Hello everyone,
I have read the threads on power attenuator and load boxes but still don't trust I understand it.
Basically I have moved my Sunn 200s into Hyde Street Studios in San Francisco and it's getting lots of love. As you can imagine, volume can't quite get past 4 or 5 without shaking the walls down, so i went ahead and purchased a Rivera Rockcrusher Recording to offer more tonal options. I know that Tube distortion at higher volumes is sometimes miagical. So I wanted to have the option.
https://www.rivera.com/product/attenuators-cab-sims/rockcrusher-recording/But The Rockcrusher Warning below, has me freaked out. Can anyone tell me if it's ok to use or not? I have already read this content, ...
"As the schematic indicates vintage Sunn tube amps came with OTs that have 4, 8, and 16 ohm taps, and the amps came with the jacks either factory wired for 8 ohm and 4 ohm OR 16 ohm and 8 ohm, and its easy (as well as not uncommon) to switch them back and forth.
So while the schematic you posted shows the 8 & 4 configuration, you should make sure that it is indeed factory wired for 8 and 4 ohm operation or that no one has performed any output tap surgery to suit their personal needs over the past 45 years.
The problem with running the amp on a variac is that you need to have a variac that can meet the current requirements for the amp, and these are as expensive or more expensive than doing the cap work unless you already have a 5 amp variac?
The other thing to consider is that there are other voltages in the amp besides the B+ voltage, and if you are going to play around with the AC supply with a variac, then it will affect these voltages too. The bias voltage, the heater voltage.....all of these will change if you change the AC supply, but they won't change linearly....in other words if you change the AC supply by 5 volts, it doesn't mean than the DC voltages in the amp will change by the same amount, and the AC voltages like the heater also won't change in proportion necessarily. The bias would also have to be readjusted to run the amp at whatever lower voltage you plan to run it at, and once that is done you can never run it at a higher AC supply without readjusting the bias.
It is much easier to go with series connected caps for the first two filter stages in the amp and get 700v rating, use a 500v cap for the third section, and a 450v cap for the last section. The can caps are stressed in these amps and discrete caps are much cheaper anyway than cans these days. Another possibility you might consider would be the cap boards the Triode sells. Personally on the Sunn bass amps, I like using higher filtration in the plate and screen supplies, which are the first two stages. The bass tightens up and the hum goes down....though if you decide to do this using a solid state rectifier is mandatory if you go over 60uF filtering on the first cap stage.
I don't know what photos you are refering to, but my two 200S heads have 2 speaker out jacks, one marked for an 8 ohm load and the other marked for a 4 ohm load.
Your 4 ohm cabinet combination will work fine!
With the 3-prong plug, the "death cap" should have been disconnected, leaving nothing for the polarity switch to do, so it having no effect is a good thing. The speaker cabinet having a flat response has nothing directly to do with volume. With a flat response, you won't get notes in one range being louder or softer than notes in another range, as can sometimes happen.
I had an issue on one of my Sunn heads due to the input jacks not being properly grounded. Sunn saved a little bit of wire by letting the chassis be the ground instead of wiring the jacks. I ran some wire to a convenient ground, and solved it. Your issue might be related. Standard warnings apply: don't open up the amp if you aren't experienced with this kind of work, lethal voltages can be present inside, even with the amp unplugged, and so on."
My 200s cab is loaded with two JBL D140F speakers
Here is the Warning From Rivera ...
WARNINGS! PLEASE READ BEFORE USING!
YOU MUST HAVE A LOAD OF THE PROPER IMPEDANCE CONNECTED TO THE SPEAKER OUTPUTS OF THE
ROCKCRUSHER WHEN OPERATING IN THE BYPASS POSITION! IF NOT, YOUR AMPLIFIER WILL POTENTIALLY
SEE
AN OPEN LOAD CONDITION, WHICH MAY RESULT IN SEVERE DAMAGE TO YOUR AMPLIFI
ER!
YOU MUST MAKE SURE THAT THE IMPEDANCE OF THE AMPLIFIER?S SPEAKER OUTPUT MATCHES THE
SETTINGS ON THE ROCKCRUSHER (8 OR 16 OHM), AND THAT THE SPEAKER(S) CONNECTED TO THE
ROCKCRUSHER IS OF THE SAME IMPEDANCE. IF MULTIPLE SPEAKERS ARE CONNECTED
(ROCKCRUSHER
SPEAKER OUTPUT JACKS ARE IN PARALLEL), THEIR COMBINED LOAD IMPEDANCE MUST MATCH THE
SETTINGS
ON THE AMPLIFIER AND ON THE ROCKCRUSHER. AN IMPEDANCE MISMATCH CAN POTENTIALLY
RESULT IN
DAMAGE TO YOUR AMPLIFIER, AND EXCESSIVE HEATING TO THE ROCKCR
USHER INTERNA
L
COMPONENTS. DO
NOT USE THE ROCKCRUSHER ON AMPLIFIERS THAT ARE HARDWIRED FOR 2 OR 4 OHMS,
OR DO NOT HAVE 8 OR
16 OHM OUTPUT IMPEDANCE CAPABILITY. DO NOT USE THE ROCKCRUSHER WITH
ANY SPEAKER LOAD LOWER
THAN 8 OHMS IMPEDANCE.
ON THE BACK OF T
HE ROCKCRUSHER, YOU MUST USE THE SPEAKER JACK #1, FIRST.
YOU MAY NOT EXCEED THE 120W RMS POWER RATING OF THE ROCKCRUSHER.
DO NOT COVER THE TOP OR BOTTOM OF THE ROCKCRUSHER, AS PROPER VENTILATION IS REQUIRED TO
DISSIPATE THE POTENTIAL HEAT GENERATED.
DO N
OT EXPOSE THE ROCKCRUSHER TO ANY MOISTURE OF ANY SORT, AS A POTENTIAL ELECTRICAL
SHOCK HAZARD OR DAMAGE TO THE ROCKCRUSHER MAY BE POSSIBLE.
EXCESSIVE USE OF YOUR AMPLIFIER?S OUTPUT POWER WILL PLACE THERMAL STRESS ON THE OUTPUT
TUBES
AND THEIR ASSOCIATED C
OMPONENTS, AS WELL AS ON THE OUTPUT TRANSFORMER, AND MAY
RESULT IN
DAMAGE TO YOUR AMPLIFIER. OLDER VINTAGE AMPLIFIERS MAY HAVE CRITICAL COMPONENTS
WHICH HAVE
DETERIORATED, SUCH AS COUPLING AND FILTER CAPACITORS, WIRING INSULATION, TUBE
SOCKETS, GRID
RESIST
ORS, AND THE INSULATION PROPERTIES OF THE OUTPUT TRANSFORMER WINDINGS.
THESE
COMPONENTS MAY BE EXCESSIVELY STRESSED WHEN SUSTAINING HIGH POWER LEVELS OVER A
PERIOD OF
TIME AND MAY FAIL. ASIAN
-
AND EASTERN EUROPEAN
-
BUILT AMPLIFIERS ARE FOR THE MOST
PART
NO
TORIOUS FOR POOR QUALITY COMPONENTS, AND SUCH COMPONENTS MAY EASILY FAIL IF
STRESSED.
PLEASE CHECK THE CONDITION OF YOUR OUTPUT TUBES, AND REPLACE THEM IF THEY ARE OLD OR
FRAGILE
BEFORE USING THE AMPLIFIER AT HIGH POWER LEVELS WITH THE ROCKCRUSHER.
WEAK AND
OLD
OUTPUT TUBES ARE THE LINK THAT CAN EASILY BREAK WHEN STRESSED. IF THERE IS OUTPUT TUBE
FAILURE,
OTHER ANCILLARY COMPONENTS MAY BE DAMAGED AS WELL.
BY RESPECTING THE CORRECT USE OF THE ROCKCRUSHER, YOU WILL AVOID POTENTIAL DAMAGE TO
YOUR
AMPLIFIER AS WELL AS THE ROCKCRUSHER.
ROCKCRUSHER IS NOT INTENDED FOR USE WITH SOLID STATE AMPLIFIERS THAT USE CURRENT FEEDBACK
AND AN UNGROUNDED OUTPUT. AS THE LINE OUTPUT GROUND IS DIRECTLY CONNECTED
TO THE
AMPLIFIER INPUT GROUND, OSCILLATION WILL O
CCUR WITH POTENTIAL DAMAGE TO THE
AMPLIFIER. IT
IS ALSO NOT INTENDED FOR USE WITH CLASS D OR PWM AMPLIFIERS.
RIVERA AMPLIFICATION IS NOT RESPONSIBLE FOR ANY DAMAGE TO YOUR AMPLIFIER THAT MAY
OCCUR
THROUGH ANY USE OF THE ROCKCRUSHER
Thank You for any help and please forgive my inabilty to fully comprehend this.
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