stay at home type 69 project

[craigmorris74]

Has anyone in the US ordered front panels for this project? Curious to know where you got them from.
Thanks,
Craig

 

[Ricardus]

Has anyone in the US ordered front panels for this project? Curious to know where you got them from.
Thanks,
Craig

I haven't yet, but when I build some I will get them from Frank Rollwn.

 

[craigmorris74]

I haven't yet, but when I build some I will get them from Frank Rollwn.

Ordered mine from Frank at frontpanels.de, and it was significantly cheaper than frontpanelsexpress, even with shipping to the US.

 

[Ricardus]

Ordered mine from Frank at frontpanels.de, and it was significantly cheaper than frontpanelsexpress, even with shipping to the US.

Yep. That's why I use Frank. He's the best and he always goes above and beyond for me.

 

[mdcmdcmdc]

Has anyone had any luck ordering the 7490E transformers from Sowter? A friend and I have had a few PCBs fabricated for the 1RU version of this project but haven't been able to get much response from carnhill on the transformers. Not sure if there's a secret handshake or...? Thanks all!

 

[TwentyTrees]

When it comes to Carnhill, I always order from AML: Transformers and Inductors

 

[mdcmdcmdc]

Thanks for the suggestion - I've reached out to AML.

 

[mdcmdcmdc]

Matt from Iron Age suspects they may no longer be available after Sowter's retirement and the subsequent purchase by Carnhill. @TwentyTrees you used Jensens for yours?

 

[TwentyTrees]

Matt from Iron Age suspects they may no longer be available after Sowter's retirement and the subsequent purchase by Carnhill. @TwentyTrees you used Jensens for yours?

I did, yes. No complaints here, though I've not compared alternatives in circuit.

 

[mdcmdcmdc]

Time to order some adaptor PCBs I guess.

 

[craigmorris74]

From Sowter:
We are offering pinned parts again on a few models. We have even found 1 off 7490C in stock! We will be changing the website in the near future, in the short term if you want to order less than 10 off then order the “E” version and then a separate email reminding me that you want the “C” version. If you require more than 10 let me know as we’ll be able to offer a discount if you pay by bank transfer

 

[mickdundee63]

I built two of the H9R and have them in a 3U case next to a pair of Neve 1290s. They sound wonderful however I have a slight whistling noise and when I hit the final two positions of gain in the mic position this becomes an almighty scream from hell. It very quickly ramps up so I'm presuming its some sort of a feedback loop. I'm a bit of a n00b but happy to read more and learn and have access to an oscilloscope so just need some guidance on where to start looking first.

Switching the eq input and other eq switches affects the screeching sound. Switching from line/pad/mic on the second unit affects the first and vice versa so thinking maybe a grounding issue or error.

I get a loud, lower noise if I ground the can of the transformer by touching it with my finger.

The Neves are dead quiet.

The power unit is a JLM audio powerplant which is in a separate 1u case and fed via XLR.

Any troubleshooting pointers appreciated!

 

[mickdundee63]

I built two of the H9R and have them in a 3U case next to a pair of Neve 1290s. They sound wonderful however I have a slight whistling noise and when I hit the final two positions of gain in the mic position this becomes an almighty scream from hell. It very quickly ramps up so I'm presuming its some sort of a feedback loop. I'm a bit of a n00b but happy to read more and learn and have access to an oscilloscope so just need some guidance on where to start looking first.

Switching the eq input and other eq switches affects the screeching sound. Switching from line/pad/mic on the second unit affects the first and vice versa so thinking maybe a grounding issue or error.

I get a loud, lower noise if I ground the can of the transformer by touching it with my finger.

The Neves are dead quiet.

The power unit is a JLM audio powerplant which is in a separate 1u case and fed via XLR.

Any troubleshooting pointers appreciated!

Oh and the transformers are the Sowter 7490F so they are sitting off the board and connected via leads.

 

[dogears]

Hm ok. Sorry to hear that. I'd probably start by just having one unit isolated by itself - disconnect power to everything else, and then see what fault modes exist (if any).

 

[mickdundee63]

Hm ok. Sorry to hear that. I'd probably start by just having one unit isolated by itself - disconnect power to everything else, and then see what fault modes exist (if any).

Thank you for responding, gave this a try, took all units except for one 69 out of circuit and same behaviour unfortunately. I note that the gain is already pretty healthy at position 4 before it starts squealing at 5 and 6 - already distorting at position 4 for singing into an sm57 a few inches away. But then also I think this is pretty normal behaviour for these units (at least the H9R)? Its pretty useable without going to positions 5 or 6 but also I feel like I must have made an error somewhere so want to track it down if I can.

I should also note that before i tore it down to trouble shoot I had all 4 units hooked up to an insert switcher board. In this mode the squealing didn't occur, although there was a much lower level whistling and some radio frequency interference.

 

[TwentyTrees]

Quick question - what voltage are you using for the H9R, and what's your power supply? Sounds like you may have some oscillation in the first amp, though it's interesting you didn't get that with the SMPS.

 

[mickdundee63]

Quick question - what voltage are you using for the H9R, and what's your power supply? Sounds like you may have some oscillation in the first amp, though it's interesting you didn't get that with the SMPS.

Sorry I should clarify - i had it hooked up to an insert switcher, not an SMPS : Mastering Insert Switcher Boards

The power supply was the same all the time - Its the JLM powerplant and its feeding 24v to the H9R. I did actually have an SMPS powering the relays for the insert switcher so thought that might be contributing but removed that and same issue.

 

[TwentyTrees]

Sorry I should clarify - i had it hooked up to an insert switcher, not an SMPS : Mastering Insert Switcher Boards

The power supply was the same all the time - Its the JLM powerplant and its feeding 24v to the H9R. I did actually have an SMPS powering the relays for the insert switcher so thought that might be contributing but removed that and same issue.

Oh, my bad - read that too quickly. Strange that the nature of the noise changed based on what you had it connected to. What are your test conditions for reproducing the noise, now that the insert switcher isn't part of the picture - mic / line / 150 ohm resistor terminating the input? What's on the output?

If I was in your shoes I'd definitely be having a close look at the soldering and parts round the gain switch and first amplifier section. The fact that it's all of your units suggests that if it is an error, it's an error common to all of them - misplaced component? Are all your ground connections solid?

 

[mickdundee63]

Sorry I should clarify - i had it hooked up to an insert switcher, not an SMPS : Mastering Insert Switcher Boards

The power supply was the same all the time - Its the JLM powerplant and its feeding 24v to the H9R. I did actually have an SMPS powering the relays for the insert switcher so thought that might be contributing but removed that and same issue.

Tried switching the power cable and the power supply itself - no dice, same almighty scream

 

[TwentyTrees]

Just to note that @pahstah had some issues with a Helios clone oscillating at high gain - turned out to be a duff transistor in the HPF in his case:

https://groupdiy.com/threads/he-569-pre-eq-500-series.72521/