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The Dynaco Tube Audio Forum

Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Tubes4hifi VTA tube amp and preamp kits and all Dynakitparts.com products


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    The Dynaco (Panor) ST-80 and ST-160 tube amps of the mid '90's

    Bob Latino
    Bob Latino
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    The Dynaco (Panor) ST-80 and ST-160 tube amps of the mid '90's Empty The Dynaco (Panor) ST-80 and ST-160 tube amps of the mid '90's

    Post by Bob Latino Fri Mar 21, 2014 8:06 pm

    In the 1990's the Dynaco name was acquired by Panor Corporation. In 1995 they came out with two tube amplifiers. Both amps were wired only - no kit versions. The ST-80 @ 40 WPC and the ST-160 @ 75 WPC. Now why they didn't call it the ST-150 for its 75 WPC, I will never know? Unfortunately both amps came out at a time when solid state gear really had a foothold on audio and neither amp sold in large numbers. Rarely will you ever see one for sale on Ebay and when you do they sometmes reach prices higher than their original sale price.

    Both amps had almost the same circuit. The ST-80 used EL34 output tubes and ran a B+ of 480 volts (about 40 to 50 VDC higher than the original Dynaco ST-70). The ST-160 used 6550 output tubes and ran a B+ of 540 VDC (!! pretty high for a 6550). Both amps had individual bias pots on each output tube that were adjust using LED's. Turn the bias pot too far down and the LED was green. Turn the bias pot too high and the LED turned red. If it did not glow at all, the bias was right on. The LED's were set so that an EL34 on the ST-80 was biased at 40 milliamps. On the ST-160, when the LED did not glow, each output tube was set at 50 milliamps. Both amps used a single 12AT7 (voltage amplifier) tube and a single 6DJ8 (phase splitter/inverter) per channel.

    Both amps also had triode/pentode (ultralinear) switches, a variable input pot and solid state rectification. I personally have never heard one of these but I have heard the PAS-4 preamp that came out at the same time. The PAS-4 is a lot better sounding than the original Dynaco PAS-(2 or 3) preamps. Maybe if these amps came out in the 2000's when tube gear and vinyl records had a resurgance or if they were also offered as KITS at a lower price, they may have caught on ?

    Below are two links to the user manuals for each amp in pdf format. I want to thank sKiZo for hosting both manuals on his web site.

    Bob

    ST-80 user manual

    ST-160 user manual

    Anther ST-160 link below ..

    ST-160 amp owned by our member lorand8



    Last edited by Bob Latino on Fri Sep 25, 2015 7:28 am; edited 1 time in total

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    audiobill


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    The Dynaco (Panor) ST-80 and ST-160 tube amps of the mid '90's Empty Re: The Dynaco (Panor) ST-80 and ST-160 tube amps of the mid '90's

    Post by audiobill Sat Mar 22, 2014 9:29 am

    I had the Panor PAS 4 and stupidly sold it........
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    discodan


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    The Dynaco (Panor) ST-80 and ST-160 tube amps of the mid '90's Empty Re: The Dynaco (Panor) ST-80 and ST-160 tube amps of the mid '90's

    Post by discodan Wed Feb 06, 2019 2:32 pm

    I Have the 2 model Dynaco PS-4 And The Ampli Stereo 80 that's realy good sound It,s Realy Différent construction and Sounds of Qualité Or the Model Fabrication 70' ,,,it'S Sound More better .The Dynaco (Panor) ST-80 and ST-160 tube amps of the mid '90's 50830610
    The Dynaco (Panor) ST-80 and ST-160 tube amps of the mid '90's 51116710
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    Post by discodan Wed Feb 06, 2019 10:10 pm

    j'ai les 2 pièces depuis plus de 20 ans The Dynaco (Panor) ST-80 and ST-160 tube amps of the mid '90's 50811210
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    boeingpilot


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    The Dynaco (Panor) ST-80 and ST-160 tube amps of the mid '90's Empty Re: The Dynaco (Panor) ST-80 and ST-160 tube amps of the mid '90's

    Post by boeingpilot Sat Oct 23, 2021 8:04 pm

    Just purchased one. It has some PCB issues. It was bought knowing that the bias indicator was not working on one channel. Looking at the PCB there is a burn through hole by one of the triode/ultra linear relays and some heat discolor by the other (like the VTA 120 and 70 these can be run in triode or ultra linear mode. However, the switching is done via relay)

    My guess is that the relay is generating heat when the coil is engaged (triode mode). Of course in troubleshooting I damaged a resistor on the bias control board (which looks like it was replaced once before). The bias monitoring trace on the PCB is adjacent to the relay, so it looks like it shorted in the past, went and is now open.

    The only real way to fix is to remove the relays, remove the carbonized PCB area and then fix any traces removed with point to point wiring. Else the carbonized area is going to start conducting.

    I’ve ordered new relays and resistors as well as the comparator IC for the bias. Hope to have it all fixed soon
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    Post by boeingpilot Fri Oct 29, 2021 2:43 am

    A little update... and perhaps some questions..

    So, had the amp apart (again) tonight to fix the issues with it. As I mentioned earlier, the initial problem was that the V8 bias LED was stuck on red. When I opened it, I found that the PC board under the triode / ultralinear relay had burned. I had probed the damaged area of the PCB, and then when I repowered the amp, arcs and sparks. So, tonight I took to removing the relay and looking real hard. The sense line for the bias runs under the relay, then goes through a plated through hole, and then to the edge of the PCB so it can connect to the bias control board. What appears to have happened is that this line ended up shorting against the output of the relay.

    Repair wasn't too bad. I cleaned up the area of the damage, and inspected the lands. Sealed the edges of the pcb with expoxy. Where the lands looked questionable, tacked point-to-point wire to bypass the lands.

    When the arcs flew, a resistor on the bias board smoked (though it still tested good). Decided to replace that with new. The circuit that drives the LED is a LM339 comparator IC. Removed the existing one and installed a socket and new chip.

    Once reassembled, it all worked. Now to the listening.

    My usual system is either my original ST-70 or my VTA board ST-70 (the original one is in use now), with a PAS-3 and Klipsch Heresy speakers. Put the ST-80 in its place. After re-biasing, amp is definitely clear. It's definitely a different sound than the ST-70. The one thing I noticed is that I could here distortion, not on the main musical notes, but seemingly underneath them (sort of like rattling piano strings). Switched back to the ST-70, not really the same. Also the ST-80 seems to be a lot more 'flat' than the ST-70, and while I'd never accuse the Heresy's and the ST-70 of being bass machines, it seemed there was much more base there than with the ST-80.

    Kind of wondering if both the distortion and the seeming lack of base is perhaps a mis-match between the PAS-3 and the ST-80?

    I'll play with the amp for a while, but right now, have to say I prefer the ST-70.

    Comments? Suggestions? Questions?

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