I've been gifted a 100 volt line amplifier but it's missing a couple of bits and pieces. Chief problem is the lack of a remote volume control to plug into a port at the rear of the unit. I'm guessing it's simply a potentiometer but there's no indication of the actual value of the pot if my guess is correct. Does anyone have experience of this unit and can tell me what I need to try the amplifier?

On 11/04/2023 15:49, John J wrote:
> I've been gifted a 100 volt line amplifier but it's missing a couple of bits and pieces. Chief problem is the lack of a remote volume control to plug into a port at the rear of the unit. I'm guessing it's simply a potentiometer but there's no indication of the actual value of the pot if my guess is correct. Does anyone have experience of this unit and can tell me what I need to try the amplifier?

User / Installer and service manuals all over the place.

https://www.audioservicemanuals.com/b/bose/bose-amplus/7074140-bose-amplus-50-and-100-business-music-amplifiers-manual

Page 9 of the service manual

"Connector J4 [A8] ties one or two 10K rheostat-connected remote volume
control
potentiometers into Q201/221,"

--
Adrian C

On 11/04/2023 20:36, Adrian Caspersz wrote:
> On 11/04/2023 15:49, John J wrote:
>> I've been gifted a 100 volt line amplifier but it's missing a couple
>> of bits and pieces. Chief problem is the lack of a remote volume
>> control to plug into a port at the rear of the unit. I'm guessing it's
>> simply a potentiometer but there's no indication of the actual value
>> of the pot if my guess is correct. Does anyone have experience of this
>> unit and can tell me what I need to try the amplifier?
>
> User / Installer and service manuals all over the place.
>
> https://www.audioservicemanuals.com/b/bose/bose-amplus/7074140-bose-amplus-50-and-100-business-music-amplifiers-manual
>
> Page 9 of the service manual
>
> "Connector J4 [A8] ties one or two 10K rheostat-connected remote volume
> control
> potentiometers into Q201/221,"
>

Log or linear value with rotation?

--
mailto : news {at} admac {dot} myzen {dot} co {dot} uk

On 11/04/2023 23:04, alan_m wrote:
> On 11/04/2023 20:36, Adrian Caspersz wrote:
>> On 11/04/2023 15:49, John J wrote:
>>> I've been gifted a 100 volt line amplifier but it's missing a couple
>>> of bits and pieces. Chief problem is the lack of a remote volume
>>> control to plug into a port at the rear of the unit. I'm guessing
>>> it's simply a potentiometer but there's no indication of the actual
>>> value of the pot if my guess is correct. Does anyone have experience
>>> of this unit and can tell me what I need to try the amplifier?
>>
>> User / Installer and service manuals all over the place.
>>
>> https://www.audioservicemanuals.com/b/bose/bose-amplus/7074140-bose-amplus-50-and-100-business-music-amplifiers-manual
>>
>> Page 9 of the service manual
>>
>> "Connector J4 [A8] ties one or two 10K rheostat-connected remote
>> volume control
>> potentiometers into Q201/221,"
>>
>
> Log or linear value with rotation?

Usually log for a volume control.

--
Cheers,

John.

/=================================================================\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\=================================================================/

On 4/11/2023 9:37 PM, John Rumm wrote:
> On 11/04/2023 23:04, alan_m wrote:
>> On 11/04/2023 20:36, Adrian Caspersz wrote:
>>> On 11/04/2023 15:49, John J wrote:
>>>> I've been gifted a 100 volt line amplifier but it's missing a couple of bits and pieces. Chief problem is the lack of a remote volume control to plug into a port at the rear of the unit. I'm guessing it's simply a potentiometer but there's no indication of the actual value of the pot if my guess is correct. Does anyone have experience of this unit and can tell me what I need to try the amplifier?
>>>
>>> User / Installer and service manuals all over the place.
>>>
>>> https://www.audioservicemanuals.com/b/bose/bose-amplus/7074140-bose-amplus-50-and-100-business-music-amplifiers-manual
>>>
>>> Page 9 of the service manual
>>>
>>> "Connector J4 [A8] ties one or two 10K rheostat-connected remote volume control
>>> potentiometers into Q201/221,"
>>>
>>
>> Log or linear value with rotation?
>
> Usually log for a volume control.
>

There is mention of a voltage controlled amplifier, a VCA.

The remote pots, might not have the actual audio signal
on them (as the pots on my home made amplifier in front of me do).

This will change the noise injection characteristic, if the
remote control pots are located some distance from the equipment.

Instead, the remote pots could have a DC voltage, and that
feeds into the VCA logic. The VCA logic also receives a
clipping-detected signal, which mutes the amp during overload.

You might guess at the transfer function, if you had the VCA chip part number.
Maybe something like a four quadrant multiplier would work.

This isn't some "home project" amp, and it looks like the designers
were let loose by the management. It's probably better that
we don't have a schematic :-) It would likely be so complicated,
you couldn't tell it was an amp.

Paul

On 12/04/2023 05:12, Paul wrote:
> On 4/11/2023 9:37 PM, John Rumm wrote:
>> On 11/04/2023 23:04, alan_m wrote:
>>> On 11/04/2023 20:36, Adrian Caspersz wrote:
>>>> On 11/04/2023 15:49, John J wrote:
>>>>> I've been gifted a 100 volt line amplifier but it's missing a
>>>>> couple of bits and pieces. Chief problem is the lack of a remote
>>>>> volume control to plug into a port at the rear of the unit. I'm
>>>>> guessing it's simply a potentiometer but there's no indication of
>>>>> the actual value of the pot if my guess is correct. Does anyone
>>>>> have experience of this unit and can tell me what I need to try the
>>>>> amplifier?
>>>>
>>>> User / Installer and service manuals all over the place.
>>>>
>>>> https://www.audioservicemanuals.com/b/bose/bose-amplus/7074140-bose-amplus-50-and-100-business-music-amplifiers-manual
>>>>
>>>> Page 9 of the service manual
>>>>
>>>> "Connector J4 [A8] ties one or two 10K rheostat-connected remote
>>>> volume control
>>>> potentiometers into Q201/221,"
>>>>
>>>
>>> Log or linear value with rotation?
>>
>> Usually log for a volume control.
>>
>
> There is mention of a voltage controlled amplifier, a VCA.
>
> The remote pots, might not have the actual audio signal
> on them (as the pots on my home made amplifier in front of me do).
>
> This will change the noise injection characteristic, if the
> remote control pots are located some distance from the equipment.
>
> Instead, the remote pots could have a DC voltage, and that
> feeds into the VCA logic. The VCA logic also receives a
> clipping-detected signal, which mutes the amp during overload.
>
> You might guess at the transfer function, if you had the VCA chip part
> number.
> Maybe something like a four quadrant multiplier would work.
>
> This isn't some "home project" amp, and it looks like the designers
> were let loose by the management. It's probably better that
> we don't have a schematic :-) It would likely be so complicated,
> you couldn't tell it was an amp.
>
>     Paul

I have a late model Fender guitar amplifier. All the pots go into a
digital chip that is serially connected to a digital signal processing chip.

The only point at which the signal is analogue is right at the input,
and then between the preamp and the power amp, which is class D.

Chances of fixing it if ever the digits go down is probably nil.

But on the plus size, there is no crackle on the pots at all!

--
"Women actually are capable of being far more than the feminists will
let them."

On 12/04/2023 09:52, The Natural Philosopher wrote:
> On 12/04/2023 05:12, Paul wrote:
>> On 4/11/2023 9:37 PM, John Rumm wrote:
>>> On 11/04/2023 23:04, alan_m wrote:
>>>> On 11/04/2023 20:36, Adrian Caspersz wrote:
>>>>> On 11/04/2023 15:49, John J wrote:
>>>>>> I've been gifted a 100 volt line amplifier but it's missing a
>>>>>> couple of bits and pieces. Chief problem is the lack of a remote
>>>>>> volume control to plug into a port at the rear of the unit. I'm
>>>>>> guessing it's simply a potentiometer but there's no indication of
>>>>>> the actual value of the pot if my guess is correct. Does anyone
>>>>>> have experience of this unit and can tell me what I need to try
>>>>>> the amplifier?
>>>>>
>>>>> User / Installer and service manuals all over the place.
>>>>>
>>>>> https://www.audioservicemanuals.com/b/bose/bose-amplus/7074140-bose-amplus-50-and-100-business-music-amplifiers-manual
>>>>>
>>>>> Page 9 of the service manual
>>>>>
>>>>> "Connector J4 [A8] ties one or two 10K rheostat-connected remote
>>>>> volume control
>>>>> potentiometers into Q201/221,"
>>>>>
>>>>
>>>> Log or linear value with rotation?
>>>
>>> Usually log for a volume control.
>>>
>>
>> There is mention of a voltage controlled amplifier, a VCA.
>>
>> The remote pots, might not have the actual audio signal
>> on them (as the pots on my home made amplifier in front of me do).
>>
>> This will change the noise injection characteristic, if the
>> remote control pots are located some distance from the equipment.
>>
>> Instead, the remote pots could have a DC voltage, and that
>> feeds into the VCA logic. The VCA logic also receives a
>> clipping-detected signal, which mutes the amp during overload.
>>
>> You might guess at the transfer function, if you had the VCA chip part
>> number.
>> Maybe something like a four quadrant multiplier would work.
>>
>> This isn't some "home project" amp, and it looks like the designers
>> were let loose by the management. It's probably better that
>> we don't have a schematic :-) It would likely be so complicated,
>> you couldn't tell it was an amp.
>>
>>      Paul
>
> I have a late model Fender guitar amplifier.  All the pots go into a
> digital chip that is serially connected to a digital signal processing
> chip.
>
> The only point at which the signal is analogue is right at the input,
> and then between the preamp and the power amp, which is class D.

I knew of helicopter comms system that worked like that for a while -
each operator's control box had a bunch of rotary knobs for the volume
of various services and radios... Some bright spark in the design office
noticed all the pots were linear, and so raised a change request to swap
to log, but without asking the engineers who designed it!

Needless to say the pots were read in software and any log processing
applied at that stage - so they ended up with a log log transfer
function on the volume, which meant it went from no sound, really quiet,
really quiet, really quiet, really quiet, WAY TO LOUD! To add insult to
injury, this was on an old system with no proper real time design on the
software - so if it got busy it could take 10 secs to get round to
adjusting the volume back to something not painful.

> Chances of fixing it if ever the digits go down is probably nil.
>
> But on the plus size, there is no crackle on the pots at all!
>

--
Cheers,

John.

/=================================================================\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\=================================================================/

On Tuesday, 11 April 2023 at 15:49:23 UTC+1, John J wrote:
> I've been gifted a 100 volt line amplifier but it's missing a couple of bits and pieces. Chief problem is the lack of a remote volume control to plug into a port at the rear of the unit. I'm guessing it's simply a potentiometer but there's no indication of the actual value of the pot if my guess is correct. Does anyone have experience of this unit and can tell me what I need to try the amplifier?
Thanks to everyone who responded. I'll try a linear pot to begin with, a log pot as a fall back if required.
Thanks again.

10K log pot?
The bbc used to use Bose stuff.
Brian

--

--:
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...
briang1@blueyonder.co.uk
Blind user, so no pictures please
Note this Signature is meaningless.!
"John J" <johnjessop46@gmail.com> wrote in message
news:576d53fb-1135-47fb-bfe2-6e8d6a92f782n@googlegroups.com...
I've been gifted a 100 volt line amplifier but it's missing a couple of bits
and pieces. Chief problem is the lack of a remote volume control to plug
into a port at the rear of the unit. I'm guessing it's simply a
potentiometer but there's no indication of the actual value of the pot if my
guess is correct. Does anyone have experience of this unit and can tell me
what I need to try the amplifier?

On Wednesday, 12 April 2023 at 12:57:54 UTC+1, Brian Gaff wrote:
> 10K log pot?
> The bbc used to use Bose stuff.
> Brian

> This newsgroup posting comes to you directly from...
> The Sofa of Brian Gaff...
> bri...@blueyonder.co.uk
> Blind user, so no pictures please
> Note this Signature is meaningless.!
> "John J" <johnje...@gmail.com> wrote in message
> news:576d53fb-1135-47fb...@googlegroups.com...
> I've been gifted a 100 volt line amplifier but it's missing a couple of bits
> and pieces. Chief problem is the lack of a remote volume control to plug
> into a port at the rear of the unit. I'm guessing it's simply a
> potentiometer but there's no indication of the actual value of the pot if my
> guess is correct. Does anyone have experience of this unit and can tell me
> what I need to try the amplifier?

Fortunately 10k pots of either flavour are available for a couple of pounds on eBay so getting the wrong one first won't break the bank. Next problem if the unit works ok is to get hold of a set of connectors for the various ports from a uk source at a reasonable price. Searches so far have only yielded US suppliers with ridiculous postage added.
https://www.ebay.co.uk/itm/115579730866?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=-doTXJkVSVq&sssrc=2047675&ssuid=rdqAivo3SaG&widget_ver=artemis&media=COPY

John J <johnjessop46@gmail.com> wrote:
> Fortunately 10k pots of either flavour are available for a couple of
> pounds on eBay so getting the wrong one first won't break the bank. Next
> problem if the unit works ok is to get hold of a set of connectors for the
> various ports from a uk source at a reasonable price. Searches so far
> have only yielded US suppliers with ridiculous postage added.
> https://www.ebay.co.uk/itm/115579730866

That looks like a Phoenix Contact MSTB:
https://uk.farnell.com/search?ost=mstb&searchref=searchlookahead&product-range=mstb

On Wednesday, 12 April 2023 at 18:15:04 UTC+1, Theo wrote:
> John J <johnje...@gmail.com> wrote:
> > Fortunately 10k pots of either flavour are available for a couple of
> > pounds on eBay so getting the wrong one first won't break the bank. Next
> > problem if the unit works ok is to get hold of a set of connectors for the
> > various ports from a uk source at a reasonable price. Searches so far
> > have only yielded US suppliers with ridiculous postage added.
> > https://www.ebay.co.uk/itm/115579730866
> That looks like a Phoenix Contact MSTB:
> https://uk.farnell.com/search?ost=mstb&searchref=searchlookahead&product-range=mstb
Excellent. I'll check the pin spacing and if it fits I'm another step forward. Thank you.