Post by lorem on May 15, 2023 3:18:14 GMT -7
Hi there,
greatings from Italy.
Fresh owner of a mid 2012 EZG50, already part of the Z family (owned a Maz 18 and now a Maz38 NR).
The amp seems in great overall conditions, I tried to remove the rear protection for tubes and, damn, it was so sticky I'd say it hadn't been removed in its lifetime.
By the way, I looked for this amp for a very long time here in Italy, a good friend of mine had one and his clean sounds were stunning, so I pulled the trigger when it showed up on the used market.
I found mine breaking up when using a suggested setting provided by my friend (pre at three quarter, post at one quarter), instead its amp stays clean with this settings and single coil.
I thought maybe the tubes worn out after 11 years and I opened it up, this is the tubes I found:
V1: Tung sol 12 Ax7, V2: Tung sol 6201 12At7W (so not a nos), V3: Tung sol 12 Ax7, V4: 6201 USA (I'd say those nos GE tubes the good doc put in), V5-V6: GT 6L6 GE - range 4, V7: Sovtek 5AR4.
Then I measured the plate voltage and I found at 459 V, measured the Bias and it was only 20 mA! A little bit too cold...
I found on doc's website the bias recommendation for 28 mA, I tried to set it up this way but I had a plate voltage of 450, ending up with around 13 Watt and 42% usage for a 30 Watt tube, seems too cold. Last setting I tried was 39 mA with plate voltage 446 V, so around 58%.
Tried again the amp, the breaking up is always there, curious thing it would go away just lowering a tiny bit the post... I found the bias meter bouncing really high when the amp was breaking up on the low E.
During tests I found my wall voltage was going up and down all the time, maybe I need a variac for a proper set.
I'd say the introduction is long enough, let's go the the questions, eheh.
1a) Is it correct to rate the GT6L6GE as 30 watt tubes as stated in the GT data sheet? Maybe the doc consider them less strong thus the 28 mA bias suggested?
1b) I'm gonna buy a fresh pair of Tung Sol STR6L6 GC, I would consider them as 30 watt tubes, am I wrong?
2) Which tube would suit me best to substitute V4? I don't think I can find here good nos 6201 at reasonable price. Having already one in V2 I tend to consider Tung sol 12At7W a good swap, maybe picking up a balanced one for PI use.
3) Is it normal a lil breaking up with those settings (pre 3/4, post 1/4)? maybe it's only my V4 which is gainer than my friend's one?
Thank you!
greatings from Italy.
Fresh owner of a mid 2012 EZG50, already part of the Z family (owned a Maz 18 and now a Maz38 NR).
The amp seems in great overall conditions, I tried to remove the rear protection for tubes and, damn, it was so sticky I'd say it hadn't been removed in its lifetime.
By the way, I looked for this amp for a very long time here in Italy, a good friend of mine had one and his clean sounds were stunning, so I pulled the trigger when it showed up on the used market.
I found mine breaking up when using a suggested setting provided by my friend (pre at three quarter, post at one quarter), instead its amp stays clean with this settings and single coil.
I thought maybe the tubes worn out after 11 years and I opened it up, this is the tubes I found:
V1: Tung sol 12 Ax7, V2: Tung sol 6201 12At7W (so not a nos), V3: Tung sol 12 Ax7, V4: 6201 USA (I'd say those nos GE tubes the good doc put in), V5-V6: GT 6L6 GE - range 4, V7: Sovtek 5AR4.
Then I measured the plate voltage and I found at 459 V, measured the Bias and it was only 20 mA! A little bit too cold...
I found on doc's website the bias recommendation for 28 mA, I tried to set it up this way but I had a plate voltage of 450, ending up with around 13 Watt and 42% usage for a 30 Watt tube, seems too cold. Last setting I tried was 39 mA with plate voltage 446 V, so around 58%.
Tried again the amp, the breaking up is always there, curious thing it would go away just lowering a tiny bit the post... I found the bias meter bouncing really high when the amp was breaking up on the low E.
During tests I found my wall voltage was going up and down all the time, maybe I need a variac for a proper set.
I'd say the introduction is long enough, let's go the the questions, eheh.
1a) Is it correct to rate the GT6L6GE as 30 watt tubes as stated in the GT data sheet? Maybe the doc consider them less strong thus the 28 mA bias suggested?
1b) I'm gonna buy a fresh pair of Tung Sol STR6L6 GC, I would consider them as 30 watt tubes, am I wrong?
2) Which tube would suit me best to substitute V4? I don't think I can find here good nos 6201 at reasonable price. Having already one in V2 I tend to consider Tung sol 12At7W a good swap, maybe picking up a balanced one for PI use.
3) Is it normal a lil breaking up with those settings (pre 3/4, post 1/4)? maybe it's only my V4 which is gainer than my friend's one?
Thank you!