You can ignore me on that one, no worries. Is a personal preference. I like an open frame 44 space rack, for cooling and ease of tube access. I don't see the point of packing tube gear into small packages, and then needing to leave open space above and below for cooling.
GroupDIY Bridge Compressor.
- Thread starter DaveP
- Start date
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Doug,
Nobody else has commented on the size of the beast so you might get your choice!
Following PRR's suggestion, I have attached a proposed table of attack and release values, obviously guys can modify them to suit their personal taste.
I have found that for punchy bass it helps to have the release just after the attack time so that is why I've got some of the values there. Six positions is a handy Lorlin switch and the R values work out nicely. Just in case some can't follow, the resistors are in series across the switch positions so they all add, this technique helps to cut down switching noise.
Its difficult to get 0.25uF caps in the UK so I intend to use 220nF with a 33nF in parallel.
More input required on the shape/rack size required, it will be going to metal very soon.
best
Davep
Nobody else has commented on the size of the beast so you might get your choice!
Following PRR's suggestion, I have attached a proposed table of attack and release values, obviously guys can modify them to suit their personal taste.
I have found that for punchy bass it helps to have the release just after the attack time so that is why I've got some of the values there. Six positions is a handy Lorlin switch and the R values work out nicely. Just in case some can't follow, the resistors are in series across the switch positions so they all add, this technique helps to cut down switching noise.
Its difficult to get 0.25uF caps in the UK so I intend to use 220nF with a 33nF in parallel.
More input required on the shape/rack size required, it will be going to metal very soon.
best
Davep
Attachments
Dave,
Thank you so much for doing this. I wish I could be of help in the design but I just don't have the design knowledge it requires. I truly enjoy reading all the discussions on this though. It's great.
My input will always be from the user standpoint.
Attack and release:
It all looks good and I'm assuming that I could still take one of the shorter releases away and gain a longer release??? From my understanding it'll just be swapping a part or two for MY taste.
Build size:
While I do love a large units look, functionality for cooling and tube access ... space is a concern. Could this be done in 3U while keeping the tubes on the back for access and cooling? I would much prefer them on the out also. If this means 4U, okay, more than that seems overkill to me but again I just don't know all the design stuff.
best indeed,
Michael
Thank you so much for doing this. I wish I could be of help in the design but I just don't have the design knowledge it requires. I truly enjoy reading all the discussions on this though. It's great.
My input will always be from the user standpoint.
Attack and release:
It all looks good and I'm assuming that I could still take one of the shorter releases away and gain a longer release??? From my understanding it'll just be swapping a part or two for MY taste.
Build size:
While I do love a large units look, functionality for cooling and tube access ... space is a concern. Could this be done in 3U while keeping the tubes on the back for access and cooling? I would much prefer them on the out also. If this means 4U, okay, more than that seems overkill to me but again I just don't know all the design stuff.
best indeed,
Michael
Michael,
Glad you're enjoying it! Users are what I need!
I am just an old amateur; I have zilch pro recording experience, so that's where I need the input. I don't want to spend time designing and building something that no-one can use, no matter how clever it is. If and when its finished, I might even be prepared to ship it to the states for trials, if anyone's interested.
Yes you can modify the attack and release times in the way you said.
3 or 4U is do-able, I'm using a toroidal power supply which can go inside the box to give more room on the back. I've got an extra tube but lost the interstage so it kind of balances out spacewise.
Thanks
DaveP
Glad you're enjoying it! Users are what I need!
I am just an old amateur; I have zilch pro recording experience, so that's where I need the input. I don't want to spend time designing and building something that no-one can use, no matter how clever it is. If and when its finished, I might even be prepared to ship it to the states for trials, if anyone's interested.
Yes you can modify the attack and release times in the way you said.
3 or 4U is do-able, I'm using a toroidal power supply which can go inside the box to give more room on the back. I've got an extra tube but lost the interstage so it kind of balances out spacewise.
Thanks
DaveP
Michael,
I'll put you on the list with lassoharp and EMRR.
I have attached the proposed power supply. In the UK its hard to get hold of cheap high voltage PT's but these 55V toroids are only about $15 each. It costs $40 in shipping to get the real thing from the US, but obviously Americans can go a more conventional route.
I found the mosfet very useful as an HT delay so it brings up the HT slowly like a tube rectifier. You can set the time by adjusting the time constant of the 47uf cap; with the values shown its about 13seconds. It also substitutes for a choke which saves that expense too. I got the basic circuit off the web so I have no idea if it infringes anyones patent or rights, if anyone knows then please let me know. I tried emailing Welborne labs but got no reply.
best
DaveP
I'll put you on the list with lassoharp and EMRR.
I have attached the proposed power supply. In the UK its hard to get hold of cheap high voltage PT's but these 55V toroids are only about $15 each. It costs $40 in shipping to get the real thing from the US, but obviously Americans can go a more conventional route.
I found the mosfet very useful as an HT delay so it brings up the HT slowly like a tube rectifier. You can set the time by adjusting the time constant of the 47uf cap; with the values shown its about 13seconds. It also substitutes for a choke which saves that expense too. I got the basic circuit off the web so I have no idea if it infringes anyones patent or rights, if anyone knows then please let me know. I tried emailing Welborne labs but got no reply.
best
DaveP
Attachments
Hi Dave- been following the thread from the start - great work and really nice to get to watch the design process! From a studio guy's point of view the attack and release times are bang on for the way I work - I pretty much never use release times over 1s. I'm sure anyone building this will tweak to taste. On the size issue all my PTP builds use a max of 3U - I think anymore on this occasion may put off folk that have little rack space. Although I admit big units look cool!! Keep up the good work...
Jay
Jay
Guavatone,
What I've got there is not ideal, but its a cheap way to get to the B+ I need. In the US you have much more choice and can do it the conventional way if you like.
I need the Bridge rectifier (x 1.414) to get to 340V or thereabouts. The transformers have plenty of current so they don't drop much under load. The regulator needs more than the final voltage in order to regulate, so can't afford to drop too much before it.
Turning in now
best
DaveP
What I've got there is not ideal, but its a cheap way to get to the B+ I need. In the US you have much more choice and can do it the conventional way if you like.
I need the Bridge rectifier (x 1.414) to get to 340V or thereabouts. The transformers have plenty of current so they don't drop much under load. The regulator needs more than the final voltage in order to regulate, so can't afford to drop too much before it.
Turning in now
best
DaveP
ruairioflaherty
Well-known member
DaveP said:
Dave,
If you want me to ship you one of the U.S. toroids for prototyping I'd be glad to.
Re the rack space issue, 3 or 4U would be great if it's not a compromise but that said please weight my vote based on the fact that it may be years before I find time to build this beauty. What I'm loving is the insight into the design process and various compromises involved.
Cheers,
Ruairi
Thanks Ruairi,
Its very kind of you but I don't think I'll need it. I don't think there are any special issues like sag involved with this comp, so as long as I can provide 320V @ 70mA it will get the job done.
The nice thing about toroids is the lack of stray field so it makes the layout simpler to pack in.
best
DaveP
Its very kind of you but I don't think I'll need it. I don't think there are any special issues like sag involved with this comp, so as long as I can provide 320V @ 70mA it will get the job done.
The nice thing about toroids is the lack of stray field so it makes the layout simpler to pack in.
best
DaveP
I have made the first stage optional.
The gain is already quite high so I won't be putting a transformer on my input to save the expense. I shall be making it single-ended on my prototype which should be fine for the majority of mic-pre outputs.
There are many tube options for this and I shall either use a 6C5 or a triode wired 6SJ7. I have chosen a very linear operating region with the 2 x 15K resistors.
best
DaveP
The gain is already quite high so I won't be putting a transformer on my input to save the expense. I shall be making it single-ended on my prototype which should be fine for the majority of mic-pre outputs.
There are many tube options for this and I shall either use a 6C5 or a triode wired 6SJ7. I have chosen a very linear operating region with the 2 x 15K resistors.
best
DaveP
Attachments
gemini86
Well-known member
oooh... I have a bunch of sj7's sitting around, too... 
This is the last post in the Drawing board on the design.
When I start construction I'll continue in the Lab.
This is the output stage and timing circuit. The rest of the circuitry is stock.
If everything goes well I'll post the final schematics and parts list/BOM when the comp is up and running. I'll run noise and freq resp at the same time.
best
DaveP
When I start construction I'll continue in the Lab.
This is the output stage and timing circuit. The rest of the circuitry is stock.
If everything goes well I'll post the final schematics and parts list/BOM when the comp is up and running. I'll run noise and freq resp at the same time.
best
DaveP
gemini86
Well-known member
I know it's been said already but we're all excited to see this taking shape.
Why would be a suitable solid state alternative to v8? Just a regular si diode? Uf type?
Why would be a suitable solid state alternative to v8? Just a regular si diode? Uf type?
