Soft start shunt update?
- Thread starter ssssly
- Start date
We are concentrating on getting the Stereomour out right now, which has fallen a little behind due to unforseen circumstances. Once we get the first of those kits out in the next three or so weeks, we will move on to the soft start update and some of the other long awaited projects.
OK, prototype is up and running nicely. Eileen is costing the parts today, and I have the assembly photos processed and ready to put into the manual. Hope to be able to take orders for the retrofit online in the next few days, and incorporate the new circuit into Paramount 1.1 in the next few weeks.
This mod is fairly extensive. It removes the existing PC board over the 12AT7 socket, the 12AT7, the nine pin socket and the terminal strips around the 9 pin socket. It will include a new, bigger and slightly more complex PC board with soft start function and the parts to stuff it, heatsinks for the active load power transistors, a new nine pin socket, new standoffs, mounting hardware and t-strips, a new beefier zener string and 5670 tube - all X 2, for the pair of monoblocks.
Do you need it in your Paramounts?
Here's what it does, to help you decide -
Firstly the new driver PC board has a soft start function. This delays the B+ to the plate of the driver tube for about 30 seconds at startup. I should note here that once fired up, the amp will need to sit for about 20 minutes after you turn it off for the circuit to "reset" itself and function with the soft start. This was added in response to a user who was using EML 2A3s in the direct coupled 2A3 version of Paramount and experiencing 2A3s arcing at startup when hit with that driver plate supply B+ before the filament could heat up. This new soft start circuit will resolve that issue. Off the top of my head we have not heard of anyone experiencing this arcing issue with anything other than the EML 2A3 and the long discontinued AVVT 2A3s. And this should not be an issue in the cap coupled 300B version. However the soft start may be useful in extending the lifetime of other tubes as well.
Secondly, the zener diode string has been beefed up. The original string worked fine unless you goofed something up in the build that overstressed it. The new string is much more tolerant of errant solder joints, miswires, etc. The circuit has been stress tested by me personally - 'nuff said.
The MJE5731As on the new PC board now sport heat sinks to extend their reliability as well.
One of the most noticeable changes is that we have gone to a 5670/2C51/WE396A tube as the driver. Why? Partly because a lot of folks found that the 12AT7 had to much gain in their system which led to hair trigger volume controls and a bit more transmission of the noise floor from front end equipment than they liked. The 5670 has a mu of 33 as opposed to the mu of 60 of the 12AT7. The 5670 is also a very sweet sounding, particularly linear tube, that we feel is step up sonically from the typical 12AT7. There's enough variety of brands to make tube rolling interesting and it is not prohibitively expensive. Even if you are running your Paramount in 300B mode like I do, you may find the 5670 the most compelling reason to upgrade your Paramounts to the new setup.
OK, the next thing you want to know is the price, right? We're gonna bite the bullet for a couple weeks and offer an introductory price of $199 for the retrofit kit. On January 1, 2011 the regular price of $249 will take effect. I'll get an order page up in the next day or two, or you can call Eileen today at 206-451-4275 to order.
I think at this point that we will be able to hold the price of the upcoming Paramount 1.1 kit that includes this upgrade to within $50 of the current price. We have some of the current version kit parts in stock, and as a little incentive to move them out we will offer six Paramount kits in the current 1.0 version (12AT7 driver, no soft start) for $100 off the regular price. That means you can get the current version of the Paramount 2A3 kit for $1349 and the current version of the Paramount 300B kit for $1399. That deal is only good until January 1st or until we sell all six kits, which ever comes first, and you will need to call Eileen at 206-451-4275 or email her at queen@bottlehead.com to get this special price.
This mod is fairly extensive. It removes the existing PC board over the 12AT7 socket, the 12AT7, the nine pin socket and the terminal strips around the 9 pin socket. It will include a new, bigger and slightly more complex PC board with soft start function and the parts to stuff it, heatsinks for the active load power transistors, a new nine pin socket, new standoffs, mounting hardware and t-strips, a new beefier zener string and 5670 tube - all X 2, for the pair of monoblocks.
Do you need it in your Paramounts?
Here's what it does, to help you decide -
Firstly the new driver PC board has a soft start function. This delays the B+ to the plate of the driver tube for about 30 seconds at startup. I should note here that once fired up, the amp will need to sit for about 20 minutes after you turn it off for the circuit to "reset" itself and function with the soft start. This was added in response to a user who was using EML 2A3s in the direct coupled 2A3 version of Paramount and experiencing 2A3s arcing at startup when hit with that driver plate supply B+ before the filament could heat up. This new soft start circuit will resolve that issue. Off the top of my head we have not heard of anyone experiencing this arcing issue with anything other than the EML 2A3 and the long discontinued AVVT 2A3s. And this should not be an issue in the cap coupled 300B version. However the soft start may be useful in extending the lifetime of other tubes as well.
Secondly, the zener diode string has been beefed up. The original string worked fine unless you goofed something up in the build that overstressed it. The new string is much more tolerant of errant solder joints, miswires, etc. The circuit has been stress tested by me personally - 'nuff said.
The MJE5731As on the new PC board now sport heat sinks to extend their reliability as well.
One of the most noticeable changes is that we have gone to a 5670/2C51/WE396A tube as the driver. Why? Partly because a lot of folks found that the 12AT7 had to much gain in their system which led to hair trigger volume controls and a bit more transmission of the noise floor from front end equipment than they liked. The 5670 has a mu of 33 as opposed to the mu of 60 of the 12AT7. The 5670 is also a very sweet sounding, particularly linear tube, that we feel is step up sonically from the typical 12AT7. There's enough variety of brands to make tube rolling interesting and it is not prohibitively expensive. Even if you are running your Paramount in 300B mode like I do, you may find the 5670 the most compelling reason to upgrade your Paramounts to the new setup.
OK, the next thing you want to know is the price, right? We're gonna bite the bullet for a couple weeks and offer an introductory price of $199 for the retrofit kit. On January 1, 2011 the regular price of $249 will take effect. I'll get an order page up in the next day or two, or you can call Eileen today at 206-451-4275 to order.
I think at this point that we will be able to hold the price of the upcoming Paramount 1.1 kit that includes this upgrade to within $50 of the current price. We have some of the current version kit parts in stock, and as a little incentive to move them out we will offer six Paramount kits in the current 1.0 version (12AT7 driver, no soft start) for $100 off the regular price. That means you can get the current version of the Paramount 2A3 kit for $1349 and the current version of the Paramount 300B kit for $1399. That deal is only good until January 1st or until we sell all six kits, which ever comes first, and you will need to call Eileen at 206-451-4275 or email her at queen@bottlehead.com to get this special price.
Great news - even though I do not own Paramounts [at least not yet], the update will work with my Paraglows, albeit with a few adjustments, yes?
If so, I'll order a kit as soon as they are available. I've actually already ordered my first pair of 5670's to roll, it would be a shame if they didn't make it into an amp.
Bryon
If so, I'll order a kit as soon as they are available. I've actually already ordered my first pair of 5670's to roll, it would be a shame if they didn't make it into an amp.
Bryon
The kit could be made to work. We are not currently publishing step by step instructions for this, I am writing instructions specific to the original Paramount first. So for now at least one would have to do some figuring on their own to adapt it to other designs.
Doc
Maybe you or PJ could post a list of kits that this will work with. From my discussion with PJ about this I know for instance that this will not work for PMour 1s because the power transformer doesn't have the headroom. Could be isolated due to the older tranny design but folks my be more apt to adopt this if at least they knew if it can work with what they have. I know for myself, if I know something can work I am more likely to buy it and then figure it out.
Maybe you or PJ could post a list of kits that this will work with. From my discussion with PJ about this I know for instance that this will not work for PMour 1s because the power transformer doesn't have the headroom. Could be isolated due to the older tranny design but folks my be more apt to adopt this if at least they knew if it can work with what they have. I know for myself, if I know something can work I am more likely to buy it and then figure it out.
