• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Carver Phono

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Administrator
Joined 2004
Paid Member
Hi reinhard,
There are schematics for that, how would they repair one?? It can be reverse engineered, but that's a long process.

Ask them how they would repair it if yours failed... If they ask, tell them you want to design a proper power supply. Of course, the schematic may be part of the Sunfire preamp schematic set.

-Chris
 
Administrator
Joined 2004
Paid Member
Unfortunately it's called IP (Intellectual Property) Rights and some manufacturers feel that sharing schematics is tantamount to inviting someone to copy their design. (And it may be.) Others quite openly share their schematics, it is a matter of corporate (or proprietor) philosophy and companies that have the wherewithal to protect their rights under copyright law sometimes are more likely to share information.

You might try to purchase a service manual for the pre-amplifier, that if available would have a schematic.

Otherwise you might try identifying the various power connections, and decoupling cap voltage values will give you some clue as to the supply voltage. (arbitrarily say 75% of rating ) Filament voltages are usually pretty obvious by inspecting tube types used and how they are interconnected.

I somehow doubt the sunfire phono is very sophisticated, the power amplifier I have seen and worked on was booringly conventional in every respect.

Kevin

edit: fixed typo
 
Administrator
Joined 2004
Paid Member
Hi Kevin,
Some manufacturers go overboard on the IP thing. Bryston used to be like that. They went nuts after I traced out the 4B 'cause they would not supply a schematic. My response to Brian was that the amp was no secret as soon as they sold the first one. Look at how they've changed!

Bob Carver isn't generally like that. He has historically allowed access to schematics. As a former Carver service center, we got everything. Interestingly, we had access to preliminary schematics as well. The engineering staff was available to us on top of that. If his current staff is anything like his original gang, they will be helpful and forth coming. As an outsider (outside his service network) there may be some resistance, you just have to maybe ask the right question.

-Chris
 
Administrator
Joined 2004
Paid Member
Hi Reinhard,
I agree with you in principle. But, you can count on Bob Carver to do something interesting. Interesting only if you have the schematic. I charged the Bryston customer with the customer's consent.

Still, service agents expect service information. It's the only way to ensure a proper repair. Or at least have the chance of a repair.

-Chris
 
Hello,

Sunfire served me with propietary information of that phono module.

The MC is a paralled 6922 with a 62 Ohm cathode resistor and a 22 k anode load running from a 90 VDC supply. This stage is coupled to a single 6922, 0,1 uF, 4,7 M. This tube is running from the same supply with 6k8 andode load and 120 Ohm cathode resistor. The next coupling cap is a 6,8 uf. After that cap comes the feedback resistor 680 Ohm to the cathode of the II 6922.

Changing the 62 Ohm to lower values changes gain. look at the manual of the preamp.

Reinhard
 
Hi Reinhard

To be honest I don't fully understand your fascination with the Carver phono. Or with anything else Carver. As you can see, the schematic is quite mundane.

As far as experience with the topology there was a similar (global NFB) circuit in Wireless World 1985. I may be able to dig out the issue. It also used cascaded ECC88 with NFB but supply voltage was much lower (24v?). To compensate for the low PS they used bipolar CCSs replacing the anode resistors.

It sounded ok as published but eventually i removed the second stage, the feedback and the CCS and the sound became a lot better.

If you really must have an active MC stage why not have a look at the Oz-Loesch front end wiith a Fet/tube cascode?


So, what's the rest of the Carver circuit like? PS?
 
hello analog sa,

the carver power supply is 7 pcs 47uF and 6 pcs. 2k4/2W. CRCRC.........

Heater is DC, rectifier, cap, resistor, cap.

Very simple.

Yes I know the WW design, was available in germany as a kit in the 90 s. Comes with PCC 88, sound? so la la, could be better.

From remembering it uses MKT caps. maybe an upgrade path

Reinhard

PS. JC Verdier uses PCC 88 in his big phono, think he paralled
some triodes.
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.