We are pleased to offer you our ULTIMATE Dynaco ST-70 upgrade kit with the AB-Q-ST70/120 Auto Bias module, the Dyna-70AB.
We have developed this kit to bring your tired old ST-70 power amp up to modern tube amp standards with many improvements over the original Dynaco driver circuit and using the AB-Q-ST70/120 Auto Bias module for the output tubes!
This is indeed a RADICAL upgrade to your ST-70, really changing how this amp operates and sounds.
We assume that all the transformers in your existing ST-70 are in working order.
Speaking of transformers, do take note of this VERY IMPORTANT point with regards to the PA 060 power transformer.
Dynaco had two types of PA 060 power transformers they used. The PA 060 transformer used in the very early kits had a very low 'stack' about 1"/25.4mm high. Then Dynaco came out with a transformer with a notably higher stack, about 1 3/4"/44.5mm high. This is the size transformer we are using in our test ST-70 and we've had NO issues with using this size. Yes, it gets warm, but this is quite normal!
Do also note, that since with our kit the 5AR4 tube rectifier tube is no longer used, the 5VAC secondary winding is also no longer used which will lessen the overall load on the PA 060 keeping its running temperature lower!
We cannot guarantee that the very early 1"/25.4mm stack height PA 060 power transformer will be able to comfortably handle the extra filament current used by the 6SN7 driver tubes!
You can of course upgrade the PA 060 by buying one from one of the many suppliers, this is even larger again with a 2"/51mm stack height and with this model PA 060 you could even use the KT88 family of tubes.
We recommend that you stick with the EL34 family of power tubes, as all our testing etc. was done using the EL34.
The cricuit is based on the classic Mullard design of the 50's with certain improvements to bring it up to 'modern' tube circuits, including an LM334 based constant current source for stable performance.
This kit uses the excellent AB-Q-ST70/120 Auto Bias module by Audio Amp from the Czech Republic, for whom we are the North American agent.
With this auto bias module, you willl NEVER have to adjust the output tubes bias again. We preset the bias level to suit the EL34 family of power tubes, so that all you need to do is to build and install this kit and enjoy tube music! It has four LED's which are mounted to the main pcb which indicate that bias on all four power tubes is healthy.
Should a tube fail or the auto bias module can no longer maintain the preset bias level, the relevant LED will go out indicating that the tube in question needs to replaced. It is that simple!
The kit comes complete with ALL parts and the AB-Q-ST70/120 auto bias module, including hardware and wires. You will need to splice some of the wires, as the original length on some wires are too short, for that, we supply colored wires and heat shrink for the joints! We also supply a 3 way power cord where the chassis will be grounded to your house ground. This is an important safety upgrade!
The full details are all covered in the comprehensive instruction manual you will get with the kit.
The coupling capacitors supplied with the standard kit are the excellent Audyn film capacitors.
We have made no compromises with the quality of the componets used for this kit.
- Nichicon, United Chemi-Con and other name brand electrolytic capacitors
- 1% high grade film resistors in the signal circuits
- Panasonic Metal Oxide resistors for the power supply
- Audyn coupling capacitors, (Russian PIO capacitors as an option)
- top quality FR4-TG standard black printed circuit board, 0.08"/2mm thick, with dual ground planes for ultimate screening
Also to note is that with our kit, the STEREO/MONO switch will no longer work/is disabled and the two front octal sockets are no longer used either.
This kit is not complicated, but your are working with extremely high voltages, in excess of 720VAC & 400VDC, so EXTREME care MUST be taken! These voltages can be LETHAL!
We also stress that good soldering skills are a must have, this can make all the difference for a trouble free project. We strongly recommend that you use a temperature controlled soldering iron, such as a Weller or HAKKO, with small as well as medium sized tips. 98% of all issues our clients have with building a kit is related to bad soldering, so AGAIN we stress, good soldering skills are a MUST!!
Please note: this kit requires assembly! The only exception is the auto bias module, which is pre assembled.
Also, all parts are mixed together, they are not packed in their individual values and/or types.
Price for the complete kit with Audyn coupling capacitors and the AB-Q-ST70/120 auto bias module: $215.00 plus $15.00, which will be added when you check out. Shipping cost is for the lower 48 only! For all other areas and countries, please contact us for additional shipping costs. Tubes ARE NOT included, see below for tubes.
Dyna-70AB
supplied components may vary from photos
a typical completed Dyna-70AB upgrade using the optional Russian PIO coupling capacitors.
a typcial assembled pcb with the optional Russian PIO coupling capacitors
the AB-Q-ST70/120 Auto Bias module
NOTE: This pcb is pre assembled!
We also offer to do the upgrade for you. You ship us your old ST-70 and any tubes you want to be used and we carry out the conversion with our Dyna-70AB kit.
We assume that all the transformers on your ST-70 are in working order and within specs. If we find any issues with any of the parts, we will contact you and go from there.
The conversion time is 2 weeks from receipt of your ST-70. We will also warranty the kit for a period of 6 months. This is for the kit only, we do not warranty any other parts.
If you also choose to buy new tubes from us, these too will have a 6 month warranty. This warranty starts the day the ST-70 arrives back at your home.
Please pack your ST-70 carefully. Remove all tubes and pack separately, use a double walled corrugated shipping box and really make sure the amp cannot move inside the box. We of course cannot and will not take any responsibilities for the shipping to us.
When we ship the amp back to you, we will insure in, we recommend you do the same when you send it to us!
The cost for us to install our Dyna-70 kit into your ST-70 is $330.00, this is ON TOP of the kit price and any tubes or other parts you decide to order as well, plus shipping back to you.
We require full payment up front, this is not negotiable
Shipping will be charged separately once your amp is packed up and ready to go.
To finish off your Dyna-70 upgraded ST-70, why not add this slick front panel to it!
It is made from anodized aluminum with black printed lettering. This will really give your ST-70 that custom look!
The panel is supplied with all the hardware consisting of two RCA jacks with pcb and machine screws.
Cost for this panel and the parts is US$ 86.25 plus $15.00 shipping to the lower 48. For all other areas and countries, please contact us for additional shipping costs. If you buy this panel together with the kit, shipping will be refunded.
NOTE: We do not keep these panels in stock, they will be ordered when we get your order. It will take 10 working days to have this panel made and then shipped out to you!
Price for a new set of 3 way speaker posts on a new pcb to replace the old unit.
This is for a pair of speaker posts:
$16.00 plus $8.00 shipping which will be added when you check out.
Shipping cost is for the lower 48 only! For all other areas and countries, please contact us for additional shipping costs.
If you buy these speaker posts together with the kit, shipping will be refunded
Price for a set of RCA jacks complete with pcb to replace those old worn out units:
$15.00 plus $8.00 shipping which will be added when you check out.
Shipping cost is for the lower 48 only! For all other areas and countries, please contact us for additional shipping costs.
If you buy these RCA jacks together with the kit, shipping will be refunded
Price for a new power switch to replace the old worn out unit:
$6.00.
The free shipping is for the lower 48 only! For all other areas and countries, please contact us for additional shipping costs.
NOTE: the above price is ONLY valid when purchased with the Dyna-70 kit!
The ultimate Dynaco ST-70 upgrade kit with AUTO BIAS!
a typical 'under the hood' view of the AB-Q-ST70/120 installed and wired up
NOTE:
the four white chassis mount ceramic output tube sockets in the photo are not included with the kit
a Dyna 70AB upgrade in action. Note the four lit 'BIAS OK' LED's between each pair of green coupling capacitors
Price for a set of Russian PIO coupling capacitors, consisting of 4x 0.22uF 400 or 500V & 2x 0.1uF 400 or 500V:
$25.00 plus $8.00 shipping which will be added when you check out. NOTE: These PIO's are ONLY sold in conjunction with the Dyna-70 kit and NOT for general purchase, thank you.
Shipping cost is for the lower 48 only! For all other areas and countries, please contact us for additional shipping costs.
If you buy these capacitors together with the kit, shipping will be refunded
