to sound stunning!
", "
There is no doubt in my mind that they will sound stunning!
", and after the mods were finished ... "
Listening tests confirm we are in the presence of greatness!
" ... and I heartily concur !!!
Many positive reviews of the VTA180M or VTA305M abound online.
I personally recommend a 72-96 hour tube burning before serious listening tests are done, since tubes have been dormant for almost 4 years in a temperature controlled storage room.
Speaker outputs
: 2, 4, and 8 ohm terminals ...
but use the 8 ohm terminal only per Bob Carvers
recommendation
for maximum power.
Built in Output Tube tester: Yes
Construction Method
: Point-to-Point hand wired axial and radial leaded components with star grounds and no circuit board traces or de-pluggable connectors.
Components
: High reliability wire wound and metal film resistors, Metal polyester capacitors in the audio signal paths.
2 HEAVY GAUGE CUSTOM "Victor Lemonte Wooten"
('Fun and Classy Purple Signature
M
usic
C
ord PRO')
power cords from ESP included.
6.6ft (2m) long
...
a free 0 value!!!!!
Soft PDF Manual for the VTA-305M can be provided . It is also available online.
Shipping Weight: 45 pounds x 2
Shipping box dimensions (WHD): 17″ x 14″ x 22″
Color: Glossy Cherry
Country of Origin: United States of America