Threshold Ta-300
Figured I'd add a bit of little known info to this thread.
I'm the proud owner of three Threshold Ta-300's. Now why on earth would I do that? LOL! (tri-amp anyone?)
The Ta-300 was a transitional product for Threshold. After Nelson sold the company, the next generation of products were to be the IGBT output based "T" serious amps. Unfortunately, it took longer to bring them to market than expected. During the transition, they needed to introduce something new to stay in the spotlight and the Ta-300 was it. It was positioned to be less expensive than the "S" series or the "T" series so it doesn't have the thick front panel and handles, but from the face plate back everything else is the same including the heat sinks. They didn't build very many of them so there is very little info about them. It was a bridge product between the "S" series and the "T" series that kept them going while they worked out switching the designs to the IGBT output devices across the entire product line.
Here's the history:
Threshold-Audio.com
In its stock configuration, it's the "e" series Stasis circuit running class AB in the S/250 chassis that is running bipolar outputs. It is rated at 150 watts per channel.
After I bought my first one I contacted Jon Soderberg who is an ex-Threshold tech to inquire about upgrading it. During the conversation (he's a great guy by the way) he shared that the Ta-300 was an S/250 with a little known secret (actually two of them):
As mentioned above, the circuit is the "e" circuit which has the later FET front end with both balanced and single-ended inputs.
The other biggie is the transformer has a second set of unconnected outputs.
What Jon shared is that one can swap to the unconnected outputs that run lower voltage and raise the bias up significantly. Essentially what you end up with is a Threshold SA3.9e that has one fewer pair of output transistors per channel (if I remember correctly).
Now note which Threshold amp Nelson mentions that he'd choose if he was going to pick one. He's mentioned this more than once. 😉
http://www.diyaudio.com/forums/pass-labs/285367-threshold-ta-300-stasis-stasis-3-a.html#post4584411
After switching my first amp as Jon instructed, it changed significantly. It is now in a completely different league. Far, far better with a huge sound stage that is both wide and deep. It turned it into a completely different animal that is simply stunning.
So there you have a bit of history on the Ta-300.
Link to a post I made shortly after chatting with Jon. Also contains Jon's contact info:
http://www.diyaudio.com/forums/pass-labs/4153-threshold-s300-output-transistors-help.html#post38014
Figured this info should also be included in this thread.
Viva la Ta-300!!!!
Enjoy,
Steve 🙂
Figured I'd add a bit of little known info to this thread.
I'm the proud owner of three Threshold Ta-300's. Now why on earth would I do that? LOL! (tri-amp anyone?)
The Ta-300 was a transitional product for Threshold. After Nelson sold the company, the next generation of products were to be the IGBT output based "T" serious amps. Unfortunately, it took longer to bring them to market than expected. During the transition, they needed to introduce something new to stay in the spotlight and the Ta-300 was it. It was positioned to be less expensive than the "S" series or the "T" series so it doesn't have the thick front panel and handles, but from the face plate back everything else is the same including the heat sinks. They didn't build very many of them so there is very little info about them. It was a bridge product between the "S" series and the "T" series that kept them going while they worked out switching the designs to the IGBT output devices across the entire product line.
Here's the history:
Threshold-Audio.com
In its stock configuration, it's the "e" series Stasis circuit running class AB in the S/250 chassis that is running bipolar outputs. It is rated at 150 watts per channel.
After I bought my first one I contacted Jon Soderberg who is an ex-Threshold tech to inquire about upgrading it. During the conversation (he's a great guy by the way) he shared that the Ta-300 was an S/250 with a little known secret (actually two of them):
As mentioned above, the circuit is the "e" circuit which has the later FET front end with both balanced and single-ended inputs.
The other biggie is the transformer has a second set of unconnected outputs.
What Jon shared is that one can swap to the unconnected outputs that run lower voltage and raise the bias up significantly. Essentially what you end up with is a Threshold SA3.9e that has one fewer pair of output transistors per channel (if I remember correctly).
Now note which Threshold amp Nelson mentions that he'd choose if he was going to pick one. He's mentioned this more than once. 😉
http://www.diyaudio.com/forums/pass-labs/285367-threshold-ta-300-stasis-stasis-3-a.html#post4584411
After switching my first amp as Jon instructed, it changed significantly. It is now in a completely different league. Far, far better with a huge sound stage that is both wide and deep. It turned it into a completely different animal that is simply stunning.
So there you have a bit of history on the Ta-300.
Link to a post I made shortly after chatting with Jon. Also contains Jon's contact info:
http://www.diyaudio.com/forums/pass-labs/4153-threshold-s300-output-transistors-help.html#post38014
Figured this info should also be included in this thread.
Viva la Ta-300!!!!
Enjoy,
Steve 🙂
Last edited:
Hiya! Let me revive the thread a bit.
Got an ancient T400 to fix. Unfortunately somebody was there already, so I can't tell whether those J74/K170 that have been resoldered are proper in the place.
Anybody? Mr Pass? The amp is not that simple to fix with no schematic.
Pleeeeze...
Maybe pm, I promise to keep it then.
Got an ancient T400 to fix. Unfortunately somebody was there already, so I can't tell whether those J74/K170 that have been resoldered are proper in the place.
Anybody? Mr Pass? The amp is not that simple to fix with no schematic.
Pleeeeze...
Maybe pm, I promise to keep it then.
T400 ?
which model exactly ?
we need more info , pictures if possible ....... simply because - for my knowledge , Nelson didn't use 2SJ/2SK Toshibas in that time
which model exactly ?
we need more info , pictures if possible ....... simply because - for my knowledge , Nelson didn't use 2SJ/2SK Toshibas in that time
Right after the input header there are pairs of J74/K170 pairs i suspect to be fried. But can they shut down the entire channel? The heatsink is cold, no quiescent current. Rails ok, both leds are lit, no transistor shorted (except the first J74 that tests 40 ohms across).
Sorry I can't help, it having been after I left. The person who replaced me
improved the product beyond recognition.
this is question for Pass himself ..... I don't have any schematic for T400
as far as I can see , T400 is made 1998 , while Pa left Treshold year before ....
so - that's probably why I don't have schematic
edit: yeah , as usual , while I was typing ...... 🙂
as far as I can see , T400 is made 1998 , while Pa left Treshold year before ....
so - that's probably why I don't have schematic
edit: yeah , as usual , while I was typing ...... 🙂
Well I do have some pairs of those jfets, dedicated for Hiraga headamp project, am fighting greed now. The question is - will dumb replacement revive the box...
point taken .... I didn't connected all dots in Wikipedia article
what I meant , according to Wikipedia ( without using da brain with fact that PL is established in 1991.) is :
as far as I can see , T400 is made 1998 , while Pa sold Treshold year before ....
what I meant , according to Wikipedia ( without using da brain with fact that PL is established in 1991.) is :
as far as I can see , T400 is made 1998 , while Pa sold Treshold year before ....
For the record, I don't contribute to or edit my Wikipedia entry.
I sold my interest in Threshold in 1987 and remained for four years, leaving in
'91 to form Pass Labs.
Threshold SA/11m
Hello everybody,
I'm new in this thread. My Name is André, living in Gemany close to Dusseldorf (North Rhine Westphalia).
Need some help from you experts, please...
Got a Problem with my SA/11m (similar to SA/10m). I have one pair which is connect to the Mid-High-Panels of my IRS Beta and a S/550e for Bass-Columns. In this configuration I can observe a humming noise in the bass and also in the Mid-high-Panels even if the Bass-SCU switched off. If I switched off one of the monos, everything is quiet. When I changed the setup and connect a SA/40s (similar to SA/4e), their is no humming noise can be hear.
For my second setup with Infinity Kappa 9, I use another pair of SA/11m for Mid-High and the above described SA/40s for bass. In this setup occures the exactly same phenomenon. So I can be sure it's no defect of the SA/11m?!
Can someone give me a hint.
Thanks a lot and happy new year to all of you.
André
Hello everybody,
I'm new in this thread. My Name is André, living in Gemany close to Dusseldorf (North Rhine Westphalia).
Need some help from you experts, please...
Got a Problem with my SA/11m (similar to SA/10m). I have one pair which is connect to the Mid-High-Panels of my IRS Beta and a S/550e for Bass-Columns. In this configuration I can observe a humming noise in the bass and also in the Mid-high-Panels even if the Bass-SCU switched off. If I switched off one of the monos, everything is quiet. When I changed the setup and connect a SA/40s (similar to SA/4e), their is no humming noise can be hear.
For my second setup with Infinity Kappa 9, I use another pair of SA/11m for Mid-High and the above described SA/40s for bass. In this setup occures the exactly same phenomenon. So I can be sure it's no defect of the SA/11m?!
Can someone give me a hint.
Thanks a lot and happy new year to all of you.
André