[AVAILABLE] TTSH V4 Build Thread

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resynthesize
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Re: [AVAILABLE] TTSH V4 Build Thread

Post by resynthesize » Mon Feb 01, 2021 9:09 pm

i found some on ebay that tested correctly and seemed to have worked fine.

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Re: [AVAILABLE] TTSH V4 Build Thread

Post by kristop » Mon Feb 01, 2021 9:56 pm

So, Synthcube suggested checking the pinout, but I've pulled them off and they are Fairchild, so I take it from the above posts that the pinout is correct and the 5460s are no good, yes?

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Re: [AVAILABLE] TTSH V4 Build Thread

Post by fallout » Mon Feb 01, 2021 10:03 pm

kristop wrote:
Mon Feb 01, 2021 9:56 pm
So, Synthcube suggested checking the pinout, but I've pulled them off and they are Fairchild, so I take it from the above posts that the pinout is correct and the 5460s are no good, yes?
You are correct, get new ones.

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Re: [AVAILABLE] TTSH V4 Build Thread

Post by kristop » Mon Feb 01, 2021 10:21 pm

fallout wrote:
Mon Feb 01, 2021 10:03 pm
You are correct, get new ones.
Soooo... What do this 5460s do? Now that I've removed them my ADSR seems to work... Or at least a lot better the attack and release are gradual now at least.

Edit... Maybe not entirely. It works as a modulation source but not an envelope for the VCA,.... I guess?

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Re: [AVAILABLE] TTSH V4 Build Thread

Post by KSS » Tue Feb 02, 2021 12:37 am

The circuit and operation of the 4020 ADSR of the ARP 2600 is fully described on pg 33 of the 112pg Service manual PDF available online. It's also described on page 4 and 5 of the 58pg PDF later 2600 service manual. Also available online. The first is preferred as it shows the circuit on the same page as the description and the page order is correct. The 58pg version is all mixed up.

Note that the page numbers given here are the actual page numbers of the original manuals and may not correspond with the PDF page numbering.
---------------

As for what the 5460 do, they are acting as a normally ON* switch. Pinching off the flow between their Source and Drain pins when a voltage is present on their Gate pin. Since they are P-channel Junction FETs, this voltage is positive to pinch off the normally ON S-D path

Think Positive Pinches for P-Fet and Negative Pinches for N-FET.

If you look at the arrow of the JFET symbol in the schematic the can see it is pointing to the Periphery for a P-ch FET and to the iNterior for an N-ch FET

Note that both of these type JFETs operate in what is called Depletion mode. The voltage at the Gate pin causes the current carrying holes and electrons running in the channel between the Source and Drain to be depleted. <--Hence depletion mode.

*Don't be fooled by the normally ON aspect. While true for the physical opertion of the JFET, the circuit can be arranged so the result acts like its either normally on or normally off.
----------------------

There are other types of FETS which operate differently, but they are not used in the 2600 or TTSH.
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Re: [AVAILABLE] TTSH V4 Build Thread

Post by fallout » Tue Feb 02, 2021 9:55 am

Thanks for the explanation, KSS!

It's great how thoroughly the circuits are explained in the service manual. Admittedly, I had to read the circuit description more than a few times for it to sink in. It's a bit like a maze how it works. Interesting stuff for sure!

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Re: [AVAILABLE] TTSH V4 Build Thread

Post by amonti » Tue Feb 02, 2021 11:55 am

ebfx wrote:
Sun Jan 31, 2021 2:41 pm
ebfx wrote:
Wed Jan 27, 2021 6:52 pm
fallout wrote:
Wed Jan 27, 2021 3:56 pm
Now that the noise problem is fixed, I've encountered another problem caused by the LM301AN.

When calibrating the internal clock, I was not able to adjust the period to slower than 1 second. The rate init trimmer would reach a point and the square wave would go flat. I swapped out A42 for one of my spare LM301AN's and the problem was resolved.

@ebfx I'm curious if you encounter this as well.
Hadn't gotten there yet, so I just took a look and I'm seeing the same thing. I've got a friend who's supposed to bring over a couple of LM301's from his stock later this week (all of mine are from Synthcube, his are not). I'll let you know what I find.
Update: The LM301's my friend had were also from National Semi (though with a different date code) and behave exactly the same in my circuit. In addition, I tried the 100k to GND as suggested by KSS but that had no effect either.

Looks like it's time to track down a LM301 from a different supplier. Anyone have any experience with the SMT-to-DIP adapters or am I better off just trying to track down some old stock in DIP packages?
I use the SMT-to-DIP adapters all the time; many people use flux, fine solder and a small tip for 1.27mm pitch with great results. I recall Boogie hand soldering an entire SMT prototype board down to 0.65 pitch with no reflow! The only issue would be the cost if I had to buy 30 of the adapters - they aren't cheap!

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Re: [AVAILABLE] TTSH V4 Build Thread

Post by kristop » Tue Feb 02, 2021 12:34 pm

KSS wrote:
Tue Feb 02, 2021 12:37 am
The circuit and operation of the 4020 ADSR of the ARP 2600 is fully described on pg 33 of the 112pg Service manual PDF available online. It's also described on page 4 and 5 of the 58pg PDF later 2600 service manual. Also available online. The first is preferred as it shows the circuit on the same page as the description and the page order is correct. The 58pg version is all mixed up.

Note that the page numbers given here are the actual page numbers of the original manuals and may not correspond with the PDF page numbering.
---------------

As for what the 5460 do, they are acting as a normally ON* switch. Pinching off the flow between their Source and Drain pins when a voltage is present on their Gate pin. Since they are P-channel Junction FETs, this voltage is positive to pinch off the normally ON S-D path

Think Positive Pinches for P-Fet and Negative Pinches for N-FET.

If you look at the arrow of the JFET symbol in the schematic the can see it is pointing to the Periphery for a P-ch FET and to the iNterior for an N-ch FET

Note that both of these type JFETs operate in what is called Depletion mode. The voltage at the Gate pin causes the current carrying holes and electrons running in the channel between the Source and Drain to be depleted. <--Hence depletion mode.

*Don't be fooled by the normally ON aspect. While true for the physical opertion of the JFET, the circuit can be arranged so the result acts like its either normally on or normally off.
----------------------

There are other types of FETS which operate differently, but they are not used in the 2600 or TTSH.
Thanks! way over my head, but one day hopefully more of this stuff will make sense!

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Is a Gateboosted TTSH with 1601 OK?

Post by funkytransport » Tue Feb 02, 2021 12:44 pm

Is it safe enough to still use the Gatebooster on my TTSH even though I'm using a nice high signal from the 1601? it wont be damaging anything on either units would it? I was using it at modular levels but I've just finished my 1601 and wanted to doublecheck. Thanks

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Re: [AVAILABLE] TTSH V4 Build Thread

Post by ebfx » Tue Feb 02, 2021 5:35 pm

amonti wrote:
Tue Feb 02, 2021 11:55 am

I use the SMT-to-DIP adapters all the time; many people use flux, fine solder and a small tip for 1.27mm pitch with great results. I recall Boogie hand soldering an entire SMT prototype board down to 0.65 pitch with no reflow! The only issue would be the cost if I had to buy 30 of the adapters - they aren't cheap!
Thanks for the info amonti. Just ordered a few and will give them a try.

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Re: Is a Gateboosted TTSH with 1601 OK?

Post by amir » Tue Feb 02, 2021 7:48 pm

funkytransport wrote:
Tue Feb 02, 2021 12:44 pm
Is it safe enough to still use the Gatebooster on my TTSH even though I'm using a nice high signal from the 1601? it wont be damaging anything on either units would it? I was using it at modular levels but I've just finished my 1601 and wanted to doublecheck. Thanks

It should be ok.. the booster is capping the signal so you wont be introducing more v into the ttsh. I run a full gate signal from a es-3 into the gate booster sometimes and haven't had any issues yet.

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Re: [AVAILABLE] TTSH V4 Build Thread

Post by resynthesize » Wed Feb 03, 2021 1:27 am

OK, next up for me is the sample and hold. The noise section and internal clock both work fine, but pin 6 of the LM301 before the output (A-2 on the schematic) is pinned at +15V. I can see both the internal clock entering correctly at SH-1 and the noise at SH-4. Any pointers here?
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Re: Is a Gateboosted TTSH with 1601 OK?

Post by funkytransport » Wed Feb 03, 2021 8:18 am

amir wrote:
Tue Feb 02, 2021 7:48 pm
funkytransport wrote:
Tue Feb 02, 2021 12:44 pm
Is it safe enough to still use the Gatebooster on my TTSH even though I'm using a nice high signal from the 1601? it wont be damaging anything on either units would it? I was using it at modular levels but I've just finished my 1601 and wanted to doublecheck. Thanks

It should be ok.. the booster is capping the signal so you wont be introducing more v into the ttsh. I run a full gate signal from a es-3 into the gate booster sometimes and haven't had any issues yet.
Thanks Amir :)

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Re: [AVAILABLE] TTSH V4 Build Thread

Post by fallout » Wed Feb 03, 2021 9:03 am

resynthesize wrote:
Wed Feb 03, 2021 1:27 am
OK, next up for me is the sample and hold. The noise section and internal clock both work fine, but pin 6 of the LM301 before the output (A-2 on the schematic) is pinned at +15V. I can see both the internal clock entering correctly at SH-1 and the noise at SH-4. Any pointers here?
Are you sure that's correct? Shouldn't clock be entering at SH-4 and noise at SH-1? I'm assuming you swapped the 301s and looked for solder bridges, cold joints, etc..

I think you should also see a trigger/pulse on the gate of Q4 and noise on drain and the 'sampled' voltage on C8. Are you seeing noise on pin 6 of A1?

Admittedly, I'm not 100% certain how the circuit works but my assumption is the pulse (from clock) is is operating Q4 like a switch, with the voltage to be sampled coming into the drain of Q4 and charges C8 to the sampled voltage when the pulse hits the gate.

Since the service manual doesn't have a description of the S&H circuit, perhaps one of the brains here can give a brief analysis on how this works. Id love to know what Q1 - Q3 are doing along with the dual JFET connected to A2 (buffer?).
Last edited by fallout on Wed Feb 03, 2021 12:02 pm, edited 3 times in total.

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Re: [AVAILABLE] TTSH V4 Build Thread

Post by fallout » Wed Feb 03, 2021 10:14 am

Just an update, I received the replacement LM301AP's from Synthcube and these also work in both noise generator and S&H circuits.

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Re: [AVAILABLE] TTSH V4 Build Thread

Post by ebfx » Wed Feb 03, 2021 10:58 am

fallout wrote:
Wed Feb 03, 2021 10:14 am
Just an update, I received the replacement LM301AP's from Synthcube and these also work in both noise generator and S&H circuits.
Thanks for the update fallout. I assume you mean LM301AN, not AP. Do the replacements have the same date code on them as the originals?

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Re: [AVAILABLE] TTSH V4 Build Thread

Post by synthcube » Wed Feb 03, 2021 10:59 am

to clarify, we have sent out LM301AP to replace the reported issues with latest batch of LM301AN
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Re: [AVAILABLE] TTSH V4 Build Thread

Post by fallout » Wed Feb 03, 2021 11:57 am

ebfx wrote:
Wed Feb 03, 2021 10:58 am
fallout wrote:
Wed Feb 03, 2021 10:14 am
Just an update, I received the replacement LM301AP's from Synthcube and these also work in both noise generator and S&H circuits.
Thanks for the update fallout. I assume you mean LM301AN, not AP. Do the replacements have the same date code on them as the originals?
It looks like the AP designation just means that the package is 'plastic'.

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Re: [AVAILABLE] TTSH V4 Build Thread

Post by amonti » Wed Feb 03, 2021 12:11 pm

fallout wrote:
Wed Feb 03, 2021 9:03 am
resynthesize wrote:
Wed Feb 03, 2021 1:27 am
OK, next up for me is the sample and hold. The noise section and internal clock both work fine, but pin 6 of the LM301 before the output (A-2 on the schematic) is pinned at +15V. I can see both the internal clock entering correctly at SH-1 and the noise at SH-4. Any pointers here?
Are you sure that's correct? Shouldn't clock be entering at SH-4 and noise at SH-1? I'm assuming you swapped the 301s and looked for solder bridges, cold joints, etc..

I think you should also see a trigger/pulse on the gate of Q4 and noise on drain and the 'sampled' voltage on C8. Are you seeing noise on pin 6 of A1?

Admittedly, I'm not 100% certain how the circuit works but my assumption is the pulse (from clock) is is operating Q4 like a switch, with the voltage to be sampled coming into the drain of Q4 and charges C8 to the sampled voltage when the pulse hits the gate.

Since the service manual doesn't have a description of the S&H circuit, perhaps one of the brains here can give a brief analysis on how this works. Id love to know what Q1 - Q3 are doing along with the dual JFET connected to A2 (buffer?).
Don T had a high-level explanation of the S&H circuit in Rev 2 discussions; the same thread has a link to a S&H schematic ("zoom-in" of a 4015 module)

Quoting from Don T:
"...the output of the amplifier is fed into a JFET, which only passes signal when receiving a clock pulse. When it receives a clock pulse, it feeds the amplifier's output into the "Hold" section, which stores whatever voltage is present on the amp's output on the 0.022uf cap. The rest of the circuit is basically an extremely high impedance buffer to insure the voltage on the cap doesn't drop until the next sample is taken."

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Re: [AVAILABLE] TTSH V4 Build Thread

Post by fallout » Wed Feb 03, 2021 1:08 pm

LED-man wrote:
Wed Jan 27, 2021 5:42 am
Please look in the TTsH rev1 build Thread or on my website.
i use mostly an BC337 16 (different pinout).
Or BC337 25 with additional 10k resistor in series on the electrolyte cap.
https://www.muffwiggler.com/forum/viewt ... start=1175

https://www.dsl-man.de/display/TTSH/TTSH+Noise+Mod
Thanks again for the BC337 suggestion! I got some BC337-16's in the mail today and auditioned 2n5172's, bc547c's and the 337's in the noise circuit. The 2n5172's and bc547c's sounded a bit 'spitty', in comparison to the 337's. The 2n5172's were the most distorted/nasty sounding of the 3 transistor types.

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Re: [AVAILABLE] TTSH V4 Build Thread

Post by KSS » Wed Feb 03, 2021 8:15 pm

amonti wrote:
Wed Feb 03, 2021 12:11 pm
Quoting from Don T:
"...the output of the amplifier is fed into a JFET, which only passes signal when receiving a clock pulse. When it receives a clock pulse, it feeds the amplifier's output into the "Hold" section, which stores whatever voltage is present on the amp's output on the 0.022uf cap. The rest of the circuit is basically an extremely high impedance buffer to insure the voltage on the cap doesn't drop until the next sample is taken."
Yes, and you can get rid of the 301, R21 and R22, and expensive Q7 if you use a Hi-Z OPA like an 071 or better, a 412 type. <--412 is a dual OPA. Can't remember its single version P/N right now.
Remember when these were designed, Hi-Z OPAs were very expensive-'rare'. There will be ZERO audible or functional change over leaving them in. They're only two places in a modern 2600 that should still use the dual FET. The sine shaper of VCO2 and the output buffer of the 4012 VCF. Any other can be eliminated without any negative audible or functional differences.

You can also add a switch across C119 to change from S/H to T/H.<--Something which was dropped when the 1036 S/H of the 2500 was 'condensed' into the S/H of the 2600. C119 is not part of the 4015 module. All RefDes P/Ns shared here are from the original ARP service manuals.
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Re: [AVAILABLE] TTSH V4 Build Thread

Post by amonti » Wed Feb 03, 2021 11:03 pm

KSS wrote:
Wed Feb 03, 2021 8:15 pm

Yes, and you can get rid of the 301, R21 and R22, and expensive Q7 if you use a Hi-Z OPA like an 071 or better, a 412 type. <--412 is a dual OPA. Can't remember its single version P/N right now.
Remember when these were designed, Hi-Z OPAs were very expensive-'rare'. There will be ZERO audible or functional change over leaving them in. They're only two places in a modern 2600 that should still use the dual FET. The sine shaper of VCO2 and the output buffer of the 4012 VCF. Any other can be eliminated without any negative audible or functional differences.

You can also add a switch across C119 to change from S/H to T/H.<--Something which was dropped when the 1036 S/H of the 2500 was 'condensed' into the S/H of the 2600. C119 is not part of the 4015 module. All RefDes P/Ns shared here are from the original ARP service manuals.
Is the single OPA you're thinking of a 351? Not to derail the thread, but I often wonder why many remakes use 'rare' parts when (as you note) relatively modern components would greatly simplify the design and construction without any audible difference. I'm assuming it's because purists might balk at changing the design, but my Weston Pro2021 uses a few modern components where convenient (due to rarity, cost, etc.) without any noticeable change in sound quality (actually, I think it sounds better than the original).

I never knew T&H was 'hidden' just outside the 4015 - I'm going to desolder one leg of C119 and add a temporary jumper/switch to test; I think track & hold is a great effect - thanks very much for your insight.

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Re: [AVAILABLE] TTSH V4 Build Thread

Post by KSS » Thu Feb 04, 2021 3:03 am

amonti wrote:
Wed Feb 03, 2021 11:03 pm
Is the single OPA you're thinking of a 351?
351 has 10mV input offset. You'd want to use an offset trim with it. LF411 has typical 0.8mV input offset, with max 2mV. You're looking for an OPA with a matched JFET input, since that's what the 3954 of the original circuit is doing there. I typically use a dual and find a mod -or existing nearby single- to use the 'extra' OPA. The 412 has max 1mV input offset.
Not to derail the thread, but I often wonder why many remakes use 'rare' parts when (as you note) relatively modern components would greatly simplify the design and construction without any audible difference. I'm assuming it's because purists might balk at changing the design,
That. Or they just don't know any better or don't take the time to discover and test for correct replacements. OR they subscribe to the silly notion that any upgrade or mod is some kind of insult to the 'original' designer. Or his design. But if you ever saw Dennis Colin's own 2600, you'd see that theory shot to hell and back! Not to mention the *very* many modded and upgraded OG 2600's that have been heard on records since the 70s.
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Re: [AVAILABLE] TTSH V4 Build Thread

Post by fallout » Thu Feb 04, 2021 9:28 am

KSS wrote:
Wed Feb 03, 2021 8:15 pm
You can also add a switch across C119 to change from S/H to T/H.<--Something which was dropped when the 1036 S/H of the 2500 was 'condensed' into the S/H of the 2600. C119 is not part of the 4015 module. All RefDes P/Ns shared here are from the original ARP service manuals.
I'm curious how this works. Is C119's purpose to create a pulse from the clock signal and by shorting C119, it's allowing the the full square wave to keep Q4 'on' for a longer (instead of a quick pulse) duration creating the 'T&H' effect?

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Re: [AVAILABLE] TTSH V4 Build Thread

Post by KSS » Sat Feb 06, 2021 6:03 am

Correct.

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